Cast in a 300 Black out

[mtgrs737]

Hi all, I am thinking about building a 300 Black out upper for an AR-15 and was wondering which twist rate would be best. I was thinking I would run all boolit weights from 130 to 220 gr. cast in it. I also was wondering about which barrel length and which brand would be best as I know a high quality smooth bore will help with leading. I have seen barrels offered for as little as $150 to as much as $270. What do you guys that have been there think?

[Huntsman52]

I really like the Rainer Arms Select I had on my. 16" with a 1-8.5 Twist. Sub MOA at 100 yards with 110grn varmiters. With Lee 312-155 about 2" at 100 yards. They run about $250 new from Rainer.

[wlc]

Most standard barrels are either an 8 twist or a 7. Mine is an 8 twist as I bought it before AAC decided that the 7 twist was the "flavor of the month". The 7 twist will stabilize the really heavy for caliber bullets like the 240-250 grainers better than an 8, but so far I've seen no stability issues with my 8 twist. I only shoot up to about 230gr in mine and have shot nothing but cast in it since getting a mold other than the Lee 230 mold.

If you can find a 16" barrel with the pistol length gas system you will be better off than a 16" with carbine gas. The pistol length system is more accommodating to different powders and is easier to load for. The 16" carbine gas system is OK (that's what I have), but it took more work for me to find a load that was both subsonic and would cycle the action in my AR. Easy to come up with loads that cycle or are subsonic, but more difficult to find that "happy place" where both are achieved. I might add that I only shoot subsonic suppressed with mine.

As far as mfg., mine is a Rock Creek barrel and I've had good luck with it. Like I said earlier look for a 16" (assuming you are not going the short barrel rifle route) with the pistol length gas system. I would also suggest going over to the 300 blackout website and doing a bunch of reading over there. http://www.300blktalk.com/forum/ IIRC there was a company selling AAC barrels like I have suggested for a very reasonable price ($130 IIRC) and there is a thread on there about it. Don't know if they are still available or not though.

Good luck!

[Smoke4320]

If you want to shoot subsonic.. Regardless of barrel length ..get a pistol length gas system..

1:7 will handle all the way to 247 gr bullet and down to 120 Gr, 1:8 will get you at least 200 grns and on many 220 Gr and down to 110 Gr

a lot of the cast shooters here are shooting 150-160 sonic

There are a lot of cheap barrels floating around and you get want you pay for .. Cheap soft steel is easier to cut so it sells for less but also wears out faster

[pilot]

I bought one of the AAC barrels, 16 inch length, 1-7 twist, pistol length gas system. I'm still breaking it in and working up loads, but so far, I like it a lot. 110 grain jacketed bullets are great, as are 168 grain BTHP Sierras. I just loaded a couple of the 155 Lee "SKS" boolits, but they look promising. So far, I've had no problem with any of the loads I've tried cycling the action.

[skeet1]

I bought a J&T distributing .300 BLK 1-8 upper and have been very happy with it but I see that their prices have gone up since I bought mine. http://jtdistributing.net/store/page17.html I was told by them that they use E.R. Shaw barrels. I have been using the Lee 312-155 and H110 with good success.

Ken

[Beesdad]

I have been shooting the Lee 230 grain slug in a Primary Arms upper. 16 inch, 1/8 twist, pistol length gas system. Has performed flawlessly with PC ... Alox was a disappointment.

I have moved up to a NOE 247 grain FB PB... Now I keep up with the demand.

The complete upper was less than $300.00 delivered... W/O BCG

[Beesdad]

Finished product..

[427smith]

I was playing with my 300 today. nothing special 16 inch ar stoner barrel dpms upper and lower. 2x8 leupold. 130-sp rcbs mold sized at .3105 weights 139 checked. using h110, groups are 1 1/4 to 1 1/2 @ 100 yds with a standard primer, and 2" with a mag primer. with a home brew of ww , 63/37 and lino. brinell 17. also did some test with same charge with brinell 14 and couldn't do any better than 3 1/2. love the 300, cost a lot less to shoot than my 270 or 375 hh

[mtgrs737]

Thanks Guys for all the info, it was just what I was hoping for! Now for another question: Can you still shoot super sonic with the pistol length gas system?

[wlc]

Yes!!!

[pilot]

So far, everything I've tried has been supersonic.

[odfairfaxsub]

16 in 1-8 twist h-bar profile w carbine port

upper threshold of subsonic using h110 and h4198

shoot 1/4 inch groups w the lee 230 gr bullet powder coated and sized .311

using a timney trigger really helped shrink groups in half

[popper]

16, 1:8 Hbar, pistol port will be WAY overgassed for super work. Get and adjustable block. Supers need to be WDWW or better for > 1600. Haven't heard any good repots about the heavy Lee BT mould. 1/3 the $ to shoot than my 308.

[Beesdad]

16, 1:8 Hbar, pistol port will be WAY overgassed for super work. Get and adjustable block. Supers need to be WDWW or better for > 1600. Haven't heard any good repots about the heavy Lee BT mould. 1/3 the $ to shoot than my 308.

Popper, did you read my comments in post #7? They have performed well for me... Are you referring only to supers?

[Moonie]

We have 2 carbine port 1-8" 16" barrels, using the proper powders we haven't had much problem with subs and supers run perfectly.

We normally shoot the Lee 155, A.C.E 235gr and the Accurate Molds 245gr, no stability issues with any of them.

[popper]

Beesdad - depends on the port size. Over gassed is really hard on the action.
edit: pistol port will be WAY overgassed for super work. Get and adjustable block. AR15 (223) carbine has been designed to work properly. 300BO hasn't, different animal. It's a blow back action (after the bolt unlocks) , when the spring bottoms out, excess force is absorbed by your shoulder (unless a pistol tube) and the lower-buffer tube connection. Supers in a pistol port can make too much pressure (force) on the BCG/spring. Theoretically, the buffer is there to reduce spring oscillation for rate of fire control. Gas should be adjusted to give reliable LB on empty and no more. POF has a pretty good analysis of the problem.

[johnnyastro22]

I have DPMS .300 ACC BLK 1-7 Chrome Lined.

So far only shot super sonic 110 GR Barnes Tipped TAC-TX and Hard Cast LEE #90385 C312-155-2R 155 Grain Bullet Powder Coated and Gas Checked. Outstanding results from both (after I finally figured out that my Hornady manual contained a trim case to 1.40 ERROR but that's really for another thread...)

I say 300 ACC BLK has been very cool to work with so far and I am just about to venture in to the sub sonic suppressed so more to do and enjoy! Build it, you won't regret it!

[mtgrs737]

Well guys I ended up with a Primary Arms complete upper like Beesdad has (I think) 1/8 twist, 16" barrel, pistol gas system, and quad rail forearm. This was a real decent buy at $269 plus shipping which was under $10. I opted for their stock BCG for $59 and a Yankee Hill charging handle for $12 which is reduced because I got the upper from them.

I want to thank all whom posted and shared their info, it helped me clear some things up and gave me places to do more research. This is really a great place to spend time!

mtgrs737

[wlc]

Popper, wouldn't an H2(?) buffer be what you'd want in a pistol gassed system? I'm asking cause mine is a carbine gassed upper with the standard carbine buffer.

Mtgrs, congratulations on your purchase. I really hope you enjoy it. I really like mine and have even been thinking of building another AR or getting the Ruger American Ranch in 300blk because I like the round so much.