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Projectiles for 1:5 twist, 300 blackout gas gun

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Ape_Factory

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Minuteman
May 23, 2020
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San Antonio, Texas
Curious what you all think would work in a 9" barrel with a 1:5 twist in both supers and subs in a gas gun. With supers the rpm is a concern so it'd be monolithic projectiles like a Hornady 110gr. CX. If I keep a jacketed bullet at or below 2000fps, I can likely get away with them but likely at the cost of actual performance on target. Something in the 125gr. non-varmint arena may work.

For hunting subs, at that spin rate, anything recommended that expands at subsonic velocities? I have a lot of the Hornady 190 Sub-x rounds but I've never had any success with those in an auto loader due to the blunt nose design. I don't want anything that could possibly frag and ruin the suppressor either. I've seen some of the Lehigh stuff but they have cuts along the length of the bullet which could come apart at a 1:5 twist. So wondering if there's something out there I just haven't come across.

I've debated changing the barrel out to something with say a 1:6 or 1:7 twist but it's out of the question as it's a Sig and no one makes aftermarket barrels for them.
 
Supers: H110

110gr Barnes TAC-TX for killing things
125gr Speer TNT for plinking

I listed the absolute BEST projectile for these short fast twist rigs. The one the 300BLK was initially designed to work with (for the SOF that commissioned) and what I have personally used on game. It's a devastating round and works great. The TNT is just a great option at a very reasonable price that shoots really well. You can kill things with it too but I like for plinking.

Subs: VV N120

188gr Discreet Ballistics Selous expanding solid
190gr or 200gr Makers expanding solid
220 SMK or the Berry's for plinking

I don't like to use subsonic rounds for hunting med size game but BOTH of the recommended bullets do quite a number on trash pandas, beavers and other vermin. Lots of people use them on med size game though with great affect, I just prefer hard hitting hydrostatic shock along with shot placement on deer. I don't like to have to track game, prefer DRT.

*You shouldn't be forced (in general) to stick with solid/bonded in the 1:5 twist bbl for 300BLK. RE: RPM's 8.6BLK and the 1:3, it's pretty much hard and fast rule that you HAVE TOO run solid or bonded supers) but as will all things, YMMV and measure twice. :)
 
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I have a load for the Speer 125's and a bunch loaded up with H110, I'll have to look at their velocity in my notes again. But I agree, superbly accurate and fairly low cost when bought in bulk.

I'm also going to try the Hornady 125gr. SST and again, keep it at 2000fps or less. I have a Hornady VMAX110 load but that's a varmint bullet and I'm thinking they won't do well with that twist above 2000fps (2000x720/5 =288,000rpm).

I've read, as the barrel heats up, it can make things much worse. So if you're running something like drills, it's far different than bench shooting at a very low firing rate.

I'll check out the Discreet and Makers, haven't looked at them before. I'd say the Berry's 220's would be off limits. I have a good load for those too unfortunately but I can't imagine such a thin jacket holding up. I do have some VV N120 as well as a ton of CFE Black. I know, dirty as hell but it's the one powder that seems to cycle anything. I've actually had ok results with it too.

But appreciate the bullet suggestions. I'll just have to approach it a bit more cautiously and test sans suppressor.
 
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I'm working through this same problem for a 6.75" MCX LVAW clone. I've always run plated or powder coated 220s for subs, but plated is out of the question now. Going to do some testing (without the supressor) to see how the powder coated bullets survive. Not holding my breath. May be relegated to using expensive SMKs or game king bullets for subs.
 
You can use plated bullets if you tailor the velocity so that the final RPM is still within limit. Berry's says their 220 gr plated has a max velocity of 1300 FPS and max twist of 1:7". That's 133,714 RPM. Which in a 1:5" twist is achieved at 928 FPS. So just load your subs appropriately.

Granted, pulled 220 jacketed bullets are about a quarter each now and work great at even faster speeds. The 110 VMAX does well in that twist rate and I've yet to see it grenade.
 
Ape_Factory said:
Curious what you all think would work in a 9" barrel with a 1:5 twist in both supers and subs in a gas gun. With supers the rpm is a concern so it'd be monolithic projectiles like a Hornady 110gr. CX. If I keep a jacketed bullet at or below 2000fps, I can likely get away with them but likely at the cost of actual performance on target. Something in the 125gr. non-varmint arena may work.

