300 blackout sbr build questions

chrisgunguy

chrisgunguy

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Full Member
Minuteman
Aug 20, 2008
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texas
#1
I hope y'all aren't bothered that I didn't search for threads on the topic first. I want to build an sbr in the above mentioned caliber. My trust is all in place and I have an aac sdn6 on the way. I plan on shooting primarily subsonic thru the gun with the can and what to know how short is too short for the barrel. Was thinking 8" initially but have been told that's too short. What are some thoughts? I've seen that Wilson offers an 11.3in in 1:8. Anyone use this setup?
 
#3
Re: 300 blackout sbr build questions

I believe the Daniel Defense SBR 300BLK uses a 10.3in barrel. The company stated they used several lengths of barrels and the 10.3 was the best suited for a variety of loads. No experience myself, just relaying what I've read.
 
#5
Re: 300 blackout sbr build questions

I have a 10" Noveske upper for mine and I'm happy with it, I wanted short but still have a little velocity with supersonic ammo.

If I had it to do again though I'd probably go with the 8" honestly. Just because I found that I don't really shoot supersonic as much as I thought I would(I always have the can attached). I've fired my dealer's 8" Noveske and I just love how short it is, really handy.
 
#6
Re: 300 blackout sbr build questions

I got Noveske 10.2" with Ops Inc model 12th and love it. I feed it with 220 SMK with A1680 at 10.6 gr or 208 a-max with the same powder charge with the same great result. It cycle perfect and the bolt locked up nicely. The rifle also runs good with supersonic round range from factory Remington 115 gr, 125 gr OTM; and handloaded 147 gr, 150 gr and 168 gr without any problem.
 
#8
Re: 300 blackout sbr build questions

My 8.2" Noveske barrel with my sdn6 runs flawless. I have not run anything but subs through. Shooting subs through a suppressed 8" barreled semi auto is just bad ass!
20120902205656941.jpg
 
#9
Re: 300 blackout sbr build questions

I have a 8" Satern barrel. If your shooting subs, 1000fps is 1000fps weather its from a 8" or a 12" barrel. I like my 8", its short, sweet, and easy to handle. Even with super, there is little difference in velocity. I also have a 16" Noveske, with supers there is only about 40fps difference between the 8" and 16" barrels.
 
#10
Re: 300 blackout sbr build questions

I got the Wilson 11" just because it was available at the time I was looking. it's very accurate with Hornady 225gr projos.

I am having cycling issues tho.... any ideas anyone? gas key is staked well, I reduced the buffer weight dramatically but it still short strokes super bad. I'm at about 1080 FPS with H110 powder. Pistol length gas tube running with suppressor. I have to stick with this powder as I have many pounds of it.

any help is most appreciated.
 
#11
Re: 300 blackout sbr build questions

I've got a Noveske 10.2" Noveske and an SDN-6. Runs subs and supersonic rounds without problems. Still at the early stages so I haven't put too many rounds through it. Probably 300-400. Working up loads and for accuracy and sound signature. Easier said than done in this environment... hard to find components. Does run dirty! You will have to double up on your cleaning and keep it well lubed.
 
#12
Re: 300 blackout sbr build questions

I've got a pistol (waiting on form 1) with an 8" Rock Creek barrel. I haven't shot it much, but it cycles just fine and i mostly use the PNW ammo.... waiting on the OTHER can to come back to run it and subs.

I saw no reason to go any longer than 8". with the can, total barrel length with still be below 15".
 
#13
Re: 300 blackout sbr build questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sagebrush</div><div class="ubbcode-body">I got the Wilson 11" just because it was available at the time I was looking. it's very accurate with Hornady 225gr projos.

I am having cycling issues tho.... any ideas anyone? gas key is staked well, I reduced the buffer weight dramatically but it still short strokes super bad. I'm at about 1080 FPS with H110 powder. Pistol length gas tube running with suppressor. I have to stick with this powder as I have many pounds of it.

any help is most appreciated.

</div></div>


H110 wouldn't cycle mine and stay subsonic... try AA1680
 
#17
Re: 300 blackout sbr build questions

Go 8"s. 8"s being too short sounds like an uninformed statement to me especially if you are shooting subs. The 300blk doesn't benefit from longer barrels the way other cartridges do. It is truly a short as hell semiauto/fullauto sbr cartridge.
 
#18
Re: 300 blackout sbr build questions

Just put my Seekins Lower and Mega monolithic upper together with the Noveske 10.2"bbl. I have the Pistol Kit on it now and running the CompM4s with it. No supressor yet but it functions well. Killing Coyotes this weekend with it.
 
#20
Re: 300 blackout sbr build questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sagebrush</div><div class="ubbcode-body">do you guys thing a low mass bolt carrier may fix my cycling issues? low mass hammer? </div></div>

Are you running a can? What gas system do you have?
 
#21
Re: 300 blackout sbr build questions

Running a 8.2" Noveske upper on Noveske lower, SAS Arbiter can and it runs subs flawless. Built it with a heavy buffer as per Noveske's full rifles and she is 100% so far. I have been running the SWAmmo 220g SMK sub loads. I plan on moving to 175g SMKs when I run out of the SW ammo as someone put up load data on here that cycles reliably with the same setup.
Good luck on your build, they are a blast!
 
