6x45mm vs 6.5 Grendel

[Scottmilk9]

Nonexistent bolt issue? A quick search of the internet says otherwise. Obviously bolts have gotten better so its not nearly the problem it used to be but to say its imaginary is a lie. You should run the numbers a 75gr amax at 3200fps is not very far at all behind many of the grendel loads. If youre shooting game animals past 500yds with a grendel then that tells me all I need to know about you. 75gr amax out of a 223 still splashes just fine on steel at 800yds and that load is way behind any of the cartridges discussed in this thread.

Maybe I'm a hater but I've never seen the point of shooting expensive compared to 223 bullets out of a grendel when you get a lot more performance out of that same bullet in a creedmoor or 260. With the DPMS G2 out now if it works out almost all of these long range variants on borrowed time. I just like the idea of a 22x6.8 as the 75gr amax is the cheapest long range bullet out there. Long barrel life, 25% less powder than the big cartridges, cheap bullets 17ish cents a bullet and hangs right there with the bigger boys in everything except energy on target way on out there. Although I'd hope no one is using these wildcats on game animals at the 500+ yard distance that there starts to be any real appreciable difference between them.

You might do your research on the internet, but I've been building AR15's for 15 years and never once have i had a 6.5 grendel bolt fail or break, granted its only been 5-6 years since ive been building grendels.

Secondly, I never said the bolt problem was imaginary, so please stick to my words, which you quoted in your post. Also, IF, IF your shooting game animals past 500 yards, where did that come into play, oh wait i said it doesn't have as much energy, which in turn you took as shooting game animals, come on man, take your head out of your ass and read. Have you ever shot a competition? If so please tell me how easy is it to see a splash at 800yds on steel using a 223 or even a 6x45? The energy of a grendel is much easier to spot hits, even out to 1000 plus yards. Next you'll be telling me my grendel can't make it that far.

Lastly, you start talking about a .260 or a creedmoor, thats not apples to apples. Nor did anyone want a comparison between a grendel and that of a larger framed(in an AR) caliber.

Go back to the internet and do your research before you come here making assumptions about what you think people say or what they might mean.

 

[corym468]

I had a 6mmAR for a while, it was great. Slinging the .530BC Hornady 105 bullets at 2770 out of a 24" barrel was no problem and the rounds fed great from the magazine. In a 6.5 Grendel the high BC bullets (the heavy/long 140ish grain stuff) won't fit in a magazine so you're stuck shooting the lower BC stuff slower than the 6mm variant can push the 105s.

Won't fit? That's incorrect. I've been working up a load with the Hornady 140gr SST (0.520 G1 BC) and have 500 140gr bthps (.580 G1 BC) on back order.

I've pushed the 140gr SSTs to 2400+fps using CFE before seeing pressure signs (24" barrel). I intend to try N540 if I can ever find any in stock.

I've got a 16" and 20" Grendel in the works. I intend to load the 140gr SST for a brush load (short range hunting) and seeing what I can do with the BTHPs.

I'm thinking about switching over to a 6x45 after I get some use out of my 223. I probably won't shoot past 300 yards and the only reason I'm considering it is because Iowa requires a 24 caliber or larger for shooting deer. I don't want to mess around with specialty magazines and I've heard the Grendel is notorious for breaking bolts.

Not with proper manufacturing and material selection you're not breaking bolts. A Grendel bolt made of 9310 or carpenter with proper heat treating will be just as reliable as a good 5.56 bolt.

As long as you've got a properly assembled, squared AR, a properly made bolt, and watch your pressure signs (not running hot loads) your bolt will last the life of your barrel.

With the newish 6.5x6.8 why would you even consider the 6.5 grendel? From what I can tell it basically has all the benefits of the grendel without the bolt shortcomings. I know those have largely been rectified but now theres talk of a new reamer for grendel, is that going through? I dont follow the grendel as I have no real need for one. I like the 22x6.8 personally, 75gr Amaxs are cheap and hang right in there with the grendel with a better bolt design and I've already got 6.8 brass. A 75gr amax at 3200 out of a 24" is pretty tough to beat IMO.

There is no new reamer for the Grendel. What you're talking about is actually a reamer archived from Bill A's development of the Grendel. It was just prior to the change to the compound throat, that has made the Grendel the incredibly versatile cartridge it is.

It had recently come to light that a certain barrel making company had been putting economy grade Grendel barrels on the market with a chamber that was not SAAMI Grendel, likely due to poor QA. In a CYA exercise the company made some asinine claims to what is part of the SAAMI spec and then began offering a chamber without the compound throat, as it's easier to produce in bulk. To have admitted they made a mistake would have required them to do a costly recall.

 

[Twelve208]

^^^^What scott said^^ If your into hitting paper and "splash" steel day in and day out trying to save a buck,go with whetever you want at that point.When I comes to game animals,kenetic energy and bullet expansion are your main concern.People talk way to unrealistic with hunting and actual ranges more often then not,they are great internet hunters.With the one in a million chance that you do get a shot at a wolf,I spare no expenses.. becuase you will regret it.
That being said,I really do like my 6X45. Its a coyote hammer.Hell it shoots better then my Grendel off the bags.
5spd has laid down some serious fur with his 6x45,and knows what its all about.
Lastly I gotta say,cutting someone's hunting integrity on the forums just tells me your a douche canoe.Hope your not the hunting expert as well..