For hunting subs, at that spin rate, anything recommended that expands at subsonic velocities? I have a lot of the Hornady 190 Sub-x rounds but I've never had any success with those in an auto loader due to the blunt nose design. I don't want anything that could possibly frag and ruin the suppressor either. I've seen some of the Lehigh stuff but they have cuts along the length of the bullet which could come apart at a 1:5 twist. So wondering if there's something out there I just haven't come across.

I've debated changing the barrel out to something with say a 1:6 or 1:7 twist but it's out of the question as it's a Sig and no one makes aftermarket barrels for them.
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Whatever projectiles you use, you will need to keep velocities below 1,400 fps, that is if you keep the 1:5 twist.

Edit: I probably f'ed up on tolerable RPMs for bullets. Formula is right but the RPM might be incorrect.
 
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alamo5000 said:
Whatever projectiles you use, you will need to keep velocities below 1,400 fps, that is if you keep the 1:5 twist.
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Well, since no one makes barrels for the Sig MCX, other than Sig, I'm stuck with what they gave me. So 1:5 it is. Thanks Sig.

Where do you get 1,400fps figure from and in reference to what bullet design? It's my understanding jacketed bullets need to stay below 300,000rpm which is a bit over 2000fps but less than 2100fps. Naturally I'd want a bit of a fudge factor. Monolithic can handle much faster rotational speeds. Plated, far, far less. Subs are all going to be below 1050fps but I've read of some subs, with cuts, coming apart and damaging barrels at a 1:5 twist rate. Rotational speed is FPS x 720/barrel twist rate.

I have some Barnes 110grain Tac-TX BT and Hornady 110 grain CX on order. I actually have some CX bullets here now and did a load development for my gas 300 blackout with a "reasonable" 1:8 twist. Saw pressure signs far, far sooner than the Hornady 110 Vmax rounds so I couldn't get the same velocity out of them using H110. That was in a 1:8 twist barrel rate, 10.5" length.

Interestingly enough, I bought a box of Fiocci 300 blackout with the Hornady 125gr. SST projectile. Box says 2200fps but it doesn't say what the test barrel length was. Guessing it's likely a 16" barrel. I have a box of the Hornady 125gr. SST's as well so I'll chrono the Fiocci rounds and see what they come in at. Using LC brass and CCI 41 primers with H110 for supers.
 
Ape_Factory said:
Well, since no one makes barrels for the Sig MCX, other than Sig, I'm stuck with what they gave me. So 1:5 it is. Thanks Sig.

Where do you get 1,400fps figure from and in reference to what bullet design? It's my understanding jacketed bullets need to stay below 300,000rpm which is a bit over 2000fps but less than 2100fps. Naturally I'd want a bit of a fudge factor. Monolithic can handle much faster rotational speeds. Plated, far, far less. Subs are all going to be below 1050fps but I've read of some subs, with cuts, coming apart and damaging barrels at a 1:5 twist rate. Rotational speed is FPS x 720/barrel twist rate.

I have some Barnes 110grain Tac-TX BT and Hornady 110 grain CX on order. I actually have some CX bullets here now and did a load development for my gas 300 blackout with a "reasonable" 1:8 twist. Saw pressure signs far, far sooner than the Hornady 110 Vmax rounds so I couldn't get the same velocity out of them using H110. That was in a 1:8 twist barrel rate, 10.5" length.

Interestingly enough, I bought a box of Fiocci 300 blackout with the Hornady 125gr. SST projectile. Box says 2200fps but it doesn't say what the test barrel length was. Guessing it's likely a 16" barrel. I have a box of the Hornady 125gr. SST's as well so I'll chrono the Fiocci rounds and see what they come in at. Using LC brass and CCI 41 primers with H110 for supers.
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Bullet RPM = MV X 720/Twist Rate (in inches)

The formula is correct, but I might be wrong on the amount of RPM common bullets can take. For some reason I had it in my head that it was 200,000. If it winds up actually being 300,000 (which could be true), then your max velocity will be 2,050 fps. I definitely could be wrong in my initial assumptions.

