.300 blackout pistol build

[just bill]

While researching the pistol build, the problem with cycling has creeped in due to the hand build vs the complete ready built models. This seems to be at the subsonic side of the topic, however the canned answer seems to be using an adjustable gas block and a low mass bcg. I plan to keep the pistol sub sonic suppressed. Any ideas from the experienced builders?
Thanks ,
BILL

[WJP]

What barrel length are you wanting to go with? If you go 8" or so and shoot heavy subs you should be fine. I use a m16 carrier, 8" cmmg barrel, with 200+ gr subs, standard spring, buffer and haven't had any issues. Built and ran quite a few in similar configuration without problems. I have yet to find a light sub load to cycle any configuration. Also if you go longer just make sure you get a pistol length gas system.

[just bill]

What barrel length are you wanting to go with? If you go 8" or so and shoot heavy subs you should be fine. I use a m16 carrier, 8" cmmg barrel, with 200+ gr subs, standard spring, buffer and haven't had any issues. Built and ran quite a few in similar configuration without problems. I have yet to find a light sub load to cycle any configuration. Also if you go longer just make sure you get a pistol length gas system.

I'm planning on a 7.5- 8" barrel with a 5" can with heavy sub bullets. 1 was trying for 12"combination, however 14" looks like what I'll end up with. I have seen a mixed bag of gas blocks, adjustable vs non adjustable.

[WJP]

I run non adjustable on everyone I have or have built for orthers. A cmmg 8" with standard non adjustable block, can, heavy subs, standard carrier, standard buffer and spring, h110, 1680, imr 4227, lil gun, will work just fine. 1680 is my least favorite of the powders. If you want ultra quiet loads try some 110 gr and trailboss. It'll be a straight pull though.

[just bill]

Thanks WJP.

[JayT]

I run non adjustable on everyone I have or have built for orthers. A cmmg 8" with standard non adjustable block, can, heavy subs, standard carrier, standard buffer and spring, h110, 1680, imr 4227, lil gun, will work just fine. 1680 is my least favorite of the powders. If you want ultra quiet loads try some 110 gr and trailboss. It'll be a straight pull though.

I second all of this. I’m running several different .300 uppers in different configurations, all suppressed, all subsonic, all chrono out at around 1000fps at sea level. The only one that I use an adjustable gas block on is a rifle length upper, where I need the adjustment capability to properly cycle the action.

Similar to what you’re building, my SBR with a Noveske 8.2” barrel has a non-adjustable block, full auto BCG, and an H2 buffer, so it has more reciprocating mass than a semi-auto BCG with stock buffer. No cycling issues with 220gr subsonic rounds in either semi or full auto fire. Bolt always stays open after last round. I load Accurate 1680. A touch louder than some other powders, but it’s what I’ve always used and I’ve worked up loads that work well for my setup.

I can’t offer a lot in terms of bullet casting, as I’m dead-new to it, but I’ll help out as much as I can with any issues you have with a suppressed AR build.

[WJP]

No problem. Glad I could help out. PM me if you have any questions. JT that's one of the reason I quit using 1680. I didn't care for the sound, velocity spreads were a little worse, even though accuracy was acceptable it wasn't the best. IMR 4227 gave me the best accuracy, velocity spread, but h110 seemed a touch quieter. I'm sure you'll get it figured out. Nothing wrong with 1680, it's the go to powder that most use.

[JayT]

No problem. Glad I could help out. PM me if you have any questions. JT that's one of the reason I quit using 1680. I didn't care for the sound, velocity spreads were a little worse, even though accuracy was acceptable it wasn't the best. IMR 4227 gave me the best accuracy, velocity spread, but h110 seemed a touch quieter. I'm sure you'll get it figured out. Nothing wrong with 1680, it's the go to powder that most use.

I started using 1680 because, when I started reloading .300 subs, it was the only powder that AAC recommended. Old dog, new tricks. I’d like to branch out and see what’s out there.

