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Posted: 8/9/2006 4:34:45 PM EDT
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Nyx, my CMMG 7.3" pistol is behaving strangely. I have fired perhaps 100+ rounds of various mfgs. of ammo., including 42gr. frangible, and experienced at different times, different mags, different problems. Today, using used Colt 20-rounders, I got FTFs, FTEs, and double-feeds with Winchester WB 55gr, American Eagle 55gr, and Wolf 55gr, but not always, and not consistently. The Golden Bear 62gr. Soft Points gave me the least trouble (the hottest loads), but toward the end of the day, even these did, too, a bit. :wtf: Now, hold on there... Using a borrowed new, USGI 30-rounder, everything fed flawlessly, and no FTFs, or FTEs. I've used the same Colt 20-rounders a week before with far fewer problems (1/10th), and even an Orlite with only a few hiccups. I know that trying good 30-rounders is the place to start, but what are your suggestions as things to examine, or do to remedy this situation? * [Chamber is not junked-up] * [Gas Tube was clean last time I maintained her (last week, no firing between then and today)] * [CAR receiver extension; CAR Buffer; CAR Spring] * [Inspected the Boltface and Extractor, working fine...] * [M4 Feed Ramps don't look like they're getting beat up, but the rounds look a bit chewed up (but likely due to the double-feeds)] Help? Thanks in advance, -Kyrinn |
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are you gripping the mag with your hand when u shoot? or have the mag sitting on something when you shoot? most double feeds happen when you grip the mag or it is on the table while shooting from a bench. that could be one problem could be other things but this is somewhere to start |
It was giving me these problems while I was standing, not resting the mag. But, when I had rested it (last week), it didn't give me any problems. I'm hoping it is just weak springs in the 20-rounders...but, I get the feeling it is more complex than that. Ugh. Thanks for your suggestion. :) |
| have you checked the feed lips of your mags? if they're bent or worn, that might contribute to a double-feed. I had a few feeding problems with my CMMG, in that it wouldn't fully chamber the round, and I found that the gas key was angled up too high, and the gas tube was striking the bottom of it. I bent it back into spec, but haven't had a chance to test since then. |
As far as the feed lips: the geometry on the Colts are not the same as othes I own, but, I think that's to be excepted considering their era of issue. They don't look bent or deformed in any way, though. The New USGI 30s are the real test of the magazines being the fault. Will report soon. Thanks again for all the replies. :) |
| In all my pistols I run wolff extra power extractor springs with a crane o-ring around the spring(ADCO). I also use a stiff black extractor spring insert. I also use a 9mm buffer from RRA. If you run new GI mags with this setup It should run. If not let the guys at CMMG know and I know they will get it working. Pistols can take some tweaking to get them running 100%. Both of mine run like champs! Hope this helps. |
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When you get them tuned right, this is the kind of fun you can expect!!!! 30 round bump. media.putfile.com/big-bump |
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h!Unfortunately, there's no place I can bump. Both ranges forbid it -- they don't even allow regular rapid fire. hinking.gif Pretty cool vid. What kind of Receiver Extension; Buffer; Spring; and Ammo.? Best, |
I use a RB Precision pistol extension tube, RRA 9mm buffer, standard car buffer spring, and I shoot winchester Q3131 when I can get it. In the video I'm shooting Wolf 62 gr polymer. None of my 8 ar's like the old laquer Wolf but shoot the new polymer fine. I dont know where you live in FL. but make friends with someone who lives in the country or owns a gravel pit or farm. (Bump on!) I am very lucky that I live where I do. My buddy from work lives 3 miles from me and has 40 acres with a pit. I can shoot there any time I want, |
Yeah! I've seen that on here before.
