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English Cartridge Designation

Toolman286Toolman286 Member Posts: 2,260 ✭✭✭✭
edited June 2019 in Ask the Experts
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

  • rufesnowrufesnow Member Posts: 250 ✭✭
    edited November -1
    Closest I could find, was 297/250 Rook. A old BP cartridge, dating to the 19th Century, used for varmints. The Rook was the name, the Brits used for what we call Crows, on this side of the pond. This was years before the 22 RF came into common usage, as the standard small varmint cartridge.

    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.
  • 35 Whelen35 Whelen Member Posts: 15,200
    edited November -1
    My first thought would be .25 Stevens Short rimfire, but being English, I don't have a clue what the metric designation would be.

    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


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  • charliemeyer007charliemeyer007 Member Posts: 7,346 ✭✭✭
    edited June 2019
    Unless the hole is off center in the adapter it will be some sort of center round. Not sure where my cartridges of the world book is. The book lists the dimensions of lots of old cartridges, but not all of them. It could be a an obscure priority round. Or perhaps something like a #3 buckshot powdered by a something like a shotgun primer.

    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.
  • MIKE WISKEYMIKE WISKEY Member, Moderator Posts: 9,750 ******
    edited November -1
    "Closest I could find, was 297/250 Rook"..............I had to make a few of these once for a friend, the .22 hornet case worked well (shortened), try a .22 hornet case in the adapter.
  • Toolman286Toolman286 Member Posts: 2,260 ✭✭✭✭
    edited November -1
    Thanks for the ideas. It is for a center fire round. I'll look at Cartridges of the World. A trimmed 22 Hornet case is .010 larger but I may be able to swage it down to fit. (The rim is the right thickness.) Then I will have to find a bullet. It's interesting, but this is starting to sound like a lot of work for the results.
  • rufesnowrufesnow Member Posts: 250 ✭✭
    edited November -1
    Toolman286 wrote:
    Thanks for the ideas. It is for a center fire round. I'll look at Cartridges of the World. A trimmed 22 Hornet case is .010 larger but I may be able to swage it down to fit. (The rim is the right thickness.) Then I will have to find a bullet. It's interesting, but this is starting to sound like a lot of work for the results.


    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.
  • Toolman286Toolman286 Member Posts: 2,260 ✭✭✭✭
    edited November -1
    I like the idea of reworking the 22 Hornet brass but I have what might be a dumb idea. What if I fired a 25 auto in it to fire form that brass? The adapter's chamber walls are 1/4" thick plus the 20 ga barrel walls. A modern top break action should hold the 25 auto pressure???
  • rufesnowrufesnow Member Posts: 250 ✭✭
    edited November -1
    Toolman286 wrote:
    I like the idea of reworking the 22 Hornet brass but I have what might be a dumb idea. What if I fired a 25 auto in it to fire form that brass? The adapter's chamber walls are 1/4" thick plus the 20 ga barrel walls. A modern top break action should hold the 25 auto pressure???



    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.
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