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badicedog
03-26-2010, 8:00 PM
I recently built a new lower for my HK 416 upper. This is not my first build, second or third. I noticed when I attach an empty magazine and pull the charging handle, the bolt locks to the rear. If I shake the rifle, the bolt will unlock and spring forward(without pressing on the bolt release!). Any thoughts? All suggestions are welcome.

technique
03-26-2010, 8:04 PM
What kinds of mags and how many different kinds have you tried?

badicedog
03-26-2010, 8:11 PM
pmags, I'll try usgi and hk mags tomorrow. Same build worked great with noveske lower. This lower is a POF gen 1

Seesm
03-26-2010, 11:09 PM
I have this problem with 2 of my many mags... never happen with the higher end ones so I just use them now...

badicedog
03-27-2010, 10:05 AM
ok guys, I've tried Pmags, USGI mags, hk mags, c products....no change at all. Bolt will unlock with mod shake. Any other thoughts???

Noobert
03-27-2010, 10:10 AM
the followers of the empty mag push against the bolt catch, which stops the bolt carrier from slamming home, so is your bolt catch high enough? i can't think of anything else

pacrimguru
03-27-2010, 10:23 AM
i had a similar problem on my 9mm build. is there a little bit of play when you pull the bolt back all the way and let it go to get caught by the bolt catch? i know its a different system but you might have the same problem i had.

on my 9mm build, the bolt would lock back but with any kind of shake or hit no matter how light, the bolt would get sent forward. to figure out why, i pulled the ch back all the way and let it go slowly to get caught on the bolt catch to see how much space there was. it was about 1/8" i think. i realized that you need way more space than that for the bolt catch to have time/space to do its thing. so i shaved off another 1/8" or so on the buffer's plastic spacer. now i have a little over 1/4" of space between the bolt when pulled back all the way and the bolt catch. it works perfectly now.

i hope i'm making sense!

ar15barrels
03-27-2010, 7:15 PM
ok guys, I've tried Pmags, USGI mags, hk mags, c products....no change at all. Bolt will unlock with mod shake. Any other thoughts???

Don't shake the gun.
Ride the bolt catch with a finger if it's important not to release.