Thanks for the tech-specs, Lumberjacker. My carbine will gladly eat lacquered Wolf. We'll see if Nyx, the pistola, will, too. he Only established, limestone berm-equipped ranges are an exception from that law, but still need a large buffer-zone of non-residential land. This part of the state used to be gorgeous and green, but now, it is being swallowed up by housing and strip malls and warehouses. |
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Robino, Just to clarify, Lumberjacker uses the 9mm Buffer, and a standard CAR Spring. - - - A/all, is my understanding of the following correct?: * The heavier Buffers increase 'Dwell Time'; the recoil forces being more or less consistent based on the ammo. used, require a longer amount of Time to Work their energy against the heavier buffer load. During this period the chambered, expended casing has more Time to receive the bleed-off gassses, and eject. The heavier buffer, now tensioned against the compressed spring, will have the full force to move forward and properly strip and chamber a subsequent round once internal pressures return to normal. This increases reliability in a shortened gas system. Yes? |
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i understand the 'slowing down process', but i just want to know if it works more reliably in short pistols, i don't see much of this being discussed, i mean i do, but i don't see anyone having done a test with a stock car buffer, then with an H, H2, 9mm. etc buffers to announce to the world (LOL) that this buffer is better than the other when used in a short pistol .223 i suppose i'll have to get a 7.3 and fire it with the standard buffer (they do offer standard, H and H2, but they fail to mention which would work better when shooting regular .223 ammo) and see how it works. i would guess that CMMG would sell a pistol that works 100% reliably, so i don't quite understand why they offer so many different variations in buffer weights. Most people will shoot regular weight .223, not 70+ grain boat tail out of their pistols. |
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Robino, hat I'm using a standard CAR extension, buffer, and spring, and haven't had any issues (so far) with the ammo. I've used (so far, once I got the magazine issue sorted out). I think that it may be more of an issue with shorter Extensions. I read on another thread in this form (light/heavy ammo. ...) that out of a 7-ish " bbl., that 40-42gr. ammo. is the defensive-use ideal, due to the short length/twist, and the subsequent loss in velocity. The International Catridge Corp. 42gr. RTP rounds seemed to do very well, accuracy-wise, out of my 7.3" bbl. More information about the cartridge can be found here: LINK * Two excerpts: "Q. How does shooting the Frangible Bullet differ from conventional bullets? A. Frangible Bullets are lighter due to their non-lead content. They are therefore longer, lighter and have a longer bearing surface. Tom Shaw was using a 1 in 8-twist barrel. Normally, that barrel won’t shoot a 42gr bullet, but it will shoot ours because it is so long. No lead, longer bullet, less weight, better trajectory, you can drive the bullet faster. Since the ballistic coefficient is good, the bullet "flies" well and doesn’t drop as much because it’s running 30% lighter." "Q. You have loading data on your site, but what do I do to develop my own loads? A. Look at the data you use now. We have a light bullet that has a heavy bullet profile and case capacity. Use the intermediate bullet weight data you already have available. For example, ... In 223, use your 55gr bullet load and drop in our 42gr bullet. In 9mm and 40 S&W, since they are high pressure rounds, our bullet is 30% lighter and therefore takes up 30% more case capacity. Go with your lighter loads using W231, Bullseye, AA#2, #5 or another fast pistol powder." |
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anyone else wanna get in on this? ... as to why the H or H2 or H3 or the 9mm car buffers are 'better' and what advantages do they provide that the standard car buffer doesn't? i'd like to get schooled on this topic, since i'm totally in the dark with it. slightly off topic, i've recently bought a new Barrett M468 6.8 and when i asked Barrett, i was told that a standard .223 Car buffer/spring will work just the same as the full A2 stock buffer/spring that my Barrett came with (which i replaced with a collaps. SOPMOD) They said the STANDARD .223 CAR buffer and spring are what should be used if i'm replacing the stock with a Collapsible one. So if the CAR buffer is ok to cycle the heavier 6.8 round, why would one need an H or an H2 or an H3 or ...? |
Am I safe in assuming that one of the ranges you attend is the Dade City Rod and Gun club ? If so, those fellows are something similar to Nazis. |
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NO RAPID FIRING!!! Is what you'll hear at most ranges, even if you're simply double tapping or just firing semi fast. After a bit of reading, i'm seeing that in a short 7" .223, most light buffers will work just fine (IN SEMI AUTO MODE), if full auto (BUMP FIRING) one would want a heavier, H3 or 9mm car buffer for the gun to function 100%. I've ordered an H, and an H3, i'll go on RRA's site and get a 9mm buffer as well and i'll try it all and see what happens. |
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i'm curious by using the heavy buffers (H3/9mm) if reliability in semi auto mode is deminished. i've also written Barrett asking a similar question about their 6.8 (which i now own), they said that if i change their A2 stock to a CAR collaps. stock, the standard car buffer/spring are fine, so is the H buffer, so long as it's semi-auto that's being fired. Since they stressed that it's "fine for semi-auto" I'm guessing full auto would require a heavy buffer. Just not sure how the heavy buffer reacts when shooting semi auto. I'll know soon. I see what you mean by firing lighter ammo, however i have a TON of 55grain .223 I'm not looking for a tac driver in the little 7.3", reliability is more important. What's that Winchester 031313 ammo the other guy was talking about, what weight is it? |
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