Hey all and thanks for any input.

First "home assembly" here and everything checks out except that my bolt doesnt "hold open" with an empty mag inserted.

Looking into the ejection port while pulling the bolt/carrier back, I can see the locking lugs of the bolt itself, lightly grazing the mag follower and pushing it down about 2millimeters (as the bolt / carrier assembly slides forward).

This is of course, lowering the bolt catch also by 2 millimeters, (because the bolt catch is pushed upward by the follower in the "emtpy" mag) , making it miss "catching" the bolt.

With the mag out and pushing the bolt catch up to try to engage the bolt carrier with my finger, the catch doesnt seem to reach far enough "up".    

Also if I go extreemly slow, I can get it to catch and hold, maybe 3 out of 10 trys.  Its barely engaging.

Lower Parts Kit is DPMS as sold by Spikes, dont know who made the Bolt Carrier.


Any suggestions?

I'm guessing you have a Sipke's lower.

What type of upper are you using?  How does the fit seem?  Is there a significant gap between the upper and lower?

Can you post some pics of the lower looking at the bolt catch from the top and sides?  Is it stiff at all or does it move up and down pretty freely?

Have you tried different mags?  Though this may not be the problem if it is only barely engaging if you manually push it.

Not a Spikes.  

Its a Mega lower fitted to a factory assembled Bushmaster Dissipator w/fluted Heavy barrel.

The fit is perfect,  no wobble or gap whatsoever.  

Working on pictures today.


Thanks for any help.   I just thought It may be a common "first timer" problem.


I'll check back later, hopefully w/ some pictures. +++


Also, is the bottom of the bolt carrier (where it engages the bolt catch) supposed to be angled?   Or squared off?      I may be looking at a worn out angle on my B/C.   Is this common?