Anyone you know with a lathe and time on their hands ?

@414gates @414gates 1 year ago

And of course, having the lathe and knowing how to use it.

I need to cut the primer pockets out of brass.

Like the pictures.

I have donor cases, I need someone to cut the pockets out. I don't mind where the person is, I'll ship them the brass, give the dimensions to cut to, and ship them back. And pay them, of course, for their labor.

The idea is to bush a magnum rifle primer in a BMG primer pocket, using a large rifle primer pocket as the bushing.

I got the idea from the load data for a 700 Nitro Express. It uses 250 grains of powder, and runs off a large magnum rifle primer. That tells me 230 grains in a BMG case is also do-able.

Then I found an article on making 700NE brass from BMG brass, and this is now the person fitted a large primer pocket into a BMG case.

I'd like to try it.

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Replies 19

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@T @tripodmvr

Is there not brass or copper pipes (tubes) that can be used as bushings?

@414gates @414gates OP

a simple tube won't work, there will be nothing to stop the primer being pushed in by the firing pin and failing to ignite, the existing primer pocket is much deeper than a normal primer

it needs an actual large rifle primer pocket to be press fitted in so the primer has something to bottom out on

@T @tripodmvr

Will it not be easier machining a solid copper/brass rod and adding the hole and primer pocket, than cutting it out of a case? It should give more accurate dimensions with the rod fitting easily into a lathe.

@O @oafpatroll

Will it not be easier machining a solid copper/brass rod and adding the hole and primer pocket, than cutting it out of a case? It should give more accurate dimensions with the rod fitting easily into a lathe.

That sounds a more practical to my non-machinist mind. If I had a little lathe and the skill what I would try would be:

  • True up the existing pocket to a precise cylinder with flat bottom end mill
  • Make brass plugs sized for a solid press fit
  • Press in the plug
  • Chuck up the case and drill a near final size pocket and then true it with a pocket reamer
@414gates @414gates OP

Anything is possible. Just much harder that way.

More operations to manage tolerences.

If the pocket is transplanted, there is only one critical dimension. Making it from bar stock means every dimension is critical, requires extraordinary skill, and time consuming.

@O @oafpatroll

Anything is possible. Just much harder that way.

More operations to manage tolerences.

If the pocket is transplanted, there is only one critical dimension. Making it from bar stock means every dimension is critical, requires extraordinary skill, and time consuming.

I don't follow your reasoning. Everything related to the case can be done without removing it from the chuck. Can't imagine how you could achieve better accuracy by cutting a pocket out of an existing case and then fitting it to a hole in another. Besides that I doubt if anything other than the press fit dimensions need to be especially accurate given that the cases aren't machined in the first place. Not my lane so just the musings of a typist.

@414gates @414gates OP

You're probably right, I'm not a machinist either.

I had to look up what others have done.

A friend of mine runs a machine shop, he's going to take a poke at it, maybe he comes up with something even simpler.

@O @oafpatroll

I'd be interested in an update when you're done. This sort of stuff interests me a lot. I think a major advantage of filling the existing pocket with a plug is that it could leave it essentially unchanged and therefore stronger. I've no idea whether drilling out the existing pocket completely has the potential to cause a dangerous weakness but if it's possible to avoid that it would make me less nervous about using them. I would also imagine that the case head of the donor would be thinner than that of the .50.

@414gates @414gates OP

Prototype.

I'll be testing these to see if in fact I can ignite the powder with a Federal 215, and if it survives a few reloading cycles.

The machinist was not happy to use the cut out primer pockets from the donor cases, so he made the inserts on a lathe.

@O @oafpatroll

Nice! What is the saving between the two primer types?

@414gates @414gates OP

R350 per hundred compared to unobtanium that retails for around USD 150 per 100 in the US, retail cost after import will be around ZAR 3000.

If it works, that is.

@O @oafpatroll

R350 per hundred compared to unobtanium that retails for around USD 150 per 100 in the US, retail cost after import will be around ZAR 3000.

If it works, that is.

Wowsers, that is what we call a convincing business case in my culture. Best of luck with the tests. I have no experience to base this on but my gut feel is that it will work just fine.

@414gates @414gates OP

My math may have been conservative, the rule of thumb for ZA retail is 2 x USD x rate of exchange for all firearm parts and components .

For example, I paid R1200 for a $30 pound of powder.

@414gates @414gates OP

Tested 6 rounds, 3 of each primer.

Preliminary test shows Federal 215 Magnum are not suitable. One fired, one misfired, one hang-fired.

Winchester LRM all ignited properly.

None of the primers pierced, surprisingly.

Velocity is down over 100 fps between the CCI 35 and WLRM.

Want to test a couple more tweaks, if all goes well, it'll be GTG.

@O @oafpatroll

Lekker. That sounds promising.

@T @tripodmvr

Do you have spare case capacity if you need to up the charge?

@414gates @414gates OP

Too much space. I've got 3 grains of dacron holding the powder down at the moment.

Lapua brass has the smaller capacity compared to TZZ.

With the Lapua, the space between just below the body shoulder junction and case shoulder junction is empty.

With TZZ, the space is 3 or 4 mm below the case shoulder junction to the neck shoulder junction.

Case capacity difference is 8 grains of water.

I've tried N570, US869, 20N and 24N - none of them give proper case fill over a CCI 35. And with the CCI 35 it doesn't matter, even if the powder is half an inch from the primer, it'll still ignite.

@T @tripodmvr

Watched a video by Halfmilesniper. His 6,5PRC gained about 50fps when he changed from CCI200 to WLR primers.

@T @treeman

Watched a video by Halfmilesniper. His 6,5PRC gained about 50fps when he changed from CCI200 to WLR primers.

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like I was suggesting, 1.6 % about"s , i do not believe we gonna outshoot that % at under 3-400 m ?
i am open to correction.