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[ARCHIVED THREAD] - Thoughts on the CMMG Guard? (Page 19 of 25)
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Like others have said, the enlarged ejection port may or may not be needed. But if you are set on getting one, this will do. No need to get CMMG's RDB stripped upper for too much money.
https://www.andersonmanufacturing.com/product/andersons-458-socom-stripped-upper-receiver/ https://www.primaryarms.com/anderson-mfg-458-socom-stripped-upper-receiver |
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Quoted:
Found this thread on a different page. Tough going through the 18 pages. But I want to build a dedicated 9mm AR-9. I want to get the CMMG RDB BCG and barrel combo, but it says that I need a widened ejector port. Don't really want to spend the $1500 on the complete banshee. Can i use an Areo Precisions M4E1 upper with the radial delay blowback BCG? Also anything special I need to get to compensate for the BCG? Lighter spring? https://www.dropbox.com/s/k7vxw49wknz1cci/filed_ejection_port.jpg?dl=0 |
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Quoted: My M4E1 upper works just fine. I did enlarge the ejection port. I did not try it before enlarging. It took an hour or two with a hand file to enlarge. https://www.dropbox.com/s/k7vxw49wknz1cci/filed_ejection_port.jpg?dl=0 |
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So in this thread: https://www.ar15.com/forums/armory/Straight-blowback-is-100-unacceptable-imo/48-500494/&page=5
I mentioned how I would hope that CMMG would sell their bolts, springs etc separately and 'bmo419' mentioned that Optics Planets has a spare parts kit for sale. https://www.opticsplanet.com/cmmg-inc-mkg-mkgs-complete-bcg-repair-parts-kit.html?_iv_code=2CM-ABA-CBCGPKT-45AFF2A They list 2 models. One is listed as .45ACP while caliber is not specified on the 2nd one but appears to be 9mm from the part number. What I thought was even more interesting is that if you click on the image to zoom in which I've pasted below for everyone's convenience, you can see it is using the new rounded ejector that we are seeing in the new .40SW bolt. So just like how CMMG initially only used their proprietary ejector spring in the .45 ACP then later made it standard in the 9mm and now .40SW, I'm wondering if they are now discovering that the rounded ejector has improved ejector spring life somehow like I've seen and are now supplying the .45ACP and 9mm with rounded ejectors?  ETA: I just sent an email off to CMMG inquiring about details on the rounded ejector. |
| Shoot, I should have looked at the 9mm bolt I received with my builders kit last week. I don't have it in front of me because the bolt face wasn't finished properly and was missing finish so I contacted CMMG and they are swapping it out for me no problem. Should have the new BCG in today straight from CMMG. I'll check the ejector when I get it. |
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Quoted:
ETA: I just sent an email off to CMMG inquiring about details on the rounded ejector. On a related note... @amphibian, what's your current round count with the 9mm/.40 bolt combo? Any issues thus far? I'm curious to see if the rounded ejector is truly helping out with spring life. |
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Quoted:
@amphibian Here is the 9mm replacement BCG I just received today straight from CMMG. https://i.imgur.com/880m7ucl.jpg They didn't answer my question regarding the reasoning for the rounded ejector....if it increased spring life or was done to influence the ejection pattern or what....so I asked again. |
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Quoted: Interested to see what they have to say. On a related note... @amphibian, what's your current round count with the 9mm/.40 bolt combo? Any issues thus far? I'm curious to see if the rounded ejector is truly helping out with spring life. Again, when did my modified 5.45 bolt (with angles similar to the .40SW bolt), the spring couldn't even make it past 30 rounds. |
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Quoted:
Just got this back from CMMG, "The round ejector will be in the 40S&W and the 45ACP, but not in the 9mm. it will continue to use the same ejector (standard 5.56)" They didn't answer my question regarding the reasoning for the rounded ejector....if it increased spring life or was done to influence the ejection pattern or what....so I asked again. "The rounded ejector was just created for better function in the 40S&W, from what I'm told." Kinda vague....I guess I'll just continue testing it and see how it goes. |
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Does the CMMG bolt work in a standard AR bolt carrier?
If not, I assume the CMMG BCG would function as a "mil sped" BCG since it works in standard uppers (?). Thinking of getting a Gibbz G4 side charging upper. Says that it works with all mil-spec BCG's (so the BCG isn't modified to fit a charging handle.....) so that should work with a CMMG BCG/barrel combo? Or I could buy the bolt part kit mentioned/photo above and put it in a "normal" AR BCG? Gibbz G4 CMMG BCG/Barrel combo |
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Quoted:
Does the CMMG bolt work in a standard AR bolt carrier? Quoted:
Does the CMMG bolt work in a standard AR bolt carrier? If not, I assume the CMMG BCG would function as a "mil sped" BCG since it works in standard uppers (?). Thinking of getting a Gibbz G4 side charging upper. Says that it works with all mil-spec BCG's (so the BCG isn't modified to fit a charging handle.....) so that should work with a CMMG BCG/barrel combo? Or I could buy the bolt part kit mentioned/photo above and put it in a "normal" AR BCG? See posts by, 'StealthyBlagga' "I used the Gibbz 9mm upper. The issue is that the key used on the Guard bolt carrier interferes with the Gibbz cam pin. I am fortunate to live close to Gibbz, and they looked at it for me. All it took was to cut off the front portion of the key with a Dremel cutoff wheel. I will post a photo when I get a moment." "Sorry it took me a while to get around to posting photos on my Guard bolt carrier modified to work in my 9mm Gibbz upper. Here you go: " Looks like he is using the Guard carrier, chopped down the key and used a Gibbz cam pin.  Here you can see the cam pin path of the Guard carrier. Just look at any standard 556 carrier and you can tell the path is different. 