 

[*Nine]

Ok, so a 24" Grendel can push a 140 with a BC of .520-.580 at 2400fps. That same rifle in 6mm can push a 105 with a BC of .530 or more to nearly 2800fps. The tiny BC advantage of even the .580 bullet can't make up for a nearly 400fps deficit.

 

[Bronco]

Have run a 6 mm RAT since it was developed and is one upper I'll always have, spare barrel is on the shelf ready to go. It is a 22" 1 in 7.5 twist, mostly shoot 105 Amax with some 87 gr. V-max. Running the 105's at 2750 fps and the 87's at 3000 fps. 105's go subsonic at 1100 yd. I've shot several Grendels, a close friend has a 24" that I've shot a lot. Great round, factory ammo is a plus, that said I'll stick with the 6 RAT, it has proven to me it is superior in accuracy and ease of hitting at distance after many range sessions comparing the two.

On a side note the 90 gr. VLD's in a .223 rock, push them at 2810 out of a 28" 1 in 7 twist Brux.

 

[bustin]

Not with proper manufacturing and material selection you're not breaking bolts. A Grendel bolt made of 9310 or carpenter with proper heat treating will be just as reliable as a good 5.56 bolt.

Not really. To figure the strength of a bolt you multiply the width of the lugs by the length behind the recess of the bolt face (x). Then draw an angle from the recess at each side of the lug to the top middle front of the bolt between the lugs. Measure the thickness of the web between the lugs and multiply that by the length of the 2 angles(Y). add X and Y together and multiply the yield strength of the material (apx 160,000 psi) for 158 and 9310. Then multiply that by 7 for the number of lugs.

Then to figure the trust of the cartridge figure the area in the diameter of the rim and multiply that by the PSI at maximum pressure.
The Grendel has much more area so the thrust will be much higher. That and the fact the web is thinner between the lugs makes the Grendel bolts much weaker than a 5.56 bolt.
In the firearm industry there should be a 2:1 safety factor engineered into every part. Meaning it should be twice as strong as the maximum pressure used. The Grendel and 7.62x39 barely have a 1:1 ratio.

 

[banditbump]

In the firearm industry there should be a 2:1 safety factor engineered into every part. Meaning it should be twice as strong as the maximum pressure used. The Grendel and 7.62x39 barely have a 1:1 ratio.

Finally some scientific jargon with a hint of math that proves the 6.5 grendel is dangerous. I own one should I sell it or would that be criminal now that I know it's dangerous? For safety purposes I will have it euthanized. Please tell aa ,hornady, and the other companies involved we must get this menace off the street!

 

[jasonfaz]

Riiiiiiight. We should probably tell all of the .458 SOCOM owners to melt down their shit too considering those bolts have even less material under even greater force. Random math with no explanation as to why some arbitrary ratio is required doesn't do much for me. I'd be more than happy to take your 6.5 to the furnace for you. Hell, I'll even do it for free!

 

[Scottmilk9]

Hey bustin, how many grendel bolts have you seen broke? Science is great, but field results tell the whole story. I'm not saying grendel bolts don't break, but if you use common sense reloading practices(loading not to exceed max recommended powder charges) then mostly likely you won't have a problem.

For the original question of 6x45 or 6.5 grendel, go with what you like best, they both have their purposes, people have their favorites(not sure how 6x6.8 and others got into this thread), people will bad mouth you to persuade you to get what they like, bottom line, they both are great shooting and have different purposes in my opinion. X factor that!

 

[corym468]

Not really. To figure the strength of a bolt you multiply the width of the lugs by the length behind the recess of the bolt face (x). Then draw an angle from the recess at each side of the lug to the top middle front of the bolt between the lugs. Measure the thickness of the web between the lugs and multiply that by the length of the 2 angles(Y). add X and Y together and multiply the yield strength of the material (apx 160,000 psi) for 158 and 9310. Then multiply that by 7 for the number of lugs.

Then to figure the trust of the cartridge figure the area in the diameter of the rim and multiply that by the PSI at maximum pressure.
The Grendel has much more area so the thrust will be much higher. That and the fact the web is thinner between the lugs makes the Grendel bolts much weaker than a 5.56 bolt.
In the firearm industry there should be a 2:1 safety factor engineered into every part. Meaning it should be twice as strong as the maximum pressure used. The Grendel and 7.62x39 barely have a 1:1 ratio.

Now, now the first half of this post is legit.

It's one thing to be able to work out a problem, it's an entirely other thing to understand that problem.

The dimensions of the bolt are critical, but only part of the equation here. You've got the bolt's strength, hardness, and the force being placed on the bolt.

The 5.56 NATO is a max 60ksi round, while the SAAMI Spec Grendel is a max 52ksi round. This results in a significant difference in your force on the bolt.

Your assumption of a FoS (Factor of Safety) of 2 for the 5.56 bolts is incorrect. The 5.56 NATO like the Grendel, 458 SOCOM, BEOWOLF, etc... were developed for a platform that wasn't initially designed for such higher powered rounds. The AR15 was initially designed for a .22 caliber round operating at roughly 50ksi. But I digress....

The bolts for all of these rounds achieve a FoS of 1, which has proven to be sufficient when supplemented with properly selected high quality materials and proper manufacturing processes.

9310 and Carpenter steel are both high quality, strong materials that are made stronger through heat treating. (see increasing yield strength) However, the metals can be heat treated to a increased strength where they become hard and brittle. This will make the material more susceptible to stress fractures from the impact of the rounds thrust. Stress fractures are your bolts worse nightmare. A small stress fracture will spread at an exponential rate. The 90 degree edges of the bolt lugs make the lugs the most susceptible area of the bolt. As you understand this, you begin to understand heat treating to be the art that it is.

