Some 6mmAR and other 6mm Grendel variants questions

[jonaddis84]

Building up a new Prairie dogging AR for myself for next year. I have a Krieger 1-10" 6mm barrel on order. Originally wanted to just do the 6mmAR, but wanted to get some opinions here.

Im looking to shoot the 75 vmax primarily (hopefully I can find some by next year), if need by I can either shoot the 87 or 58 as I believe both of those are still being made. I also wouldnt mind being able to shoot something in the 90-100 class target bullet, possibly 95smk.

Anyone with a 6mmAR, can you give some measurements on OAL at the lands for what bullets you are using? Ideally Id like to know 1. Is 1-10" going to stabilize the 95smk 2. Where are the lands at if you load one to mag length?

If anyone would be willing to sell me one 6mmAR lapua or AA case that would be awesome, as, depending on what the basic chamber looks like, I may have PTG make a few adjustments for my particular situation. I feel like it was originally intended for shooting the over 100gn bullets, so the freebore is probably pretty long. Alternatively I guess I could just order a zero FB reamer and throat it to my needs.

It looks as though the 6mm Fat Rat was designed to use Lapua brass, and is less proprietary of a chambering. Is that still true? I called redding and they only sell the 6mmAR dies to Whitley, so getting them could be a challenge as he is impossible to get ahold of. Im wondering if the fat rat would be better if I can get the dies and what not easier.

 

[5spd]

I am building a 6x6.8 for the same use, coyote, p-dogs, antelope.
Is there a reason you have a need for the heavy bullets, sure the bc and wind bucking is good, but from all my p-dog shooting all I have ever used in my 6mms is the 58 & 65g vmax bullets and have not a single problem to 800 yards when needed & I shoot many thousands of them out here every year.
My antelope bullet is the 85g sierra gkhp & 95g nosler HBT bullets.
What bbl length will that be in. My 6x68 will be 22" 1/9" twist this time.
I do not shoot off a bench like many, my shoots are all prone since I have lots of territory, clean out one place & walk to the other hill/valley.
I have a 6x45, 1/10" twist 24" bbl and it handles the 95 nosler HBT like a charm and very accurate to 700 yards.
I do not shoot "target" style or vld bullets.

 

[jonaddis84]

I do like the idea of the 58gn also, just wasnt 100% sure they would shoot as well in a chamber throated for longer bullets also. I will probably use the 58's for pdogs exclusively for the most part.

That 6x6.8 looks pretty sweet also, the one thing I like about the Grendel based stuff is being able to get Lapua made brass for only $70/100 from Alexander Arms.

Wonder if you can just use 6.5 Grendel bushing dies to neck down to 6mmAR? Since thats the process for the 6x6.8 is just having two bushings and necking down in steps. Ive always been under the impression that necking down is best done with a standard FL die due to the fact it sizes all the way down to the shoulder junction, but Im sure after firing it probably sizes it to what you need anyway.

 

[bustin]

I do like the idea of the 58gn also, just wasnt 100% sure they would shoot as well in a chamber throated for longer bullets also. I will probably use the 58's for pdogs exclusively for the most part.

That 6x6.8 looks pretty sweet also, the one thing I like about the Grendel based stuff is being able to get Lapua made brass for only $70/100 from Alexander Arms.

Wonder if you can just use 6.5 Grendel bushing dies to neck down to 6mmAR? Since thats the process for the 6x6.8 is just having two bushings and necking down in steps. Ive always been under the impression that necking down is best done with a standard FL die due to the fact it sizes all the way down to the shoulder junction, but Im sure after firing it probably sizes it to what you need anyway.

Yes you can use Grendel bushing dies. Long bullets like the SMK require a shorter throat so short stubby bullets need to be seated to a shorter OAL. Most have a freebore around .100, ours is .118" so a SMK can be seated to 2.295". PRI 6.8 mags allow loading to 2.3"
10 twist with the 95 SMKs at low velocity does not work that well IMO, zipping out of a .243 at 3200fps the 10 twist seem to shoot fine.

 

[jonaddis84]

Yes you can use Grendel bushing dies. Long bullets like the SMK require a shorter throat so short stubby bullets need to be seated to a shorter OAL. Most have a freebore around .100, ours is .118" so a SMK can be seated to 2.295". PRI 6.8 mags allow loading to 2.3"
10 twist with the 95 SMKs at low velocity does not work that well IMO, zipping out of a .243 at 3200fps the 10 twist seem to shoot fine.

What freebore would you recommend I run if I want to seat the 95smk at mag length and Ill just jump the 58 and 75 vmax? Looks like the stock PTG reamer is .093fb, I would guess I need to be a touch shorter than that?

Also, are you using lapua/AA brass? Whats your neck diameter loaded?

