I just bought a new DPMS bolt/carrier from Brownells for a DPMS upper I bought off a member here.When I attach it to my PWA lower, the carrier sticks halfway after charging it.It only does this when I push the rear take-down pin in.When the rear pin is out, it cycles just fine.Does anyone know what might be causing this?

Definatly a bind at the junction of the upper and lower near buffer, is there anyway to try a buddies carrier to make sure it is not out of spec?

Check to see if.

-The buffer retainer is free and retained by the receiver extension properly.

Robert


www.rbprecision.com

I don't have a carrier to borrow but the buffer retainer seems to be free.If I pull back the charging handle and let go quickly, it goes into battery.I haven't fired the rifle yet and thought maybe it needs some kind of break-in with the new bolt/carrier?

Bolt group does not require a break in look for any unusual scraping of the coatings(burr etc)any way to get a picture? Might be able to see something obvious.

Sorry not much help on theis one

Robert
www.rbprecision.com

Redbone,

Does the bolt still stick if you cycle the bolt with the charging handle while holding the trigger to the rear?

Does your rifle use a slotted carrier?

Oh, I don't know, mebbe check the Glossary? There might even be a picture of them.

[url=http://ar15.com/forums/topic.html?b=3&f=66&t=167990]National Match-XM barrel[/url]

While you're there check out "Notched Hammer."

Bingo! We have a winner.I have both.What are my options?

Depends, like everything else, does the spool of the firing pin extend down into the ramped section of the slotted carrier? The larger spool of the M16 firing pin can hang on the hammer as the carrier closes.

If it's not the firing pin then you can either buy a shrouded carrier (recommended) or lightly round (requires some caution) the hooked portion of the hammer so that it no longer catches the firing pin spool.

Would replacing the hammer with a non-notched hammer solve the problem?The firing pin spool doesn't look to be protruding but is a little shiny where the hammer may be catching.

hi to all! Two easy options here! Grind the firing pin ring dia, down to less then .330, or grind the hammer notch deeper with more angle releif....  works every time! til...lat...GT
BTW Colt & Bushmaster have had this figured out for decades!

Sometimes, depends on how high the hammer sits when it's cocked. Even the normal hammers can drag on the firing pin. Plus, changing one part in the FCG may require retiming the lower. You're better off to try breaking the edge of the hook first (look for the shiny spot) and going from there. Is your firing pin retaining pin bent or difficult to reinstall?

The hammer could be sitting to high bc of a short trigger (distance from pin hole to sear face) a bad hammer (mislocated hammer notch) or mislocated T/H pin holes in the lower (not likely with PWA).

Remember, this interference only happens when cyling the rifle with the trigger forward. Except for the initial loading, the trigger is to the rear while the bolt is moving while you're shooting. So while it is irritating, and a sign of improper parts and/or assembly, it's not fatal.

Thanks guys.I ground down the hammer a bit and it cycles smoothly now.