Now let's look at the Grendel(actually originally the Beowolf) Bolt again from a true overall viewpoint. The Grendel was always intended for the AR15 platform, thus all the factors we've discussed above were balanced to fit within the parameters of the AR15. When you understand all of this you begin to understand the fine engineering job that is the final Grendel Bolt.

The Grendel Bolt design was proofed at 60+ksi. Per the design the Grendel can be fired at the pressures of the 5.56 NATO, as some people do. This is where you've seen bolts break as the Grendel Bolt won't sustain continuous operations at 55+ksi. Eventually material fatigue sets in and you get stress fractures.

 

[1slow01z71]

WTF? What bolt issues are you referring to? There are two different chambers offered up for 6.5Gs requiring two different bolts. Ive heard of no issues with either in terms of reliability. As for the comments about taking game at 500+ yards I take personal offense to. I consider myself a very ethical hunter in all regards. I've passed up shots at least 20 times based on the fact I don't know for sure that I can make a hit at a given distance. That said, I've worked my ass off gaining proficiency around reading wind and drop and shoot enough that I'm 100% comfy shooting at 500-700 with a 6.5 on 200-250lb game. No issue there. Not sure what you mean by saying "if you're shooting game animals at 500+ I already know who you are" means, but if you're implying its unethical in anyway I'd recommend you get a little time under your belt shooting at distance with the appropriate tools for the job before you go bitching at people for something they've worked long and hard to accomplish...

Bolt lugs shearing off. Im not going to bother linking to the plethora of broken bolt threads strewn through the internet. Most are from people running them hard with handloads. People will say its because we pushed the cartridge past its design parameters but Im pretty sure all numbers on these cartridges being discussed are max numbers. Fact of the matter is there is less margin of error with the Grendel bolt.

My comment about taking long shots like that with Grendel is just that, theres much better tools to make that shot. I don't abide by the 1000ftlb rule like so many preach, hell Ive taken animals with subsonics but to use a Grendel for those kinds of shots is nothing more than a braggadocios notch on your belt. Its akin to using a butter knife to cut a steak, sure it gets the job done but there are much better ways to do it.

You might do your research on the internet, but I've been building AR15's for 15 years and never once have i had a 6.5 grendel bolt fail or break, granted its only been 5-6 years since ive been building grendels.

Secondly, I never said the bolt problem was imaginary, so please stick to my words, which you quoted in your post. Also, IF, IF your shooting game animals past 500 yards, where did that come into play, oh wait i said it doesn't have as much energy, which in turn you took as shooting game animals, come on man, take your head out of your ass and read. Have you ever shot a competition? If so please tell me how easy is it to see a splash at 800yds on steel using a 223 or even a 6x45? The energy of a grendel is much easier to spot hits, even out to 1000 plus yards. Next you'll be telling me my grendel can't make it that far.

Lastly, you start talking about a .260 or a creedmoor, thats not apples to apples. Nor did anyone want a comparison between a grendel and that of a larger framed(in an AR) caliber.

Go back to the internet and do your research before you come here making assumptions about what you think people say or what they might mean.

You sound like the guys I deal with all the time being a construction inspector. When I tell them their shit is screwed up, their reply is often "Ive been doing this for XX years" well, its quite simple. They've been doing it wrong for that many years. Even if you've built a couple hundred Grendels you've still got a VERY small sampling of the market and is no way indicative of what the true market condition is.

You said the "bolt issue is non-existent", imaginary, one-in-the-same. Youre saying the bolt issues don't happen when they do. Maybe you chose your wording poorly?

On the energy thing I was simply commenting that at the extended distances we are talking about they all have plenty of power to ring steel and spot splash. 77gr 223 can be self-spotted at 1000 on a dry day. On damp ground I seriously doubt splash would be easy to see on any of these, or at least not enough difference to be appreciable. So logically I figured you were talking about taking game at those distance where energy on target really would matter.

If youll notice I mentioned the DPMS G2, instead of flying off the deep end, read and comprehend. The G2 is essentially the same size and weight of an AR15 but fires full size cartridges. In the past other than the "just because" crowd the argument for shooting the AR15 calibers has been weight of platform, that is no longer a viable excuse if the G2 pans out to be a reliable platform.

Riiiiiiight. We should probably tell all of the .458 SOCOM owners to melt down their shit too considering those bolts have even less material under even greater force. Random math with no explanation as to why some arbitrary ratio is required doesn't do much for me. I'd be more than happy to take your 6.5 to the furnace for you. Hell, I'll even do it for free!

Actually the 458 socom only operates at 35K so you might want to revisit your calculations if you can figure out how to work the calculator. The socom has to work at a lower operating pressure due to the large bolt face so it WONT have lug problems like many grendels have. That's where many Grendel owners get in trouble pushing it too hard. I don't think anyone in their right mind would say the Grendel bolt is bad in stock form. The 6.5x6.8 simply affords a stronger bolt design that allows you to push it hard like many of us do. Plenty of the "Grendel bullets" have been shot of the 6.5x6.8 just fine.

 

[Scottmilk9]

So, with this latest post, you're rationalizing on all the holes we put into your earlier posts, but it still has no merit. Just because its on the internet, it must be true or that ar15.com states that grendel bolts break, I'll hold that in higher esteem that someone who builds them?
The more you talk the more you sound like a construction inspector right out of college with a degree and no field experience.
the blackAhole 6.5x6.8(if it has rifling in the barrel, one of mine didn't) is probably a pretty good round, Rich knows his stuff, but again the original poster was asking about a 6x45 or a 6.5 grendel.

