View Full Version : CMMG Bolt Upgrade ?'s
I have a CMMG MOD4SA M4gery. I'm happy with the gun. It is primarily a self defense/training/recreation rifle chambered in 5.56mm. I purchased it this past summer when the prices started coming back down to pre-election normalcy.
I've read some of the sticky's by Gotm4 and RobS. I just want to say thanks gentlemen for all the tech questions and info passed along. I was Army infantry from 86-90 and I would be amazed if I new 1/10th of the information the two of you have provided regarding my M-16 back then.
Okay the BCG question. I've taken a look at "The Chart" and noticed that the CMMG is lacking a lot of X's in the BCG section. I'm really not freaked out by the info on the chart after having read the explanations provided. I'm positive about the decent quality of the rifle I purchased. I do part time firearms instruction and the range I work at have complete Colt BCG's for sale. Is it worth my time to purchase one of these and use the one that came with the rifle as a back up? Right now I fall within the category of far less than a 1000 rounds so far. I plan to up that well past the 1K rounds/year, as my interest in the AR system increases.
Thanks in advance for any and all responses.
as a bare minimum I'd recommend you pick up one of these (http://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm%20extractor%20spring%20upgrade.htm) and install it on your current bolt, whether you wind up using it as a backup or not.
If you're shooting your rifle low volume, recreationally than you should otherwise be just fine and dandy with what you've got... what concerns me is that you mention that your rifle also performs a defense role. Home defense guns don't have to stand up to high volumes of fire between cleanings and usually don't have to suffer adverse conditions, but they also MUST WORK WHEN NEEDED. In that case, it becomes sort of a question of how reliable is reliable enough? And that's really something only you can answer.
I still run a handgun for my home defense as I just got in the AR game recently myself.
I was on the BCM sight right after I posted my initial message and saw that kit and yes I think I will purchase one. I don't know what the install process is like. I am at best a tentative "tool guy." Worst come to worst I'd have a buddy of mine who's really into AR's install the kit. Your suggestion is a good one.
In all honesty I am more likely to run one of my Glocks as a home defense gun, speaking of reliability. I am NOT a combat guru by any means, spent some time in the army as mentioned, and dabbled with careers in law enforcement and executive protection. Along the way I've had some good training at some local shooting schools. I primarily teach elementary school.
With my experience and from what I understand many a gun fight is anything from a presentation to a 1-3 shot affair. I'm confident my rifle can handle that. I don't anticipate being in or having a situated visited upon me by which my 736 square foot apartment starts resembling somewhere in Fallujah. If anyone comes in and I'm involved in a firefight requiring me to go through a 30 round mag and possibly multiple mag changes thereafter, I probably wouldn't be able to sustain that kind of fight. I suspect that my home invaders at that point are not looking for my extensive amount of cash and valuables, (did I mention I'm a teacher), but may very well have the ability to call in a fire mission on me, in which case I'm done!:eek:
Still you present an interesting question. As of now I have 100 trouble free rounds through the gun and no cleaning. I'm going to simply run it and just wipe down the bolt and clean the gas tube, and mark when I have my first stoppage. I don't know how empirical that is but it will be interesting for me none the less.
BTW in my long windedness, thanks for the suggestion. I will try it out.
I got in the habit of running a handgun for HD when I lived in a 1920s Victorian-style home that I swear had half it's square footage used up in half-flights of stairs (3 stories, so 6 half-flights), in a situation like that the manueverability penalty of any long-gun is absolutely untenable. I've since downsized my lifestyle (read: got screwed by the economy like everyone else) and now live in a 900 square foot apartment. While the layout is MUCH more conducive to facilitating the use of a long gun, I still run a handgun for three reasons.
1. It's what I'm used to, it's what I have confidence in, and I have waaaaay more hours training with a handgun (I used to be in the law enforcement game myself) than with a rifle.
2. Contact ranges would be close enough that I figure I'm more likely to have sight-bore offset problems than not with an AR (since the longest shot in my apartment is around 7 yards).
and 3. At 7 yards or less, I'm confident a 9mm or .45 autopistol will be effective and accurate enough, ballistically speaking - it should also be a lot less rough on my hearing.
If anyone comes in and I'm involved in a firefight requiring me to go through a 30 round mag and possibly multiple mag changes thereafter, I probably wouldn't be able to sustain that kind of fight. I suspect that my home invaders at that point are not looking for my extensive amount of cash and valuables, (did I mention I'm a teacher), but may very well have the ability to call in a fire mission on me, in which case I'm done!
Believe me when I say I totally get that attitude and agree wholeheartedly.
I'm going to simply run it and just wipe down the bolt and clean the gas tube, and mark when I have my first stoppage. I don't know how empirical that is but it will be interesting for me none the less.
