I've been reading about several who have converted their breech
plugs from 209 to 25ACP using J size drill bits. I looked up some
25 acp cartridge specs and some show a slight
taper to the cartridge from base to neck. If this is true pehaps
the actual 25 ACP reamers have a taper built into them.
The use of the actual reamers if tapered would cause a tighter
fit when inserting the 25 cases much like when sizing fired
cases I would think. The NEF breechplugs now cost only $6.20
each and that is not very much cost to experiment with.
As a point of trivia, the SAMMI pressure specification for 25ACP
is 25,000 psi. The max SAAMI pressure for all shotguns is less than
12,000 psi except for 3.5 inch 12 ga magnums. Those are 14,000 psi
The 25 aCP cases should swell upon firing and seal in the breech
plug to prevent blowback better than the 209s which obviously
is why we are talking about them.
Here are the Letter Guage drill bit sizes
H 0.266 in
I 0.272 in
J 0.277 in
I am seeing some contradictory case size info
on the internet compare the drawings and info
at the links with the wikipedia info below it:
http://stevespages.com/jpg/cd25acp.jpghttp://www.dave-cushman.net/shot/25_acp.htmlhttp://www.reloadbench.com/specs/25acp
bullet..length base neck base
251" .615" .298" .276" .277"
Wikipedia case specifications:
Case type Semi-rimmed, straight
Bullet diameter .251 in (6.4 mm)
Neck diameter .276 in (7.0 mm)
Base diameter .277 in (7.0 mm)
Rim diameter .298 in (7.6 mm)
Case length .62 in (16 mm)
