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English Cartridge Designation
Toolman286
Member Posts: 2,982 ✭✭✭✭
In going through a box, I found a shotgun cartridge adapter. It's from Bisley Works in England & is marked "4GP" & "20 Gauge - 250". A 25 acp fits very loosely so I measured the chamber & bore. The chamber is .284" dia & is .635" deep. The bore is .250" between the lands & the groove dia is .260". All of these dimensions are slightly larger that the 25 acp. I didn't find anything on the internet; so, any ideas if there's a different 250 cartridge in England?
Comments
I wasn't aware that they used it in shotguns? Mostly small single shot, Martini action rifles. Could be also on one of the old cape type shotguns that had a partially rifled barrel. These had adjustable sights, so at short range they could wack a crow. Without scaring the bejesus, out of the neighbors.
Measurements of the .25 Stevens Short, from Wikipedia:
Bullet diameter .251 in (6.4 mm)
Neck diameter .276 in (7.0 mm)
Base diameter .276 in (7.0 mm)
Rim diameter .333 in (8.5 mm)
Case length .599 in (15.2 mm)
Overall length .877 in (22.3 mm)
Primer type rimfire
There are modern chamber adapters for sale. Some are even rifled. I try and not assume strength and pressure issues. I have seen many wasted firearms.
Years back, I use to own and shoot a lot of the late 19th Century BP military cartridges. Because of the BP fouling, many of them were deliberately made under size. I found that the data in COW regarding the dimensions of the cartridges and chamber dimensions weren't always accurate. As compared to modern smokeless powder cartridges.
With modern high pressure ammo, tolerances have to be held within a couple of thousand at most. With the old BP guns the brass could be .005 or more under size and chambers/groove diameter, could be that much over size or more oversize. Since BP generates much lower pressures, there was very little likely hood of safety problems.
To make a long story short. Don't regard the data in COW, as gospel. Rework the Hornet brass so that it will fit the chamber dimensions in the shell.
According to COW, the Rook cartridge has a rim diameter, .045 larger than the .25 Auto. If this is correct? Best prop the stock in a old used tire, with the barrel pointed straight up. Attach a cord to the trigger, and pull it from behind cover. Good luck.