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View Full Version : berdan primer/boxer primer size difference?


tteng
12-11-2006, 4:52 PM
I was experimenting w/ the idea of converting once-fired berdan-primer case to boxer case (especially for my K31's GP11 case) until I found out that berdan primer pocket is bigger than the boxer primer. Are there boxer primer that will snug-fit the berdan-primer pocket?

Fjold
12-11-2006, 5:01 PM
The common boxer primers only come in three sizes, small rifle 0.175" in diameter. The large rifle primers are 0.210" in diameter and the 50 BMG uses a 0.510" diameter primer.

How were you going to mill out the anvil out of the Berdan cases?

uglygun
12-11-2006, 5:19 PM
50 BMG uses a 0.510" diameter primer.



It's big but not that big.

.310 maybe...

http://home.bak.rr.com/varmintcong/50sbigger/primers.jpg

tteng
12-11-2006, 6:44 PM
I'm thinking about making a fixture the shape of a small window-frame (roughly 4"x4"x1"x0.5", Height x Width x Depth x thickness )where you thread a 5/16" (or 8mm) threaded post (which slip-fits the 30-cal case neck) from the bottom sill, and you bore a hole roughly the size of the case base on the top sill. You insert the case up-side-down thru the top hole and seated it on top of the threaded post (which need to be counter-sunk on the tip for boxer-primer hole drilling relief). With the fixture clamped, hopefully with the downward mill tip pressure, the exterior-wall/interior-post support (and maybe your finger to prevent excess wobbling, not safe I know), you can mill out the anvil. With same fixture, you can also center-drill for boxer-primer decap purpose)...Just thought/picture in my head...All is for naught if the berdan pocket is too big for the boxer primer, though ( I tried w/ Winchester WLR primer in a spent GP-11 primer pocket, it was loose. BTW, the PMC large-rifle berdan primer is list as 0.217". If the large-rifle boxer is 0.21", why is it so loose in the primer pocket??)

Fjold
12-11-2006, 6:52 PM
It's big but not that big.

.310 maybe...



Oops, .510 is bullet diameter, Mic a primer will ya?

Thanks

Fjold
12-11-2006, 7:01 PM
I'm thinking about making a fixture the shape of a small window-frame (roughly 4"x4"x1"x0.5", Height x Width x Depth x thickness )where you thread a 5/16" (or 8mm) threaded post (which slip-fits the 30-cal case neck) from the bottom sill, and you bore a hole roughly the size of the case base on the top sill. You insert the case up-side-down thru the top hole and seated it on top of the threaded post (which need to be counter-sunk on the tip for boxer-primer hole drilling relief). With the fixture clamped, hopefully with the downward mill tip pressure, the exterior-wall/interior-post support (and maybe your finger to prevent excess wobbling, not safe I know), you can mill out the anvil. With same fixture, you can also center-drill for boxer-primer decap purpose)...Just thought/picture in my head...All is for naught if the berdan pocket is too big for the boxer primer, though ( I tried w/ Winchester WLR primer in a spent GP-11 primer pocket, it was loose. BTW, the PMC large-rifle berdan primer is list as 0.217". If the large-rifle boxer is 0.21", why is it so loose in the primer pocket??)

.007" difference is enough to make it real loose. If you mill out the center anvil then drill a center hole, you would wind up with three holes in the bottom of the case for the primer to fire through. This might effect how fast the powder burns and the thrust on the primer after the powder fires and it could blow the primers

762cavalier
12-12-2006, 4:48 PM
tteng check out this link http://www.geocities.com/d_henry1@sbcglobal.net/berdan-boxer.html This guy has developed a method for converting Berdan brass to use boxer primers. Lots of good info. check out the rest of his page also he is an avid reloader of other calibers also