Part 10: Checking and adjusting Bolt Catch overrun.
The amount of Bolt Catch overrun is important, as too little may not allow the Bolt Catch time to fully engage, and too much (most common) beats excessively on the Catch and causes a "slamming" feel when the bolt locks back on the last shot of a mag. It is also hard on your lower receiver.
On Large frame AR's, this is a common cause of premature Bolt Catch breakage, as the heavy parts really slam the Stop. Doubly important if you have added mass with a Tubb weight or heavy buffer.
First (for A1 and A2 style stocks only), remove the Buffer and Buffer Spring, take a flashlight and look down the Buffer Tube and MAKE SURE the Buttstock Screw is below the level of the Buffer Tube end. Many of these screws are too long and protrude into the end of the tube. This is where the Buffer strikes and stops the rearward movement of the Buffer. If it is too long, grind or file off the end of the screw until it is below flush.
With the rifle fully re-assembled (if you have a Tubb weight, install it also), pull the charging handle ALL the way to the rear and hold it there.
Push in the Bolt Catch and hold it.
Check how much gap there is between the Catch and the Bolt face, it should be about .075 inches (2mm). This is about the thickness of a nickel.
If it is too close, you can sand or file some off the plastic snubber on the rear of the Buffer.
If it is too wide (most common), remove the buffer and spring, then place shims (Quarters are almost the perfect size, and work well) down in the bottom of the Buffer Tube until the gap is correct. When you get the gap correct, remove the shims, and drill a small hole in the center of them so the air hole in the Buttstock Screw is continued.
Check all your mags and make sure they engage the Bolt Catch properly, sometimes the follower hangs a little in the last little bit of travel and will not engage the Catch fully.
The amount of Bolt Catch overrun is important, as too little may not allow the Bolt Catch time to fully engage, and too much (most common) beats excessively on the Catch and causes a "slamming" feel when the bolt locks back on the last shot of a mag. It is also hard on your lower receiver.
On Large frame AR's, this is a common cause of premature Bolt Catch breakage, as the heavy parts really slam the Stop. Doubly important if you have added mass with a Tubb weight or heavy buffer.
First (for A1 and A2 style stocks only), remove the Buffer and Buffer Spring, take a flashlight and look down the Buffer Tube and MAKE SURE the Buttstock Screw is below the level of the Buffer Tube end. Many of these screws are too long and protrude into the end of the tube. This is where the Buffer strikes and stops the rearward movement of the Buffer. If it is too long, grind or file off the end of the screw until it is below flush.
With the rifle fully re-assembled (if you have a Tubb weight, install it also), pull the charging handle ALL the way to the rear and hold it there.
Push in the Bolt Catch and hold it.
Check how much gap there is between the Catch and the Bolt face, it should be about .075 inches (2mm). This is about the thickness of a nickel.
If it is too close, you can sand or file some off the plastic snubber on the rear of the Buffer.
If it is too wide (most common), remove the buffer and spring, then place shims (Quarters are almost the perfect size, and work well) down in the bottom of the Buffer Tube until the gap is correct. When you get the gap correct, remove the shims, and drill a small hole in the center of them so the air hole in the Buttstock Screw is continued.
Check all your mags and make sure they engage the Bolt Catch properly, sometimes the follower hangs a little in the last little bit of travel and will not engage the Catch fully.