You may still want to read through that thread as some are stating about doing some fitting as well. Some mentioned about a break in with the CMMG Guard but I never really noticed that. However, I was tinkering w/ various buffer/springs/etc when I first got my Guard so I'm not sure about the break in. I would have thought we would hear more about that as I think quite a few people have gotten CMMG RDB setups since then and I don't recall seeing many posts about requiring a break in. |
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I picked up a CMMG MkG-45 Guard early this year from GAG, it had a very low serial #. I mounted a new to me Holosun 510c and off to the range, it ran well on ball cartridges but chokes on HSTs.
While cleaning I noticed there was no spring on the bolt, I thought I had seen a spring in photos of the bolt on this forum. The manual that came with the Guard showed no spring but a newer manual from CMMGs site showed a "bolt alignment spring". I emailed CMMG about it and they replied quickly, he said they made changes at serial# 100 and send it back. It was returned to me quickly, I know they replaced the bolt and carrier not sure if they did anything with buffer and spring. The new bolt had the spring and I noticed a rounded ejector. It now feeds HSTs from 13 round Glock mags fine but but won't feed them well from the Kriss mag extension. |
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Welp I'm loving this CMMG 8" 9mm guard so far. Finished the build on Friday and ran my first ever competition, IDPA PCC, with it this morning.
Bought the 8" 9mm builders kit and installed it on a PSA standard mil spec upper. I did NOT enlarge the ejection port and so far, through 450 rounds, I have had zero issues. Also should mention that I'm running it with a mill spec lower and the endomag/ cmmg 9arc mags. Wonderful combination. I should also add that it does not seem to like the 150gr offering of Federal Syntech. Throws about every third round low and right. This ammo was very accurate in another of my 8" PCCs though. 124gr S&B RN seemed to be dead on though only shot 50 rounds of it compared to the 400 of syntech. |
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Quoted:
Does any have any accuracy reports with their 9mm 8" barrel? I wasn't too impressed when I put mine on a bench and rest today. I am by no means an expert bench shooter. But for me, it is more than accurate with range ammo for my needs. |
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Quoted: My CMMG RDB barrel was cut down by ADCO from 16" to ~11" and lightweight reprofiled. With my 115gr FMJ reloads, @ standard factory 9mm 115gr velocities, I can get about 2.5" at 50 yards with a red dot from a bench front rest. When I've tried X-treme Bullets (Freedom Munitions) 115gr copper plated or 147gr copper plated reloads and remanufactured, accuracy goes to shit. I don't this it is the barrel, I think it's the ammo because my other Olympic Arms 9mm PCC was the same, it hated Freedom Munitions plated ammo at longer distances. FMJs group the best in my experience so far. I bought some mixed 115gr FMJ pulldowns/seconds projectiles, and loaded them the same as the others and they grouped the same 1.25" at 25 yards or 2.5" at 50. I haven't tried for accuracy with factory ammo yet. I am by no means an expert bench shooter. But for me, it is more than accurate with range ammo for my needs. I am by no means an expert either but I know I'm a better shot than what I was getting out of the setup yesterday. I can easily shoot sub moa groups at 100 yards with my 9x scoped 5.56 rifle and sub 2 moa groups at 50 yards with a 2moa rds setup 5.56 rifle without magnification. This is with factory loaded Frontier 77gr rounds and 5 shot groups off a bipod or rest. Yesterday I tried 4 different factory 9mm loads in the CMMG, using a bench and rest, because when I zeroed the rifle quickly on Friday, before my match, I wasn't seeing good consistency but was just shooting off the mag. I shot S&B 124gr RN, Blazer Brass 124gr RN, Federal Syntech 115gr RN, and Federal Syntech 150gr FN. All groups were shot at 20yrds. First four groups were 10 shot groups using my new Holosun HS510c(2moa dot) and Holosun 3x magnifier. Rifle also has a Geissele G2S trigger. S&B 124gr RN: 2.3" or 11.12moa Blazer Brass 124gr RN: 2.63" or 12.55moa Federal Syntech 115gr RN: 2.65" or 12.64moa Federal Syntech 150gr FN: 3.27" or 15.62moa Next I decided to remove the 3x magnifier and just shoot with the 2moa red dot. This time I chose two rounds and only did 5 shot groups. S&B 124gr RN: 2.02" or 9.66moa Federal Syntech 150gr FN: 1.64" or 7.84moa Finally I zeroed the red dot based off the last 5 shot group of Syntech 150 and then put the 3x magnifier back on to shoot one last 5 shot group. Federal Syntech 150gr FN: 2.33" or 11.12moa 
Now I can't 100% rule out that the optic is not the issue since its brand new. But it doesn't seem like the zero is grossly moving around. More so the rifle is just consistently shooting large groups. If I was getting 1-1.5" groups at 20-25yrds I think I'd be fine with that. But not this. |
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Quoted:
I have 2 of the original CMMG 9mm bolts. Is it worth contacting them for replacement? For 9mm, the early ones were using 556 extractors and then later they changed them. I have this documented here: http://c3junkie.com/?page_id=1077 The early ones were also using 556 ejector springs and later went to the same proprietary ones they use in the .45 and .40. I have this documented here: http://c3junkie.com/?page_id=954 If your CMMG RDB is working fine, don't bother. If you are having occasional issues where the extractor doesn't hop over the rim of the case, maybe you have the early extractor (standard 556). If you are having stovepipes and/or failures to eject, maybe you have a standard 556 ejector spring. The proprietary ones are .003 thicker. |
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Quoted: Thanks for the response. I am by no means an expert either but I know I'm a better shot than what I was getting out of the setup yesterday. I can easily shoot sub moa groups at 100 yards with my 9x scoped 5.56 rifle and sub 2 moa groups at 50 yards with a 2moa rds setup 5.56 rifle without magnification. This is with factory loaded Frontier 77gr rounds and 5 shot groups off a bipod or rest. Yesterday I tried 4 different factory 9mm loads in the CMMG, using a bench and rest, because when I zeroed the rifle quickly on Friday, before my match, I wasn't seeing good consistency but was just shooting off the mag. I shot S&B 124gr RN, Blazer Brass 124gr RN, Federal Syntech 115gr RN, and Federal Syntech 150gr FN. All groups were shot at 20yrds. First four groups were 10 shot groups using my new Holosun HS510c(2moa dot) and Holosun 3x magnifier. Rifle also has a Geissele G2S trigger. S&B 124gr RN: 2.3" or 11.12moa Blazer Brass 124gr RN: 2.63" or 12.55moa Federal Syntech 115gr RN: 2.65" or 12.64moa Federal Syntech 150gr FN: 3.27" or 15.62moa Next I decided to remove the 3x magnifier and just shoot with the 2moa red dot. This time I chose two rounds and only did 5 shot groups. S&B 124gr RN: 2.02" or 9.66moa Federal Syntech 150gr FN: 1.64" or 7.84moa Finally I zeroed the red dot based off the last 5 shot group of Syntech 150 and then put the 3x magnifier back on to shoot one last 5 shot group. Federal Syntech 150gr FN: 2.33" or 11.12moa https://i.imgur.com/K1Q35jXr.jpg Now I can't 100% rule out that the optic is not the issue since its brand new. But it doesn't seem like the zero is grossly moving around. More so the rifle is just consistently shooting large groups. If I was getting 1-1.5" groups at 20-25yrds I think I'd be fine with that. But not this. |
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Quoted:
For the 9mm, CMMG is not changing the ejector design...only the .45ACP and the new .40SW use the rounded ejector. For 9mm, the early ones were using 556 extractors and then later they changed them. I have this documented here: http://c3junkie.com/?page_id=1077 The early ones were also using 556 ejector springs and later went to the same proprietary ones they use in the .45 and .40. I have this documented here: http://c3junkie.com/?page_id=954 If your CMMG RDB is working fine, don't bother. If you are having occasional issues where the extractor doesn't hop over the rim of the case, maybe you have the early extractor (standard 556). If you are having stovepipes and/or failures to eject, maybe you have a standard 556 ejector spring. The proprietary ones are .003 thicker. |
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Quoted:
Thanks for the response. I am by no means an expert either but I know I'm a better shot than what I was getting out of the setup yesterday. I can easily shoot sub moa groups at 100 yards with my 9x scoped 5.56 rifle and sub 2 moa groups at 50 yards with a 2moa rds setup 5.56 rifle without magnification. This is with factory loaded Frontier 77gr rounds and 5 shot groups off a bipod or rest. Yesterday I tried 4 different factory 9mm loads in the CMMG, using a bench and rest, because when I zeroed the rifle quickly on Friday, before my match, I wasn't seeing good consistency but was just shooting off the mag. I shot S&B 124gr RN, Blazer Brass 124gr RN, Federal Syntech 115gr RN, and Federal Syntech 150gr FN. All groups were shot at 20yrds. First four groups were 10 shot groups using my new Holosun HS510c(2moa dot) and Holosun 3x magnifier. Rifle also has a Geissele G2S trigger. S&B 124gr RN: 2.3" or 11.12moa Blazer Brass 124gr RN: 2.63" or 12.55moa Federal Syntech 115gr RN: 2.65" or 12.64moa Federal Syntech 150gr FN: 3.27" or 15.62moa Next I decided to remove the 3x magnifier and just shoot with the 2moa red dot. This time I chose two rounds and only did 5 shot groups. S&B 124gr RN: 2.02" or 9.66moa Federal Syntech 150gr FN: 1.64" or 7.84moa Finally I zeroed the red dot based off the last 5 shot group of Syntech 150 and then put the 3x magnifier back on to shoot one last 5 shot group. Federal Syntech 150gr FN: 2.33" or 11.12moa https://i.imgur.com/K1Q35jXr.jpg Now I can't 100% rule out that the optic is not the issue since its brand new. But it doesn't seem like the zero is grossly moving around. More so the rifle is just consistently shooting large groups. If I was getting 1-1.5" groups at 20-25yrds I think I'd be fine with that. But not this. Quoted:
