All my ar's are ok except 1 my bushy M4, when I run a safety check pulling the charging handle back and holding the bolt catch button to hold the carrier back, it will not hold all the time, what causes this problem the bolt carier or the bolt catch release button? I look at the bolt  catch on the lower and it looks OK.....

.....any ideas or similar experiences.....

Quoted: Does the bolt catch come up far enough to grab the bolt? Does the bolt come back far enough for to clear the bolt catch.

I gotta press the bottom part of the bolt catch real good to engage it...

Quoted: Can you lock an empty mag into the well, pull the bolt to the rear with the CH, and have the bolt lock open? If not, I'd pull the bolt catch and make sure you don't have a disconnector spring under it. Check to make sure the "finger" on the bolt catch is actually contacting the rear of the mag follower. Once you have the catch out slide it back and forth in its slot and check for any binding. Any battering on the rear of the bolt catch where the bolt hits it?

Tweak thanks! I am at work right now I am gonna try it when I get home.

Quoted: Quoted: Can you lock an empty mag into the well, pull the bolt to the rear with the CH, and have the bolt lock open? If not, I'd pull the bolt catch and make sure you don't have a disconnector spring under it. Check to make sure the "finger" on the bolt catch is actually contacting the rear of the mag follower. Once you have the catch out slide it back and forth in its slot and check for any binding. Any battering on the rear of the bolt catch where the bolt hits it? Tweak thanks! I am at work right now I am gonna try it when I get home.

I put an empty mag into the well, pulled the charging handle to lock the bolt back, and it is intermittent, does not lock back more often than not, when I hinge the upper forward the finger is below the follower (not good). It will lock back a few times. Should I order a new bolt catch assy. and have a gunsmith put it in or is it another problem?

Shotgun the upper open, and work the bolt catch by hand, it should move freely with only the catch return spring tension pulling it back down.  If the catch is binding, then you will need to pull the catch and clean the spots that are rubbing, or lube it and work it by hand until it no longer binds. My guess is that there may be a bur in the spring channel that is not allowing the catch to full raise.  The cross roll pin retains the catch, and it consistes of the catch, spring and detent.  Use a 1/16" punch and drive out the roll pin to remove the catch.  Also, a little tape on the receiver will prevent maring if you slip with the punch.

If the catch is not binding, then chances are the mag spring is not pushing hard enough up on the mag follower to activate/fully lift the catch. Here a new mag spring may be in order.

Bottom line is that you should be able to push the bolt catch below the lever by hand to cam it up and catch the bolt.  Also, a good test once you have the bolt locked back is to bounce the butt stock off the ground.  If the catch in not binding, then as the recoil of the bounce is transfer to the bolt (pulling it away from the catch and the catch lowering back down), the bolt should snap closed.

Quoted: Shotgun the upper open, and work the bolt catch by hand, it should move freely with only the catch return spring tension pulling it back down.  If the catch is binding, then you will need to pull the catch and clean the spots that are rubbing, or lube it and work it by hand until it no longer binds. My guess is that there may be a bur in the spring channel that is not allowing the catch to full raise.  The cross roll pin retains the catch, and it consistes of the catch, spring and detent.  Use a 1/16" punch and drive out the roll pin to remove the catch.  Also, a little tape on the receiver will prevent maring if you slip with the punch. If the catch is not binding, then chances are the mag spring is not pushing hard enough up on the mag follower to activate/fully lift the catch. Here a new mag spring may be in order. Bottom line is that you should be able to push the bolt catch below the lever by hand to cam it up and catch the bolt catch.  Also, a good test once you have the bolt locked back is to bounce the butt stock off the ground.  If the catch in not binding, then as the recoil of the bounce is transfer to the bolt (pulling it away from the catch and the catch lowering back down), the bolt should snap closed.

Thanks Dano, I am gonna take to a smith that works on Bushys here in my neighborhood...

GunDoc, my gunsmith measured the magwell and found it  a little larger than my Colt's, used a micrometer, funny he pulls out a mag(GI) and it locks back.....