I went to clean my AR and after cycling the BCG a couple of times the bolt would not close. It took me a few mins of WTF to realize the buffer detent pin was caught in the BCG.

I took it all apart and found this:







Well, I was hoping that Spikes Tactical would see it my way but they say that's not a manufacturers defect.

So who do you guys like for stripped lowers?

No pictures visible. I’ve had no problem with the ST lower that I have. The other stripped lowers I’ve used are Aero Precision, and no problems there either.

Seems to me that the only thing that could cause that is some part, or combination of parts, being out of spec, allowing the buffer to contact the detent during the firing cycle. Something about the gun wasn't right.

quote:

Originally posted by Dwill104:
No pictures visible. I’ve had no problem with the ST lower that I have. The other stripped lowers I’ve used are Aero Precision, and no problems there either.

If you right-click on the pic and open it in a new page, they are visible.

quote:

Originally posted by KSGM:
Seems to me that the only thing that could cause that is some part, or combination of parts, being out of spec, allowing the buffer to contact the detent during the firing cycle. Something about the gun wasn't right.

BCM upper, Spikes lower and magpul stock.

Why not just get a captured recoil spring system and do away with the buffer detent altogether? You could keep the lower you already have that way.

quote:

BCM upper, Spikes lower and magpul stock.

I wasn't implying you used poor-quality components. That damage doesn't just happen all on it's own; something acted upon that detent, that shouldn't have. I have seen it before, and it was caused by the buffer contacting it. Are there signs of contact on the buffer edges? Are there signs of contact on the inside or aft edge of the channel in the rear of the carrier?

quote:

Originally posted by SigM4:
Why not just get a captured recoil spring system and do away with the buffer detent altogether? You could keep the lower you already have that way.

I'm hoping you can help me here as I'm not an expert by any means on the AR platform.

Where do I go to find one? And is that all I need?

quote:

Originally posted by KSGM:
Are there signs of contact on the buffer edges? Are there signs of contact on the inside or aft edge of the channel in the rear of the carrier?

I'll have to look tonight.

This message has been edited. Last edited by: Shaql,

It looks to me that you have caused the problem yourself by not having the buffer retaining pin depressed while installing your receiver extension/buffer tube (whatever you want to call it)... then over tightened the receiver extension/buffer tube to get it to line up rather than depressing the retainer.

kimberkid may be on to something; I just now looked at the pictures, and that's certainly possible.

quote:

Originally posted by Shaql:

quote:

Originally posted by SigM4:
Why not just get a captured recoil spring system and do away with the buffer detent altogether? You could keep the lower you already have that way.

I'm hoping you can help me here as I'm not an expert by any means on the AR platform.

Where do I go to find one? And is that all I need?

JP Rifles Silent Captured Springs --> https://www.jprifles.com/1.4.7.2_os.php

quote:

kimberkid may be on to something; I just now looked at the pictures, and that's certainly possible.

Probably so but it's been years since I put it together and have no recollection of not following the instructions. Doesn't mean I didn't do it wrong....

quote:

JP Rifles Silent Captured Springs --> https://www.jprifles.com/1.4.7.2_os.php

Thanks!

^This right here. That’ll fix you up right quick. Best part is no spring bounce back noise.

quote:

Originally posted by Shaql:

quote:

Originally posted by SigM4:
Why not just get a captured recoil spring system and do away with the buffer detent altogether? You could keep the lower you already have that way.

I'm hoping you can help me here as I'm not an expert by any means on the AR platform.

Where do I go to find one? And is that all I need?

quote:

Originally posted by KSGM:
Are there signs of contact on the buffer edges? Are there signs of contact on the inside or aft edge of the channel in the rear of the carrier?

I'll have to look tonight.

Nothing special as far as I can tell. But something beat the hell out of the pin:

https://drive.google.com/file/...hMR/view?usp=sharing
https://drive.google.com/file/...8Wc/view?usp=sharing
https://drive.google.com/file/...-N5/view?usp=sharing
https://drive.google.com/file/...zYu/view?usp=sharing

If the carrier isn't pushing the buffer back when the upper is closed the buffer pounds the crap out of the retaining pin.
Buffer will look like this.


Either the JP spring or a Law Folder will fix that up.
But you have to check the folder to make sure it doesn't eat the pin before you shoot it.
That's what chewed up two of my buffers, had to make a shim for the adapter.

I was wondering from the pics if perhaps the hole was drilled too far forward and that caused the issue. It's awfully close to those threads compared to what I recall.

I have a spare JP enterprises captured spring I'm not using if you want a little better deal.

quote:

Originally posted by PGT:
I was wondering from the pics if perhaps the hole was drilled too far forward and that caused the issue. It's awfully close to those threads compared to what I recall.

I have a spare JP enterprises captured spring I'm not using if you want a little better deal.

That's what I was hoping ST would say but they don't agree.

That's very nice of you but unfortunately I ordered one earlier in the day. Thank you though!

I once had an issue getting a rifle to open. It was a Sun Devil billet lower and an Alexander Arms 50 Beowulf upper.

When I finally got it open, the buffer came popping out. The retained "pin" was gone. Actually I found it inside the buffer tube at the bottom. The hole it goes in was kind of oblong, stretched out, forward. I took a punch and hammer and tapped it back closer to round. Put everything back together.

WHY it did this I couldn't say, it never did it again. Not in several hundred more 50B rounds, or the thousands of 5.56 rounds after that upper was sold.