Originally Posted by
Chev. William
NoZombies,
Your arranging for a supply of ready made Brass is very considerate of you, thank you!
I will be looking forward to the Reloading dies and Commercially listed Chambering reamers. as that is a pair of markers of a 'successful' Wildcat Cartridge.
As to the Extractor cut dimensions, may I suggest the Depth and width of the cylinder portion be such that the rim of one cartridge will 'nest' in the cut so the bodies are parallel and touching. John browning did this with the .25ACP and it Works well; he also found that the Taper going toward the Mouth of the Case needed to allow easy 'ramping' of the nested rim up ward to clear the Body of the Lower Cartridge during the feed from a 'stacking' magazine. From a tube magazine , these conditions do not apply.
To recap:
Subtract the body diameter from the MAXIMUM rim diameter; then divide that result in half to get the Depth of the Lathe cut (half diameter).
Example: 5.7x28mm rim diameter is 7.8mm (.30708+") per CIP standard.
.30708 - .24700=.06008+ rounding off to four places gives .0601" which divided by 2 yields .03005" truncated is .0300" cut depth. Check: .247-.060=.187" With a Small Pistol Primer diameter of .175", that leaves a (.187-.175=.012/2=).006" wall between extractor clearance cut and primer pocket wall. Minimal but still usable if the wall is at least 1/2 Hard Brass Alloy.
Of course since the .25ACP Rim is slightly smaller in diameter; using that dimension might make things more robust.
J.M. Browning used a Half Angle of 20 degrees for the Taper on his .25ACP/6,35 Browning Semi-Rimed design cartridge per CIP Standard.
FN used a Half Angle of 25 degrees for the Taper on their 5.7x28mm cartridge even Though the design is RIMLESS.
I used CIP dimensions as they are a Legal Standard Enforced in Europe an most of the Rest of The World; while SAAMI dimensions are only Recommended Practices published for use in the USA.
As to the Pressure choice: I would recommend a variation allowing two or more Pmax levels for the Cartridges. Your 25,000psi Pmax MAP for Conversions on old 22 RF rifles. A higher "+P", and even "+P+" Pmax for use in 'more robust firearms designs'
up to your commented 45,000psi or so.
Unless there are some exceptions, I believe the extractors of all .22 RF cartridges are designed and manufactured to have a small Clearance over both rim Diameter and rim Thickness; so Unless made with an unusually Long flat tip to lay alongside the Case body when engaged with the rim, most should easily extract your Ladybug and Ladybug Repeater cases.
I note that the Ruger "Single Six' is capable of handling .327 Fed. Mag. pressures in its frame (45,000psi Pmax MAP) so a Six shot conversion using the Ladybug design and a Quality Six shot, or Seven Shot cylinder, should be capable of such cartridge pressures.
My experiments with eight shot cylinders and .25ACP diameter Wildcats limit my Chamber to Chamber and chamber to Locking cut wall thicknesses; so I limit my Conversions to about 30,000psi or less Pmax MAP for a margin of safety.
Chev. William