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+--- Thread: Reading rim sign (/showthread.php?tid=1094)
Reading rim sign - Diesel Pro - 12-25-2023
Not sure how well the pictures will show, but I'm seeing gouges on the rims even with Hornady Black 105's. I'm assuming this is likely due to something on the extractor needing to be deburred? How does a guy know what is a pressure sign and what is not?
The starline is a hand load based on Uncle Bob's results and N135 so it may actually be pushing it, but the Hornady brass is the Black factory ammo.
The blacks were mag fed. The hand loads were single fed as they throw to the correct location, but do not have quite enough push to cycle the bolt.
[attachment=768]
RE: Reading rim sign - CZ527 Guy - 12-25-2023
I see nothing to be concerned over. Perhaps you can cycle live ammo without firing to evaluate feed & extraction performance without firing.
RE: Reading rim sign - Diesel Pro - 12-25-2023
I'm working with the extractor to get the fangs polished up a bit based on some posts I have read, They are very sharp hence the gouging when chambering.
RE: Reading rim sign - Old Bob - 12-25-2023
The extractors on 6mm ARC/6.5 Grendel bolts can have some sharp points on them & they will leave marks on your brass rims. I used a cratex wheel to do a little rounding-off on the points of my extractors.
RE: Reading rim sign - Diesel Pro - 12-26-2023
I've got mine to where it still leaves fairly defined thin lines, but MUCH better. Can a guy get them to load clean without evidence on the rim or is it not worth chasing that?
RE: Reading rim sign - Old Bob - 12-26-2023
There are some threads about this on the Grendel forum - https://www.65grendel.com/forum/forum.php
In the search box, type in "extractors" & see what comes up. I think there are some youtube videos as well.
RE: Reading rim sign - Diesel Pro - 12-27-2023
While on the subject or brass markings these are from a CMMG upper that I just picked up. I don't quite recall if I was manually feeding these or single shot from a mag, but I almost have to assume these scratches on the necks are from the feed ramps? Working on my photo skills. I don't have a macro lens so I am using std from a distance and zooming in.
Looking to see of I can get away with polishing while attached to the upper. I have a 1/8 pneumatic pencil grinder just need to find the right accessory.
[attachment=769]
RE: Reading rim sign - grayfox - 12-27-2023
Those are from the barrel/extension teeth that mate up with the bolt...inner pointy spots IIRC.
I'm not the one to ask about polishing, I'm afraid I'll mess them up...
RE: Reading rim sign - Diesel Pro - 12-27-2023
CMMG says:
Those actually come from the lower lugs of the bolt while it cycles over the round in the magazine. There isn't much that can be done to stop it. It isn't something that will affect functionality, reliability, or safety.
RE: Reading rim sign - UncleBob - 12-28-2023
(12-27-2023, 12:20 AM)Diesel Pro Wrote: While on the subject or brass markings these are from a CMMG upper that I just picked up. I don't quite recall if I was manually feeding these or single shot from a mag, but I almost have to assume these scratches on the necks are from the feed ramps? Working on my photo skills. I don't have a macro lens so I am using std from a distance and zooming in.As Grayfox mentioned, those are from the barrel extension. Those sharp points and the big hump in the middle need to be knocked down and polished for Grendels and ARCs. If you look up pictures of the barrel extension on the Bushmaster 7.62x39, you'll see there is no hump in the middle. That is the one you want to get close to mimicking. Remove the barrel for doing any feedramp work.
Looking to see of I can get away with polishing while attached to the upper. I have a 1/8 pneumatic pencil grinder just need to find the right accessory.
RE: Reading rim sign - Diesel Pro - 12-31-2023
I'm planning to get me an armorers wrench and the Brownells, barrel extension TQ tool so I can pull the CMMG apart. My Cobalt is doing well with the fangs polished on the MPI bolt. In hindsight I probably should have just went with one of these: https://www.sixfiveoutfitters.com/product/ar15-improved-6-5-grendel-6mm-arc-extractor/
Or even their complete bolt and be done with it.