300 BLK - CMMG 8" Barrel Break-In and Accuracy Tests
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- เผยแพร่เมื่อ 22 ก.ค. 2017
- Testing a new CMMG 8" 300 Blackout barrel in my SBR upper.
UPDATED 09/27/2018 - All links have been removed to comply with TH-cam content policies.
www.patreon.com/reloading
Your videos are incredibly helpful in working up loads for my 300Blk, thank you.
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.
New to 300 blk thanks for the awesome data!!
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
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.
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.
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?
Surprised to see so many different powders used. I figured you'd stick with 296 & 1680 respectively.
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?
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.
I'ma look those up.
I am convinced that 300 blackout is just awful for accuracy. Doesn’t matter the load setup configuration I get about 2 moa accuracy out a factory Daniel defense 10.3 pistol. Ranging from 110 grain at about 1.5 MOA all the way to berrys 220 grain getting me about 2 moa. I’m fine with it though. It’s a self defense gun and hog smacker. Will get the job done at anything under 200 yards for hunting and will most certainly do the job for defensive distances.
As one poster said Id try re-torquing the barrel nut. I always found torque & loosen at least 4 times at 60 ft/lbs to seat the threads/nut whenever you change a barrel (especially if using a new nut) then final tightening at or above 60ft/lbs. The heavier end of the torque spectrum tightens groups in most AR platforms. Vertical stringing usually is an indicator of the barrel wanting more torque to better bed up to the action. But ultimately (and Unfortunately) the 300 Blackout is not an inherently precision accuracy round. I wouldn't go nuts chasing the holy grail of accuracy with a 300 blackout. Thrown down a short barrel and you further handicap it. The short dwell in pistol barrels is not favorable for stabilization in my experience and you get more flyers. This is supported by my 300's always shooting tighter groups through 14"-16" barrels at 100 yards. So with a 1:7 twist it will favor heavier bullets so the lighter bullets having flyers was no surprise (the good group with the Barnes 120 was a surprise) and that is probably not something a load "tweak" will fix. However, the vertical stringing with heavier bullets may be minimized with more barrel nut torque. So I d focus on heavier bullets and playing with that torque...and go back to the Rainier if it was more promising than the CMMG. P.S; I always had better groups with 1:8 with all bullets from 125 to 220 vs 1:7.
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... SHOTDOG and I agree... i suspect the can... for the shotty groups.
Much better groups Johnny!
Built 300 BLK with a BCA 8.5 ss barrel ,adj gas block CMC 2.5 lbs single stage trigger , Blue buffer spring , heavy spike Tactical buffer .Used a FF3 Burris .At 50 yards using cheap Remington 300 AAC 120 grain , I managed to group at .250 inch to .500 inch .Shooting off a 4x6 wood carpeted block , no bag .
I get 3 Jonny videos in a week. is it youtube birthday?
I would have really liked to see the same powder in each round powder is an extra variable and can really range on accuracy velocity ect and I didn't hear it mentioned that if the brass was all the same as well as reloading process or differences I think its your videos ive watched about crimps and stuff. In my Lyman Manuel it is saying that 1680 is usually the most accurate powder and I always hear of lapua as a top premium brand and it shows in your results. Also in order to really get down and see whats most accurate you would want to develop each load for best possible and then see where everything struggles and accels none the less very informative thankyou really hard to find happy mediums to get started in reloading and where i want to head with 300 blackout. So far for my 8.5" 1:8 im seeing the lighter the better So far im looking at these 125 grain bullets with 1680 powder to be that happy medium im looking for
Who in the hell gave a thumbs down what a jackass Great vid Johnny
Thumbs downs are still indicators of traffic, which still improves his ratings for youtube's push algorithm.
*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.
John why don't you bag up instead of the bipod? It might tighten things up a bit...
Good vid BTW...
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.
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 vid it helped make up my mind ,I will spend a little more money for a Daniel defense.
Do an actual load development work up for a couple of the bullets?
since you were using a bipod, should have just looked through the scope (POA) and adjust elevation+windage until POA is over POI
I think you just need to work up the loads a little bit, with different powder charges.
Have you reloaded with the Sierra 135gr HPBT MatchKings in your 300blk? Ive got some in route and Im looking forward to trying them.
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
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?
I think that's what I'm going to do. I will get a nice 10.5" barrel for this upper and make it my only test gun for 300 blackout. I am getting tired of shooting two guns for all the 300 blk vids anyway. Then I'll turn my 16" 300blk into a 22 Nosler or 6.8 SPC.
Johnny's Reloading Bench that would make the most sense. I went through the same situation 2 years ago... Gave up on 8" barrels. Went to a 10.5" and never looked back. I have 2 now one is a 7 twist and the other is an 8" twist. I shoot primarily 220 smk subs through a form 1 suppressor and will shoot 325 yds on steel. Love it!!!!
I have 2 300 blks, 16" & 10.5", 1/8 twist. On average, with subs, the 10.5" shoots 25 fps slower with the same loads. haven't compared supers due to lack of interest. I hardly use the 16", it's just a test bed mostly. The 10.5" I built for hunting. I do believe (after the buttload 300 short barrel vids i've watch) that you need min. of 9" to really stabilize the bullets well and you need 1/7 twist at that length. of course this my opinion only. "they" say the powder burns up in 8"... I know this is BS because I handload. No blanket statement can cover all different types of powder. Shorter barrels like those are great cqb weapons but lacks the stability for ranged shooting. I don't like bragging, and certainly not over one sample, but... I have had great success with the ar stoner 10.5" ss barrel. maybe I just got the good one, or maybe (they, whomever) had already figured out what's needed to make a great barrel. Midway has a great return policy, if you don't like it, send it back...... been thinking a lot about the 6.8 spc as of late. A 7mm AR, what could be wrong with that. 22 Nosler... just get a 20" barrel 5.56 if you want that extra 300 fps..