 

[1slow01z71]

So, with this latest post, you're rationalizing on all the holes we put into your earlier posts, but it still has no merit. Just because its on the internet, it must be true or that ar15.com states that grendel bolts break, I'll hold that in higher esteem that someone who builds them?
The more you talk the more you sound like a construction inspector right out of college with a degree and no field experience.
the blackAhole 6.5x6.8(if it has rifling in the barrel, one of mine didn't) is probably a pretty good round, Rich knows his stuff, but again the original poster was asking about a 6x45 or a 6.5 grendel.

How did my story change? I simply had to elaborate for the slow folks such as yourself whp are reading comprehension impaired. Its not like I'm gwtting my info off 68 forums. Theres plenty of threads on the grendel forum alone but sure there are plenty on arf as well. Id expect a large majority of bolt failures to be documented on the largest AR forum on the internet. Now I know thats using facts and logic and that can be a little rough for you but try your best to follow along.

ive built everything from 44 story highrises, the north end zone of the UT stadium large civil projects and everything in between all with just field experience. While I do have most of my civil engineering degree completed I prefer to rely on real world results and practices. Theres some things the books cant teach, like common sense, something you obviously lack along with your abysmal reading comprehension skills.

Are you sure youre not bipolar? You call blackhole weaponry "blackAhole" then say Rich knows his stuff... Harrison makes his version of it as well. Trim a 6.8 case to 41mm and neck it down, then youve got a cartridge that can shoot the beloved 123gr SST at 10k higher psi with a steonger bolt design. I refuse to buy from him due to his outright lies about other cartridges and his childish temper tantrum on arf but he does make some nice stuff. Makes no sense to buy a grendel when you can buy a cartridge that does the same damn thing but has a large safety net. Should yoy want to push it, by design its got more meat on the lugs so you go further.

Again with yiur reading comprehension problems, the OP is open to other suggestions thus I gave a suggestion. Just because youre juvenile and resort to chest thumping antics doesnt mean my suggestion isnt valid. It seem my suggesting of a cartridge that essential out grendels the grendel has struck a chord with you.

 

[Scottmilk9]

How did my story change? I simply had to elaborate for the slow folks such as yourself whp are reading comprehension impaired. Its not like I'm gwtting my info off 68 forums. Theres plenty of threads on the grendel forum alone but sure there are plenty on arf as well. Id expect a large majority of bolt failures to be documented on the largest AR forum on the internet. Now I know thats using facts and logic and that can be a little rough for you but try your best to follow along.

ive built everything from 44 story highrises, the north end zone of the UT stadium large civil projects and everything in between all with just field experience. While I do have most of my civil engineering degree completed I prefer to rely on real world results and practices. Theres some things the books cant teach, like common sense, something you obviously lack along with your abysmal reading comprehension skills.

Are you sure youre not bipolar? You call blackhole weaponry "blackAhole" then say Rich knows his stuff... Harrison makes his version of it as well. Trim a 6.8 case to 41mm and neck it down, then youve got a cartridge that can shoot the beloved 123gr SST at 10k higher psi with a steonger bolt design. I refuse to buy from him due to his outright lies about other cartridges and his childish temper tantrum on arf but he does make some nice stuff. Makes no sense to buy a grendel when you can buy a cartridge that does the same damn thing but has a large safety net. Should yoy want to push it, by design its got more meat on the lugs so you go further.

Again with yiur reading comprehension problems, the OP is open to other suggestions thus I gave a suggestion. Just because youre juvenile and resort to chest thumping antics doesnt mean my suggestion isnt valid. It seem my suggesting of a cartridge that essential out grendels the grendel has struck a chord with you.

Story change? Who needs reading comprehension? I said you were rationalizing, big difference. You should have learned that in college. Then you go and tell us all the cool stuff you built, which is cool, but nobody needs you to justify your place in the construction world. But good on ya.

lets hit the "bi-polar issue", I dog out blackhole, yes carl the owner is an A-hole, but then you say, "I refuse to buy from him due to his outright lies about other cartridges and his childish temper tantrum on arf but he does make some nice stuff." The exact same thing I was saying, without all the misspelled words.
Lastly, there is no chest thumping here, not telling you all the big jobs I've done(sound familiar) I'm just stating facts.

 

[1slow01z71]

Congratulations "custom AR builder" you win the internet. Maybe if I put that in my user title itll magically come true. Ive got a set of roll punches and a giessele reaction rod.

If you reread my post once again you didnt comprehend, my comment about not buying a barrel was in reference to Harrison aka ar15performance.com aka hater of all that isnt 6.8SPC or one of his wildcats.

I've said my piece, ignorance is bliss. Hopefully the OP does his proper research to see through the internet fan boys. There are a lot of better choices available to us today than even a year ago. If I was the OP I'd wait for DPMS to come out with their G2 in 6.5 Creedmoor or 260 and smoke any of the cartridges discussed and it all be in a nice light package at a reasonable price.

 

[1slow01z71]

Congratulations "custom AR builder" you win the internet. Maybe if I put that in my user title itll magically come true. Ive got a set of roll punches and a giessele reaction rod.

If you reread my post once again you didnt comprehend, my comment about not buying a barrel was in reference to Harrison aka ar15performance.com aka hater of all that isnt 6.8SPC or one of his wildcats.

