Converting GP11

[mwells72774]

-First step was to run in a FL sizing die with drill bit collet inserted to hold the drill bit steady.
-Next I beveled the old primer.
-Next step was to drill out primer cap but leave the sidewalls.
-Next to swedge primer pocket with RCBS swedger.
-Next to drill out depth with Lyman adapter.
-Next to seat primer and go!

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Bruce_in_Oz]

I can almost understand people doing this for cases that originally use the BIG Berdan primers, eg. .250" (.303Brit) or .256" (A lot of the older "big" European stuff like 8 x 56R and some 7.62 x 54R). However, I have never even contemplated it for the "standard" .217' jobs. Part of the problem is that the web thickness may be a bit of a problem, because the Berdan pockets are shallower, because the Berdan primer cups are shallower. Are the .217" Berdan primers THAT hard to get? Go and ask your local Vihtavouri distributor some hard questions. See also RWS.

Also, when it comes to reforming / de-crimping primer pockets, I have used and got very annoyed with both the CH and RCBS systems and now use the much more robust and versatile Dillon bench-mounted unit. All you have to do to make it "Berdan-friendly" is to use a small centre-drill in the lathe tail-stock chuck or collet and cut a recess in the "forming plunger" to clear the anvil. I have done thousands of Berdan-primed, .217" size cases for 7.62 NATO, .30-06, 7.92 x 57, 7.62 x 54R etc. Once the pockets are de-crimped once, they never need the process again. Also works on pistol brass like "surplus" 9mm NATO and .45ACP.

The modified plunger still works fine on boxer-primed cases. The unit also comes with a set of parts to handle "small" primers.

[mwells72774]

Bruce, here there aren't any V dealers that I know of and berdan primers aren't exactly easy to get. I've never seen any in person.

Plus I'm a tinkerer.

[WarPig1976]

So what's going on here? Are the walls of the old primer left in the hole as a sort of spacer?

[mwells72774]

So what's going on here? Are the walls of the old primer left in the hole as a sort of spacer?

Yes, that's correct

[Bruce_in_Oz]

I guess that I had better get over to my friendly supplier of "odd stuff' and clean out the last of his Berdan goodies.

Has anyone ever thought of using a hydraulic press and a a couple of "custom" punches, to solve this problem?

1. Flatten the anvil and deepen the Berdan pocket slightly.

2. Use a "ring" punch around the outside of the pocket , to reduce the diameter to hold large-rifle Boxer primers.

3. Punch or drill out a new central flash-hole.

GP-11, being almost exclusively fitted with lead-based primers, should not crack and fail like the common, 1/4", mercuric-primed .303 brass.

I am just a little dubious about the retention of a very thin collar, especially when it comes time to go for the second reload.

Keep us posted, please.

[mwells72774]

Bruce, these are fitted with large rifle primers. They're 10-20 thou smaller than the original berdan primer.

[Bruce_in_Oz]

I certainly admire your dedication.

We never seem to have received any of the surplus GP-11 here, except in tiny batches sold as collectors ammo.

When I bought my K-11, I got some Lee dies and a bag of new Winchester .284Win brass from my local friendly gun shop. Body diameter at the web is almost identical to Swiss spec, the neck is a whisker short. The rim of a .284Win is rebated to the same diameter as .308Win. They were run through the Lee FLS die using a .308 shell holder and were basically ready to go.

These ersatz cases worked well, except for the smaller rim not engaging the extractor properly at the point of ejection. Fortunately the Serbian brass arrived on the scene to make things all good.

[Parashooter]

. . .these are fitted with large rifle primers. They're 10-20 thou smaller than the original berdan primer.

Swiss Berdan primer diameter: .217"
Large Rifle Boxer primer diameter: .210"
Difference: .007"
Thickness of material required to reduce diameter by .007" = .0035"
Average human hair thickness: .004"

Here is another approach -

[mwells72774]

Swiss Berdan primer diameter: .217"
Large Rifle Boxer primer diameter: .210"
Difference: .007"
Thickness of material required to reduce diameter by .007" = .0035"
Average human hair thickness: .004"

Here is another approach -

https://www.milsurps.com/images/impo.../33zbjwn-1.jpg

I hadn't ever measured, my guess was way off seems.

Can you go into detail on step 3 a little. I'm trying to figure out how you went about shrinking the primer pocket.