Mr. GunsnGear did a 300 BLK video a long time ago where he chrono'd all different barrel lengths so I was using that as a guideline for velocity. On a side note I have a 9" 300 BLK myself.

I would venture to say that depending on the actual bullet type, design, construction etc that a 125 grain bullet would probably be the max you could shoot barring something solid.

I would venture to say that somewhere between 200-300K is probably the max, but this is HIGHLY dependent on the bullet itself.
 
volucris said:
You can use plated bullets if you tailor the velocity so that the final RPM is still within limit. Berry's says their 220 gr plated has a max velocity of 1300 FPS and max twist of 1:7". That's 133,714 RPM. Which in a 1:5" twist is achieved at 928 FPS. So just load your subs appropriately.

Granted, pulled 220 jacketed bullets are about a quarter each now and work great at even faster speeds. The 110 VMAX does well in that twist rate and I've yet to see it grenade.
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I'd definitely go with pulled 220s at that price. Any chance you could share where you're seeing them?
 
Guessing you can find the pulled pills on Gunbroker or similar.

Going by my past Form 1 times, I have a few days until it's approved. I have a suppressor mount on the end currently so I may stick the stock flash hider back on for testing purposes. Less to ruin that way, LOL.
 
alamo5000 said:
Bullet RPM = MV X 720/Twist Rate (in inches)

The formula is correct, but I might be wrong on the amount of RPM common bullets can take. For some reason I had it in my head that it was 200,000. If it winds up actually being 300,000 (which could be true), then your max velocity will be 2,050 fps. I definitely could be wrong in my initial assumptions.

Mr. GunsnGear did a 300 BLK video a long time ago where he chrono'd all different barrel lengths so I was using that as a guideline for velocity. On a side note I have a 9" 300 BLK myself.

I would venture to say that depending on the actual bullet type, design, construction etc that a 125 grain bullet would probably be the max you could shoot barring something solid.

I would venture to say that somewhere between 200-300K is probably the max, but this is HIGHLY dependent on the bullet itself.
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I've watched the video you mentioned. Good stuff.

On the bullet weight, it's going to be easier to stay below a certain MV with a heavier bullet vs. a lighter one. My 110gr. loads are all faster than my 125gr. loads. So I suppose you could use a 150gr. pill or similar but I'd imagine, keeping the speed down, it's not going to be much fun to shoot.

None the less, I have two different solid projectiles on the way and will develop a load with them just to be safe. Just seems dumb Sig would release a barrel where most off the shelf ammo isn't safe to run.
 
I'm shooting a Ruger ranch rifle with a 10" 1-5" twist barrel on it and 190 gr Hornady's come apart.
220gr Makers work great, as do most 220-225gr bullets.
haven't got around to trying supers yet.
 
Ok...so I took both my 300 Blk. guns to the range with my Magnetospeed to get MV for the two supersonic rounds I load in addition to two factory loads.

The first gun is a DI SBR with a 10.5" barrel. It has a 1:8 twist barrel and was suppressed with an OSS 7.62Ti flow through suppressor. Second is the Sig Spear LT with a 9", 1:5 twist barrel. I did five rounds of each except for the Speer TNT's as I forgot to load 10 in the mag and only had five with me.

10.5" Barrel MV Results (avg, suppressed)
-Hornady 110gr. V-Max: 2259fps
-Speer 125gr. TNT: 2071fps
-Fiocchi 125gr. SST (Hornady): 2045fps
-Barnes 110gr. Tac-TX-FB: 2261fps

Sig 9" Barrel MV Results (avg, unsuppressed)
-Hornady 110gr. V-Max: 2132fps
-Speer 125gr. TNT: N/A
-Fiocchi 125gr. SST (Hornady): 1950fps
-Barnes 110gr. Tac-TX-FB: 2143fps

The 10.5" barrel is nicely broken in and is a 416R stainless nitrided barrel. The suppressor adds a bit of velocity. This was the first time firing the Sig so as that barrel breaks in, it'll pick up a bit of speed. Being a pistol, it had no stock. It was surprisingly easy to shoot but having left the suppressor off, it was LOUD as my suppressor mount is a muzzle brake. It was loud enough to piss myself off.