Quoted: My CMMG RDB barrel was cut down by ADCO from 16" to ~11" and lightweight reprofiled. With my 115gr FMJ reloads, @ standard factory 9mm 115gr velocities, I can get about 2.5" at 50 yards with a red dot from a bench front rest. When I've tried X-treme Bullets (Freedom Munitions) 115gr copper plated or 147gr copper plated reloads and remanufactured, accuracy goes to shit. I don't this it is the barrel, I think it's the ammo because my other Olympic Arms 9mm PCC was the same, it hated Freedom Munitions plated ammo at longer distances. FMJs group the best in my experience so far. I bought some mixed 115gr FMJ pulldowns/seconds projectiles, and loaded them the same as the others and they grouped the same 1.25" at 25 yards or 2.5" at 50. I haven't tried for accuracy with factory ammo yet. I am by no means an expert bench shooter. But for me, it is more than accurate with range ammo for my needs. I am by no means an expert either but I know I'm a better shot than what I was getting out of the setup yesterday. I can easily shoot sub moa groups at 100 yards with my 9x scoped 5.56 rifle and sub 2 moa groups at 50 yards with a 2moa rds setup 5.56 rifle without magnification. This is with factory loaded Frontier 77gr rounds and 5 shot groups off a bipod or rest. Yesterday I tried 4 different factory 9mm loads in the CMMG, using a bench and rest, because when I zeroed the rifle quickly on Friday, before my match, I wasn't seeing good consistency but was just shooting off the mag. I shot S&B 124gr RN, Blazer Brass 124gr RN, Federal Syntech 115gr RN, and Federal Syntech 150gr FN. All groups were shot at 20yrds. First four groups were 10 shot groups using my new Holosun HS510c(2moa dot) and Holosun 3x magnifier. Rifle also has a Geissele G2S trigger. S&B 124gr RN: 2.3" or 11.12moa Blazer Brass 124gr RN: 2.63" or 12.55moa Federal Syntech 115gr RN: 2.65" or 12.64moa Federal Syntech 150gr FN: 3.27" or 15.62moa Next I decided to remove the 3x magnifier and just shoot with the 2moa red dot. This time I chose two rounds and only did 5 shot groups. S&B 124gr RN: 2.02" or 9.66moa Federal Syntech 150gr FN: 1.64" or 7.84moa Finally I zeroed the red dot based off the last 5 shot group of Syntech 150 and then put the 3x magnifier back on to shoot one last 5 shot group. Federal Syntech 150gr FN: 2.33" or 11.12moa https://i.imgur.com/K1Q35jXr.jpg Now I can't 100% rule out that the optic is not the issue since its brand new. But it doesn't seem like the zero is grossly moving around. More so the rifle is just consistently shooting large groups. If I was getting 1-1.5" groups at 20-25yrds I think I'd be fine with that. But not this. |
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Quoted: Yeah. At 20 yards I'd expect tighter groups than that. That's horrible. Check your barrel nut torque, and torque to specs. Also, check your crown and muzzle device. If the crown is damaged/burred, that could be throwing your rounds out. If your muzzle device is in the way, or touching the rounds on their way out, that would also show poor accuracy. Take the muzzle device off and check accuracy. And lastly, swap your optic out for another known working one, or run some irons to make sure it isn't the optic. The upper is a 8" CMMG Guard barrel + BCG. A PSA Upper and a cheaper free float 7" handguard. This exact upper and handguard was previously used by me for an 8" 300blk build and is also known good as that setup would shoot under 3moa. I only have a thread protector on the end of the CMMG barrel and it clears everything. Shot groups with and without the thread protector last session with no significant difference in group size. Crown looks fine as far as I can tell. Barrel nut is torqued well. I can't measure it because it has to be installed with a cressent wrench. But again same barrel nut as used on a previous build that was fine. I also slapped my magpul bipod on for yesterday nights trip instead of the cheap rest I was using and supported the rear with a sand bag. Same shooting setup as my scoped 5.56 rifle. First I started off shooting the Federal HST 147gr and Hornady Critical Duty 135+P with the Holosun HS510c red dot on the upper that was on it in the last session. Again all groups shot at 20yrds. Federal HST 147gr: 1.28" or 6.14moa 
Hornady Critical Duty 135+P: 1.33" or 6.34moa 
Now these groups were more promising. So just to double check it wasn't the shooter, me, the other day that was the problem. I shot a couple groups of the Federal Syntech 150 with the Holosun just to check. Federal Syntech 150 group1: 2.07" or 9.88moa 
Adjusted zero based off group above and shot second group. Federal Syntech 150gr group2: 2.43" or 11.61moa 
Nope, doesn't look like I am the problem. But now I need to move on and rule out the optic. So next I removed the Holosun HS510c and installed the Primary Arms MD-ADS 2moa dot, mounted on an ADM mount, that I know is good. Roughly sighted it in on another target and then went back to shooting groups. First group I decided to shoot was Federal Syntech 150gr. So I could immediately compare. PA Federal Syntech 150gr: 3.38" or 16.15moa 