I wonder what is special about Whitley's dies over the grendels...Obviously the standard FL die would have to be different, but the Type S bushing die should be the same.

 

[varmint slayer]

How many times do I have to tell you Ohio boys that a 22-250 is all you need for prairie dogs? He'll you are the only one that runs one and are always the deadliest out of the bunch. This just something to shoot while the 22-250 is cooling off of just for the long shots?

 

[jonaddis84]

How many times do I have to tell you Ohio boys that a 22-250 is all you need for prairie dogs? He'll you are the only one that runs one and are always the deadliest out of the bunch. This just something to shoot while the 22-250 is cooling off of just for the long shots?

Dammit Trevor don't you realize I'm never happy unless I bring 6 different rifles out there and only use one of them.

I'm hoping this thing will perform right up there with the 250 shooting the 58's. I enjoyed shooting the AR at the little fuckers, was just disappointed in the carnage, hopefully this will fix that. They're getting 3100 with the 75s, so I'd think 3400 or so could be possible, that's not far off what my 250 is running the 53's.

Galaxy S3 on tapatalk

 

[varmint slayer]

Dammit Trevor don't you realize I'm never happy unless I bring 6 different rifles out there and only use one of them.

I'm hoping this thing will perform right up there with the 250 shooting the 58's. I enjoyed shooting the AR at the little fuckers, was just disappointed in the carnage, hopefully this will fix that. They're getting 3100 with the 75s, so I'd think 3400 or so could be possible, that's not far off what my 250 is running the 53's.

Galaxy S3 on tapatalk

I've always wanted to try the 58 VMax out of the .243. Should be able to get 3700 or so out of it and probably more with the Ackley. That with a 1-8 twist and 330,000 rpm it would make for a real destructive bitch that would surely make for some aerobatics.

 

[bustin]

What freebore would you recommend I run if I want to seat the 95smk at mag length and Ill just jump the 58 and 75 vmax? Looks like the stock PTG reamer is .093fb, I would guess I need to be a touch shorter than that?

Also, are you using lapua/AA brass? Whats your neck diameter loaded?

I wonder what is special about Whitley's dies over the grendels...Obviously the standard FL die would have to be different, but the Type S bushing die should be the same.

Short bullets have short noses. You can jamb them in the lands when you must jump the 95s. I had to seat the 80gr Noslers at 2.155 to keep them out of the lands. You can't load short bullets to a full 2.28 because there will be no body in the neck. The .093 should allow the shortest bullets to work fine.
Lapua brass .266 dia at the neck. Whitleys dies are just 1 piece, no bushing. Any Grendel bushing die will work fine, just adjust them so the sized case shoulder is .004 shorter than the fired case.

 

[McLarenross]

Im on the same path your on currently and have settled on a 6mm Fat Rat chamber for 2 reasons.

1. The reamer is not proprietary, like Whitley's calibers are, so I can get it from Dave Kiff.
2. The Fat Rat can push the 105-107 class bullets ~2800 from a 26" barrel and that will shoot about 8 Mils to 1k.

There is a thread on the page behind this by a member here, FriedChickenBlowout (bad ass name), who has just built a Fat Rat and chronicled in detail every aspect of his adventure.

If you would like to look at the Fat Rat print that Kiff has on file I can send it to you.

 

[jonaddis84]

Ive definitely found the Dies from Redding to be proprietary, at least the one he sells. But as far as the reamer goes, I called PTG yesterday and they sent me a reamer print for the 6mmAR and gave me the option to purchase it... Shoot me your email address if you want me to send it to you.

The FatRat is definitely interesting, Im just not sure I want to go to the trouble of fireforming brass or not. I had concerns of magazine feeding with it also, although I didnt see in that other thread where he said he had any issues with it.

That freebore in the fatrat looks extremely long, I would not think the 105's are anywhere close to the lands at mag length with that reamer, could be wrong though.

 

[jonaddis84]

Man, I wonder if Im making a mistake doing 6mm in my application. I have 3000 or so 53gn VMAX I run in my 22-250, maybe I should go with the 224AR instead? Get even more speed with the pdog bullets, and still be able to shoot 90gn bullets that have what appears to be the same BC as the 95gn 6mil SMK.

Decisions decisions

 

[flounderv2]

Man, I wonder if Im making a mistake doing 6mm in my application. I have 3000 or so 53gn VMAX I run in my 22-250, maybe I should go with the 224AR instead? Get even more speed with the pdog bullets, and still be able to shoot 90gn bullets that have what appears to be the same BC as the 95gn 6mil SMK.

Decisions decisions

Do BOTH...

Im here to help.. Not really. I suffer from the same afflictions as you.

