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Posted: 11/11/2011 8:43:58 AM EDT
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I have a brand new CMMG dedicated 22 with the stainless upgrades and the new BHO. When I tested the firearm I had a lot of failures to fire, around half per mag! sometimes only 2 or 3 rounds per mag. I even noted that I went through one full mag without fireing a single shot! ! ! I was using Winchester 333 and CCI mini mags. Surprisingly the mini mags were giving me the most problems; I gave up after about half a brick of the mini mags and continued to use up the 333's. I used this on two different lower setups: one heavily used with a standard trigger, the other with a fairly new Geissele trigger. The Geissele gave me fewer problems. Another thing I noticed was that although the BHO worked when installed, that is when I had most of my FTF. I did not notice any extra pressure when installing the BHO device versus without (then again I'm kinda known for gorillaing things) so I didn't notice that the bolt group, if that's the term for it, move or have any extra pressures on it that might cause a misalignment. I was using a combination of Black dog mags and 2 of the new CMMG evolution mags. The lube I was using was Rem-Drilube.
Would this be considered normal brake in? I'm going to try another box of the 333's to see if I continue to have the multiple FTF and hopefully it clears up. Any recommendations would be helpful. |
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First thing I would look at is the firing pin denting the rim good? Or are you getting light strikes on the rim of the cartridge?Knowing this will help alot diagnosing whats wrong...I am just going to assume you are getting light strikes on the primer or they would fire..Or your bolt is not closing completeley on every round for some reason,look at that too..
Not saying this is possible with multiple misfires but maybe bad ammo..That would be a stretch I know especially getting two bad batches from two differant makers...And I have never had problems with either of those 22 rimfire manufacturers.. Also are you using a rounded hammer or notched ones? I know some people have had problems with using the notched ones but do not know if that would be related to misfires or not.... Oh one other question as I am a little confused after rereading you post..Are you rounds not firing once in the chamber or are they not even feeding into the chamber in the first place..The way you state things I am unsure if it is misfires or failures to feed or both..Cause if you are getting rounds in the chamber the mags are definitley not the problem..... |
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Quoted:
First thing I would look at is the firing pin denting the rim good? Or are you getting light strikes on the rim of the cartridge?Knowing this will help alot diagnosing whats wrong...I am just going to assume you are getting light strikes on the primer or they would fire..Or your bolt is not closing completeley on every round for some reason,look at that too.. Not saying this is possible with multiple misfires but maybe bad ammo..That would be a stretch I know especially getting two bad batches from two differant makers...And I have never had problems with either of those 22 rimfire manufacturers.. Also are you using a rounded hammer or notched ones? I know some people have had problems with using the notched ones but do not know if that would be related to misfires or not.... Oh one other question as I am a little confused after rereading you post..Are you rounds not firing once in the chamber or are they not even feeding into the chamber in the first place..The way you state things I am unsure if it is misfires or failures to feed or both..Cause if you are getting rounds in the chamber the mags are definitley not the problem..... Sorry for not stating more facts, this was about a week ago and the coffee hasn't set in yet. I removed the possibility of having bad ammo by firing both types of ammo through my mosquito and the ammo worked fine. I honestly can't remember how the strikes looked right now so I'll double check, but that was the first thing I looked at too  . Nothing stood out to me as looking light. The one thing I did notice was that the firing pin strike appeared a lot larger than compared to a MKIII. The triggers were both rounded. Every stoppage was a failure to fire, all rounds fed and extracted fine, including the unfired ones. I only mentioned the mags just to inform what equipment was being used. I appreciate the help. I'm hoping to test it out again soon though.
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Quoted: Yup. Hmmm, never the obvious is it. 1. Make sure your firing pin moves freely in the bolt. I've also heard of the firing pin spring being too stiff and causing light strikes. 2. Try polishing the chamber with a bore brush and a drill per the sticky above. 3. Try w/o the BHOA installed. 4. Throw it down and cuss. Will it fire after hand cycling a round into the chamber? |
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I had the same problem. I was getting REALLY light primer strikes. I was getting ~20 light strikes per 26rd mag.
1st thing is your hammer Notched or rounded? CMMG says that their uppers wont work with a notched hammer. (I replaced with a rounded hammer. Went from 20 down to 15.) 2nd pull your firing pin spring and try it. BE VERY CAREFUL NOT DROP YOUR RIFE. (With no spring I had nice HARD primer strikes.) What I had to do was cut just 1 spin off my firing pin spring. After that I have fired 500+ rd with zero light primer strikes. |
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Is the bolt closing completely? Is there movement in the bolt assembly. Check for a flush fit at the end of the receiver. If there is a gap, the bcg could have movement and absorb the energy from the hammer strike.
Make sure the firing pin is moving freely. Dave N |
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Thanks everyone for all the tips, to check and trouble shoot. It seems that the failure to fires is lessening. It seems that in my retest, I compared it with other type of 22's and asked for others opinions on the strikes, it does seem like I have been getting like strikes. So extra power hammer spring from brownells is on it's way. I did get 50/50 reviews as to whether or not they were light strikes, so I just went with the fact that they are.
I gotta say though, I am having a blast with this thing! ! ! |
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I had similar problems with a CMMG upper that came as part of a complete rifle.
With stock springs, there were no problems although inspection of the cases showed lighter than expected hits. Trigger pull 6.75 to 7 lbs on a Lyman digital gauge. With a timney trigger or jp yellow spring, I had 100% failure rate. To make a long story short, I believe that the shape of the firing pin is very inefficient. It is far too long. It makes too large of a dent in the cartridge. As a result it isn't making a deep enough dent for reliable ignition. Check out my thread here: http://www.ar15.com/forums/t_3_15/553288_Light_Strikes_on_a_CMMG_dedicated_AR.html I just really dug into this today and seem to have completely solved it, although i want to do more testing next time I go to the range. Don http://www.ar15.com/forums/t_3_15/553288_Light_Strikes_on_a_CMMG_dedicated_AR.html |
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Here is something to look at. Check the forward assist block for any sign the hammer is hitting inside it. I've been checking all mine and even while I've had no problems, I can see how it could dampen the hammer strike. If you see any hammer marks, just sand the forward assist block down slightly.
You would see these on the underside close to the firing pin. Dave N |
| Dave thats a good tip on the forward assist block..I never thought to look at the underside of the block you helped us get ordered awile back..There is light marking on ours on the underside from the hammer obviously now that I take a look, but no function problems for us.I am not going to sand it as we have no problems but a good tip for others to look at if they have a problem...Thanks |
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