Well crap. Probably not the optic or me but let's shoot some more groups just to be extra sure. Next, with the PA optic, I shot groups of the same other three factory ammos as the first session. S&B 124gr: 1.23" or 5.88moa 
Blazer Brass 124: 1.85" or 8.86moa 
Federal Syntech 115gr: 1.75" or 8.36moa 
Ok, so those 3 groups were semi decent but still in line with the 5 shot groups I was shooting from the first session. The S&B, if you take out the outliers, is seeming to be the most consistent. Also I think I was able to get the dot on the PA optic finer by dimming it more and shot a little better as the session went on. Still though not a world of difference with most groups being over 8moa. Finally since the PA optic was shooting slightly better I decided to put some Federal HST and Hornady Critical Duty through it to see. Federal HST 147gr: 0.78" or 3.73moa 
Hornady Critical Duty 135+P: 1.28" or 6.09moa 
Shot on far right is from another group. That final HST group was the best it's shot. But just barely sub 4moa from one of the highest quality ammos shot seems very disappointing. If the cheap ammo or even middle ground was all sub 4moa I could probably work with that. But when most ammo is shooting 8-16moa I think there is something else wrong here. MrGunsNGear, in his review video, easily shot 1.5-5moa with his demo gun and very similar ammo selections. At this point I feel like I have ruled out myself and the optic as being the issue. I think the barrel could still be part of the problem. Though there is still a difference between range and defensive ammo selections. None of which though are consistently sub 5moa. What do you guys think? 
All groups shot at 20 yards |
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I have gone through this thread in anticipation of an upcoming build.
I have a question that I don’t think has been brought up. Has anyone had a CMMG RDB boot carrier modified to work with any of the PDW style systems or the Dead Foot MCS? I know many people don’t like those systems due to the non-standard parts used, but that reservation seems less of a concern when you’re building a PCC. In my mind the advantages of PCC type builds is all about being as compact as possible while still maintaining the stability advantage of the stock or brace. The super short stocks and braces seem to be conceptually a perfect match. I’m especially interested in the Dead Foot MCS Tailhook combo. |
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Quoted:
I have gone through this thread in anticipation of an upcoming build. I have a question that I don't think has been brought up. Has anyone had a CMMG RDB boot carrier modified to work with any of the PDW style systems or the Dead Foot MCS? I know many people don't like those systems due to the non-standard parts used, but that reservation seems less of a concern when you're building a PCC. In my mind the advantages of PCC type builds is all about being as compact as possible while still maintaining the stability advantage of the stock or brace. The super short stocks and braces seem to be conceptually a perfect match. I'm especially interested in the Dead Foot MCS Tailhook combo. |
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So all this talk about accuracy got me curious as I've never really 'benched' mine. I've been so focused on getting the cyclic rate and smoothness to where I want it. However with all the rounds I've been shooting, I have been getting good enough accuracy for the SMG matches I shoot at which is really about 50 yards max. Pictured below is the configuration I tested. 3x Vortex magnifier and range was like 35 or 40 yards. 
As mentioned before, I have two 8" 9mm BCG/BBL combos. The first one is the one I tested and came with an M4 extension. I forgot to bring my second one out. I reload my 147GR. I recently switched to RMR bullets and if you look here: https://www.rmrbullets.com/shop/bullets/pistol/9mm-355/9mm-147-gr-rmr-full-metal-jacket-round-nose-bullets-new/ It mentions, "However, there are some handguns that have a very short leade that will not allow for the bullet to be seated that long." I noticed that these bullets would go in my first barrel just fine. In my second CMMG barrel with the single feed ramp extension, the RMR bullets were getting stuck so it has a shorter leade than my first barrel. I ran a finishing reamer in the bore of the second barrel to stop the sticking but I unfortunately forgot to bring my 2nd barrel out to do a comparison if it is any better or worse than the first one. All that said, it is obvious that CMMG made some changes in the barrels. In regards to accuracy, the first barrel is definitely ammo sensitive. I got the best groups with some old factory Winchester 147Gr TCMC bullets. 2 groups below on top. All groups are 5 rounds. The bottom two groups are old batches of Berry's plated I had from a long time ago. I stopped using Berry's a long time ago as I found some really bad accuracy problems where I got batches that were undersized. Their plated bullets are supposed to be .356 and I found I had some that were .354. 
