Solution for dented case necks?

[pontoon]

I just finished my 6.5 Grendel build. It has a 20 inch barrel and an adjustable gas block. The bolt carrier is a low mass type. I took a standard buffer and removed the weights and replaced them with wood. Yes, I know that's weird. Even though it's weird, other people have this issue with normal weight buffers too.

When I went to fire the gun, I turned the gas way down. Then I turned it up and up until the rifle would cycle properly. Once it was cycling properly, it was denting the brass. If I turn it one click less, the brass doesn't fully eject. I was thinking maybe adding one or two of the weights back to the buffer might allow me to have more fine grained control over the cycling of the rifle, so I might find a sweet spot where it still cycles properly, but it also doesn't dent the brass. I don't have my hopes up though since this does happen to people who have normal weight buffers as well. Some people put felt or padding on the brass deflector (the deflector is what causes the dent)... I'd rather solve it another way if I can. Also some people say to just live with it, because the brass will be reshaped when reloading. But I wonder: will this reduce the amount of times the brass can be reloaded?

Anyone got any ideas?

[Klem]

Cut the ejector spring shorter, by the amount it protrudes from the bolt-face when slack (a couple of coils).

Padding on the deflector eases the symptoms but does not fix the problem. You won't need padding if you shorten the spring. Cases might occasionally collide with the deflector but none will be dented.

[pontoon]

Thanks!

[rabiddawg]

You are willing to expose your rifle to termites but don't want to put some Velcro on the deflector. Hmmm.

[NugginFutz]

As Klem said, the velcro treatment only addresses the symptom, but not the root cause. The ejector spring mod did the trick for both of my Grendels, neither of which use modified buffers, wooden or otherwise.

[pontoon]

There's no way termites can get inside the buffer... Just the weights are wood, not the whole buffer.

Also, how do I stop the case from being gouged? I noticed one or two lines where the casing is gouged. Does this little gouge line pose a problem for reloading?

[NugginFutz]

Cases can be gouged at the shoulders by the feed ramps, and if this is your case, you may wish to polish them.

See this older thread...

http://www.65grendel.com/forum/showt...ll=1#post19182

If you're talking about gouging under the case head lips, then extractor problems are possibly the case (either early extraction or sharp corners on your extractor). This is a completely different set of problems, of course.

Without pictures, it's difficult to pin down your issue.

[pontoon]

NugginFutz, it's much like this:

[Beerswimmer]

Start small. One baby step at a time.

Replace the extractor completely...extractor, springs, and o-rings. No change, then replace your weights. No change, then replace your recoil spring. Only then move forward and cut parts*.

* Terrible practice





But that's just how I do things.....

[Klem]

The parallel score marks on the neck are from the feed grooves in the barrel extension. Filing the feed grooves smooth fixes that.

The small dings in the body are from bouncing against the upper on ejection. Shortening the ejector spring will fix that.

The advice given to replace parts before cutting them is, with respect, dogma. The expertise on this forum transcends dogma.

[rabiddawg]

There's no way termites can get inside the buffer... Just the weights are wood, not the whole buffer.

Dude, I hope you didn't think I was serious about the termites

One thing I do know is wood swells with moisture. I would use a different substance.

[LRRPF52]

What I call the "vampire effect" on the case necks comes from when the spent case is extracted from the chamber, and the ejector forces the case out of line with the bore once it clears the chamber, hitting the lead edges of the barrel extension teeth in the ejection clock position.

[jawbone]

i tightly wrapped some super-fine sandpaper around a chopstick, then carefully, gradually slighly rounded the tips off those two sharp teeth. no marks or no probs since. take it slow and easy in there, though, because sandpaper.

[diddlyv]

I too am getting dented mouth of the case from my grendel. I hve an adjustable gas block set to the first click that allows the bolt to lock to the rear using 1 round in a mag. Wondering if using a rifle buffer vs standard carbine would cure the problem. It will be easy enough to test as I have 3 lowers with rifle buffers in them.

The gurus' thoughts on this???

[NugginFutz]

Dented case mouths can be eliminated or mitigated by performing one or more of the following:

1. Shortening the ejector spring, via one of the several threads found in the forum.
   
2. Adding Velcro (soft side) to the case deflector. (Treats the symptom, but not a cure).
   

http://www.65grendel.com/forum/showthrea...case-necks

http://www.65grendel.com/forum/showthrea...tor+spring

[SG4247]

What I call the "vampire effect" on the case necks comes from when the spent case is extracted from the chamber, and the ejector forces the case out of line with the bore once it clears the chamber, hitting the lead edges of the barrel extension teeth in the ejection clock position.

Klem and LR are 100% correct in this. Some manufactures of barrel extensions and good gunsmiths will cut a small chamfer on the barrel extension lugs, in the lathe, from the barrel side. This is done before the extension is screwed onto the barrel threads and locked in place.

This actually accomplishes two things:
1. Keeps vampire tracks off your case necks.
2. Provides extra clearance to for the radius on the back side of the BOLT lugs. Hopefully your bolt lugs have a slight radius on the root to prevent cracks from forming. If the radius on the bolt lugs is too large, there could be interference with the extension lugs and headspace will be inconsistent - and bad things could result.

Ask your smith to check for or add the chamfer if you ever have a custom AR barrel made.