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February 6, 2015, 03:11 PM | #51 |
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Need some advice from handloaders for .308
Kind of a diverent thread but for slam fires in Garand and M16 or AR15.
There are or were Titanium firing pins available for the M16. I haven't ordered on since I've not had the problem. It might take a bit of a search for them, if still available. Lither firn pins help with slam fires. I have a Garrand and ran across mention of a spring loaded firing pin. I didn't book makr it but others I'm sure know a lot more about these two subjects. |
February 6, 2015, 05:36 PM | #52 | |
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Quote:
I don't know if I have the words to explain why you have two dimples, but I'll try. But, what I expect the two dimples are is one from the bolt pushing the cartridge into the chamber on loading, and the other on early extraction. I think the brass is catching in the chamber before the bolt rotates into the locked position. As your ejector spring weakens with time and the chamber dimensions grow, expect one of the dimples to start fading away. Hope this helps, Jimro
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February 6, 2015, 05:50 PM | #53 |
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There's one section of extruded brass back from the case head normal flat surface for each cutout in the bolt face that lets brass extrude back into it.
Look at the bolt face and its cutouts will be a mirror image of the case heads. Would be good to see pictures of both bolt face and case head for the most extruded case for all to see and compare. |
February 7, 2015, 02:48 PM | #54 |
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So are you saying it's normal for the brass head to extrude back in to the bolt face holes? Is it going to continue to do this even when the gas block is adjusted correctly? I hope not. That kind of ruins my reloading brass!! Here's a picture of the bolt.
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February 7, 2015, 02:57 PM | #55 |
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You have twin ejectors, so twin ejector marks are to be expected with high pressure signs. I was wrong in my previous assessment.
But during normal firing the brass will push back into the bolt face. Under normal pressure this will not prevent your brass from being reloadable. Properly adjusted, you shouldn't be ruining brass. Jimro
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February 7, 2015, 03:10 PM | #56 |
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Very good. Thanks Jimro. I was hoping that would be the case.
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February 7, 2015, 07:04 PM | #57 |
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Cartridge brass starts extruding into bolt face holes at about 65,000 cup or 75,000 psi. Pressure in those cases is way too high for safety. Cut the charge 5 grains then try again.
I've shot .308 proof loads that didn't have anything like those cases do. |
February 7, 2015, 08:20 PM | #58 |
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Bart B
Thanks sir, but if you look back, that ammo is factory Hornady ammo. That's why I've been asking the questions. If it were my handloads I would assume full ownership and of course reduce the charge.
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February 7, 2015, 10:29 PM | #59 |
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I forgot about it being factory ammo.
Now I think the barrel is bad. Have someone measure chamber, bore and groove dimensions. Something is way too small. My first guess is the chamber is too short from bolt face to chamber mouth. The firing pin drives the case mouth hard into the chamber mouth crimping it into the bullet. That raises pressure. Fire an empty primed case in it then see if the case mouth is crimped in. Last edited by Bart B.; February 7, 2015 at 10:35 PM. |
February 8, 2015, 09:14 AM | #60 |
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Bart B.
The ammo in question is Hornady Superformance, which has a different pressure curve than standard ammunition. The adjustable gas block should fix the problem, which is that the sooner than expected peak pressure is causing earlier unlocking while the cartridge is still under significant pressure. It may turn out that the lot of Superformance being used is just unsuitable to that rifle, although I think the adjustable gas plug will work. But a potentially bad lot of ammo isn't out of the realm of possibilities either. We used to see this when people would try to run "Hornady Light Magnum" loads through Garands and M1As without adjustable gas plugs and they'd ruin the op rods. Jimro
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February 8, 2015, 09:11 PM | #61 |
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As someone already said before, try some Federal GMM in the rifle and see how it shoots with that. If it shoots good with that, then work on your loads. If not, then think about what may be wrong with the rifle.
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