I've said my piece, ignorance is bliss. Hopefully the OP does his proper research to see through the internet fan boys. There are a lot of better choices available to us today than even a year ago. If I was the OP I'd wait for DPMS to come out with their G2 in 6.5 Creedmoor or 260 and smoke any of the cartridges discussed and it all be in a nice light package at a reasonable price.

 

[Scottmilk9]

I like winning! It helps to win when you don't double post nor misspell words so one can understand your post. Enjoy making goal posts or whatever construction projects you have next. I'll look for those roll pin punches you speak of.

 

[SRSDriver]

.223 77g at 1000 yards? Not in a mag length that I've seen. At 1000 yards, a Grendel will torch a 77g SMK.

I've seen guys try to engage targets at 750+ yards in real field conditions with 77g SMK's. Not a single hit on the clock, despite unlimited rounds.

 

[shooter3225]

Well guys I appreciate all the info and feedback. This thread has a lot of great opinions and facts in it. I've been thinking about what to go with and I have decided on 6x45. If I wanted the more energy or the ability to reach out to 1k plus with my AR, I would go Grendel or maybe a 6.5 wildcat. But for me wanting to have a deadly accurate AR from 200-600 it seems like 6x45 is the better choice.

I have a couple bolt rifles and will be building a new .260 on a defiance action here pretty soon, so that will serve as my long range precision rifle. I really want the 6x45 for more mid range engagements.

So with that much decided, I've seen a lot of different posters say what is the best load to run in a 6x45, I'm curious what your guys' opinion is. Once I get my barrel ordered, what loads should I start trying right away?

 

[8AteEight]

Well guys I appreciate all the info and feedback. This thread has a lot of great opinions and facts in it. I've been thinking about what to go with and I have decided on 6x45. If I wanted the more energy or the ability to reach out to 1k plus with my AR, I would go Grendel or maybe a 6.5 wildcat. But for me wanting to have a deadly accurate AR from 200-600 it seems like 6x45 is the better choice.

I have a couple bolt rifles and will be building a new .260 on a defiance action here pretty soon, so that will serve as my long range precision rifle. I really want the 6x45 for more mid range engagements.

So with that much decided, I've seen a lot of different posters say what is the best load to run in a 6x45, I'm curious what your guys' opinion is. Once I get my barrel ordered, what loads should I start trying right away?

Thanks for bringing this thread back from the shitter.
Im starting to look into getting an AR, but I cannot justify a 5.56 for any real uses; however, I am thinking the 6x45 may have a reason to exist in my world.

 

[BERTMAN77MK2]

Ha! What Scottmilk said............this IS the HIDE, not barf.com!!
Keep up the good work Scott, and thanks for your help and advice
in the past.

 

[bustin]

The bolts for all of these rounds achieve a FoS of 1, which has proven to be sufficient when supplemented with properly selected high quality materials and proper manufacturing processes.

9310 and Carpenter steel are both high quality, strong materials that are made stronger through heat treating. (see increasing yield strength) However, the metals can be heat treated to a increased strength where they become hard and brittle. This will make the material more susceptible to stress fractures from the impact of the rounds thrust. Stress fractures are your bolts worse nightmare. A small stress fracture will spread at an exponential rate. The 90 degree edges of the bolt lugs make the lugs the most susceptible area of the bolt. As you understand this, you begin to understand heat treating to be the art that it is.

Now let's look at the Grendel(actually originally the Beowolf) Bolt again from a true overall viewpoint. The Grendel was always intended for the AR15 platform, thus all the factors we've discussed above were balanced to fit within the parameters of the AR15. When you understand all of this you begin to understand the fine engineering job that is the final Grendel Bolt.

The Grendel Bolt design was proofed at 60+ksi. Per the design the Grendel can be fired at the pressures of the 5.56 NATO, as some people do. This is where you've seen bolts break as the Grendel Bolt won't sustain continuous operations at 55+ksi. Eventually material fatigue sets in and you get stress fractures.

Stoner designed the bolt in the 60s, the Grendel didn't exist then. The Grendel bolt isn't any different than a 5.56 bolt except more material has been removed from the web that attaches the lugs to the bolt body making it weaker. The MAX yield strength for 158 and 9310 is apx 160000 PSI set by the companies that manufacture the material if the heat treat is perfect. You can't make it stronger than perfect but you can make it weaker if the heat treat isn't perfect. You need to read the definition of Yield and Tensile strength from an engineering reference handbook.

 

[corym468]

Stoner designed the bolt in the 60s, the Grendel didn't exist then. The Grendel bolt isn't any different than a 5.56 bolt except more material has been removed from the web that attaches the lugs to the bolt body making it weaker. The MAX yield strength for 158 and 9310 is apx 160000 PSI set by the companies that manufacture the material if the heat treat is perfect. You can't make it stronger than perfect but you can make it weaker if the heat treat isn't perfect. You need to read the definition of Yield and Tensile strength from an engineering reference handbook.

I know very well the difference in yield strength and tensile(ultimate) strength. I'm assuming your a Mechanical Engineer Undergrad Student or another discipline of Engineer. You clearly understand the basics of materials and statics, but lack an understanding of design.

Actually you can make it stronger(raise the strength of the material) if you heat treat it for an extended of time. However, when you do this the material becomes to hard and ductile. When a material becomes ductile, its yield strength becomes its ultimate strength, as it will not longer yield before break, it just breaks when you exceed the material's yield/ultimate strength.