None of the bullets fragmented but I was only shooting 25 yards for testing purposes. My V-Max hand load is likely too hot for the Sig. It'd be fine shooting on a bench where the firing rate is fairly low but I wouldn't run drills or a class with them. The 125 grain Speer TNT load is borderline. The Fiocchi factory rounds will work and the Barnes will be just fine.

I've already started to develop a load using the Hornady 110gr. CX monolithic bullets. I started to get pressure signs at 20 grains of H110 in the 10.5" barreled DI rifle. 19.8 grains produced an MV average of 2310fps. Best accuracy was at 19.6 grains with an SD 0f 4.3 and avg. MV of 2293fps. I've always struggled a bit with monolithic bullet hand loads vs. jacketed bullets.
 
I inquired with Hornady on the 190 grain Sub-X and they stated it can handle up to 280,000 rpm and said it should be just fine out of the Sig at subsonic velocities. I've had no luck getting these to cycle problem-free in any gas gun so it may be a moot point.

Lehigh says their 194 grain sub will do great. Haven't heard anything from Maker's yet.
 
Have a few projectiles in hand, still waiting on the Barnes 120 grain bullets to arrive. But here's a visual comparison between the Hornady CX and the Barnes, both 110gr. Going by the cannelure, the Hornady should fill the case a bit more. Both are beveled which'll make seating them easier. Interesting to see the differences between them.
 
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Upper 200k and the hardline in the sand is 300k. Bullets will start coming a part. Now factor in barrel wear, cleaning damage etc...and the bullet takes more of a beating.

I built my son a 300BO on a AR15. 16" barrel and 7.5 twist. Only have shot box ammo thru it. All Hornady. From 208Amax to the 110gr bullets. All shoot great with no issues. He uses the 135gr bullets/ammo for deer hunting. That gun will sling the 208's and box 190gr ammo into .5moa groups. Just a treat to shoot!

Later, Frank
Bartlein Barrels
 
Frank Green said:
Upper 200k and the hardline in the sand is 300k. Bullets will start coming a part. Now factor in barrel wear, cleaning damage etc...and the bullet takes more of a beating.

I built my son a 300BO on a AR15. 16" barrel and 7.5 twist. Only have shot box ammo thru it. All Hornady. From 208Amax to the 110gr bullets. All shoot great with no issues. He uses the 135gr bullets/ammo for deer hunting. That gun will sling the 208's and box 190gr ammo into .5moa groups. Just a treat to shoot!

Later, Frank
Bartlein Barrels
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So Frank...want to make a barrel for the Sig with a 1:6 or 1:7 twist, same 9" length, to slow things down a bit???? I'd be willing to send my barrel in :)
 
Without reading all these posts, I have one question…Why?

Our 300 Whisper, shooting 220 and 240 grain bullets with a 1-7 twist has no issues with bullet stability at subsonic velocities. While our barrel is longer (14.5 inches) the velocities are the same. Further, going much slower in velocity always brings the possibility of a stuck bullet in the barrel. So

Why a 1-5 twist? Sounds very much overkill.
 
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Wiillk said:
Why a 1-5 twist? Sounds very much overkill.
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I have no idea what Sig was thinking. I'm usually a spec whore and for some odd reason, I totally overlooked the fact the barrel was 1:5 twist. I likely would not have purchased it had I known in advance. I have a 10.5" barrel on my DI 300 blackout, 1:8 twist, that stabilizes subs out to 220gr. just fine. I think they're following the "more energy on target" theory by spinning the bullet faster. Same thing as you hear from the 8.6 Blackout folks. Just seems stupid in a consumer gun.
 
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Wiillk said:
Without reading all these posts, I have one question…Why?

Our 300 Whisper, shooting 220 and 240 grain bullets with a 1-7 twist has no issues with bullet stability at subsonic velocities. While our barrel is longer (14.5 inches) the velocities are the same. Further, going much slower in velocity always brings the possibility of a stuck bullet in the barrel. So

Why a 1-5 twist? Sounds very much overkill.
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Because Kevin Brittneyham, marketing, and "we're extra speshul".

