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Posted: 4/17/2011 3:10:50 PM EDT
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Hey everyone, I'm having a failure to fire problem with my 16" Midlength BCM. I think it's probably related to the ammo that I'm using (Silver Bear, 62g). This is a brand new rifle and the only other ammo that I've shot through it is M855 built in Turkey that shot great (about 60 rounds). I keep my rifle lubed well with a good synthetic lube. It was 60* out today.
What I'm experiencing is: - I load up 30 rounds of the Silver Bear in my PMAG - I load the first round by pulling back the charging handle - The first round always fires - The second round gets loaded in but sometimes it fails to cock the hammer (can tell by trigger not being reset) - So I pull the charging handle back to eject the round (ejects just fine) - When I visually inspect the round I can see a small dimple in the primer where the firing pin has made small contact with the round even though I didn't pull the trigger (is this normal?) - This failure to fire seems like it can effect about 1/3 of the rounds in the magazine - I haven't had one failure to feed out of all this - I shot about 100 rounds today and experienced this 1/3 rate of failure to fire throughout The specs on my rifle are: - BCM BFH 16" Mid Length (Light Weight) Upper Receiver Group (.625FSB) (Mil-Spec) - BCM Gunfighter (Preproduction) Charging Handle w/ Mod 4 (Medium) Latch - RRA Complete Chromed Bolt Carrier Group - Lower Receiver - JD Machine CalGuns Bear (Mil-Spec) - Lower Parts Kit - Stag Arms Standard Single Stage Trigger - Magpul MOE Enhanced Trigger Guard - Magpul MOE Handguard - Magpul MOE Pistol Grip - Magpul PMAG 30 Magazine - Magpul MBUS Rear Sight - Rear Stock - Vltor Carbine Modstock Basic - Stock Install Kit - BCM Stock Hardware Mounting Kit (Mil-Spec) with Standard Buffer Is there anything relatively easy that I can do to keep shooting cheap ammo? Change to a different buffer? Should the firing pin be dimpling the failure to fire rounds? Any other thoughts? Thanks! |
Dimpled primer is normal on a chambered round due to free float firing pin.
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It sounds like something is wrong with your fire controls not your BCM upper. I would change your title to failure to fire before you get heckled for implicating BCM. If your bolt is cycling far enough to eject and load a new round it should reset your trigger but something is not catching it. Sure your disconnector spring is in right?
The AR has a floating firing pin so when the bolt comes forward the firing pin will go forward as well with enough momentum to lightly strike the primer but not discharging. |
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A dimple on the primer is normal when you chamber a round. I guess it is possible that the hammer is not resetting, but I would rule out ammo first. You should not change anything on your rifle yet, a 16 middy has plenty of gas to run the bolt and buffer you have even with the weakest of ammo.
If it is not the ammo my guess is you have a problem with your trigger. |
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I was having the same problem with my rifle; had JP Springs for the normal fire control, and every fifth or sixth round I had a failure to fire. The round that failed to fire just had a dimple on the primer. I changed out to factory springs and have not had any problems with failure to fire since.
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Quoted: It sounds like something is wrong with your fire controls not your BCM upper. I would change your title to failure to fire before you get heckled for implicating BCM. If your bolt is cycling far enough to eject and load a new round it should reset your trigger but something is not catching it. Sure your disconnector spring is in right? The AR has a floating firing pin so when the bolt comes forward the firing pin will go forward as well with enough momentum to lightly strike the primer but not discharging. When and if you shoot same again, hold trigger back while ar cycles, when you release the trigger you should (hear, feel) if release from the disconnecter and catch on the hammer. |
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I would say weak hammer spring on hard primer but you did shoot military ammo and you said it worked fine.
I've never heard of a primer getting a light dent in it just from the round chambering, at least not in a properly functioning rifle. I thought they were built to prevent that from happening inadvertantly. Pretty sure there was a discussion out that that couldn't happen. |
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Quoted:
I would say weak hammer spring on hard primer but you did shoot military ammo and you said it worked fine. I've never heard of a primer getting a light dent in it just from the round chambering, at least not in a properly functioning rifle. I thought they were built to prevent that from happening inadvertantly. Pretty sure there was a discussion out that that couldn't happen. the floating firing pin always makes light contact with the primer due to momentum it carries when the bolt locks. totally normal. |
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Some culprits that MAY be in the soup.
1. Brand new action! Shoot that rifle A LOT!! Ya gotta take her out and love her hard and fast many times! 2. Some less than ideal ammo, BUT, after she has been thoroughly broken in and loved a bunch, she'll even chew THAT stuff good and plenty. An old well loved rifle will pretty much eat whatever (appropriate) ammo you feed her. Now, get off the net and finger your girl (rifle). |
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Thanks everyone for the replies.
