If you perform a couple of simple test prior to assembling the bolt catch assembly you can save yourself some major and minor grief.

1.  Take the bolt catch and insert the roll pin in the roll pin hole, it should rotate freely.  If not open the hole a bit with a drill bit to clean it up.

2.  Place the bolt catch in the required position in the lower receiver, DO NOT PIN IT !! Just check it for free movement.  If it does not move freely check the receiver for casting flaws, you may need to clean the slot up a little with a fine diamon file or alternatly the catch may need to be cleaned up a little with some emery or a fine file.  If this all is moving freely take the next step, and the most critiacal one.

3.  The plunger.  Lube the plunger and with needle nose pliers very, very carefully and gently, slowly check it in the hole in the receiver, a little at a time.  It should move very freely.  If you feel ANY resistance STOP!!!
The hole in the receiver may have some extra anodizing in it or the plunger may be slightly out of spec.  This part, if stuck in the lower is a bitch, capital B, to get out if it gets stuck as this is a blind hole.  Either clean up the hole in the receiver or emery the Plunger.
With the spring in place the plunger should move in and out with just finger pressure.

Once you are sure all the parts in the bolt catch assembly move very freely assemble.

Remember the only thing that is holding your bolt open is the mag spring and follower.

Maybe this sounds like a lot to go thru for such a simple part of the build, but it is worth it.

A plunger stuck in a receiver is a major problem and a semi working bolt hold open is a major pain in the ass.  It is worth the time.

Hope this helps all you new builders

Denny

Let's keep on with the builders tips.  Anyone who reads these and other posts here on ARF, with decent skills can build a blue printed AR that is better than factory due to more fine tuning of all the parts and selecting exactly the parts they need without the needless cost of throwing away the factory stuff they elect not to use on their project.

Everyone one has their own visions of what their perfect AR or ARs consist of.  They should be able to get the info here on how to get it right the first time, with a minium of hassle and mistakes.

I use similar methodology when building a custom Harley.  Fit it all first, mock it up and check it all out before final paint and assembly.

Check everything out.  Even the best parts from the best suppliers can need some minor tweaking.

Denny

Oops, sorry about the tweaking comment[BD]
Tell Val Hi from Denny