View Full Version : How is a 7.5" barrel with pistol gas for 300BLK?
My 300 BLK rifle is a 16" right now. I typically only shoot it suppressed with subs, so that's a bit big overall with 8" can. Has a DD barrel right now and have had 0 luck getting good groups with it too. About 2.5" @ 100 yds is best I can get it with any load from a 110gr VMax to a 240 gr MBC. And I tried a ton of stuff in between. This is it's 2nd DD 16" barrel - I returned 1st one for same issue and kind of gave up on it after similar results with replacement.
Anyway.....the 300BLK has been shelved mostly & want to start getting back into it some more. I want to do an upper for my SBR using a 7.5" barrel which would give me about 15" overall with can. What I don't know is how well pistol gas works with suppressed 300BLK. My current is carbine gas and it runs everything well from supersonic to the slowest subs, suppressor on or off, it just runs anything & doesn't care. Standard carbine buffer, M16 bolt carrier, non-adjustable gas block. Would a 7.5" barrel swap & either straight or pigtail gas tube run as well under those same conditions?
Also, if anyone knows, I'm thinking I might have to increase the powder charge in my subsonic loads by a tenth or two to get the same velocity from the shorter barrel? Anyone have experience moving to a shorter barrel and needing to adjust the load to stay at the MV you want?
Any 300 BLK barrel under 16" should use a pistol gas system.
A very good combo is the 9" pistol gas.
This allows good function in all 4 modes and was the original configuration AAC launched with.
I have the 7.5" on order. I should cancel that & replace with a 9" or is 7.5" acceptable for good function? (especially on suppressed subs, but still want it to work on whatever its fed).
Below 8.5" makes it hard to find a handguard and mount a silencer. 8.5" or 9" runs everything great. Because of the larger bore and faster powder used in the 300, pistol gas is optimal rather than the problem it is in a 5.56
300blk would never be available with a 16” barrel if not for the NFA.
KB developed the 300blk with AAC and now runs Q. His barrel is 7” with 1:5 twist. They have them in stock at the moment complete with gas block. All reports I’ve seen is that the barrel does a great job. Many reports of hogs taken subsonic at 100-150yds. Look at Discreet Ballistics as examples of effective subsonic hunting ammo.
https://www.liveqordie.com/products/honey-badger-barrel-assembly/
Their sugar weasel has a handguard designed for the forged upper (unlike the honey badger). Not sure when they handguard will be released. I’d look at SLR for handguard lengths since they are a known quality and have every size imaginable.
If not that, I’d go for the 9” barrel for the benefits stated earlier of of other handguard options.
RobertTheTexan
06-13-19, 21:35
300blk would never be available with a 16” barrel if not for the NFA.
KB developed the 300blk with AAC and now runs Q. His barrel is 7” with 1:5 twist. They have them in stock at the moment complete with gas block. All reports I’ve seen is that the barrel does a great job. Many reports of hogs taken subsonic at 100-150yds. Look at Discreet Ballistics as examples of effective subsonic hunting ammo.
https://www.liveqordie.com/products/honey-badger-barrel-assembly/
Their sugar weasel has a handguard designed for the forged upper (unlike the honey badger). Not sure when they handguard will be released. I’d look at SLR for handguard lengths since they are a known quality and have every size imaginable.
If not that, I’d go for the 9” barrel for the benefits stated earlier of of other handguard options.
Interesting thought. I believe that supersonic 300BLK wasn't even on AAC's chalkboard back when they were developing that round. That said, I'm going to build me a "Super 300" mainly because I think it sounds cool and secondly because it's going to be my AK killer. More accurate, more modular, and I don't have to jack with muscle memorizing the 2nd platform. Besides, I just don't like AK's. But I've been chewing on the ballistics of 110gr supersonic ammo. It's got some respectable terminal ballistics even at 400m. I still love my 300 shorty and subs n all. But I'm feeling it. I just can't decide on the barrel. I don't want to do a 16", but maybe a something 12.5-14.5.
RobertTheTexan
06-13-19, 21:35
I have the 7.5" on order. I should cancel that & replace with a 9" or is 7.5" acceptable for good function? (especially on suppressed subs, but still want it to work on whatever its fed).
OP - I'd go with a bit of a longer barrel myself. Is there a reason you want to do a 7.5?
I have an original AAC 9” upper and Ballistic Advantage 8.3” Hanson. The BA is lighter, but I would not part with either.
The BA is on sale right now. https://ballisticadvantage.com/8-3-inch-300-blackout-hanson-pistol-ss-premium-barrel.html
I believe that supersonic 300BLK wasn't even on AAC's chalkboard back when they were developing that round.
They developed the subsonic that cycles closer to supersonic.