You can not make a material weaker through heat treating, you can fail to heat treat the material enough to reach the optimal strength. You can get away with not quite heat treating the bolt enough. However, over heat treating a bolt has proven to be catastrophic.

Your initial assumption is incorrect. The 7.62x39 bolt isn't any different than a 5.56 bolt except more material has been removed. The Grendel(Beowolf) bolt is different from the 5.56 bolt in other critical dimensions as part of designing to make the bolt stronger.

Show me more than one ALEXANDER ARMS bolts that have broken in the last 24 months.

Stoner designed the bolt in the 60s, the Grendel didn't exist then...

No shit. Just how is this relevant?

 

[bustin]

I know very well the difference in yield strength and tensile(ultimate) strength. I'm assuming your a Mechanical Engineer Undergrad Student or another discipline of Engineer. You clearly understand the basics of materials and statics, but lack an understanding of design.

Actually you can make it stronger(raise the strength of the material) if you heat treat it for an extended of time. However, when you do this the material becomes to hard and ductile. When a material becomes ductile, its yield strength becomes its ultimate strength, as it will not longer yield before break, it just breaks when you exceed the material's yield/ultimate strength.

You can not make a material weaker through heat treating, you can fail to heat treat the material enough to reach the optimal strength. You can get away with not quite heat treating the bolt enough. However, over heat treating a bolt has proven to be catastrophic.

Your initial assumption is incorrect. The 7.62x39 bolt isn't any different than a 5.56 bolt except more material has been removed. The Grendel(Beowolf) bolt is different from the 5.56 bolt in other critical dimensions as part of designing to make the bolt stronger.

Show me more than one ALEXANDER ARMS bolts that have broken in the last 24 months.



No shit. Just how is this relevant?

The only way to increase strength is by not removing as much material from the finished product. Show me where the Grendel bolt has more material than a AR15 5.56 bolt.
I'm not a engineering student, I machine AR15 bolts all day, every day and I did modify the bolt design to make them stronger. A guy called not 10 minutes ago looking for bolts because he and his brother broke bolts in the last 2 months.

 

[corym468]

...I'm not a engineering student, I machine AR15 bolts all day, every day and I did modify the bolt design to make them stronger...

Well that's a scary thought.

And "I did modify the bolt design to make them stronger"?????

The only way to increase strength is by not removing as much material from the finished product. Show me where the Grendel bolt has more material than a AR15 5.56 bolt...

I never once claimed this. Go back and reread my post, slowly this time. You clearly understand how to machine a piece of steel, but don't understand the heat treat process or what defines material strength. Which is fine if you can admit it and are willing to learn.

Intelligence is knowing what you know. Wisdom is knowing what you don't know.

... A guy called not 10 minutes ago looking for bolts because he and his brother broke bolts in the last 2 months.

I asked you to show me multiple AA bolts. I'm betting this were from a certain company that produces a variant of the Grendel. Several months ago I became aware of several of these that broke. From the information that I obtained, I'd be willing to bet my reputation that they were either not either 9310 or carpenter steel or they were heat treated to the point of becoming to hard. I highly suspect the former.

If I'm correct it was likely made of 8XXX steel. (for the life of me I can't remember the full nomenclature. If you're familiar with the history of the AR you'll know which material I'm referencing.) 5.56 bolts made of this material will commonly shear lugs, as well.

 

[bustin]

Look at the 2 photos posted above. You can clearly see there is no additional material around the lugs of the Grendel bolt. It looks just like the 7.62x39 and 5.56 bolts. Why? because they use the same broaching tool to cut the lugs. Same design, same square corners.
Anyone with a caliper can measure and compare the bolts in 5 minutes and understand nothing was changed in the design except that the Grendel bolts have a .135" deep recess removing more material. That does not make it stronger.
The way I posted to calculate strength is engineering 101...first year. Even though that was 30 years ago it's such a simple thing we don't forget. X x Y x Yield. There is no voodoo to make metal stronger than what Carpenter gives as MAX yield. The thing that could make bolts stronger is a radius at the root of the lugs, it adds attachment strength. Or the recess could be made shallower if the extractors would work and the chambers were cut to match for headspace.
Now look at these bolts. Notice the radius at the root of the lugs that is absent on the Grendel bolt. X on these bolts include 50% of the radius on each side increasing the strength 28% It increases the X and the thickness of the web at the same time.

 

[bustin]

Well that's a scary thought.

And "I did modify the bolt design to make them stronger"?????



I never once claimed this. Go back and reread my post, slowly this time. You clearly understand how to machine a piece of steel, but don't understand the heat treat process or what defines material strength. Which is fine if you can admit it and are willing to learn.

Intelligence is knowing what you know. Wisdom is knowing what you don't know.



I asked you to show me multiple AA bolts. I'm betting this were from a certain company that produces a variant of the Grendel. Several months ago I became aware of several of these that broke. From the information that I obtained, I'd be willing to bet my reputation that they were either not either 9310 or carpenter steel or they were heat treated to the point of becoming to hard. I highly suspect the former.

If I'm correct it was likely made of 8XXX steel. (for the life of me I can't remember the full nomenclature. If you're familiar with the history of the AR you'll know which material I'm referencing.) 5.56 bolts made of this material will commonly shear lugs, as well.

How hard do you think we should harden the bolts and what process? ...exactly.
That steel that you can't think of would be 8620, the same steel carriers are made from but the guy said they were AA uppers. Bill A. has said several times he uses 9310.

 

[corym468]

How hard do you think we should harden the bolts and what process? ...exactly.
That steel that you can't think of would be 8620, the same steel carriers are made from but the guy said they were AA uppers. Bill A. has said several times he uses 9310.