Next up, my Precision Delta 147 Gr reloads, RMR 147 Reloads, Factory 158 Gr Fiocchi (horrible), 158 Gr IMI projectiles (my reloads). 
Lastly, my 2 more groups of my 147 GR RMR bullet reloads, 124 Gr Geco, FNM 147 Gr factory. 
I also tried with the suppressor off and found it to be about the same and I am really concerned with how my groups would be with the suppressor for an upcoming match so shot all the groups with the can. Definitely not great but again, should be good enough for a fast shooting SMG match. I'll try to do another test with my second barrel that I suspect most people out there have which came with the single feed ramp extension. |
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Quoted:
So all this talk about accuracy got me curious as I've never really 'benched' mine. I've been so focused on getting the cyclic rate and smoothness to where I want it. However with all the rounds I've been shooting, I have been getting good enough accuracy for the SMG matches I shoot at which is really about 50 yards max. Pictured below is the configuration I tested. 3x Vortex magnifier and range was like 35 or 40 yards. http://c3junkie.com/wp-content/uploads/2019/07/CMMG-RDB-3-1024x512.jpg As mentioned before, I have two 8" 9mm BCG/BBL combos. The first one is the one I tested and came with an M4 extension. I forgot to bring my second one out. I reload my 147GR. I recently switched to RMR bullets and if you look here: https://www.rmrbullets.com/shop/bullets/pistol/9mm-355/9mm-147-gr-rmr-full-metal-jacket-round-nose-bullets-new/ It mentions, "However, there are some handguns that have a very short leade that will not allow for the bullet to be seated that long." I noticed that these bullets would go in my first barrel just fine. In my second CMMG barrel with the single feed ramp extension, the RMR bullets were getting stuck so it has a shorter leade than my first barrel. I ran a finishing reamer in the bore of the second barrel to stop the sticking but I unfortunately forgot to bring my 2nd barrel out to do a comparison if it is any better or worse than the first one. All that said, it is obvious that CMMG made some changes in the barrels. In regards to accuracy, the first barrel is definitely ammo sensitive. I got the best groups with some old factory Winchester 147Gr TCMC bullets. 2 groups below on top. All groups are 5 rounds. The bottom two groups are old batches of Berry's plated I had from a long time ago. I stopped using Berry's a long time ago as I found some really bad accuracy problems where I got batches that were undersized. Their plated bullets are supposed to be .356 and I found I had some that were .354. http://c3junkie.com/wp-content/uploads/2019/07/target1.jpg Next up, my Precision Delta 147 Gr reloads, RMR 147 Reloads, Factory 158 Gr Fiocchi (horrible), 158 Gr IMI projectiles (my reloads). http://c3junkie.com/wp-content/uploads/2019/07/target2.jpg Lastly, my 2 more groups of my 147 GR RMR bullet reloads, 124 Gr Geco, FNM 147 Gr factory. http://c3junkie.com/wp-content/uploads/2019/07/target3.jpg I also tried with the suppressor off and found it to be about the same and I am really concerned with how my groups would be with the suppressor for an upcoming match so shot all the groups with the can. Definitely not great but again, should be good enough for a fast shooting SMG match. I'll try to do another test with my second barrel that I suspect most people out there have which came with the single feed ramp extension. Can I ask what size pasters those are? I'd love to run your pictures through my Range Buddy app and see exactly what size groups those are but I need something to reference for size. Also I do have the single feed ramp barrel and have also read others statements about a short throat on these barrels. I do not reload and don't fully understand the effects that a short or long throat would have on accuracy. As I understand it that is more about reliability of feeding but correct me if I am wrong. But all the rounds I tested seem to pass the "plunk test" with the exception of some of the 150gr Syntech sticking a little. |
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Quoted: @amphibian thanks for going out and testing what you had. Having another data point is good. Those first two groups you showed look great. Can I ask what size pasters those are? I'd love to run your pictures through my Range Buddy app and see exactly what size groups those are but I need something to reference for size. Also I do have the single feed ramp barrel and have also read others statements about a short throat on these barrels. I do not reload and don't fully understand the effects that a short or long throat would have on accuracy. As I understand it that is more about reliability of feeding but correct me if I am wrong. But all the rounds I tested seem to pass the "plunk test" with the exception of some of the 150gr Syntech sticking a little. Yeah, I would think a proper leade would be better in engaging the rifling but if the rifling is crap then who knows...don't really know till I test it. |
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Quoted:
So all this talk about accuracy got me curious as I've never really 'benched' mine. I've been so focused on getting the cyclic rate and smoothness to where I want it. However with all the rounds I've been shooting, I have been getting good enough accuracy for the SMG matches I shoot at which is really about 50 yards max. Pictured below is the configuration I tested. 