Unfortunately, like with the 8.6 Blk, way too many people buy into the marketing BS and don't realize until it's too late that the stupid fast twist took something that worked fine and made it finicky and picky for no good reason.
 
Where can I send hate mail to Kevin Brittneyham? :ROFLMAO: Edit: It's Brittingham. Didn't realize you were talking about Q's owner. Not much of a fan so it makes cosmic sense. I'd think, Sig being Sig, and doing lots of testing (right?) would have found some benefit to the faster spin for working folks. But not so much for the recreational side. I have over a thousand supersonic rounds I can't use now (at least with a suppressor).

C'mon Frank, make me a barrel! Shooting without a suppressor is just savage.
 
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reubenski said:
Barnes 110 TAC TX for supers. (Actually not sure why anyone would shoot anything else)

Maker 200gr REX for subsonic. Try 8.5 to 9gr H110 or W296
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Scroll up to post #17, already there my friend. Only reason I wouldn't want to shoot with it is cost. For a training/plinking round the solids are damn expensive. I was going to part out the DI rifle and I'm now having second thoughts. Plus I already have well over 1K rounds of the Speer 125 grain TNT and the Hornady 110 grain Vmax already loaded. It'd be nice to load up a bunch of Berry's 220gr. for fun as well. Hornady says their 190 gr. Sub-X will be fine but I've not had good luck with them in auto loaders. We'll see if the Sig is any better.
 
See post #15 and then #18 with what Frank B. has to say. Yes, you can likely shoot a few of say the Hornady VMAX at 2200fps + but with a suppressor, it's a ticking time bomb, especially if you're shoot a lot of rounds quickly. As the barrel heats up (or wears over time), it gets a lot tougher on bullets. With the velocity my hand loads are producing, it's over 300,000 rpm for the VMAX and likely at about 290,000 rpm for the Speer. I did shoot a handful of each, sans suppressor, to see what would happen. I had a muzzle brake suppressor mount and it was brutal. I actually just purchased the flash hider mount/muzzle device as the brake was so bad and I'm not testing with the suppressor on.

The goal is to not reach the point where a bullet comes apart as I almost always shoot with a suppressor on the end. Supers out of a 9" barrel, from a sound standpoint, are not fun.

I did read one account where someone was in a class, 300 blackout fast twist with a suppressor, and the bullets eventually came apart and blew out the front of the suppressor. I think they were using 110 grain V-Max rounds. Started out well but as the gun/barrel heated up, it caused them to break up before exiting.
 
reubenski said:
So you haven't?
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Yes, that's the general idea, to avoid that happening. I'm still waiting on my Form 1 to come back so while I've shot it, sparingly, I haven't used it in anger. If you think it's a non-issue with those bullets, just come out and say so. Math says otherwise.
 
Barrel length is irrelevant. All that matters is muzzle velocity and twist rate. If Hornady says not to exceed 280,000 rpm on a particular bullet, you can simply plug MV into the formula and get your rpm. Barrel length is not part of that formula. Bullet rpm=MV x 720/barrel twist.
 
reubenski said:
What if the formula isn't accounting for everything?
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It simply doesn't work that way. If I load two different cartridges to produce the same muzzle velocity out of two different barrels, one 9" and one 16", the muzzle velocity is the same and thus the RPM of the bullet will be the same.

If I load the same cartridge and it's 2000 fps out of the 9" barrel and 2250 out of the 16" barrel, the rpm of the bullet out of the 16" barrel will be greater.

The limiting factor, the one that determines whether the bullet has potential to break apart is rpm, not barrel length. Perhaps a longer barrel "wears" on the bullet more than a shorter barrel but again, manufacturers set limits based on rpm. And whether I reach that rpm limit out of a short or long barrel, MV is all that matters.
 
Actually my premise is that a 1:5 isn't good for jacketed bullets for the average consumer who wants to use low cost projectiles. This is based on the manufacturer's recommended max rpm for a particular bullet. I've written to and received that number, except from Speer who hasn't responded yet. As such, it requires careful choice of said projectiles, making sure one doesn't exceed their mechanical limit as set by the manufacturer. This excludes pretty much any jacketed bullet on the market at effective expansion velocities and requires the end user to use expensive monolithic bullets.

My DI 300 Blackout has a 1:8 twist out of a 10.5" barrel and I've never had stability issues up to 220 grain pills. Stability and bullets coming apart mid-air due to their physical limitations being exceeded are two different things. I've also used an 8.5" 1:8 twist and no stability issues with it either. But again, a bullet coming apart mid-air is far different from tumbling. I'm not concerned about tumbling.

If Hornady or Speer tells me to not exceed 280,000 rpm with a particular projectile, I can easily calculate that with the bullet rpm formula. Again, doesn't matter if the barrel is 2" or 20" as rpm is determined by muzzle velocity and twist rate. So whatever my barrel length is, if I measure the muzzle velocity, I can determine bullet rpm for that barrel's twist rate and compare it against the manufacturer's tested mechanical limit for that projectile. If I exceed it, I could risk damage to muzzle devices or a mounted suppressor.

I'm sure if I used the Sig hard in a training session, with my current VMAX hand load as an example, eventually I'd start seeing bullets come apart just after the muzzle. The goal is to never let that happen. Another member suggested the Speer TNT's but after reading about their construction, they categorize it as a thin jacket with internal fluting for expansion. I'm not willing to risk it. I may be able to shoot 100 rounds down range without an issue but it only takes one to fuck up a $1200 suppressor. Maybe you're ok with that risk factor but I am not.

My hand load Hornady VMAX averaged 2132fps out of the sig. Add the suppressor and another 50fps. We have an MV of 2182fps. Plug it in to the formula. 2182 x 720/5=314,208rpm. Hornady says 280,000 rpm max. Yes, there's a fudge factor built in to their recommendation but are you personally willing to replace my suppressor if it gets damaged?
 
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Yep, I bought it and if you read the thread from the beginning instead of making me beat a dead horse, you'd see that I overlooked the twist rate on the barrel. I already have a DI 300 BLK SBR, I wanted a piston/folding stock rifle which is why I purchased the Sig.
 
Look...I just want facts. If you can back up your statements with physics, great, I'll listen, otherwise I'll stick with the math as to do otherwise could be catastrophic to the equipment and even me physically. Plenty of people have made suggestions in this thread that I am taking to heart. Let's see...random guy on the internet who clearly doesn't understand the physics of the situation vs. what the manufacturer says is the mechanical limit of their product as well as real world experience from various users including one of the top barrel manufacturers anywhere.

If you know of an inexpensive jacketed projectile in 30 cal that can withstand 300,000 rpm in a hot barrel over prolonged semi-auto firing, let's hear it, would be a huge relief! Otherwise I'll go with the monolithic pills as well as the subs several other users have recommended, maybe risk my Speer hand loads with just the muzzle device and no suppressor until I feel comfortable. As I've posted above, I've reached out to several bullet manufacturers to get their opinion. I only reached out to them after receiving recommendations from forum members. I just want a safe starting point.

I was agreeing with your initial reply on the Barnes and if it didn't come across that way, I apologize. Was just a bit of a Groundhog Day moment as it came across like you didn't read any of the proceeding posts. I know the mono's are safe, never was a question. I was more concerned with jacketed supers and subs, especially ones with flutes for expansion purposes. And I get what you're saying about the duality of supers/subs in 300 blackout and the compromises involved but that wasn't part of my initial request for feedback. I've been shooting/loading for 300 blackout for some time now.

Your initial reply suggested that because I hadn't personally experienced bullets breaking up in a 1:5 twist barrel, there should be no concern. I've had the gun to the range exactly once, shooting only a handful of rounds, enough to get MV on the various cartridges. Not exactly a finite data set to draw conclusions from.

Tell you what...I'm going to write to Sig and see what their recommendation is and we'll go from there.
 
reubenski said:
Here's my premise. 300BO isn't really a Super or Subsonic capable dual use gun. If you really want to sling 110 TAC TX bullets 2100fps is weak sauce. If you want to sling heavy subs out of a gasser, you don't need a 16" barrel bc you're going to have ejection port noise anyway. So just understand that when you buy a shorty it really only makes sense for subs.
Click to expand...

Here's my premise. You're wrong about pretty much everything you've "shared" in this thread, and opinionated without real facts to back it up.
Geez, man.
 
Ape_Factory said:
Look...I just want facts. If you can back up your statements with physics, great, I'll listen, otherwise I'll stick with the math as to do otherwise could be catastrophic to the equipment and even me physically. Plenty of people have made suggestions in this thread that I am taking to heart. Let's see...random guy on the internet who clearly doesn't understand the physics of the situation vs. what the manufacturer says is the mechanical limit of their product as well as real world experience from various users including one of the top barrel manufacturers anywhere.

If you know of an inexpensive jacketed projectile in 30 cal that can withstand 300,000 rpm in a hot barrel over prolonged semi-auto firing, let's hear it, would be a huge relief! Otherwise I'll go with the monolithic pills as well as the subs several other users have recommended, maybe risk my Speer hand loads with just the muzzle device and no suppressor until I feel comfortable. As I've posted above, I've reached out to several bullet manufacturers to get their opinion. I only reached out to them after receiving recommendations from forum members. I just want a safe starting point.

I was agreeing with your initial reply on the Barnes and if it didn't come across that way, I apologize. Was just a bit of a Groundhog Day moment as it came across like you didn't read any of the proceeding posts. I know the mono's are safe, never was a question. I was more concerned with jacketed supers and subs, especially ones with flutes for expansion purposes. And I get what you're saying about the duality of supers/subs in 300 blackout and the compromises involved but that wasn't part of my initial request for feedback. I've been shooting/loading for 300 blackout for some time now.

Your initial reply suggested that because I hadn't personally experienced bullets breaking up in a 1:5 twist barrel, there should be no concern. I've had the gun to the range exactly once, shooting only a handful of rounds, enough to get MV on the various cartridges. Not exactly a finite data set to draw conclusions from.

Tell you what...I'm going to write to Sig and see what their recommendation is and we'll go from there.
Click to expand...

Here's a relevant fact I've observed - the 110 V-Max bullet is relatively fragile even in the 300 Blackout world, so I think you're right to be cautious. (Even if, per ruebenski, it's better to go ahead and blast away till you destroy your suppressor, then think about addressing the issue. :rolleyes: ) I don't think that 300,000 rpm "limit" is actually the limit for all bullets, but it's probably more true for the 110 V-Max than most others that fit the 300 Blk. Although IMO the 110 Varmageddon is possibly worse, so you might want to avoid that one.

You might be more likely to get away with no issues with the 125 TNT bullet, and they are/were cheaper IF you can find them. But you already covered that.
 
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-You were trolling with your first reply to this thread. It was clear you didn't read any other posts and going by your last post above, still haven't.

-Maybe YOU were talking every caliber in every barrel with a fast twist rate but I was pretty broadly specific, 300 blackout, good/bad bullets to use in a 1:5 twist, supers and subs, any to watch out for and those that are the go-to. You seemed to have gotten bullet tumbling in your head when we were talking bullets coming apart before they've left the suppressor. It's happened with supers AND with subs of a certain design in a 1:5 twist. I'm not just inventing it.

-I have chrono data for the rounds I already have loaded, out of two different barrels, one of them being the Sig. This is why I even mentioned the Hornady and Speer. I can therefore say, based on the math, that I should be cautious with them if I am exceeding the manufacturer's suggested upper limit. Sorry if you think it's ok. You're wrong.

-Spend some time on the 300 Black forum. There are some folks there who have had first-hand experience with bullets coming apart in 1:5 barrels. In fact, here's one where someone ruined their suppressor and it includes a photo: http://www.300blktalk.com/forum/viewtopic.php?f=128&t=108715&sid=65114c471684e6d09a4fa2b01a157d8a

If you have a 22 cal bullet spinning at 300,000 rpm and a 30 cal bullet spinning at 300,000 rpm, the jacket of the 30 cal bullet will be subject to more energy than the 22 cal bullet. Fact. Force times distance. Math is your friend and can provide a safety framework so risk can be reduced. Kind of like when you load above a loading manual's recommended charge. You know you're getting close and approach it with caution. That tipping point can move forward or back based on cartridge components and the gun itself.

Now if you know to take rpm into account, and then look at a lot of the popular 300 blackout super bullets, a lot of jacketed bullets are varmint style. Not a good mix once you get into the fast twist barrels. No one is making this up.
 
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I finally gave up on the ATF approving my Form 1 any time soon and ordered the Sig adapter to run the upper on my already SBR'd lower (and yes, I sent in a note to the ATF). Went to the range and I tested out several different rounds I already had loaded and I then used them in anger. At least as much as I can get away with at an indoor range.

I shot 20 rapid rounds of the Speer 125gr. TNT's and the Hornady 110gr. Vmax. No key holes, nothing exploded.

I then tested five rounds of Berry's 200 grain projectiles, sans suppressor or Magnetospeed attached and again, nothing but nice round holes at 100 yards. I then threw the suppressor on and it lived to tell another day. With that said, I don't plan on running any more of the Berry's with the suppressor as their stated limit is 130,000 rpm. Playing with fire there. I was at approximately 148,320 rpm out of the Sig barrel.

I also tested out the factory load for the Hornady 190 grain Sub-X rounds and they ran flawlessly. Quite accurate as well! I'm well within that bullet's rpm range.

The other plus is the Sig had zero failure to feeds or function. Just a simple twist of the gas adjustment lever between supers and subs and you're good to go, bolt locks back no problem. The adjustment lever doesn't get hot either, at least at bench range rate of fire. Super easy.

On the downside, my hand loads with solids weren't all that spectacular from an accuracy standpoint. I probably need to run more rounds through it before it'll start to group.

Still working out the logistics of a new barrel with Bartlein and finding someone to finish the barrel.
 
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quote, "I also tested out the factory load for the Hornady 190 grain Sub-X rounds and they ran flawlessly. Quite accurate as well! I'm well within that bullet's rpm range."

The ones we shot thru my sons 300AAC with a 7.5 twist...those things have been hammers accuracy wise!
 
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I was pretty surprised actually...I think they'll get even better once I have more rounds through the barrel. I'll need to go to an outdoor range to shoot more unsuppressed as it's just stupid loud, even with doubled-up ear pro when indoors. Then we'll see what she's capable of. My Sig Cross barrel took almost 100 rounds to produce tight groups.
 
I have run thousands of rounds through both a 9” Mcx and a rattler with 110 hornady amax and the 110 grain Sierra varmint king all suppressed and all with absolutely no issues.
 
What velocity are you getting with either round? That matters more than the number of bullets down the barrel because you could be within rpm limits of those particular bullets, especially on the Rattler with it's ultra-short barrel and lower velocity numbers.

I've run a few hundred of the Speer 110gr. and the 110gr. Hornady VMAX (they don't make a 110 grain Amax) and so far no issues either. Still, if you ask Hornady or Speer what the max recommended rpm is, they'll tell you it's lower than what I'm seeing with my loads. Maybe there's a margin of error. Dunno. But even Bartlein has said I'm exceeding the safety margin of jacketed bullets.
 
Ape_Factory said:
What velocity are you getting with either round? That matters more than the number of bullets down the barrel because you could be within rpm limits of those particular bullets, especially on the Rattler with it's ultra-short barrel and lower velocity numbers.

I've run a few hundred of the Speer 110gr. and the 110gr. Hornady VMAX (they don't make a 110 grain Amax) and so far no issues either. Still, if you ask Hornady or Speer what the max recommended rpm is, they'll tell you it's lower than what I'm seeing with my loads. Maybe there's a margin of error. Dunno. But even Bartlein has said I'm exceeding the safety margin of jacketed bullets.
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And that's why. You're on the cusp but on the safe side of the 280,000 rpm "limit". 1923x720/5=276,912 rpm. My 110gr VMAX round is a good bit faster (2100+) and my Speer round is just under 2000fps @ 70F which is why I am a bit more at ease using them. Now on a hot 105 degree Texas day? Dunno...

The shorter Rattler barrel is keeping your FPS down to a safe level.
 
Gary Paugh said:
I'm shooting a Ruger ranch rifle with a 10" 1-5" twist barrel on it and 190 gr Hornady's come apart.
220gr Makers work great, as do most 220-225gr bullets.
haven't got around to trying supers yet.
Click to expand...
Interested in details and pics on that build…I have one I’m considering cutting down to 11” with pin and welded YHM R9
 
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