 

[McLarenross]

I was interested in the 6mm AR Turbo 40 reamers which are proprietary and PT&G could not sell me. Hornady bushing dies are available for the Fat Rat from Lee Wells at Accurate and Reliable Rifles. I havent heard anyone have a single feeding problem with the 40* shoulder and Ive been doing a lot of reading. As for .224 vs .243 I have to lean toward the 6mm's for the ballistic advantages and for the extreme spread of bullet weights available.

 

[Mod Adahy]

I have just started with a 240 tomahawk, essentially it is a 6woa but and improved version. 105 gr hpbt hornady at 2910 out of a 24" barrel. I have had a couple woa in the past and just could not get the velocity I was looking for. The only downfall is the fireforming of the brass but the feeding reliability of the 6.8 parent case is the great part about it. Over 350 rounds through the 240 in less than 2 weeks and have had zero feeding problems. 7.1 mils to 1000 yards with 8500da.

 

[jonaddis84]

I have just started with a 240 tomahawk, essentially it is a 6woa but and improved version. 105 gr hpbt hornady at 2910 out of a 24" barrel. I have had a couple woa in the past and just could not get the velocity I was looking for. The only downfall is the fireforming of the brass but the feeding reliability of the 6.8 parent case is the great part about it. Over 350 rounds through the 240 in less than 2 weeks and have had zero feeding problems. 7.1 mils to 1000 yards with 8500da.

What kind of brass are you using? Who makes dies and where do you get them? Is the reamer readily available? Looks interesting!

 

[Unknown]

Although I am a true fanboy of the 6.5 Grendel, for someone in your position, I would strongly recommend that you consider the 6x45 cartridge. It is merely a 5.56x45 case expanded to accept 6mm bullets. The advantages of this over the Grendel and it's variants are:
1. you can use standard ar15 mags
2. you can use a 5.56 bolt that is much stronger than the grendel bolts that often break lugs (I have had 3 broken bolts)
3. All you need to convert a rifle is a new barrel.

 

[jonaddis84]

Although I am a true fanboy of the 6.5 Grendel, for someone in your position, I would strongly recommend that you consider the 6x45 cartridge. It is merely a 5.56x45 case expanded to accept 6mm bullets. The advantages of this over the Grendel and it's variants are:
1. you can use standard ar15 mags
2. you can use a 5.56 bolt that is much stronger than the grendel bolts that often break lugs (I have had 3 broken bolts)
3. All you need to convert a rifle is a new barrel.

My only issue with that is I wont be gaining anything in the way of velocity with the lightweight varmint bullets.

My main requirements for this to begin with were:

- AR15 platform
- Speeds near my 24" 22-250 pushing 53 vmax at ~3500, using the 58 vmax (I know I wont match it, but a lot closer than a 223)
- Ability to shoot a DECENT long range bullet just to play around with at the range

I know the majority of guys wanting to do a 6mm AR15 are wanting to shoot the 105 hybrids for their smokin BC, but I will never use this rifle for anything that I want to spend that kind of money on bullets. If I can shoot something like the 95SMK out to 1k, and inside 600 it will be a 1/2 moa rifle or so, I will be happy.

 

[Mod Adahy]

What kind of brass are you using? Who makes dies and where do you get them? Is the reamer readily available? Looks interesting!

Silver state brass. Dies are from Keystone accuracy and no idea on the reamer since I bought the barrel from him.

 

[Mod Adahy]

My only issue with that is I wont be gaining anything in the way of velocity with the lightweight varmint bullets.

My main requirements for this to begin with were:

- AR15 platform
- Speeds near my 24" 22-250 pushing 53 vmax at ~3500, using the 58 vmax (I know I wont match it, but a lot closer than a 223)
- Ability to shoot a DECENT long range bullet just to play around with at the range

I know the majority of guys wanting to do a 6mm AR15 are wanting to shoot the 105 hybrids for their smokin BC, but I will never use this rifle for anything that I want to spend that kind of money on bullets. If I can shoot something like the 95SMK out to 1k, and inside 600 it will be a 1/2 moa rifle or so, I will be happy.

The 65 grain bergers are at 3250 out of the 240.

 

[bustin]

My only issue with that is I wont be gaining anything in the way of velocity with the lightweight varmint bullets.

My main requirements for this to begin with were:

- AR15 platform
- Speeds near my 24" 22-250 pushing 53 vmax at ~3500, using the 58 vmax (I know I wont match it, but a lot closer than a 223)
- Ability to shoot a DECENT long range bullet just to play around with at the range

I know the majority of guys wanting to do a 6mm AR15 are wanting to shoot the 105 hybrids for their smokin BC, but I will never use this rifle for anything that I want to spend that kind of money on bullets. If I can shoot something like the 95SMK out to 1k, and inside 600 it will be a 1/2 moa rifle or so, I will be happy.