3x Vortex magnifier and range was like 35 or 40 yards. http://c3junkie.com/wp-content/uploads/2019/07/CMMG-RDB-3-1024x512.jpg As mentioned before, I have two 8" 9mm BCG/BBL combos. The first one is the one I tested and came with an M4 extension. I forgot to bring my second one out. I reload my 147GR. I recently switched to RMR bullets and if you look here: https://www.rmrbullets.com/shop/bullets/pistol/9mm-355/9mm-147-gr-rmr-full-metal-jacket-round-nose-bullets-new/ It mentions, "However, there are some handguns that have a very short leade that will not allow for the bullet to be seated that long." I noticed that these bullets would go in my first barrel just fine. In my second CMMG barrel with the single feed ramp extension, the RMR bullets were getting stuck so it has a shorter leade than my first barrel. I ran a finishing reamer in the bore of the second barrel to stop the sticking but I unfortunately forgot to bring my 2nd barrel out to do a comparison if it is any better or worse than the first one. All that said, it is obvious that CMMG made some changes in the barrels. In regards to accuracy, the first barrel is definitely ammo sensitive. I got the best groups with some old factory Winchester 147Gr TCMC bullets. 2 groups below on top. All groups are 5 rounds. The bottom two groups are old batches of Berry's plated I had from a long time ago. I stopped using Berry's a long time ago as I found some really bad accuracy problems where I got batches that were undersized. Their plated bullets are supposed to be .356 and I found I had some that were .354. http://c3junkie.com/wp-content/uploads/2019/07/target1.jpg Next up, my Precision Delta 147 Gr reloads, RMR 147 Reloads, Factory 158 Gr Fiocchi (horrible), 158 Gr IMI projectiles (my reloads). http://c3junkie.com/wp-content/uploads/2019/07/target2.jpg Lastly, my 2 more groups of my 147 GR RMR bullet reloads, 124 Gr Geco, FNM 147 Gr factory. http://c3junkie.com/wp-content/uploads/2019/07/target3.jpg I also tried with the suppressor off and found it to be about the same and I am really concerned with how my groups would be with the suppressor for an upcoming match so shot all the groups with the can. Definitely not great but again, should be good enough for a fast shooting SMG match. I'll try to do another test with my second barrel that I suspect most people out there have which came with the single feed ramp extension. The best group your first Winchester 147 was 1.86moa The worst factory group your Fiocchi 158gr was 13.35moa And a middle of the pack factory load, Geco 124gr was 5.77moa. I couldn't touch your best group with a 10ft pole seeing as my best was just over twice that size. Though my best group of S&B 124 is very very similar in size to your Geco 124 group. This is really interesting to me. And my worst groups are vastly larger than your worst group of Fiocchi. I wonder if there is an issue with how the bullets are stabilizing during flight. I wonder if at the 20yrd distance they haven't quite stabilized right yet and at 50yrds I may see better groups. I know this can be an issue in 5.56 some times. So maybe that will be what I test next time I get to the range. |
| I'm having kind of a weird issue with my cmmg guard barrel and carrier, though it could be mags. I'm shooting 115 gr fmj, and about every 2 or 3 rounds the round will get jammed at an angle at the 12 o clock position. In using the guard endomags but they say that they arent familiar with that being a problem. Is it possible the 115gr is too light and it requires 147 gr to push the bcg far enough back to push the round full in? I thought it was the feed ramp being too sharp on the mag but the mag company, though helpful, says they havent see that be an issue. |
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Quoted:
I'm having kind of a weird issue with my cmmg guard barrel and carrier, though it could be mags. I'm shooting 115 gr fmj, and about every 2 or 3 rounds the round will get jammed at an angle at the 12 o clock position. In using the guard endomags but they say that they arent familiar with that being a problem. Is it possible the 115gr is too light and it requires 147 gr to push the bcg far enough back to push the round full in? I thought it was the feed ramp being too sharp on the mag but the mag company, though helpful, says they havent see that be an issue. Also, what kind of buffer and spring are you using? |
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Quoted:
I shoot 115gr all the time with no problems using the endomags "Gen2". Where did you buy your endomags from? And when did you buy them? There are essentially 2 versions: Mean Arms modified endomag adapters to work with the CMMG Guard system ("Gen1", these are no longer being made), and CMMG 9ARC adapters and fully assembled mags made specifically for the Guard system ("Gen2", either sold by CMMG or Mean Arms, although Mean Arms I dont think is selling them under the "9ARC" name). Also, what kind of buffer and spring are you using? Quoted:
Quoted:
I'm having kind of a weird issue with my cmmg guard barrel and carrier, though it could be mags. I'm shooting 115 gr fmj, and about every 2 or 3 rounds the round will get jammed at an angle at the 12 o clock position. In using the guard endomags but they say that they arent familiar with that being a problem. Is it possible the 115gr is too light and it requires 147 gr to push the bcg far enough back to push the round full in? I thought it was the feed ramp being too sharp on the mag but the mag company, though helpful, says they havent see that be an issue. Also, what kind of buffer and spring are you using? The early 'gen1's' on the left, notice you can tell where the front 'ears' were cut off and the lack of 'wings' that go over the rounds on the 'gen2's' on the right. Before the 'gen2's' came out, I had a couple friends that had the exact issue you were describing while I had no issues. Turns out, I was doing a majority of my testing w/ 1st CMMG RDB barrel that had the dual cut M4 extension while my friends were using the later barrels w/ the single feed ramp. I Dremel'ed in the dual feed ramps and their issues went away. After, the 'gen2's' came out, I spoke to MEAN on the phone and they mentioned that rounds would sometime jump up and jam which the 'wings' correct and the same problem my friends had. I think using the 'gen2's would have fixed their issues and not require cutting the M4 dual feed ramp cuts. If you already have the 'gen2's', then like the other poster mentioned, I'd like to hear your buffer/spring configuration. I haven't had any issues with 115, 124, 147, 158 from a functioning perspective. 
