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Berdan to Boxer |
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A square 10 
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 Posted: January 30 2024 at 7:36pm |
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was the boly head actually damaged or just needing cleanup ? it did not appear damaged - only filthy and it looks like it can be cleaned up ,
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britrifles
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Posted: January 31 2024 at 3:38am |
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Badly melted around the primer. This bolt head already had some pitting from a cracked primer that happened a few years back, but this issue made that much worse. The picture I took was after wiping it “clean” with Hoppes.
On the tenth shot, I could see a flash of flame coming from the back of the breech, that must have been the worst of the three primer pocket bushing failures. I had looked at the case head after the first shot, and it looked OK, so went ahead and shot the remaining nine.
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DarioPirovano
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Posted: January 31 2024 at 3:11pm |
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Geoff, do you think it is still safe to use that bolt head?
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britrifles
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Posted: January 31 2024 at 4:19pm |
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No, I wouldn’t chance it. Which is why I now have fitted one of my NOS spare bolt heads. I just hope the heat didn’t do any damage to the back of the barrel. It looks fine, and should be able to take that heat, but the bolt head sure did not. The only visible damage is to the front face of the bolt head.
The flash was very noticeable, must have been like a blow torch. |
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Sapper740
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Posted: February 01 2024 at 2:06am |
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I've been following your odyssey with great interest britrifles as I was considering expanding my repertoire of converting Berdan to Boxer beyond the 7.65 X 53 Argentine. To date I've only converted the FN brass, none of the FMMAP that I have on hand and only loaded mild BL-(C)2 loads with the original 154gr. bullets I pulled. I did find that about 20% of the bullets I pulled were 174 gr. BT making me think that ammunition would have likely been for a machine gun and thus thicker brass for the violent extraction process? I should have marked those cases separately as they might have been the few that leaked a little gas. So far there has been no damage to the bolthead on my M1891 but after seeing the issues you've experienced I might shelve the idea of converting my old .303 brass.
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Zed
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Posted: February 01 2024 at 6:58am |
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Bad news about that bolt head Geoff. Those cases look horrendous!
Personally I don't think the an insert between the case and the new primer is a good idea. You have two circumferences to seal. A bit like fitting two headgaskets! With the amount of pressure and heat, an insert would need to be threaded into the case to be reliable; but probably not enough material for that method.
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britrifles
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Posted: February 01 2024 at 7:12am |
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Yes, that could be. But, these have apparently worked on 7.62 NATO cases.
Perhaps the aluminum was work hardened too much because of the large interference, 0.013 interference on 0.243 diameter Berdan pocket. I don’t think these bushings are the correct size for these primer pockets.
Still have not heard back from the vendor. |
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shiloh
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Posted: February 01 2024 at 9:31am |
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I would also assume that with the large hole you drill centre and the 2 other berden holes, one would think your creating a path of lesser resistance. Basic physics. Not a great idea really. Gas will push back for that split second it takes to over come pushing the bullet out of the case. And in your experiment that`s exactly whats happening. Plus as Zed said having 2 circular sealing surfaces further exasperates the chance of failure.
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Goosic
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Posted: February 01 2024 at 10:20am |
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I know of an individual that has been doing this conversion but he is creating a Fail-Safe by taking a dab of Devcon or JB Weld on a tooth pic and sealing the Berdan primer holes before seating the new primer cup.
According to him, he hasn't had one blow out, "YET."
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britrifles
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Posted: February 01 2024 at 11:14am |
This happens in all center fire cartridge cases. The gas pushes on the primer, and it expands radially to form a seal and is prevented from blowing out the back of the case via the bolt. This is a commercial kit that I bought, and has successfully been used. But for some reason, the aluminum bushings are not sealing against the case head primer pocket. My thoughts are because they have been overly strained to get them to fit into the primer pocket (they are too large in diameter for these cases). Once squeezed down past the yield point, they must be springing back just enough to no longer seal, or just on the edge of sealing. Wish the guy who makes these would call me back, he may be able to get a different size of bushing. |
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DarioPirovano
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Posted: February 01 2024 at 5:05pm |
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I know that might sound stupid but why not?
you could try test on some worn brass. Why not tig weld material inside the berdan primer pocket and then machine the pocket? If you are scared about melting holes everywhere when welding I can tell you I have seen people tig welding aluminium cans |
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britrifles
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Posted: February 01 2024 at 5:51pm |
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I suspect TIG welding would anneal the case head making it very susceptible to rupture.
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DarioPirovano
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Posted: February 01 2024 at 5:54pm |
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Even with pre&post heat treatment?
The potential annhealing is something I didn’t considered.. |
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britrifles
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Posted: February 01 2024 at 6:38pm |
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Brass can only be hardened by working it (work hardening). This is done when brass cartridges are formed by drawing/extruding. If you heat the brass up to annealing temperatures, you remove the work hardening. That why you must be very careful when annealing cartridge case necks, overheating will not only burn the neck it can soften the case head which is a dangerous condition.
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DarioPirovano
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Posted: February 01 2024 at 6:39pm |
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Clear explanation, thank you
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Shamu
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Posted: February 02 2024 at 10:30am |
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This is why savvy reloaders use some form of "heat shield" when annealing the shoulder & neck. It keeps the direct heating focused towards these areas while protecting the rear half. Midway has just started selling one, but I have no experience with it. Many, like myself, cobble something together from things we have lying about. Like deep well sockets of the appropriate size!   |
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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shiloh wrote: