.300 Blackout 1:5 vs 1:7 for barrels < 8.3"

The White Death

The White Death

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Minuteman
Jul 22, 2020
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5
#1
I am about to purchase a short barrel (<8") for my .300 Blackout build and I need help choosing the right barrel for me. I would like the capability to shoot 110gr up to 225gr without the bullet exploding on me or my suppressor. I will be shooting suppressed with a 6" can, and would like sub MOA groupings at 100yards.
Some of the barrels I narrowed it down to:
Faxon Match Series 7.5" Gunner 1:5 416R SS QPQ Nitride 5R -- My favorite barrel, but what grain bullets do I have to worry about using with this?
Ballistic Advantage 8.3" Hanson 1:7 416R SS -- This barrel is pushing the max length I would like for my build, but seems like the perfect middle option.
KAK Special 1:5 6.25" or 1:7 8" 416 SS 5R -- The KAK 6.25" states it can run both subs/sups suppressed while the 8" version with the 1:7 twist rate doesn't mention anything. Also, I have seen negative reviews mentioning the gas block hole size and to avoid anything with KAK. What are y'alls thoughts on this?

I am worried the 1:5 twist rate will be too much for 110-150gr and would hate to just limit myself to strictly subs or high gr rounds.

Let me know what barrels you recommend for this build & feel free to drop some knowledge on me. Thanks!!
 
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#2
1:5 is fine for barrels under 8 inches. A 9" barrel I would probably do a 1:6.

In 2017 we had a local police agency that was looking for a very short (AAC honey badger like) SBR that would take a full BCG, had adjustable gas, MOA or better, and a carbine handguard (their were some other things but that was the jist of it). We tested a lot of barrels and the X-Caliber 7.5" in 1:6 shot lights out. At the time 1:6 was as low as they would go. That year Q came out with the honey badger and at the Q ball at SHOT Show I asked Kevin and Ethan about twist and if in their testing there was two fast of a twist. Both said no.

In all honesty I am not impressed by any of those barrels you listed. I am at the point where I need to rebarrel my OG 9" AAC SBR and I will order an X-Caliber in a 1:6. They will be a little more expensive than some of the barrels listed but they will be at top tier level barrels for about $100 less.
 
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#3
I've been quite impressed with the honey badger barrel assembly. The accuracy is pretty darned good, for what it is. That said, I want to try a 9" 1:5 twist from Mos-Tek next. I'm becoming a believer in faster twist rates across the whole spectrum of rifles in general, but I especially see the difference in 300 blk.
 
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#4
Not a really short barrel but we've built several 300AAC guns. My youngest son got one and it's with a 7.5 twist barrel. Yes his barrel is a 16" long barrel and it gets shot suppressed as well.

Shooting 208gr Amax box ammo thru the gun which if I recall correctly comes out subsonic already with out the suppressor even on it. That box ammo will print .5moa groups at a 100 yards with out even working at it. I like that gun so much I'm thinking of building one for myself. Besides him just liking to shoot it he does also use it for deer hunting as well. 30-30win. power that shoots flatter in a semi auto and suppressed....probably the nicest deer hunting gun in the woods!

5R rifling on all of the ones we've done here.

I've run box ammo with bullets as light as 110gr up to the 208gr bullets. No issues.

At 1100fps which is just above the speed of sound (lowest my twist rate calc goes) with the 208gr bullets which are 1.530" long. You need a 1-8.31 twist min to stabilize the bullet. Like I said we are running 7.5 twist barrels.

I don't see the need for anything even faster than a 7 twist. Unless the bullet is a solid bullet and really long...then maybe. Bullet length dictates twist more than bullet weight. Yes usually as the bullet gets heavier it gets longer but not all the time.

Later, Frank
Bartlein Barrels
 
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#5
the monk said:
In all honesty I am not impressed by any of those barrels you listed. I am at the point where I need to rebarrel my OG 9" AAC SBR and I will order an X-Caliber in a 1:6. They will be a little more expensive than some of the barrels listed but they will be at top tier level barrels for about $100 less.
Click to expand...
Yeah, I am trying to stay under 8", I haven't looked at that many 1:6 barrels so I will have to do some research on those and X-Caliber. I've heard good things about Q's barrel which is why I thought the Faxon 1:5 would be a great option since I know Faxon and Q have been working together on the 8.6 with a 1:3 twist. What puts you off on the Faxon barrel I listed, and does the 1:6 twist allow for a wider range of bullets that can be used over a 1:5?
 
#6
Not sure how short you want to go but I have an SLR 5" 1:6 that I've been happy with cycling and running everything from 110's to 220's. I obviously can't add anything about the twist rate over what Frank mentioned above. Not sure about sub moa out of it either because that seems pointless to check to me for a 5" barrel, but it doesn't noticeably disappoint in the accuracy department. Im just hitting man size targets out to a hundred or two hundred yards though
 
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#7
The White Death said:
Yeah, I am trying to stay under 8", I haven't looked at that many 1:6 barrels so I will have to do some research on those and X-Caliber. I've heard good things about Q's barrel which is why I thought the Faxon 1:5 would be a great option since I know Faxon and Q have been working together on the 8.6 with a 1:3 twist. What puts you off on the Faxon barrel I listed, and does the 1:6 twist allow for a wider range of bullets that can be used over a 1:5?
Click to expand...
In regards to Faxon, I have had a number of their barrels and I was never impressed. I know there will be people that love their barrels but they have never worked out for me. I think you are good to go with 1:5, I will just probably go with 1:6 with a 9" barrel because its longer.

If you wanted 7.5" I would not dismiss the Q barrel. They are pricey but you have to factor in the gas block and gas tube.
 
