This Thread is about a "Mildcat" cartridge that is small of capacity but long on Potential. It is a Proposed cartridge design for inclusion on another Forum's "Cartridge Data Base".
My progress on this design is noted on this Forum in thread titled:
.250/.257 Cartridges to .25ACP/.25 Stevens Diameters from 5.7x28mm once fired brass.
The name Chosen for my proposal is "6.35x32mmSR STEWART" with a Short name of "6.35x32mm STEW".
The Dimensional characteristics are mix of original and as reformed numbers.
- The cartridge rim Diameter and Thickness, the Extractor Clearance cut Diameter and height along with the angle cut are as per the original 5.7x28mm FN Cartridge drawing as Standardized by CIP in Europe.
- A 'Redding' #34 Universal Shell Holder or equivalent holds both the 5.7 originals and the .6.35 reformed cases. Lee #15 may or may not fit, depending upon the Lot Brass variations.
- Case Body is Basically Straight walled at .276" to .278" except for a tapered area starting about .300" above the cartridge Base and expanding to about .280" diameter just at the top of the Extractor Clearance cut. this taper is eliminated by forcing the formned case into a .277-.278" drill bushing mounted in a repurposed diebody down to the top of the Rim, yielding a truly cylindrical case .
- Case Length is Specified as nominally 32mm (actual = 1.250" +0.010"/-0.030") or a range of 1.220" minimum to 1.260" maximum.
- Overall Cartridge length is Specified as nominally 42mm (~1.653") for Spire Point Bullets with a practical loaded OAL for FMJ-RN 50 grain bullets of 1.500".
- Head space uses the Rim, like the .25ACP but with more diameter margin.
- Bullet Diameter is specified as .250" for Jacketed bullets and .251"-.252" for Cast lead.
- Maximum Peak Average Chamber pressure is the same as the 5.7x28mm parent as specified by CIP (~50,000psi Piezio). I am deliberately 'downloading' for my personal use as I do not presently own a Firearm with Sufficient 'Strength of Action to use the Full pressure loading. I am using between 25,000psi to 30,000psi for my load testing presently.
- Twist is Specified as one turn in 9 inches. I am using barrels with 1:14 to 1:9.4 Twist presently.
The Case neck/Shoulder is expanded to fit a .250" diameter bullet by use of a .2500" diameter Expander Punch made from a HSS Drill Blank. Brass spring-back leaves the neck ID suitable for intended bullet diameters.
Use an "RCBS Small Primer Swage Punch" or Equivalent, along with the "RCBS Primer Pocket Swaging Tool Kit" Stripper Cup topped with a 3/16" internal Diameter 'Fender Washer' to support the case primer pocket in the reforming process as the cases MUST be pushed into the Sizing dies to the Point the Top of the Rim is Flush with the bottom of the Die.
At least Three Sizing dies should be used to minimize destruction of cases in the reforming process. Lee Charges $30.00 to "open" a Carbide ring sizing die to a custom size, shipping cost is added.
I use Four Lee Carbide Ring .25ACP Sizing dies with three opened to .300", .288", and .284"-.280" respectively, the forth is the Lee standard .276" to .277" (.25ACP resizing) size.
The Factory Applied Polymer case coating survives and eases the reforming process, save a very narrow ring just above the Extractor Clearance Groove which is removed by a thin ring of displaced Brass in the last reforming/sizing operation. This ring of displaced brass is caught by the groove and is removed manually after extracting the Case from the die.
I use a Custom machined case extraction Punch made from a "6 inch long Roll Pin Punch of 7/32" size. This punch has the working tip cur square; tapered down to about .165" with rounded edge to clear the case internal wall taper; and the 'handle' area cut down to fit inside the top of the Lee die.
For my light Stevens Favorite Actions, I am Starting with light, and subsonic, charges/loading recipes:
74 grain Lead RFN-GC bullet; WSP primer; 1.0 grains Bullseye; OAL = 1.500".
74 grain Lead RFN-GC bullet; WSP primer; 1.1 grains Bullseye; OAL = 1.500".
74 grain Lead RFN-GC bullet; WSP primer; 1.2 grains Bullseye; OAL = 1.500".
74 grain Lead RFN-GC bullet; WSP primer; 1.3 grains Bullseye; OAL = 1.500".
50 grain Magtech FMJ-RN bullet' WSP primer; 1.0 grains Bullseye; OAL = 1.500".
50 grain Magtech FMJ-RN bullet' WSP primer; 1.1 grains Bullseye; OAL = 1.500".
50 grain Magtech FMJ-RN bullet' WSP primer; 1.2 grains Bullseye; OAL = 1.500".
50 grain Magtech FMJ-RN bullet' WSP primer; 1.3 grains Bullseye; OAL = 1.500".
50 grain Magtech FMJ-RN bullet' WSP primer; 1.4 grains Bullseye; OAL = 1.500".
50 grain Magtech FMJ-RN bullet' WSP primer; 1.5 grains Bullseye; OAL = 1.500".
Enjoy This "mildcat" in old ".25 R.F." rifles converted to Center Fire or make a newer rifle and play with the maximum performance possible
Best Regards,
Chev. William ETC USN Retired.