That's actually not a bad AR reliability litmus test. Let us known your results when you finally do hit that first stoppage.
I don't know what the install process is like. I am at best a tentative "tool guy." Worst come to worst I'd have a buddy of mine who's really into AR's install the kit.
In terms of the actions involved, the installation is incredibly simple. You remove the bolt carrier group from the rifle, remove the bolt from the carrier, drift out the extractor pin, pull the old spring and insert, plug in the new spring and insert, stick the o-ring over the spring, reseat the extractor and reinsert the pin.
There are, however, two tricky points in there, and I shall now share with you the benefit of hours (yes, HOURS) wasted, my sore fingers, and my extreme frustration:
1. You must "click" the new extractor spring into the extractor - this is tricky because the spring isn't really flat and will resist diagonally, just keep trying 'til you get it. You'll know when you get it because the spring will no longer fall out of you hold the extractor upside down.
2. Here's where the trouble was for me, and I was shocked that no one else on the internet seemed to address this, installing the o-ring with the new extractor spring at the same time was pretty much IMPOSSIBLE because the resistance was so strong I couldn't get the drift pin back in. What I wound up having to do was install the spring and insert by itself for a week or so to let the spring break in and then return to install the o-ring which, while still physically difficult, became comparatively much easier to do.
This may just have been my bolt, yours may be no trouble, but if you find yourself having a particularly difficult time installing the new spring and extractor together, try doing what I did before you press your fingers raw and throw fits along the lines of declaring to never again have anything to do with assembling AR parts yourself.
If you're really serious about upping your round count, you may want to invest in another weapon. Not many here would stake their life(as in HD weapon) on a CMMG.
Not trying to be a di**, at all. If you can sell the CMMG, there are great deals on 6920's, BCM's, DD's, etc.
Not sure a CMMG would hold up in an EAG, VT, TS, LV, GG, etc. 3-day carbine class.
If you are in a firefight with home invader's(not likely) then a rifle that can make it through mag after mag and hold up is a necessity. If you don't think you could hold up, take some classes. You'll be amazed at what you learn and what you become capable of. Will give you the confidence and edge that might just save your life. Best of luck to you.
Not sure a CMMG would hold up in an EAG, VT, TS, LV, GG, etc. 3-day carbine class.
Betcha it would if you replaced the bolt. CMMG's mechanicals are generally pretty sound, they just cut a few corners.
I appreciate the encouragement. Though I plan to take more classes and get more training I think the gun I have will sustain me in 99.9% of the scenarios that I'm likely to face. I'm not saying that a multiple home invader with multiple mag change scenario is out of the realm of possibility, I just don't think for where I live it's not likely to be a smash and grab operation. If said smash and grab crew chose me as a target to advance themselves financially, then they have failed on many levels. As I was saying tongue and cheek, that kind of scenario would probably involve people with grenades, machine guns, and the ability to call in fire support. I would like to think that if that were to occur that I would have had the brains to bug out long before they showed up.
To keep the thread focussed I will get that kit from BCM, and I'm going to look at some of those Colt BCG's today. As to selling the CMMG, I don't think so. It would mean selling it to someone who knew less than I did. Though I have to say at said range there is a S&W M&P15 that I can get at a discount, and that is 3 columns to the left of me on "The Chart." Hmmmmm.:D
I do want to add for anyone reading this that the more I involve myself with this sight the more I like it. There seems to be a fair degree of knowledge, professionalism, and good naturedness here with a minimum of macho posturing that seems rampant on other sights. Of course I've only been here a short time.;)
CT- There is a reason no .mil, LE agency, or three letter agency uses CMMG. There is a reason they are not highly thought of on M4C. You replied they cut corners. The items they cut corners on are not something to gloss over. Don't get angry when someone offers input on a brand that does not meet the TDP. I've made it clear I'm not trying to be a di**. Simply: CMMG is a borderline POS rifle and very few on M4C would ever use it as a gun to stake their and/or their families lives on.
DS- Buy a BCM BCG and be done with it.
Don't get angry when someone offers input on a brand that does not meet the TDP.
First and foremost, I'm not angry. I truly believe that a simple bolt replacement will cure the vast majority of issues one could have with a CMMG rifle, as apparently you do:
DS- Buy a BCM BCG and be done with it.
What I'm suggesting is that your standards for a "POS" are actually pretty high, and/or that the difference between "Borderline POS" and "Tier 1 rifle" are a lot smaller than you seem to indicate.
My argument is simply that CMMG builds receivers as decent as anyone, cranks out a respectable LPK, and uses decent barrels. They cut corners on the bolt, so I suggest the bolt be upgraded or replaced. I just don't feel it's appropriate to scrap an otherwise very salvageable rifle because it could use a new bolt.
