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Been thinking about putting a subsonic only upper together for one of my SBRd lowers. Ive got a rather long Form 1 suppressor I can use with it as well as a few others. But my thoughts are to keep it short.

What is the shortest 300 black that will cycle and stabilize subs?

Thanks!

Reno
 
Bueller?

Found a lot of 7.5" stuff. Anything shorter? I know specialty rifles like Sigs have shorter. Just not seeing anything shorter than 7.5" available?
 
My Rattler is a 5.5" barrel, that I run exclusively with a can (AAC 7.62 can) and subs. I have had zero cycle issues.

I bought the gun w/ the 5.56 upper and bought the additional .300 upper, but I've never run the 5.56 upper. Too loud, and my ears are old like the rest of me.
 
Not a great pic since I screwed the can on for the pic, but that's her w/ the .300 upper installed. She's tiny, her bark is quiet, but she bites just right.

20200131_151043.jpg
 
Ya, the Sig is definitely a very nice little rifle! Have you had any issues with subs tumbling?

I found two short barrels, a bit rich for my blood. But at least I know they exist!

6.5"
1590698701543.jpeg
5.5"
1590698736972.jpeg
Just need to find out if any one has run something this small on there AR and if they run well!
 
No evidence of tumbling that I've seen. Crisp clean holes every time.


But I will definitely keep eyes out in case that changes. I've only shot 220gr through her, but I'll mix it up with some 208grs.
 
I believe that for optimal performance you need ~9inch barrel.
your milage may vary depending on powder/projectile combo.
 
I believe that for optimal performance you need ~9inch barrel.
your milage may vary depending on powder/projectile combo.
This might be true.

In my head the 200+ grain 300 Black at around 800-1000fps is a glorified 45acp with better bullet coefficients. Get a fast enough twist, they should stabilize.
 
This might be true.

In my head the 200+ grain 300 Black at around 800-1000fps is a glorified 45acp with better bullet coefficients. Get a fast enough twist, they should stabilize.
they sound like they hit harder on steel at 100 yrds too vs 45acp.
the steel test is the real test. :rolleyes::D;)

i think an ultra short 300blk would be cool. youre definately not doin the bullet or suppressor any favors though.

for 300blk subs, "they" say the powder is burnt in the first 7.5-8" of barrel.

my 10" blackout is a 1/7 twist 5R
 
I believe that for optimal performance you need ~9inch barrel.
your milage may vary depending on powder/projectile combo.
My son, who was a USMC armorer for a decade, tells me in his experience the sweet spot for 300BO is about 10". Which is why I bought a Ballistic Advantage 10.3" barrel for my upcoming build. Agree, YMMV and of course this is very load and application dependent. One opinion.....
 
5.5" Rattler and its brother a Canebrake (the FDE) with a larger foregrip for a fixed mounted suppressor, both shoot Subs fully stabilized. 220 ELDX. I run 150 Suppers through them an so far no keyholes.

I picked up the top (gray) 9" Virtus in .300blk since all the reloading books reference 9" as the optimal length. Sold the 9" to a buddy a few months back as I just never shot it as the 5.5" with that 1:5 fast twist just works.

IMG_0556 2.jpg IMG_0666.jpg
 
My son, who was a USMC armorer for a decade, tells me in his experience the sweet spot for 300BO is about 10". Which is why I bought a Ballistic Advantage 10.3" barrel for my upcoming build. Agree, YMMV and of course this is very load and application dependent. One opinion.....
I heard the same so I went w/ 10.5 myself.
 
Ya, the Sig is definitely a very nice little rifle! Have you had any issues with subs tumbling?

I found two short barrels, a bit rich for my blood. But at least I know they exist!

6.5"
View attachment 702984
5.5"
View attachment 702985
Just need to find out if any one has run something this small on there AR and if they run well!

Its the fast twist rate that you need. That 5.5" if it has a 1:7 is slow for that short. SIG did their homework with their 1:5 twist rate, it works. I have not tried any 110 or lighter grain bullets through mine, it's not built for those.

I do have some 168 Lehigh Defence Controlled Fracturing Subs to work uploads to see if I can get them to cycle in the Rattler. They are recommended for bolt only but have heard of others getting them to feed.

Screen Shot 2020-05-28 at 4.39.23 PM.png
 
Ya, after you posted the twist rate I rechecked those two barrels. Darn.
 
Ya, after you posted the twist rate I rechecked those two barrels. Darn.

Ya my buddy that ended up buying my 9" Virtus came close to buying a PSA 300blk build kit but all the short barrels had fast twists. Then he held the SIG and done.

I have no doubt guys are using them for builds for sure, they probably work but some might tumble.
 
My son, who was a USMC armorer for a decade, tells me in his experience the sweet spot for 300BO is about 10". Which is why I bought a Ballistic Advantage 10.3" barrel for my upcoming build. Agree, YMMV and of course this is very load and application dependent. One opinion.....

In the end I went with a 12" 5r 1:7 twist Seekins Precion barrel for my 300Blackout.
 
Seems like the verdict is fast twist rate is essential in the itty bitty barrels.

I couldn't find any manufacturer that makes one. The two tiny barrels I found by V Seven have zero presence online in terms of anyone talking about running one.
 

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