That would be a question for the designer of the bolt. (Bill A.) While I understand the science of heat treating, I don't have the experience or the knowledge to make those recommendation.

Thank you. That is the steel I was referring to earlier. Did they buy them from AA or is that what the seller told them? What did Bill A. say when they contacted him?

Are they sure they were Grendel Bolts and not 7.62x39 bolts? The Grendel bolt should have a recess of 0.135" and an OAL of 2.810". Ok I just pulled those dimensions off the top of my head. I know the recess is correct. However if the OAL seems way off it could be. I know for certain that it should be 0.01" longer than a standard 5.56 or 7.62x39 bolt.

 

[corym468]

Look at the 2 photos posted above. You can clearly see there is no additional material around the lugs of the Grendel bolt. It looks just like the 7.62x39 and 5.56 bolts. Why? because they use the same broaching tool to cut the lugs. Same design, same square corners.
Anyone with a caliper can measure and compare the bolts in 5 minutes and understand nothing was changed in the design except that the Grendel bolts have a .135" deep recess removing more material. That does not make it stronger.
The way I posted to calculate strength is engineering 101...first year. Even though that was 30 years ago it's such a simple thing we don't forget. X x Y x Yield. There is no voodoo to make metal stronger than what Carpenter gives as MAX yield. The thing that could make bolts stronger is a radius at the root of the lugs, it adds attachment strength. Or the recess could be made shallower if the extractors would work and the chambers were cut to match for headspace.
Now look at these bolts. Notice the radius at the root of the lugs that is absent on the Grendel bolt. X on these bolts include 50% of the radius on each side increasing the strength 28% It increases the X and the thickness of the web at the same time.

Again I've never claimed that the Grendel bolt was stronger than 5.56 bolts. However it is stronger than 7.62x39 bolt in critical locations.

I've only claimed that it is sufficiently strong enough for a round that's held to a of 52 ksi limit as opposed to the 5.56 NATO 62ksi limit.

 

[bustin]

Again I've never claimed that the Grendel bolt was stronger than 5.56 bolts. However it is stronger than 7.62x39 bolt in critical locations.

I've only claimed that it is sufficiently strong enough for a round that's held to a of 52 ksi limit as opposed to the 5.56 NATO 62ksi limit.

The only reason the Grendel bolt could be stronger than a 7.62x39 is if the 7.62x39 bolt was made from 8620. If both were made from 9310 and received the same heat treat the 7.62x39 would be 7.5% stronger due to the shallower recess in the bolt face.
Yield strength is always less than tensile strength. The material will yield(bend or compress) before it breaks unless fatigue causes stress cracks lowering the UTS ultimate tensile strength below the yield strength. Whether the bolt bends or breaks it is done and the yield strength is used to calculate strength of parts.
It takes at least 2 machines to make bolts. We run in pairs and can produce apx 280 bolts a week/pr of machines or apx $22,000 worth. Each machine cost 100-$300,000. For someone to make a wild assed guess at the proper heat treat for even 1 batch of bolts worth $22000 would be stupid...really stupid. The military has run thousands of tests to determine what works best. We use heat treat programs that tell us what temperature, how long and how to cool the bolts and use computer controlled furnaces. These days there shouldn't be any guessing going on when it comes to producing firearm parts.

 

[sobrbiker883]

Ha! What Scottmilk said............this IS the HIDE, not barf.com!!
Keep up the good work Scott, and thanks for your help and advice
in the past.

Oh hell yeah!
I have yet to see George Gardner pick an upper other than Scott's from a prize table at a match.
Y'all can quibble what you like, but that speaks volumes to me aboutScott and his roll punches....

 

[346ci]

We run in pairs and can produce apx 280 bolts a week/pr

I didn't see where you mentioned these bolts sell out so fast, you can't keep them in stock. Now get back on those machines, I need some bolts!!

As a side note to stay on topic, when I had the .264 ARP Superbolts listed on the website, I would get a call at least once a week from guys wondering when I would get some as they heard they would not break like their other .264/G bolts. While that would not tell me for sure there were lots of other brand .264/G bolts breaking, it made me wonder why these guys were looking for the strongest bolt out..

 

[bustin]

I didn't see where you mentioned these bolts sell out so fast, you can't keep them in stock. Now get back on those machines, I need some bolts!!

As a side note to stay on topic, when I had the .264 ARP Superbolts listed on the website, I would get a call at least once a week from guys wondering when I would get some as they heard they would not break like their other .264/G bolts. While that would not tell me for sure there were lots of other brand .264/G bolts breaking, it made me wonder why these guys were looking for the strongest bolt out..

The other machine should be here in June, that will help even out the bolt production while we're running muzzle devices. Now if we can just get enough springs to last more than 2 weeks.

 

[45ar]

My maxim Grendel bolt has held up well.
Will get another one if needed.
My Grendel is so accurate I'll pay for the bolts.
I like the Grendel extractor better than the 7.62x39.
Does anyone make a 6mmAR or 243 LBC type barrel that uses the Grendel bolt.
Maybe one could get a little of both the 6x45 and Grendel in one barrel.

 

[LRRPF52]

None of these cartridges were ever meant to be stuffed into the AR15, not the 5.56x45, not the 5.56 NATO, not any of the wildcats, and Stoner didn't design the bolt in the 1960's. Stoner didn't design the AR15 bolt at all. It was Jim Sullivan and Robert Freemont, who were also working for Fairchild/Armalite (the real Armalite), and the work was done in the late 1950's, starting in 1957 at the request of CONARC.