Longer supersonic bullets like UMC and blacktip that stack well in 5.56 mags.
Supersonic performance was always part of the picture.
And then Magpul came along and developed a mag that works with nearly every 300BLK load without binding.
https://www.magpul.com/products/pmag-30-ar-300-b-gen-m3-300-blk?ProductColor=VO343
OP - I'd go with a bit of a longer barrel myself. Is there a reason you want to do a 7.5?
Just for the overall length with can. And figured since the load was being worked down to be subsonic, no benefit to any additional barrel length.
But, don't really know - why I'm asking :) Just going off assumptions since my only experience has been with the 16" build.
I have 6”, 8” and 16” blackouts. 16” in carbine length and is iffy with subsonic loads unless suppressed. For your short barrel you want the pistol length.
As I understand it, it was developed for interchangeable use of supers and subs. A soldier could swap between the two as needed and have perfect functioning.
Anything under 16" should be pistol gas. I have had more than a few 300 blk. As of right now I have narrowed it down to a 7.5" custom X-Caliber Barrel and the OG 9" AAC.
The 7.5" is more of a PDW - 150y and in. The 9" has no issues going out to 300y. The X-Caliber Barrels are MOA or better and the AAC is probably 1.5-2 moa.
I went 7.5" because as stated above not a ton of options for handguards when you get shorter. The X-Caliber Barrel along with a SLR adjustable gas block (I have it set not to lock back with subs without a can) and a Sig 762ti is quieter with sellier and bellot 220gn subs than my 9mm suppressed ar. The 7.5" is my go to now and I never really grab the AAC unless im hunting.
In regards to handloads, I went down a half a grain off my 16" loads.
RobertTheTexan
06-15-19, 18:40
Anything under 16" should be pistol gas. I have had more than a few 300 blk. As of right now I have narrowed it down to a 7.5" custom X-Caliber Barrel and the OG 9" AAC.
The 7.5" is more of a PDW - 150y and in. The 9" has no issues going out to 300y. The X-Caliber Barrels are MOA or better and the AAC is probably 1.5-2 moa.
I went 7.5" because as stated above not a ton of options for handguards when you get shorter. The X-Caliber Barrel along with a SLR adjustable gas block (I have it set not to lock back with subs without a can) and a Sig 762ti is quieter with sellier and bellot 220gn subs than my 9mm suppressed ar. The 7.5" is my go to now and I never really grab the AAC unless im hunting.
In regards to handloads, I went down a half a grain off my 16" loads.
OP don’t want to hijack your thread so I hope you don’t mind my question . It’s sorta related. [emoji51]
Hey Monk,
Since you own or have owned way more 300blk rifles than I have (1), I want to pick your brain.
I have an 8.3” 300BLK that has mostly been dedicated to subsonic suppresses use. I built it before BA started making 9” barrels 300BLK barrels, and I have had such a good experience with BA barrels, they have become my defacto go-to barrel more or less save a DD CHF barrel here and there.
But I want to build another 300BLK and use it primarily for supers. I want to take advantage of the very respectable ballistics I’ve seen from the 110gr (Barnes I believe) ammunition, but would rather not go out to a 16” barrel. Do you see value in going with something like a 12.5 or if I went with X-Caliber i think I could go 12” or 14”. It’ll probably be a mix of suppressed and unsuppressed depending on what in doing, but dedicated to supersonic ammo.
Thanks for any input.
Sent from my iPhone using Tapatalk
The 110 and 120 Barnes Black Tips are performers on game.
My experience is limited in 300 Blk with these bullets in hand loads (H110) and at max velocity.
I run 16” and 14.5 L/W barrels.
Gotta look at the 300 Super’s as, at best, .30/30’s in regards to effective range.
I’d push a shot to 200 yds given ideal conditions, longer shots are a Hail Mary in my book.
Both the 110 and 120 Barnes BTs are light for caliber.
Being monolithic copper, they are long for their weight.
Still, their BCs suck in comparison to heavy, even medium weight 30 caliber rifle rds.
Just my input for your consideration RtT.
57688
For RobertTheTexan;
I’ll try to attach a chart giving velocities with different length barrels.
Out of my 8” SBR I get 2105 fps with the Barnes 110gr Blacktip factory load and 1915 fps with the Remington 130gr Hog Hammer (a Barnes bullet, I think).
RobertTheTexan
06-16-19, 00:49
The 110 and 120 Barnes Black Tips are performers on game.
My experience is limited in 300 Blk with these bullets in hand loads (H110) and at max velocity.
I run 16” and 14.5 L/W barrels.
Gotta look at the 300 Super’s as, at best, .30/30’s in regards to effective range.
I’d push a shot to 200 yds given ideal conditions, longer shots are a Hail Mary in my book.