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| Thanks for the help all. I have gen 1s. My buffer set up is the ARC pdw with the regular 223 buffer. I have the 9mm buffer but it seems too heavy to reliably cycle all the way back. It really seems to me it's just an angle issue with the feed ramp/mag but I bought then fron MEAN and while they are willing to troubleshoot they seem to act like it's a completely bizarre issue they havent come across. |
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Quoted:
Thanks for the help all. I have gen 1s. My buffer set up is the ARC pdw with the regular 223 buffer. I have the 9mm buffer but it seems too heavy to reliably cycle all the way back. It really seems to me it's just an angle issue with the feed ramp/mag but I bought then fron MEAN and while they are willing to troubleshoot they seem to act like it's a completely bizarre issue they havent come across. |
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Quoted:
Thanks for the help all. I have gen 1s. My buffer set up is the ARC pdw with the regular 223 buffer. I have the 9mm buffer but it seems too heavy to reliably cycle all the way back. It really seems to me it's just an angle issue with the feed ramp/mag but I bought then fron MEAN and while they are willing to troubleshoot they seem to act like it's a completely bizarre issue they havent come across. Start there. Come back if you still have issues. |
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Quoted: Like others have said, if you have the Gen1's, get rid of them. I also had issues with Gen1's. Contact Mean Arms and tell them you have some Gen1 CMMG endos and would like to have them exchanged for Gen2's. I sent all 12 of my Gen1's some time back and they replaced all of them for brand new Gen2's in a timely manner free of charge. I believe shipping was on me, but I can't remember. Start there. Come back if you still have issues. |
Well finally received an email back from CMMG yesterday morning, about my accuracy concerns, after sending a second follow up email just a bit earlier yesterday morning. Below is the email that their Technical Support Representative sent me. So I went ahead and sent an email to the Senior Repair Tech, he listed, about his opinion on what bullet weight, profile, ect he recomended and what their accuracy standards were for these barrels. Haven't heard anything back in over 24 hours.
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Quoted:
Why is a 2” group at 20 yards acceptable when shooting 9mm, but that same group shooting just about anything else would be cause for concern? CMMG’s answer sounds fucky to me. |
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Quoted: Some cheap pistol ammo really is inherently inaccurate / inconsistent. |
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Quoted: Thanks all. I will try that. Kinda strange after multiple emails back and forth they didnt offer that though... |
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I have some pre-sale blow-back ones and emailed them about swapping them for CMMG style and they told me to just modify them (remove ejector). I don't have the CMMG parts yet (or a gun to do it with), so haven't bothered doing anything with them. |
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Seeing the accuracy results posted here had me wondering how well my Guard build shoots, so I did some testing today. Guard 8" barrel bolt combo (single feed ramp), endomags gen 2, Griffin tri-lug for looks, aero upper, & holosun 510C. I was sitting at a bench, resting mag on table, with a red dot sight, at 50 yards: (I know it's not the most accurate testing, but I wanted ballpark idea of accuracy for an upcoming PCC event.) HST 147gr - 5 shot group was 3.5", but I'd probably count one of those as a flyer, dropping the group below 2". (1st shots of day, cold bore) https://www.dropbox.com/s/nug3fftay7hbbzq/FED_147_HST_50YD.JPG?dl=0 FM 115 RN New - 5 shot group was 2.75" tall and 1" wide, so I may have strung those shots. (2nd grouping) https://www.dropbox.com/s/b7kfhvdetfudbm3/FM_115_RN_50YD.JPG?dl=0 FM 124 Match - 5 shot group was under 2", surprised because I had issues with this load with the old Endomags. (3rd grouping) https://www.dropbox.com/s/m9u3mrfhx34ooxe/FM_124_MATCH_50YD.JPG?dl=0 Handloaded 147gr HP xtreme bullets - 5 shot group was 2.5" strung to the lower right. (4th grouping) https://www.dropbox.com/s/5b436djui7mmxoa/XB_147_HP_50YD.JPG?dl=0 So it's around 4MOA with a red dot, which is good enough for me. ETA: Aero lower, KAK blade gen 2, geiselle buffer system, & Larue MBT. |
[ARCHIVED THREAD] - Thoughts on the CMMG Guard? (Page 19 of 25)
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