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Posted: 1/22/2012 10:24:28 AM EDT
| I have been lurking this sight for months and have not posted as you guys have so much more knowledge than I so I've just been reading and learning. Anyway long story short I caught the bug. I had enough of the M 16 to last me a lifetime in the army or so I thought but I bought a new RRA 308 in october then in Late November an AR 15 and then I just had to build my own and already have the next one planned. I quess you can't have too many. Anyway I built my spikes lower a couple weeks ago and finished the upper this week put them together and tried it out. I had test fired a few rounds the lower prior on my other upper and it worked but on this upper I am having FTF with the rounds barely dimpled by the firing pin, and yes the hammer spring is in correctly( a common problem I read about here) but today after watching another assembly video I realised I put the disconnector spring in upside down. It did not want to go in w/o forcing it with the large taper down so I thot at the time it must go the other way. So the question is will that cause my problem?? I am going to break it down this evening and turn the spring over and make it go in but am wondering if I have another issue. Thanks for any help you might offer . |
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The slighlty dimpled primers on civilian primers is normal and is because of the free floating firing pin. When they FTF are they just not going into the chamber all the way?
I'm assuming they line up and go mostly in the chamber or the firing pin wouldnt be dimpling the primer. 1. Are they reloads? 2. Are there any visable burrs on either the feed ramps or the chamber? 3.Can you push a round into the chamber by hand with no pressure? (should drop in when the barrel is pointed straight down) |
| All out of the box brand new ammo and drop right in the chamber. I just finished changing the disconnector spring and went out and tried it. It failed 3 times out of 20 rounds and I reloaded them and all 3 fired. I am going the right direction as prior it failed to fire every forth round. Comparing this lower to my factory built lower the hammer spring is not as heavy but both are the same brand. The LPK was a DPMS, and I now know that was not my best choice but it should still work. The BCG is a spikes and when I put my factory built lower on it is 100 percent. I am stumped, could it just be that since everything is new and stiff the hammer spring is a bit weak and just doesn't make it? |
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Ah thought you meant FTF as Failure to Feed, not Fire.
I would check a few things, make sure the hammer is in the correct position with the bolt closed, what I mean is when you pull the trigger is it coming up 90 degrees and sitting flat against the bolt face, or is it angled slightly due to an out of spec hammer or out of spec bolt and not fully contacting the firing pin with full force. It could also possibly be an out of spec firing pin, I'd measure the length with calipers. |
| Firing pin is the same legnth as my other one and as I say when I put the factory built lower on it is 100 percent so it is something in this lower. The hammer does set at a 90 degree angle, I even installed this BCG in my other AR and it works perfect. I tore this lower down today and rechecked everything as well as lubing everything and it still fails to fire 3 out of 20. |
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Well, one option which would be a bit or work but would slowly eliminate every variable, would be to completely dissamble the factory lower then put all the parts in the malfunctioning lower.
If it then worked fine that would eliminate the possibility of the lower holes being out of spec. Then slowly replace parts one at a time from known working parts to the LPK of the malfunctioning one. If your lucky at some point you'll go from 100% working to malfunctioning with 1 part changed and that will give you the bad part. It's sorta the ghetto way to do it but it's hard to diagnose some issues without seeing it in person 
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