Both the 110 and 120 Barnes BTs are light for caliber.
Being monolithic copper, they are long for their weight.
Still, their BCs suck in comparison to heavy, even medium weight 30 caliber rifle rds.
Just my input for your consideration RtT.
Thanks Monk. I realize the distance is just an inherent compromise when talking about a .30 cal round in 5.55”6 casing as opposed to a 308. I’m looking for something that will function similar to a 30-30, just in a common platform for me.
Thanks for the input.
Sent from my iPhone using Tapatalk
RobertTheTexan
06-16-19, 00:53
57688
For RobertTheTexan;
I’ll try to attach a chart giving velocities with different length barrels.
Out of my 8” SBR I get 2105 fps with the Barnes 110gr Blacktip factory load and 1915 fps with the Remington 130gr Hog Hammer (a Barnes bullet, I think).
That’s not bad performance out of a short barrel with that round.
I shot you a PM.
Thanks
RTX
Sent from my iPhone using Tapatalk
OP don’t want to hijack your thread so I hope you don’t mind my question . It’s sorta related. [emoji51]
Hey Monk,
Since you own or have owned way more 300blk rifles than I have (1), I want to pick your brain.
I have an 8.3” 300BLK that has mostly been dedicated to subsonic suppresses use. I built it before BA started making 9” barrels 300BLK barrels, and I have had such a good experience with BA barrels, they have become my defacto go-to barrel more or less save a DD CHF barrel here and there.
But I want to build another 300BLK and use it primarily for supers. I want to take advantage of the very respectable ballistics I’ve seen from the 110gr (Barnes I believe) ammunition, but would rather not go out to a 16” barrel. Do you see value in going with something like a 12.5 or if I went with X-Caliber i think I could go 12” or 14”. It’ll probably be a mix of suppressed and unsuppressed depending on what in doing, but dedicated to supersonic ammo.
Thanks for any input.
Sent from my iPhone using Tapatalk
Sorry, was MIA all weekend.
12.5" was one of the original lengths offered by AAC. Their original thinking as best as I could tell was the OG Honey Badger (6" barrel) was PDW (SOF only) the 9" was general do all, and the 12.5" was for hunting and getting the max out of the round but still in an SBR format. They also sold a 16" for non-friendly SBR states.
I am of the thinking that unless you need to have a 16" gun for some reason (and that's getting harder to find now with the advent of pistols) there really is no reason for a 16" 300 blk. I think you can get 95% of the round out of a 9". If you have a use case for a 12.5" like hunting or benchrest shooting I think it may be a better way to go than a 9" just for velocity and stability.
Done as far as assembly & happy with the look & feel of it with the shorter barrel + suppressor. Sadly being a 2-stamp gun, tax stamps are single most expensive thing on the build :) Looking forward trying it out along with the slightly hotter subsonic load (ver 1.0) this weekend.
57747
57749
Specs on the overall rifle (if anyone cares - nothing fancy about it)....
80% lower
PSA stripped upper
RRA hard chrome BCG
RRA 2 stage trigger
RRA LPK
Generic 12" rail - MAS Defense? Not sure but needed something fat enough to go over suppressor
Magpul rail ladder covers, CTR stock, grip
Anderson 7.5" stainless barrel (yeah, I know - I very much dislike Anderson mfg like many others, but on sale, in stock, & what I wanted)
Sig Romeo 5 & mount it came with
Suppressor is my form 1 homemade, 416 stainless & titanium
Cerakote is Magpul FDE & graphite black
* sorry...can't get pics working right
the_1iviper
06-21-19, 21:55
Done as far as assembly & happy with the look & feel of it with the shorter barrel + suppressor. Sadly being a 2-stamp gun, tax stamps are single most expensive thing on the build :) Looking forward trying it out along with the slightly hotter subsonic load (ver 1.0) this weekend.
57747
57749
Specs on the overall rifle (if anyone cares - nothing fancy about it)....
80% lower
PSA stripped upper
RRA hard chrome BCG
RRA 2 stage trigger
RRA LPK
Generic 12" rail - MAS Defense? Not sure but needed something fat enough to go over suppressor
Magpul rail ladder covers, CTR stock, grip
Anderson 7.5" stainless barrel (yeah, I know - I very much dislike Anderson mfg like many others, but on sale, in stock, & what I wanted)
Sig Romeo 5 & mount it came with
Suppressor is my form 1 homemade, 416 stainless & titanium
Cerakote is Magpul FDE & graphite black
* sorry...can't get pics working right
looks great , it should handle nice for a suppressed rifle
i recently put together a similar dsr upper with a 6" BA barrel. i've had it out twice now and it shoots nice with subs and supers
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