#22
Re: 300 blackout sbr build questions

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sagebrush</div><div class="ubbcode-body">I got the Wilson 11" just because it was available at the time I was looking. it's very accurate with Hornady 225gr projos.

I am having cycling issues tho.... any ideas anyone? gas key is staked well, I reduced the buffer weight dramatically but it still short strokes super bad. I'm at about 1080 FPS with H110 powder. Pistol length gas tube running with suppressor. I have to stick with this powder as I have many pounds of it.

any help is most appreciated.

</div></div>

H110 is the problem, try 1680 or Lil' Gun.
 
#23
Azprc said:
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sagebrush</div><div class="ubbcode-body">I got the Wilson 11" just because it was available at the time I was looking. it's very accurate with Hornady 225gr projos.

I am having cycling issues tho.... any ideas anyone? gas key is staked well, I reduced the buffer weight dramatically but it still short strokes super bad. I'm at about 1080 FPS with H110 powder. Pistol length gas tube running with suppressor. I have to stick with this powder as I have many pounds of it.

any help is most appreciated.

</div></div>

H110 is the problem, try 1680 or Lil' Gun.
Click to expand...

I am using 1680 with Amax 208 without any problem around 1050 fps. The H110 if I am not mistaken is for supersonic. I tried that with Vmax 110 and did not see any problem at all.
 
#25
I have a Gemtech Quicksand can and asked them for their recommendation. They say it depends on the twist rate of your barrel as to how short you can go. My barrel on my 300 is a 1 - 8" twist. Gemtech says you want the length to be the same as the twist rate so I am gonna have mine cut to 8". Hope that helps.
 
#26
sagebrush said:
oops, my bad. just checked my load data and I WAS using A1680

10.8gns 225hornady projo 2.02 OAL

feeds fine manually

now I'm befuddled
Click to expand...
I see all kinds of stuff out of whack . 10.8 grains of 1680 will put you super sonic plus 2.02 over all length is very short . 2.20 would be a more useable length. , If you are not using a factory crimp die you should it will help . I dont know if this helps or not but I load the 225 grain subs with 10.2 grains of 1680 and average 1020fps out of my 16 inch smith and wesson and pretty close to the same velocity out of my 8.5 inch pistol build . both will cycle with or without the suppresor. the h110 should work great with the 110 v-max.
 
#27
I went with the AAC 9". Sort of in between the selections mentioned. Figured that AAC would put out barrels that would go best with the cartridge they developed. Haven't had a chance to test mine yet.
 
#28
I hope I may chime in.
I'm rebuilding my AR15 currently and considering the .300 blk with supersonic loads for hunting.
1. Does anyone use Hornady factory loads (110gr V-Max) in his and if so, what velocities are you getting with which barrel lenght?
2. Does anyone run a 14.5" barreled carbine gas system with rifle buffertube and buffer? Does it work reliably?

Thanks in advance.
 
#29
Cuga said:
I hope I may chime in.
I'm rebuilding my AR15 currently and considering the .300 blk with supersonic loads for hunting.
1. Does anyone use Hornady factory loads (110gr V-Max) in his and if so, what velocities are you getting with which barrel lenght?
2. Does anyone run a 14.5" barreled carbine gas system with rifle buffertube and buffer? Does it work reliably?

Thanks in advance.
Click to expand...
I have a 16 inch carbine with carbine gas , buffer and spring I dont see the point of a rifle tube and buffer with a carbine gassed gun .
I shoot hornady v-max 110 loaded to 2250 fps I run the load on up to max and was getting 2340 fps but backed off to the 2250 fps load . it groups much better in all 3 of my rifles and the brass looks much better . I would suspect factory ammo to be with in the ranges I stated.
 
#32
Mine is an 8" I went as short as possible since that is the point of the 300blk. My barrel is a 1-8 twist couldnt find the 1-7 at the time. Mine shoots hand loaded smk 220 with 1680 powder to around 1 1/2" at 100yds I am using a tbac 30ba suppressor. The gun is so much fun. GO SHORT!!!
 
#33
I built my 300 last year using a 14.5 Black Hole Armament with 8.5 twist. I have carbine gas and car buffer and spring. I did drill out the gas port to optimize the sub use, but haven't worked too hard on sub loads yet (we don't get to have cans in the Peoples Republic of Kalifornia). For supersonic, I am loading 17.7 gr of Lil' Gun behind 147gr pulldown surplus bullets. They are giving good results at an average of 2100 fps. I picked up some 245gr FPRN lead bullets from Missouri Bullet Company to start my sub-sonic work up. According to Greenhills formula the 245gr should be good in the 8.5 twist. They sell them as 300 Blackout Bullets and have optimized the alloy to achieve a 20 Brinell to minimize fouling ( and they were inexpensive too).
 
#34
Anybody know where to find barrels in stock? Preferably under $250?

Also, you guys running a 14.5 with pinned devise, are you doing brakes or flash sup? Probably not that much flash out of a 14.5 huh?
 
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