I was hoping to see the Palmetto Projectiles to see if you get any leading in this barrel...Also any difference without the silenceco?
What you need is a 10.5" mega arms 1 in 8" barrel. Good shooters
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
That’s basically what I’m realizing, liking criterion as well.
Pick a round to work up a super round and a round to work up sub. I'd go ELD 208 grain or SMK 200 grain and work up loads and then SMK or hornady for a super as well.
what size rail did you use for your build?
I'm going to try a Faxon 7.5 with 5R rifling.
What size rail is that on the 8” barrel? I only ask cause I love the look of the riffle and would like to build one myself
cmmg rkm 7in rail.
I THOUGHT YOU SAID 1680 AND 300BLK WERE YOUR GO TO POWDERS FOR SUBSONIC LOADS YOU NEED TO WORK WITH THEM TO GET YOUR TIGHTEST GROUPS I NEED INFO ON THE 220 SMK I THINK IT IS GREAT YOU ARE TESTING SO MANY DIFFERENT POWDERS AS I DO NOT HAVE THE ABILITY TO DO SO MYSELF BUT READING THROUGH SOME FORUMS I HAVE READ THAT LIL GUN IS ALSO A GOOD CONTENDER FOR SUBSONIC LOADS ALL THE 200 GRAIN UP BULLETS WILL BE HELPFUL
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?
I think that's what might have happened. That 240 went transonic and destabilized. Good call.
I agree about mixing powders and bullets, but I usually only worry about that when I am really narrowing down a load and need to split hairs.
I always think this too when I see youtube accuracy tests. I know doing it right makes it a long process and almost unfeasible for filming/editing but I have found the results to be more than splitting hairs. Its time to do harminics testing too with that being a new barrel.
Your shooting loads you developed for a different barrel. In order to accurately judge it you should try redeveloping those loads for that barrel.
Still not sure why you didnt get a ballistic advantage or faxon barrel
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 realize this is an older video, but I'm hoping you'll see this comment. Wondering if you've found an accurate, 1 moa, pistol length 300aac barrel. Appreciate you putting your vids up.
sail2awe I have a Noveske 10.5 1-7 twist. It shoots 1 moa or less with Barnes factory ammo at 100 yards
@Magus Joseph 110
Great video, when you gunna pull out the 6.5 grendel again! haha
Maybe the new barrel will stabilize cast bullets better than the 8 1/2"?
That's what I'm hoping! We'll see.
Johnny's Reloading Bench so did it?
I'm sure you've been asked this a buttload of times, but what chrono are you using, Sir Shoots-A-Lot?
In this video I was using a Caldwell Ballistic Precision. It's a pretty cheap unit that has worked well for me. I have heard of people having problems getting their app to work with certain phones. It works well with my Ipad so that's what I generally use to interface with it.
I also have a Magnetospeed V3 chronograph that I use in a lot of videos. If I was going to spend a lot of money on a chrono these days it would be a Labradar.
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.
Why does 300blk suck so bad at grouping I really want to build one for hogs but I have yet to see a group that is worth the risk have you been able to find anything that is sub moa even at 16inch
what about rainier wedge
What scope are you using on this rifle?
(imo) free volume of suppressor maybe too small, allowing gasses to overtake bullet and disrupt flight in the rush to exit muzzle....as gases are traveling faster and need room to expand. (too many baffles or needs larger chamber at exit).
Bcm barrel or a noveske barrel? Might do better
What would a faster twist do?
Why are you not using 9 or 10 inch twist barrel with the longer bullets? I watch your videos and short bullets work well with 7 inch twist barrel. You can’t have a barrel that shoots 1 inch groups with short and long bullets... The military would have adopted it. I wish you would point this out on your vids. I like them and I not an expert. I just think you need 2 uppers (one 7 inch twist and other 9 inch) and make a vid compare them. Thank you for your work.
Johnny, just my thought, but i would do the same test without the can
If it can't shoot with a can then it's worthless to me.
i agree, but maybe it's just "that can" , another brand may work, i just brought it up cause it seemed to shot pretty good with out it!
As soon a you switched to the can... groups WAY opened up.
Kind of weird, can usually helps with accuracy. I guess that's not always the case... sub sonics are definitely not know for small groups
I wish I had a 8 incher !!!!
What hand guard is that?
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.
Huge velocity hit as well. I think I am going to get a 10.5" barrel next. Hopefully we see better accuracy and pick up some serious velocity as well.
Johnny's Reloading Bench i have trouble seeing a 200+ grain bullet stabilizing when BARELY doing 1 revolution in a barrel. The 10.5 sounds like a good idea to me.
I have a 10.3 Ballistic Advantage barrel, and can tell you that it shoots better than i can. If you're going to spring for another barrel, I'd take a look at those.
Surprised you didn't go with AAC's optimum length of 9".
Try the same test without the muffler and see what happens
I got my ballistic advantage 300 blk barrel for 70 bucks off ebay
To me you had better grouping with better ammo...... stay with that type of ammo for the time being
Johnnie,
"Make for a decent platform to test from"
Your words....!
I hope your having fun. Looks like it.
However, it looked to me like you were just making noise.
When I see multiple bullets, bipods, various seating depths, all kinds of different powders being used in
your "decent platform" I have to say you might want to read up on bench rest load development techniques.
Yes I know this is not a benchrest gun and you probably want it for self defense or as you said deer hunting but why take the shotgun approach?
Sorry for the harsh assessment but I don't like seeing guys wasting their time or money.
Further for those just getting starting in reloading
DON'T use Johnnie's methods
Just get 12 inch