I have built an AR Pistol that functions perfectly EXCEPT the bolt stop. The bolt stops, but it stops short of being back far enough to pick up a round. The bolt catch when operated MANUALLY does the very same thing: it stops the bolt carrier but not back far enough at all. The bolt stop, when operated manually stops the bolt about 1" forward into the ejection port. I have replaced the entire bolt catch system, I have tried a 2nd bolt carrier group, nothing seems to stop my bolt in the right place when operated manually or at full function upon empty. When you change to the next magazine, this forces you to drop the bolt, insert the newly loaded mag, then rack the bolt and it does fine. If you empty a mag, the bolt stops, but too far forward and it will not pick up a round.

Suggestions? No it has not been dry fired, yes I have tried 2 bolt carriers-same thing.

DR

Which part are you referring to when you say "bolt stop?" Also, what length buffer tube, buffer, and type of spring are you using?

Is the bolt catch actually catching the bolt face or catching on the carrier for some reason? Possibly the wrong length buffer spring?

The bolt catch is catching the carrier not the bolt face

The Buffer tube is a pistol style. The carrier will pull back PLENTY far enough for the bolt catch to catch the bolt, it just doesn't. It's almost like there is no bolt face there, but the bolt carrier is  perfect. The bolt is NOT beating up the buffer either, not a mark on the buffer other than slight paint wear.

Pic coming....

DR

 
This, or perhaps you have a strange receiver extension tube that is shorter than the standard.


How about some pics of:


-The BCG, buffer weight, and spring all removed from the gun.


-The receiver extension (aka buffer tube)


A close up of the bolt catch as viewed with the upper removed, to see if it is damaged or broken in some way.

Did you use a pistol length buffer spring?

Anderson lower?

Would either be the buffer tube length or wrong spring size.

I had a similar issue with a cheap unnamed buffer tube with a notch cut out for the detent. It made the buffer tube length a hair too short. Totally unusable.

Yes Anderson Lower.

Pic's later tonight

My buffer is:
PC-armament, Model 4/15 .223 5.56 Style tube extension kit. Anodized RED.
Sold by: PC-Armament

My buffer has no notch but it is cutout in a weird way:

http://www.pc-armament.com/#!Exciting-New-Products-Release/fcc7r/563ad41d0cf275e9c5986bac

DR

What do you mean, doesn't have a notch?  The pictures on the website show the end plate groove with the notch in the extended section. I like the Red!  A picture of the buffer tube, an angle showing the buffer retainer with buffer would be helpful.  Maybe a picture with the buffer spring removed.  Maybe they gave you the wrong spring length.  Also, I would look inside the tube itself and make sure it's empty.  I had a similar tube and they packed an additional pad in there at the bottom.

 
That is the buffer tube, or more accurately, the receiver extension.


The buffer is the weight that reciprocates in the extension, between the BCG and the action spring.


Some are longer than others, and may limit the full travel distance of your BCG, thus preventing lockback.


You should have a traditional carbine sized buffer and action spring, as seen in the bottom of this image:

Sorry, you're correct, mine has a notch.

Seems I had two things at play that fixed the problem. I loosened the castle nut and backed off the buffer tube one turn, and I compared the springs length to another AR spring I had on the bench. My spring was 2.5 turns LONGER. So...I backed off the buffer tube one turn and cut off 2.5 rounds off the spring. Works perfectly now!!!

Thanks SO MUCH TO ALL OF YOU WHO HELPED!!!!!!

DR

Sounds like it had a rifle spring in it. I would buy a replacement carbine spring. Damage Industries has their enhanced carbine springs on sale for $6 pretty regularly.

jaqufrost,

Why buy another spring? I used bolt cutters on this spring, so the temper has not changed. I also filed the cut round and smooth.

I do not at all mind buying another spring! Not at all, I'm just trying to understand why.

Thanks so much!

DR

No need to buy a new spring if you cut it to the right length. Unless it will make you sleep better at night.  It will make no difference.

Careful how far you back out the receiver extension. When I did mine, it barely held onto the buffer retainer pin. So after the bolt cycled a few times, the retainer slip out and jammed the bolt.