Bolt catch not catching on last round

AR/M4 AR Technical Discussion
1

so i have a new build and had to replace the bolt catch the first one was sticking so i thought that was the problem… the second one doent stick so i thought i was good to go but no such luck…last shot still doesnt lock back…

it is a rock river lower daniel defense parts

pretty sure its a cheaper BCG maybe dpms my friend got me a deal on it and i have to check with him again to see brand…all commercial spec

so i took the bolt catch out again and shaved off about .015" of the rear face and i have not shot the gun since but not sure if it is going to work

does anyone know the clearance that is supposed to be between and bolt catch and bolt with the charging handle all the way back?

anyone have any ideas?

i was thinking maybe buffer and or buffer spring

i was shooting a combination of ammo

pmc brass 55gr .223
federal 55gr brass .223
tula 55gr steel .223
and federal 55gr 5.56

runs good with whatever ammo i though at it except the lack of catching on last round thanks for the advise in advance

2

Before you ruin another bolt catch, read this … http://m4carbine.net/showthread.php?t=138

3

going to read it now …but the first bolt catch was sticking in the lower and was defective DD replaced it and the new one fits perfectly …thanks for the link

4

The bolt face should retract approx .250" past the bolt catch at full recoil.

What receiver extension & buffer?

5

Check the buffer spring length.

6

Lot’s of possibilities.

We know the lower and BCG, what else is the rifle comprised of?

Did you build the upper or buy one outright?

Just simplify this and list all the parts in your rifle, including what mags you are using.

7

For sure. How “thumpy” is the recoil? Does it feel weak/slow when cycling?

If it’s thumping pretty good and postively ejecting… it could be overgassed and out running the follower.

8

This question led me to believe he is not having the BCG physically retract far enough.

I agree, a list of items if you built it yourself.

9

Over gasses, under gassed, no name mag, dirty mag, buffer, spring…we really need more info.

10

OKAY…shot it again today and saw im leaking gas out the gas block in front i believe this is the problem…can i fix this myself? i have never taken off or installed a gas block im really not too worried and i know they can move …the gun shop i bought it from said they have to test it first…next week… they are dumber then i thought… can i take it off and see if its installed the right way…

idk about biffer and spring i would have to measure it and find out it might be adding to the problem its a carbine 16" build

11

ok so .250’’ is a good number i can work with…if its not going past that far…what is blocking it?

12

under gased is my opinion and i ONLY run pmags and for it being dirty its all brand new prob 3-400 down tube and i cean every time even if i shoot 5 rnds

13

Pmags have difficulty engaging bolt stops on some rifles. Take your upper off, install an empty magazine, and see how much over lap there is between the mag’s tab and the bolt catch.

Advntrjnky

14

Is the BCG not moving back far enough? If so what spring, buffer tube or buffer brand/type is being used.

If the BCG is moving back far enough then the problem you found in the gas system would be the first area to address. Keep up the good work and solve one problem at a time.

15

I repaired someone’s rifle with the same problem. They built the rifle out of parts and the fixed buttstock was replaced with an Ace stock. The butt stock screw was too long for the new stock, so there was enough screw sticking out inside the receiver extension to stop the buffer from traveling far enough to the rear to allow the bolt to be engaged by the bolt stop. I replaced it with a shorter screw and the rifle functioned properly.

On another occasion, I was running a rifle class and I saw a working rifle start to malfunction. Initially I thought it was a gas problem and it turns out there was dirt in the vent hole on the upper buttstock screw. The buffer fit tight enough inside the receiver extension that pressure built up and would not allow the bolt to travel far enough to the rear. I cleaned the dirt out of the vent hole and it cured the problem.

Try using a magazine that you know will work in another rifle.

There are a lot of possibilities and without seeing the rifle it is hard to troubleshoot. Please give us an update when you find the problem.

16

ok here are some pics gas block w crap that had come out of it(looks like rusty oil)… i checked the key to see if there were any leaks and there are none…the biffer is 3 1/4" the buffer spring is 9" i do NOT know the make of buffer, buffer spring or tube…

other then that the lower is rock river
daniel defense lower parts kit
stainless steel trigger group

the upper was complete from M&A…dont know much about them…it is a crome lined 5.56 1:9

17

18

Photos did not come up, so you will have to fire again.

Repeat. Send it.

19

so the last pic is of me holding the charging handle back and pressing the bolt catch up…there is like .010-.015" clearance …but thats with the handle not sure if when its running it will retract further …also its a cheap cheap charging handle i plan on replacing it soon but just spent lots of money on ammo and a few more pmags because of this stupid government trying to take away our 2nd amendment rights

20

…what im looking at them right now…i used the img link off photobucket… do i see something you dont…i posted the text then in my next post posted just photos…do i use the html link or …???