I am in a process of build a new AR to use with the suppressor, would like to know which barrel length I should pick and why, thanks…
10.5"
Why? because you want the shortest possible barrel
Thanks, and is that length works ‘optimum’ with suppressor? I like it to be as reliable as possible cause I think there is some others factor that involve while using w/the can, just dont know the technicality of it…
In 5.56? I’ve got a 10.5" Noveske Switchblock with an AAC M4-2000 that works very well (for me, low speed civilian).
If you are considering .300 blk, AAC and Noveske (and others too) make them in even shorter lengths to run suppressed.
thanks bro…
I wouldn’t go any less than 10.5" as mentioned here already. Anything less and you will increase the chances of a baffle strike.
This is what I ended up doing and now I have a 9" upper in 300 Blackout that I’m quite happy with.
Why do you think there is a bigger chance for a baffle strike on a shorter 5.56 barrel compared to a 300BLK?
The bullet might not stabilize, but that depends on the bullet length/weight.
There are lots of factors but the likelihood of a 5.56 round not stabilizing properly is much higher. The 300 Blackout round was developed specifically with this in mind and the bullets stabilize in much shorter barrels.
This is one of those statements I keep seeing but haven’t been able to find any hard data on. Do you have something? Some kind of reference for this that shows the instability of a 5.56 round out of say… an 8" barrel as compared to the 300 out of the same length barrel?
If you will find a suppressor manufacturer that warranty their 5.56 can on an 8" barrel, let me know.
But that’s not what you said.
There are lots of factors but the likelihood of a 5.56 round not stabilizing properly is much higher. The 300 Blackout round was developed specifically with this in mind and the bullets stabilize in much shorter barrels.
I would like to know what you base this on. I have heard for years that the reason the 5.56 silencers AREN’T advisable on <10.5" barrels is due to “instability” but I have yet to see any data on it. I’m wondering if you’re just repeating what you heard or if you have some data or information that backs it up.
I too would like real facts to back this up… I’m not sold on the notion that increased velocity = increased stability.
Rob,
I have no “hard data”. The following is from my own experiences with stupid friends that just had to have short barreled (pistol) AR15s.
I’ve found when you get below 8", and this is solely my speculation, that the velocity being so slow, coupled with the 17,000 PSI pressure “blast” at the muzzle, is enough to deflect the round and cause instability initially. We were not keyholing and still got decent accuracy out of the 8" but out of the 6.5" we had some problems.
On the 6.5" barrel we could see strikes on the muzzle brake and accuracy at 10 yards was almost non existent. This was with an Olympic Arms upper. I’m sure the 1:9 twist did not help any.
However, when we removed the muzzle brake all those issues went away. The accuracy came back and there was no keyholing. I really do suspect that the initial blast of pressure at the muzzle causes some issues especially because the round is traveling about 1000 FPS slower than it is out of a 20" barrel.
I would like to see a chart of barrel pressures in 300BLK because they do not have this problem and the lack of blast at the muzzle on short barrels is obviously less. I do not necessarily think that it is the short barrel itself that causes instability but rather the barrel pressure. I think the round wobbles a bit as it exits the muzzle but the twist stabilizes it after a few inches, otherwise there is no way we could get the accuracy we were getting at 25 yards.
A great test to run would be some super short barrels with varying twist rates with both super and subsonic ammo. I bet with subsonic ammo on a 6.5" barrel and 1:7 twist there would be no issues leading me to believe that the blast of the 5.56mm on short barrels is what causes stability issues, not the slow velocity or short barrel itself.
That’s a good point. We load .308 ammo for our Bolt guns that stabilizes just fine. Velocity is about 1050 fps compared to 2515 for full powered ammo.
the shorter barrel warranty on a 300BLK setup versus 5.56 doesn’t have anything to do with stability, it has to do with baffle erosion from unburnt powder.
300 BLK works very well in SBRs and VSBRs because of its small/fast burning powder charge.
AAC will warranty the 762-SDN-6 and SR7 down to 7.5" on a 5.56…
The larger bore gives you more can life (spread out the abrasive abuse).
And as for stability, you can probably find the right [wrong] combo- a very short 5.56 barrel in a slower twist shooting a longer bullet… That’ll screw up your day.
This is essentially what I was wondering/getting at, without any concern for 300, in the original question.
“Michelin won’t warranty my tires if I go 200 MPH on a dirt road. Ergo it is unsafe to ever go 200 MPH!”
Everyone ASSUMES the issue is unstable rounds, mostly because that’s what someone else that didn’t know told them and it was easier to believe it than question it, but nobody ever seems to produce evidence of same.
I’ve seen umpteen reports of endcap and baffle strikes on cans mounted on barrels under the mythological 10.5", but all too often they are shit barrels from shit makers anyway, so it’s hard to say that it was the fact that it was 7.5" that caused the strike and not the fact that it’s an Oly arms with an 88* shoulder instead of 90.
Who, aside from Jer, assumes that? I thought it was pretty well known, all over this forum, that baffle erosion on short barrels in 5.56mm weapons was the reason.
The world does not begin and end with m4c.