Now if we were talking about a DPMS or Olympic... THAT would be something worth scrapping to start over again anew.
Here we go again!:confused::mad::rolleyes:
This post removed due to miscommunication.
Hey all my intent is nor was to start a "chart" war. Just asked a question and it appears to be answered. Thanks to all for your responses. I appreciate the insight and advice. I think a new bolt will be in order. Again thanks.
CT- OP started he could not get rid of the rifle and buy a new one. This is why I said go BCM and be done with it. If he had answered he could afford to get rid of it...
I guess I was not making myself clear. For plinking, CMMG is fine. For staking your life on, no.
For me, the fact no agency uses them speaks volumes, as does the chart.
Sparky- Got a good laugh from your post. Maybe in the next month or so we can arrange some shootin' time. New 6920 I bought as a BUG for classes hasn't been shot yet.
So from what I understand is that CMMG cuts corners on the bolt. Mostly everything else is decent. Okay got it. So when I replace the stock BCG, with say a BCM model, I'll be able to fill in 5 or 6 x's on the CMMG column of "The Chart" and have paid less overall than say an LMT, (range discount where I work), but have moved to a better part of the neighborhood on "The Chart." And here I thought for a second I'd have to sell my $950 rifle, but instead I just upgrade to a what $150-$200 part. I wonder how much a staked receiver endplate and an "H" buffer would cost. That would give me two more x's in the CMMG column, move me past the LMT and have me rubbing shoulders with the Noveske.
Awesome I love how this works! It's almost like the Hollywood Squares of AR's!
Thanks again for all this valuable information. I can't believe how much I've learned in such a short time here.
Ah, didn't realize you were still running a CAR buffer. I'd get that switched to an H pronto (don't worry about the installation on that, an untrained monkey could do it).
Don't worry about staking the endplate, just loc-tite your castle nut and you'll be fine as long as you don't deploy in a warzone... as a plus, if you ever decided to replace your receiver extension, it won't be an epic PITA to do so.
As far as changing parts to move to the left, this is kinda where using the chart as a yardstick for quality breaks down. If you'll recall, I said CMMG uses decent barrels - BCM, Colt, LMT, Noveske, and DD use exceptional ones. CMMG uses CMT LPKs (I believe) which are not as good as Colt or LMT LPKs, these are things that the chart doesn't really show.
Just because you replace enough parts on your CMMG to check all the same boxes an LMT or Noveske does, doesn't mean your CMMG is as nice as an LMT or Noveske. The CMMG is a good rifle, replace the bolt and it'll be a very good rifle. There's nothing you can really do but start over to have a GREAT rifle.
Not trying to rain on your parade, but facts is facts. If your heart's desire is a tier 1 rifle, nothing less will do.
No rain at all. I kind of knew just by looking at the barrels that there had to be a qualitative difference that would not be solved merely by upgrading parts. Thanks again for all of your advice.
DS- Make sure to use Loc-Tite 242(Blue) which any Home Depot or Lowe's carries. This way if/when you need to remove the Loc-Tited(is this now a word?) castle nutyou'll be able to break it free without extreme measures. Most generally stake the nut which isn't a prob. to remove when need be.
So when I replace the stock BCG, with say a BCM model, I'll be able to fill in 5 or 6 x's on the CMMG column of "The Chart" ...
I have a CMMG 14.5 lightweight mid-length. I'm not saying it's "good enough," but the configuration was exactly what I wanted and the price was right.
The guy who built it for me staked the gas key and the castle nut, and I promptly replaced the bolt (not the whole BCG) with one from BCM (I would've wanted a spare, regardless).
Those minor changes dealt with all the "sub-standard" issues on the chart, except the barrel's only 4150 and only batch tested, and it still only has single-shield handguards. I've never shot enough fast enough to get the handguards hot, and I'm unconvinced that the barrel is going to be a problem for me. Done.
I don't run my gun hard, but I've had no problems whatsoever, and it is my "go to" gun.
except the barrel's only 4150
4150 is good stuff, it's 4140 that's crap.
Most anyone in their right mind will admit that 4150's as good as make's no difference to the mil-spec steels (B-11595E and S-11595), it's just not a military contract steel. (Again, when measuring mil-spec or not mil-spec, all you're measuring is whether or not something MATCHES the TDP - there's no room for acceptable or superior substitutes in the chart).
Now then, I will admit that the tier 1 companies do turn out better barrels, not because of the steel they use but because of issues like heat treat, internal dimensions, crowning, and Q.C. - things that are not specified in the chart but can make a small difference in reliability and a BIG difference in accuracy.
Most anyone in their right mind will admit that 4150's as good as make's no difference to the mil-spec steels...
I agree, especially for my pedestrian uses, but there are people here who will have kittens if the steel's not actually "mil-spec."
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