The AR15 bolt was designed around the .222 Remington with 50,000psi SAAMI Maximum Average Pressure. It was never meant to handle 5.56x45 and 5.56 NATO pressures. 5.56 didn't even exist when the AR15 was designed, but was an evolution of the .222 Remington due to the Army Ordnance Board goal post moving. Metallurgy was readdressed because of bolt fatigue with 5.56x45, and has been improved significantly over the decades of AR15 development.

Dave Kiff's "6.8 SPC II" (he claims development for it) run at pressures listed by Accurate Powders has a Factor of Safety of less than 1, which will apply to any wildcat based off the 6.8 if you run those pressures. It also has more bolt thrust than a Grendel due to higher pressures, but bolts are the least of your worries. Hoop stress is where you really need to be watchful of what you're doing, and the lego set mentality commonly applied to the AR15 needs to go out the window from a barrel/extension manufacturing standpoint.

I have broken bolts in 5.56 AR15's. I have never broken a bolt in a Grendel, and I've been shooting an AA Grendel barrel/bolt combo since 2009. Granted, I don't run my Grendel in tortuous high volume sessions training for 3-gun like I do 5.56's, but with the pressure constraints and metallurgy, I'm confident the Grendel bolt will hold up well. AA's QC is totally different than any other manufacturer I know of, to include regular destructive testing.

 

[bustin]

Yield strength bolts using 160,000 psi yield
Remington 700 308 bolt =32856 PSI
A mil spec 5.56 or 6.8 bolt=10805
Grendel with a .135 recess=9518
ARP 5.56 or 6.8 superbolt =12506

Thrust produced by cartridges
5.56=6337@58kpsi-
6.8=7692@55kpsi-
Grendel=7978@52kpsi-

I agree on the hoop stress. All stainless barrels are very close to the limit of strength. Only the 5.56 in a 4150 CMV 11595E barrel meets the 2:1 safety factor. The larger the cartridge diameter the weaker the barrel.

 

[Scottmilk9]

My maxim Grendel bolt has held up well.
Will get another one if needed.
My Grendel is so accurate I'll pay for the bolts.
I like the Grendel extractor better than the 7.62x39.
Does anyone make a 6mmAR or 243 LBC type barrel that uses the Grendel bolt.
Maybe one could get a little of both the 6x45 and Grendel in one barrel.

We just got a 6mmAR reamer and will be using LBC bolts.

 

[5spd]

I've seen a lot of different posters say what is the best load to run in a 6x45, I'm curious what your guys' opinion is. Once I get my barrel ordered, what loads should I start trying right away?

Shoot me a PM with what bullets you have already & Ill drop you my loads.
I run 55-65g bullets for coyote
80-95g bullets for antelope. A 70g would do both if you wanted just 1 bullet to cover it all to 400 yards with ease.

 

[TenZero]

Ok, so a 24" Grendel can push a 140 with a BC of .520-.580 at 2400fps. That same rifle in 6mm can push a 105 with a BC of .530 or more to nearly 2800fps. The tiny BC advantage of even the .580 bullet can't make up for a nearly 400fps deficit.

Unless you're an animal that gets hit with that extra .18 of bullet weight at 550 yds. Ouch.

 

[Bevan]

1: are there not stronger bolt designs available for the 6.5G, with radiused lugs etc., that allow higher than SAAMI pressures without danger of breaking lugs?
2: I don't believe there is a better factory cartridge than the 6.5G that will fit in an AR15 (with factory parts, ammunition, etc) as far as ballistics go.
3: Alexander Arms load data for 6.5G exceeds SAAMI pressures when entered to Quickload. This is mildly concerning (but the validity of the QL calcs is of dubious merit).
4: I will buy a 6.5G bolt, mags and barrel exactly one second after cheap, bulk factory ammunition is widely available - and I will throw my 5.56 barrel in the trash.
5: Parts compatibility of 6.5G is ridiculous to complain about. Mags are cheap and if buying a new barrel for any AR15 it's wise to buy a new bolt rather than re-use the old one. "I can keep the same bolt and mags" is a joke benefit, where the cost of the required replacement parts is negligible compared to the cost of shooting, or the rifle in general. Particularly a joke if one is building a totally new rifle, rather than rebuilding an old one.

 

[LRRPF52]

Yield strength bolts using 160,000 psi yield
Remington 700 308 bolt =32856 PSI
A mil spec 5.56 or 6.8 bolt=10805
Grendel with a .135 recess=9518
ARP 5.56 or 6.8 superbolt =12506

Thrust produced by cartridges
5.56=6337@58kpsi-
6.8=7692@55kpsi-
Grendel=7978@52kpsi-

I agree on the hoop stress. All stainless barrels are very close to the limit of strength. Only the 5.56 in a 4150 CMV 11595E barrel meets the 2:1 safety factor. The larger the cartridge diameter the weaker the barrel.

6.8 SPC II pressures are listed as 58,850psi on Accurate Powders data set. That exceeds all of the above at 8188. Bolts have been addressed though, which could be a bad thing for chambers and barrel tennons in the long run for those who think that shearing lugs are their primary worry. Hornady was smart with the 6mm Hagar to keep it at 55,000psi, and increase the case volume.

Moving forward, I'll be looking at CMV barrels a lot more. Stainless are easy to machine due to the sulfur content, which I don't see as a plus as the customer, but understand totally for the manufacturer.