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#8
ELCO82 said:
Not sure how short you want to go but I have an SLR 5" 1:6 that I've been happy with cycling and running everything from 110's to 220's. I obviously can't add anything about the twist rate over what Frank mentioned above. Not sure about sub moa out of it either because that seems pointless to check to me for a 5" barrel, but it doesn't noticeably disappoint in the accuracy department. Im just hitting man size targets out to a hundred or two hundred yards though
Click to expand...
Do you have to adjust the gas block at all when changing between 110gr to 220gr rounds? I was thinking the KAK 6.25 was about as small as I wanted to go, but if I can get the same performance from a 5" as a 7.5" then I see no reason not to switch :)
 
#9
The White Death said:
Do you have to adjust the gas block at all when changing between 110gr to 220gr rounds? I was thinking the KAK 6.25 was about as small as I wanted to go, but if I can get the same performance from a 5" as a 7.5" then I see no reason not to switch :)
Click to expand...
It all depends how you set it up. So you could set it up that it's perfect with supers or you could set it up so it's perfect with subs. I essentially have mine set up so it's the least amount of gas that I can get away with subs (lock back) and then supers just always work.

I think 7.5” is a great do all length. If you want a super small PDW I would go with a rattler upper or the full gun. That is probably realistically 150 yard and in. With a 7.5” I think you are good to go to 300 with supers (black tip Barnes).
 
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#10
The White Death said:
Do you have to adjust the gas block at all when changing between 110gr to 220gr rounds? I was thinking the KAK 6.25 was about as small as I wanted to go, but if I can get the same performance from a 5" as a 7.5" then I see no reason not to switch :)
Click to expand...
I have an SLR adjustable gas block on there, so yes. But if you used the same ammo consistently you could probably find a happy medium for switching from subs to supers. Honestly an 8" barrel would be more versatile I admit, but I like to take everything to the nth degree and I wanted to make it as short as possible. But for me it's all use case. Like monk said above, my 5" is a 150 yard gun for subs. That's why I have it and that's how it's set up. I think you're probably over thinking the twist rate. Unless you have some unusual ammo, 1:7 is completely fine. So is my 1:6. And I shoot my brother in laws rattler all the time and I think that's a 1:5. They're all fine.....
 
#11
Faster twists are not always sunshine and roses. Traditional cup and core bullets that are designed for controlled expansion in 1:7 or 1:8 twist barrels will often shed petals in gel. Sometimes this makes more impressive bare gel results, sometimes it makes it dramatically worse. Almost every time it makes it a failure through any type of barrier (wall board, plywood, steel, glass, etc.. the "FBI protocol" stuff). The only exception is a very narrow market of monolithic projectiles. Not all monolithics are immune, either.

Just something to keep in mind. It's not make or break for everyone but I've seen more than one entity purchase fast twist guns that ended up cornering their ammo purchasing decisions unexpectedly.
 
#12
Ledzep said:
Faster twists are not always sunshine and roses. Traditional cup and core bullets that are designed for controlled expansion in 1:7 or 1:8 twist barrels will often shed petals in gel. Sometimes this makes more impressive bare gel results, sometimes it makes it dramatically worse. Almost every time it makes it a failure through any type of barrier (wall board, plywood, steel, glass, etc.. the "FBI protocol" stuff). The only exception is a very narrow market of monolithic projectiles. Not all monolithics are immune, either.

Just something to keep in mind. It's not make or break for everyone but I've seen more than one entity purchase fast twist guns that ended up cornering their ammo purchasing decisions unexpectedly.
Click to expand...
Yeah, that is what I am trying to avoid. I read about someone whose bullet fragmented inside their suppressor with a 1:5 twist in a 7.5" barrel but they said it happened in a firing course after the barrel was already pretty hot.
 
#15
The White Death said:
I am about to purchase a short barrel (<8") for my .300 Blackout build and I need help choosing the right barrel for me. I would like the capability to shoot 110gr up to 225gr without the bullet exploding on me or my suppressor. I will be shooting suppressed with a 6" can, and would like sub MOA groupings at 100yards.
Some of the barrels I narrowed it down to:
Faxon Match Series 7.5" Gunner 1:5 416R SS QPQ Nitride 5R -- My favorite barrel, but what grain bullets do I have to worry about using with this?
Ballistic Advantage 8.3" Hanson 1:7 416R SS -- This barrel is pushing the max length I would like for my build, but seems like the perfect middle option.
KAK Special 1:5 6.25" or 1:7 8" 416 SS 5R -- The KAK 6.25" states it can run both subs/sups suppressed while the 8" version with the 1:7 twist rate doesn't mention anything. Also, I have seen negative reviews mentioning the gas block hole size and to avoid anything with KAK. What are y'alls thoughts on this?

I am worried the 1:5 twist rate will be too much for 110-150gr and would hate to just limit myself to strictly subs or high gr rounds.

Let me know what barrels you recommend for this build & feel free to drop some knowledge on me. Thanks!!
Click to expand...
I have had no issues with my 1:7 barrel from Wilson Combat.
 
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#17
The White Death said:
Do you have to adjust the gas block at all when changing between 110gr to 220gr rounds? I was thinking the KAK 6.25 was about as small as I wanted to go, but if I can get the same performance from a 5" as a 7.5" then I see no reason not to switch :)
Click to expand...
I have had a 6.25” KAK for a number of years. It has been 100% reliable with everything I’ve ever run through it without an adjustable gas block.

It shoots well, but not subMOA as some others say theirs are. Plenty good for hunting, although I did eventually go to a longer barrel for a little better terminal velocity.
 
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