[HATCH]

-following

I have a 10.5 inch SBR AR.
It doesn't cycle the action on 240 grain subs (1050-1100 fps)
The Subs are VERY accurate in the AAC Rem #7 16 inch barrel rifle.
I no longer have to load for the AAC rifle so I may play around some before I open up the gas port.

[popper]

All my ARs have adjustable blocks so I can set them right. My 10" pistol with pistol port gas I use standard carbine buffer, BCG, spring but cut off 3 coils to get the BCG to LSLB. Basically buffer tube is shorter than carbine. Shot some factory 220 subs but mostly supers. 150 & 155 gr do ~ 2 MOA hand held @ 50 & I push them hard.

[JayT]

+1 on adjustable gas blocks.

Fixed gas block is good for factory rounds only. Otherwise, it’s like having a performance car with a big cam that you can’t adjust the timing on.

[Handloader109]

Fixed gas block here, 9* std pistol buffer. Thru suppressor. Had issues with H110 and noe's heavy 230hp (247gr solid) works perfectly with cfe blackout cycles with zero problems. Use the right powder....

[just bill]

This has been an interesting research project. As I was picking through vendors to see product and prices, as is usually done for researching. I seem to find more vendors daily, however one thing that amuses me is charging handles. What is really the difference in charging handles?

Another things is barrels, YouTube has loads of comparisons between manufactures, both informative bad ridiculous, however not to many for Shilen or McGowan or other custom builders. I chose McGowan for my long shooter, however narry a thing on ar's, only on their web site for ordering. Any input?
Bill

[popper]

KAK had some good ones on sale a while back. 10" 1:8 shoots good.

[just bill]

The 300 blackout build continues, I've searched the YouTube and AR manufactures, however the custom barrel builder that I've used in the past has a 9.25 1/10 twist. This seems to be a little higher than most AR barrels I've looked at including the top rather AR manufactures. I'm just throwing this out there to see how it floats. All my bullets will be my swaged subsonic 190-220 range, however I need to finish the build to confirm the best for my needs.
Thanks,
Bill

[WJP]

I'd run a 1:7 or 1:8. 8.5-9"

[just bill]

As the build continues I have another upper question? I blindly bought an upper from the person I had build my .458 socom, however the upper was completely incomplete and all he had was an ejector cover. I have never, so far, used the forward assist, other than rifle instructions in basic training, so is it really necessary to have one? My AR-10 doesn't have one so my thoughts are just thread the hole and fabricate a plug and loctite it in the upper. Thanks in advance for the info.
Bill

[popper]

Just fill the hole with hot melt glue or some epoxy or leave it open. No real need for dust cover either.

[WJP]

For $10 or less I'd order one. You'd loose more than that when you go to sell the upper if it's not there. No you don't need it but it looks better than an empty hole.

[Handloader109]

Non adjustable here on my 9.5". Suppressed, totally reliable action with 247 noe while using cfe blackout powder. Not so much with hH110....... Get the powder designed for the gun and it just works..

[just bill]

Non adjustable here on my 9.5". Suppressed, totally reliable action with 247 noe while using cfe blackout powder. Not so much with hH110....... Get the powder designed for the gun and it just works..

I find your information about the cast boolets interesting. Years ago I was led to believe that cast boolits would lead to gas block and tube fouling problems, however I've seen where quite a few reloaders use them. I'm interested in what composition, other than wheel weights which is what I've used in my pistol plunkers. Thanks,
Bill

[dragon813gt]

I have never, so far, used the forward assist, other than rifle instructions in basic training, so is it really necessary to have one? My AR-10 doesn't have one so my thoughts are just thread the hole and fabricate a plug and loctite it in the upper. Thanks in advance for the info.
Bill

You can buy plugs for them. I have one Anderson upper where the hole is slightly off. Try as I might I was unable to install a forward assist. I tried a few of them because I was building three rifles at the time. A few minutes on Amazon and a plug arrived two days later.