There are several versions of the 6.8 necked down to .224. 55gr Noslers hit 3400+ out of a 20"barrel. I shortened the neck in the chamber design and trimmed the necks to 42mm so I could shoot the 75Amax around 2900fps. With light 55gr bullets you can use 28gr H322. 62gr bullets will reach 3350+-

 

[peaceatwar]

Are these 6mm AR variants barrel burners like their bolt gun cousins? I have looked at 224 AR on 6mm AR .com and other variants and am left curious about barrel life.

 

[bustin]

Not near as bad as a 243 if that is what you are asking. All of the cases have apx 36gr H2O capacity compared to a 243, 308 at 52-54gr

 

[Unknown]

If you do get the velocity of a 22-250 out of a 6mm-6.5mm semi-auto you will have a barrel burner. Barrel burners aren't necessarily a bad thing as long as you know what you are getting into from the start.

My Grendel will easily keep a 123 grain bullet supersonic past 1100 yards. If you went for one of the 6mm variants of the Grendel, I'll guess that you could easily get the range you want (600-1000 yards). But like they say, there is no free lunch. With high velocity comes barrel errosion, and shortened brass life.

What cartridges are you considering, and what do you see as the benefits and problems with each one? Perhaps making a list showing the positives and negatives for each one in a side by side comparison will assist you in your choice.

There is usually already an existing ballistic equivalent for most of the new cartridges...for example, a 243 necked down to 224 is pretty much a 22-250. If you are set on a given caliber (either .224, .243, or .264), examining the various velocity for bullet weight for each cartridge might help your decision.

I agree with your thoughts on not wanting to need a super expensive bullet in order to gain performance. I only know one fellow who actually owns a 6x45, and I haven't heard his range reports yet, so I can't give any info on what has worked there. I do have pretty extensive experience with a number of Grendels, and barrel lengths for the Grendel, so that is the only one I feel comfortable giving true first hand experience about.

 

[Mod Adahy]

I have a 6x45, 6WOA and a 240 T. They is a 16", 18" and a 22". I have stuck with the 16" so far. It pushes a 95 grain Berger at 2550 with VV530. The WOA pushes 105 bergers at 2710 with 8208 and the 240 pushes the 105 berger or hornady at 2910. 6x45 barrel life is over 4000 rounds at this point, WOA gets about 2500 and no idea on the 240 but I hope to get 2000 out of it.

 

[jonaddis84]

Heres another wrench in my decision... I decided to change the twist on the 6mm from 10 to 8, either way I think that is a better choice. Anyway, I guess I never realized when I first ordered the barrel that Krieger is quoting almost a year for barrels right now!

So, heres my thought, I can get my hands on a Rock Creek AR blank in 224 right now. Maybe I try out a Grendel necked down to 224 for next years trip.

I assume I the same goes for the 224, I could just run 6.5 grendel brass through a bushing die, but maybe do it in 3 steps? Whitley suggests using a .270-.272 bushing first, then his "secondary size die", then finishing with a .250 bushing. Im guessing his secondary sizing die is just a standard FL die.

This way I dont have to buy any new bullets, I can scream the 77SMK for just target shooting out to 600, and I can have it done by next years trip in June easily. This is all assuming Ill be able to get the reamer from PTG, which could be an issue....

 

[jonaddis84]

In trying to get the 224AR reamer print from PTG, she sent me the 224LBC. I am guessing this is virtually the same exact cartridge? Sounds like grendel dies can still be used along with AA/Lapua brass. Thoughts?

The only real difference I can see between the actual cases behind the shoulder (since they are not the same caliber), is the base diameter. The LBC is 0.0006" larger in diameter, cant imagine thats going to make much difference.

 

[Dave Kiff]

We have over 100 custom prints for the Grendel . I will get a couple more for you Monday including the 224 AR .

 

[jonaddis84]

That would be awesome, thanks Dave! If you have any 6.8spc necked down to 22 Id be interested to see those too.

 

[45ar]

BHW is making a whole line of cartridges off the 6.8 case.22,6mm,257,6.5,and 30 cal.You can see pictures and test results on 6.8 forum under Blackhole Weapontry.It's on Arfcom also under variants.I'm thinking about the 25 cal for a dual purpose rifle.The 85 grain ballistic tip would hammer yotes and the 100 grain would do the same to deer.The 22x6.8 looks to be very accurate and fast.They've had the 6mmx6.8 for a while and it been working pretty good.

 

[Redcreek1]

I looked at the 6mm AR and 6mm AT Turbo, etc and finally settled on the 6mm HAGAR. I really like the cartridge, Hornady makes brass and dies, Redding also makes dies, reamers and guages are available. it uses 6.8 SPC brass as the parent, so uses 6.8 bolt and mags, which are readily available and is a simple neck-down from 6.8 for brass. Same pressure MAP as .223/5.56, so tuning is easy...

I'm building my second rifle now. Rumor has it Hornady is looking at making this (or nearly identical round) a factory offering...