Buffer Wear

[army_eod]

I am running a Spikes Tactical carbine lower on my Grendel Hunter 20 inch upper.
I note I am beating up the buffer. It is getting worn and scratched by the retaining pin.
Pretty new to the Grendel and I did a quick search.

Does anybody know a fix? Do I need a different buffer/spring combo?

Note photo

20210808_145046.jpg

[Klem]

army.

Never seen that before however Montana was posting recently about out of spec lowers where the retaining pin hole has been drilled too far to the rear. Instead of the pin only stopping the buffer when the upper/lower are separated it does it every cycle. The buffer should be stopped on the forward stroke by the BCG when it goes into battery and not touch the retaining pin.

When you put the gun together and finally tilt close the upper does the BCG push back the buffer slightly as it closes or does it look like the retaining pin is still holding the buffer and recoil spring in?

[army_eod]

army.

Never seen that before however Montana was posting recently about out of spec lowers where the retaining pin hole has been drilled too far to the rear. Instead of the pin only stopping the buffer when the upper/lower are separated it does it every cycle. The buffer should be stopped on the forward stroke by the BCG when it goes into battery and not touch the retaining pin.

When you put the gun together and finally tilt close the upper does the BCG push back the buffer slightly as it closes or does it look like the retaining pin is still holding the buffer and recoil spring in?

You know, I think you hit the nail on the head. I checked that AR against several other of my ARs and it looks like the retaining hole is too far rear/out of spec.
I ordered a new lower from Aero Precision. Maybe that will fix it.
I did send Spikes Tactical the info with pics. I will see what they say.

[montana]

You know, I think you hit the nail on the head. I checked that AR against several other of my ARs and it looks like the retaining hole is too far rear/out of spec.
I ordered a new lower from Aero Precision. Maybe that will fix it.
I did send Spikes Tactical the info with pics. I will see what they say.

A buffer tube that is out of spec, or a short bolt carrier can cause this problem. https://www.youtube.com/watch?v=kvfr4Xb3wLY A barrel shim that is installed incorrectly,"between the receiver and the barrel" can also cause this problem. You could remove the buffer retaining pin and spring and replace it with a JP SCS that needs no retaining pin. They also make an offset buffer retaining pin, for lower receivers with an out of spec drilled buffer retaining pin hole. I have never used one, so I can not vouch for how well they work..https://gallowayprecision.com/offset...r-AR-15-rifles..

[StoneHendge]

Could also be an out of spec upper. Try the lower with a different upper. Or try the upper with a different lower. That will indicate where the problem is.