Tweet
I had to replace the bolt on my Grendel. I'm using 3x-4x fired Hornady brass. My fired brass measures .441 at the base. My reloaded brass measures .440 at the base. I've cleaned the chamber and cleaned it again. The extractor is releasing from and bending the rim on the cases and does not eject the cases . I have an Adj. GB that is ejecting @ 3 oclock. When it was ejecting @ 1 oclock the problem didn't seem to be. I checked the extractor and it has the black o ring and 5 coil spring. Hornady factory brass is .437 at the base. I'm wondering if i need to size it down more. I have used both Redding and Forester sizing dies, and they resize the same .440 at the base. Thought about milling some material off of the shell holder, but at present my shoulder set back is .012 with a 330 comparator. Also thought about getting a diifferent extractor. The replacement bolt is a MPI 7.62x39.
-
-
As far as I know, 7.62x39 bolts all have .125 boltface depth (someone correct me if I am misinformed here). Was your rifle originally chambered for that bolt? do the cartridges try to stick in the chamber when cycling by hand? Sizing isn't going to do anything to the rim. You are bumping the shoulder too far. .003-.005 should be plenty. Could you post a picture of a few of those bent rim cases? What bbl. do you have?Last edited by Mad Charlie; 03-04-2019, 12:28 PM. -
Brass
thumbnail.jpgthumbnail.jpg
Using the 330 comparator .012 set back the 350 shows .008 set back. Looks like i need to work on the inside edge of the extractor.Comment
-
Brass
brass 002.JPG Mondays. If i drop a cartridge into the chamber it won't come out by bumping the upper on my work bench. I need to use a cleaning rod. BHWLast edited by glk45; 03-04-2019, 01:46 PM.Comment
-
I am no expert here, but I think you need to verify if your new bolt has the same face depth as your old one(.125 or .136), you also need to search this forum for extractor mods( you need to "de-fang" your extractor). The search results has pictures. Your cartridge seems to set in too deep into the chamber, it should fall in and out without help(sizing problem??).
Anyway, this might give you some direction to pursue.
RedraiderComment
-
May I ask why the bolt had to be replaced? Did you have any of these problems with the old bolt? Can you put the old bolt back in a safely fire the gun to test for problems?
Thank you for sharing. This is interesting.Comment
-
Fix this problem first. You're either jamming the bullet into the lands or you may have a tight chamber. Color a round with a sharpie and drop it into the chamber. Bump it out and see where the ink is rubbed off.Originally posted by glk45 View Post
Will factory ammo drop into the chamber and fall out?Comment
-
Looks like hard extraction from pressure. What are the loads?Comment
-
Bolt is/was .125. Broke a lug on the old one.Comment
-
I dehorned the extractor. To damn cold to go give it a try. 11 degrees with 14 winds. I'm thinking resizing issue also. .441 base diameter on fired case and .440 on resized case. Don't leave much room.Comment
-
-
Your extractor certainly looks like it needs to be smoothed but broken bolt lugs and hard extraction is a sign of excessive pressure. Your load is full grain over the book max load.Originally posted by glk45 View PostComment
-
The online Western data shows max charge of Accurate 2520 as 29.6 with a 123 grain SMK, 29.5 grains with 123 grain Lapua Scenar with Winchester small rifle primers. If the cartridges are requiring a cleaning rod to be knocked out of the chamber plus running over recommended pressure is a good way to break bolts. Sounds like the barrel may have a short chamber and might need to be checked. On many BHW barrels they are marked 264 LBC Type I to designate 7.62X39 bolt with .125 bolt face depth. If the barrel is marked 264 LBC Type II it is chambered to use .136 bolt face depth 6.5 Grendel bolt.
Some of Alexander Arms reloading data showed over 30 grains of Accurate 2520 powder with 123 grain bullets but it has been discussed before that these are probably to hot and probably not adviseable. Whether there is an actual difference in the powder from when Isreal contracted production from the Czeh’s for Accurate 2520 or just Western’s current testing has never been disclosed. I think it is prudent to use Western’s load data for Accurate powders.Last edited by VASCAR2; 03-04-2019, 06:54 PM.Comment
-
Alexander Arms 6.5 grendel loads are what i went by. I worked that load up from 27.5 grns. At 30.5 no flattening or piercing of primers. It runs out at 2435 from my 18" at less than 3/4 MOA. It duplicates Horn. Custom ammo. The case i pushed out with the cleaning rod i pushed in with some force by hand. Went up to the shop and the Horn ammo and my reloads drop in and fall out. It is a 264 LBC.Originally posted by VASCAR2 View PostThe online Western data shows max charge of Accurate 2520 as 29.6 with a 123 grain SMK, 29.5 grains with 123 grain Lapua Scenar with Winchester small rifle primers. If the cartridges are requiring a cleaning rod to be knocked out of the chamber plus running over recommended pressure is a good way to break bolts. Sounds like the barrel may have a short chamber and might need to be checked. On many BHW barrels they are marked 264 LBC Type I to designate 7.62X39 bolt with .125 bolt face depth. If the barrel is marked 264 LBC Type II it is chambered to use .136 bolt face depth 6.5 Grendel bolt.
Some of Alexander Arms reloading data showed over 30 grains of Accurate 2520 powder with 123 grain bullets but it has been discussed before that these are probably to hot and probably not adviseable. Whether there is an actual difference in the powder from when Isreal contracted production from the Czeh’s for Accurate 2520 or just Western’s current testing has never been disclosed. I think it is prudent to use Western’s load data for Accurate powders.Comment
-
Now you've lost me. What was it that you had to knock out with the cleaning rod?Originally posted by glk45 View PostComment
Comment