300 BLK – CMMG 8″ Barrel Break-In and Accuracy Tests

I'm going to try a Faxon 7.5 with 5R rifling.

Much better groups Johnny!

Hello @ Johnny's Reloading Bench . Did things improve with the cmmg barrel? Im looking at buying a complete upper in auction that ends in a 3 days and it has this barrel. Looking for mainly suppressed subsonic 220 grains. Looks like everyone is recommending 10.5 inch barrels and wondering if thats the direction I should go.Also is 1/8 twist good for a 10ish inch barrel for sub loads? Thanks in advance

Using this many different grain slugs and different powders why aren't you doing a +.2 grains as well as -.2 grains powder for all the way though the high low as stated per manual for every different grain slug? Changing the powder grain from where i started helped out a ton for my .75 grain 223 had tightened my groups from 2.5 moa down to 1.0 moa. Play around with light and hot rounds with the same powders and slugs.

Great vid it helped make up my mind ,I will spend a little more money for a Daniel defense.

Bcm barrel or a noveske barrel? Might do better

I have this same exact barrel I picked up at a gun show. It was dead accurate with my first reloads ever. Your videos taught me and now I'm ready to contribute. I'll attempt to duplicate whatever loads you do and see the results. If there is a quality control issue then you should be able to get a free barrel. CMMG is good quality. I won't have a bunch of time due to work and school but on my relaxation time, I'll do some loading. I don't have a silencer, and I'm using a KAK micro flashcan. I can still do subsonic and chrono them in though.

sigh I feel your pain. Load development like these takes me days to complete and they get expensive.

My 16" UltraMatch likes 208grn ELD-M/N120 (quarter sized group @ 75yd) but that combo can get pricey. So I'm gonna step to CFE BLK and hope I can still shoot it accurately.

Also thinking about going 175gr ELD-M or 175gr Sierras with CFE BLK for light subsonics to cut down on costs. Do you think those lighter subsonics will be louder than what I'm used to? Sucks I can't find any subsonic data for 175gr bullets… it looks like I gotta experiment down the velocity readings.

Thanks for making videos like these.

Still not sure why you didnt get a ballistic advantage or faxon barrel

Be sure to christen it with some cast boolits soon!

This barrel shooting faster than the Ultramatch shouldn't be a surprise. It has a smaller gas port, giving more gas to push the bullet. That is confirmed with the no bolt lock back. Too bad it didn't shoot any better.

I love your load development series, keep it up! It surprised me that you went with a CMMG barrel as opposed to say a Noveske considering you already had a high end Ranier. Are you considering trying any others?

I'm sure you've been asked this a buttload of times, but what chrono are you using, Sir Shoots-A-Lot?

Surprised to see so many different powders used. I figured you'd stick with 296 & 1680 respectively.

Its an 8inch Barrel. But nice to know the high-end barrel is on par with a mid priced barrel. I am a Faxon guy. My 16inch 300blk Faxon is sub Moa at 50yards with your load data. At a 100yards it 1.5 Moa but I only have an 1-8 power scope and its a little hard to see. Im getting older. If I get a 14x or 16x scope I think it will tighten my groups at 100yards.

Great video, when you gunna pull out the 6.5 grendel again! haha

Maybe try a SEEKINS Precision 8 inch barrel, thats what I run and its sub MOA all day long with 220gr SMKs. 11.6gr if 1680. I also run a Thunder Beast Arms 7 inch Ultra suppressor direct thread. Keep up the good work man. Best 300blk info on youtube!

Johnny, Just my thought, I believe that you are experiencing an chambering thing. also.. a 7 inch barrel is all I had on my Bowen .44 mag Ruger conversion silhouette pistol and that gun was used to fire at 200 meters. So, my point is fitting. You may have a fitting thing that isn't agreeing with the bolt face. Anytime you want supreme accuracy you have to make Shure things are tight as a drum. the smallest fitting problem is amplified as accuracy and consistency. The reason I bring up pistols is because any .45 auto match pistol has to go through the hands of a good pistolsmith, I believe your AR SBR is reacting due to that issue.. I really don't think you can do much about it other than send it to be fitted. all in all you still put out the best content on you tube and it is much appreciated by new and old shooters alike. Keep up the good work. Dave.