I'm glad to know that the light primer strike normal and just due to the free floating firing pin. I'm going to try a box of the same M855 tomorrow that worked completely fine before this issue with the Silver Bear. I'll report back the results. It seems like most people believe the issue is either with poor quality ammo or the lower springs have some issue. I just checked the lower and the springs look correctly installed. |
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Quoted:
Some culprits that MAY be in the soup. 1. Brand new action! Shoot that rifle A LOT!! Ya gotta take her out and love her hard and fast many times! 2. Some less than ideal ammo, BUT, after she has been thoroughly broken in and loved a bunch, she'll even chew THAT stuff good and plenty. An old well loved rifle will pretty much eat whatever (appropriate) ammo you feed her. Now, get off the net and finger your girl (rifle). Ha ha. Yeah, I definitely need to put some more rounds down range with it. |
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Quoted:
If it was short stroking bad enough that it wasn't resetting the hammer, how would the bolt be moving back far enough to chamber a new round? I was wondering this myself. It chambered a new round perfect every time but always failed to reset the hammer. |
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Quoted:
Quoted:
If it was short stroking bad enough that it wasn't resetting the hammer, how would the bolt be moving back far enough to chamber a new round? I was wondering this myself. It chambered a new round perfect every time but always failed to reset the hammer. I have experienced this with Brown Bear. PMC is a little more expensive, but much better IMO.... brass cased too. |
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To test if your short stroking, simply shoot 1 round from the magazine. If the bolt locks open, the cartridge has enough pressure and your not short stroking.
Test the trigger. Simple way to do a dry fire test. This test is the same for any semi-auto. Empty gun, magazine removed. Cock action by running the slide (or pull the charging handle) Dryfire gun, maintain pressure on the trigger Cock gun again by running the slide (or pull charging handle) Now let go of the trigger, you should hear a click (If no click, the disconnect is not working = FULL AUTO) Dryfire gun again While running the drill, test your safety by turning it on then off, like your really shooting it. On your gun. I'd look into your trigger. I feel it's a trigger problem. Either the springs are weak or it's not resetting. |
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Quoted:
Quoted:
Quoted:
If it was short stroking bad enough that it wasn't resetting the hammer, how would the bolt be moving back far enough to chamber a new round? I was wondering this myself. It chambered a new round perfect every time but always failed to reset the hammer. I have experienced this with Brown Bear. PMC is a little more expensive, but much better IMO.... brass cased too. +1 on PMC some of the best ammo ive ever shot(not match ammo though  )
but PMC ammo has always been flawless its all my rifle or handguns get through them get teh PMC from palmettostatearmory they have a big selection and the ammo actually isnt that expensive |
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Quoted:
To test if your short stroking, simply shoot 1 round from the magazine. If the bolt locks open, the cartridge has enough pressure and your not short stroking. Test the trigger. Simple way to do a dry fire test. This test is the same for any semi-auto. Empty gun, magazine removed. Cock action by running the slide (or pull the charging handle) Dryfire gun, maintain pressure on the trigger Cock gun again by running the slide (or pull charging handle) Now let go of the trigger, you should hear a click (If no click, the disconnect is not working = FULL AUTO) Dryfire gun again While running the drill, test your safety by turning it on then off, like your really shooting it. On your gun. I'd look into your trigger. I feel it's a trigger problem. Either the springs are weak or it's not resetting. First, thanks for the great info on how to simply run the tests. I tested the trigger like you outlined above 10 times in a row. I heard the click every single time. I'll perform the short stroking test by firing 1 round, like you outlined above, today. |
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Ok, now I'm a little more confused.
I did the single shot per magazine with the Silver Bear as suggested and all 10 rounds fired and the bolt stayed open after each shot. So after that was successful I decided to shoot a magazine with 20 round of the M855 good ammo and then right after 20 rounds of the Silver Bear in a separate mag. I fired 20 M855 rounds rapidly, dropped the mag, loaded the 20 Silver Bear and fired those rapidly. Not one problem round out of the whole bunch. The only thing that I can think of that might have changed is that I really lubed it up yesterday while we were shooting and maybe the lube soaked into everything while my rifle was sitting overnight. I didn't nearly lube it that well prior to shooting yesterday and it hadn't been sitting in a bunch of lube. I'm really glad the issue is gone at the moment but I really don't want it to pop up again at a bad time. Thoughts? Also, after reading the great review of the Geissele 3 Gun trigger on here and elsewhere (and wanting a new trigger before this issue happened) I purchased the trigger from MidwayUSA and it should be here next weekend. Hopefully that can only help things. |
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