Took my 2nd ar15 (Anderson) build out to test mon.went great but bolt did not stay open on last shot, will stay open when has empty mag.what could be the issue?
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Last shot bolt hold open
- Thread starter Gacowboy
- Start date
Try a different mag.
AK's dont stay open.
Usually will only stay open on Last Round, not your last shot!
Probably just a bad interface between the magazine follower, and the bolt hold open tap inside the magwell. I had a cheap mag that would activate the bolt hold on two of my better ARs but wouldn't on a cheaper one. It would kinda work if I dry cycled with an empty mag, but when stuff moves fast shooting there is alot more vibration and play in the parts. Cheap mags and parts run a higher chance of being out of spec. Try a new mag. Also what lower reciever and LPK did you use?
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Really could be a number of things. Without knowing your set-up, hard to tell. What I would look at:
1. Gas system. Gas block aligned properly? Gas tube aligned properly and creating a good seal with the carrier? Good seal on the gas block? If adjustable gas block, open it some more.
2. Buffer. Are you using the correct length buffer? Could possibly get a lighter buffer or spring.
3. Try different mags like others have suggested (easiest)
4. Bolt catch installed correctly and in spec not hanging up on anything?
If I am understanding correctly, sounds like you can pull the bolt back on an open mag and it catches, but not when firing? If so, I would tend to think it's not getting enough gas or the buffer/spring is too heavy not allowing the bolt to fully travel to the rear.
1. Gas system. Gas block aligned properly? Gas tube aligned properly and creating a good seal with the carrier? Good seal on the gas block? If adjustable gas block, open it some more.
2. Buffer. Are you using the correct length buffer? Could possibly get a lighter buffer or spring.
3. Try different mags like others have suggested (easiest)
4. Bolt catch installed correctly and in spec not hanging up on anything?
If I am understanding correctly, sounds like you can pull the bolt back on an open mag and it catches, but not when firing? If so, I would tend to think it's not getting enough gas or the buffer/spring is too heavy not allowing the bolt to fully travel to the rear.
AR running an adjustable gas block?
You say "build", so did you assemble the upper or buy a completer upper?
If I understand your OP....The bolt locks to the rear when the charging handle is pulled all the way to the rear on an empty mag (s).....but the bolt fails to lock to the rear when the last round is fired from the same mag (s), and you are sure it's not magazine specific...if that the case your magazine springs could be worn/weak or more likely the rifle is short stroking.
Many things can cause short stroking:
Underpowered ammo....although an inspec AR should cycle just about any commercial ammo avaliable
Out of spec gas port drilled in barrel or debris in the port
Worn/out of spec gas tube (at the carrier key/gas tube interface)
Misaligned gas block/front sight base
Poor gas seal between the carrier key and bolt carrier (usually caused by improperly torqued/staked carrier key screws)
Rifle buffer spring used in a carbine stock
and the list goes on.......
If I understand your OP....The bolt locks to the rear when the charging handle is pulled all the way to the rear on an empty mag (s).....but the bolt fails to lock to the rear when the last round is fired from the same mag (s), and you are sure it's not magazine specific...if that the case your magazine springs could be worn/weak or more likely the rifle is short stroking.
Many things can cause short stroking:
Underpowered ammo....although an inspec AR should cycle just about any commercial ammo avaliable
Out of spec gas port drilled in barrel or debris in the port
Worn/out of spec gas tube (at the carrier key/gas tube interface)
Misaligned gas block/front sight base
Poor gas seal between the carrier key and bolt carrier (usually caused by improperly torqued/staked carrier key screws)
Rifle buffer spring used in a carbine stock
and the list goes on.......