Have you reloaded with the Sierra 135gr HPBT MatchKings in your 300blk? Ive got some in route and Im looking forward to trying them.

CMMG is a good brand for basic AR builds, however for quality and fair priced MOA barrels use WOA, Balistics Advantage premium series, and Faxon. Just my 2 cents

I have a video series on a 300 blackout pistol build using a 10.5 inch Faxon barrel that I got from Right to Bear Arms. I was inspired by your videos to start making a few of my own. I only shoot subs through it, and have another build I use for Supers. Just easier for me, and they both are MOA with loads I developed with your help. Thanks.

As soon a you switched to the can… groups WAY opened up.

Johnny… SHOTDOG and I agree… i suspect the can… for the shotty groups.

Who in the hell gave a thumbs down what a jackass Great vid Johnny

Thanks for the video, Sir. Sad to see you disappointed, but…. that kind of stuff happens. 10.5" sure gets better velocities but I strongly urge you to try something of a higher quality ( and sadly .. price ) I'm currently waiting for my new barrel because I got a bit disappointed of the groups my 10.5 KAK value line does. Velocities are good ( 2200 with a zmax is nothing to sneeze at ) and I'm happy with them, but accuracy is another story…. 2 MOA at best, so what I've decided to do is get a 16" Odin Works and if the accuracy is ok, I'll start cutting it down to either 9-10.5 and keep it as a pistol or 14-ish + welded QD mount and put it on a rifle lower. I'm to the point where I want to see what a slightly more expensive barrel has to offer because going back just feels terrible. Keep the great videos coming and thanks again for sharing your experience.

Your shooting loads you developed for a different barrel. In order to accurately judge it you should try redeveloping those loads for that barrel.

Do an actual load development work up for a couple of the bullets?

are you going to try those coated cast 265 gr ds specials?

10.5" barrel sounds interresting though

i thought for sure cfe blk would do well for that last sub group…who knows.

I don't understand all this 300 blackout crap. Are there any military's in the world using this round? Nothing but a marking ploy to sell more stuff to us gun nuts

I was hoping to see the Palmetto Projectiles to see if you get any leading in this barrel…Also any difference without the silenceco?

WTF!!!!!! you need to trash that gun and scope ,, start over

Johnny, just my thought, but i would do the same test without the can

retighten your barrel nut to torque specs; loosen and repeat this process three times. It looks like the threads might have stretched. Also check your bolt face depth to make sure it is in spec as well.

I think you just need to work up the loads a little bit, with different powder charges.

Barrel seems a bit short IMO to expect really good accuracy. Plenty good for close-in hunting though. Excellent for a home defense weapon with the silencer too.

Johnny, I'm a firm believer in not mixing different powders/bullet manufacturers when im trying to shoot groups. When you switch to a different powder the barrel has to refoul itself almost like a clean bore shot. The same with different bullet manufacturers use different copper which will take multiple shots or a cleaning to remove that copper. Your groups sucked, I'm not blaming it all on that but i think it was part of your problem.
Was the one 240gr flyer from transitioning from super to sub?

Love the vids man! A lot of guys I know who shoot 300blk with that barrel length have switch to the 10.5" due to the same results. May be that there is not enough length available to stabilize the bullets?

Surprised you didn't go with AAC's optimum length of 9".

what about rainier wedge

John why don't you bag up instead of the bipod? It might tighten things up a bit…
Good vid BTW…

I get 3 Jonny videos in a week. is it youtube birthday?

Maybe the new barrel will stabilize cast bullets better than the 8 1/2"?

Hi Johnny,

Than you for the video. As always – great one.
I consider you one of the best, if not the best, for "load development" videos/ channel out there.
Content, presentation and video quality – what else a viewer can ask for…

Thank you again,
Ariel

Great video as always we always have lots of good information on my personal experience I found that 10 and a half inch barrels seem to work the best

Your videos are incredibly helpful in working up loads for my 300Blk, thank you.

Johnny I love these 300 blk out videos but I would like to know if 308 butt kickin bullets would be a possible future series?