I had a chance to try loading(W748 in the 25-223AR*
*.223 parent brass opened up to .25-cal; shortened to 43mm; maintains .223 body taper, same body shoulder junction height, does't require fire-forming.
Load Data: (standard disclaimer as with any wild-cat, use at own risk and work up slow) Note: The powder was loaded into the case using an eight drop tube. This facilitated a more dense/compact powder column.
100 gr Speer SPBT (16-inch barrel)
25.5gr W748 = 2350 fps
26.0gr W748 = 2411 fps
26.5gr W748 = 2435 fps
27.0gr W748 = 2475 fps
27.5gr W748 = 2510 fps
28.5gr W748 = 2548 fps
No signs of high pressure. Am interesting phenomena occurred with this load. The ejected brass was was cool to the touch. The barrel was was only mildly warm after each five shot string. SO this powder must burn pretty cool. There was NO powder residue in the barrel after each shot so W748 must also burn fairly clean. In addition, all 30 round from this test grouped within 3-inches over the 200 fps velocity spread. I was not trying to shoot for groups.
I used the published loads for BL-C(2) in the 6x45mm found the Hodgdon reloading manual for a starting reference. The Hodgdon web site shows that W748 is ranked at 82 and Hodgdon BL-C(2) is ranked at 83 on their burn rate chart.
For example Hodgdon lists:
85 gr SPR SP BL-C(2) (24" barrel)
Start: 25.5gr.-2566 fps; Max: 27.5gr.-2811 fps
90 gr SPR SP BL-C(2) (24" barrel)
Start: 25.05gr.-2523 fps; Max: 27.0gr.-2744 fps
100 gr HDY SP BL-C(2) (24" barrel)
Start: 24.5gr.-2404 fps; Max: 26.5gr.-2619 fps
Originally Posted by 320pf
Well I finally got my 6.35.43mm (257/223) project together. Here are some early results:
Load Data: (standard disclaimer as with any wild-cat, use at own risk and work up slow)
100 gr Speer SPBT (16 inch 1:10 twist barrel)
23.0gr H4895 = 2294 fps
23.5gr H4895 = 2336 fps
24.0gr H4895 = 2350 fps
24.5gr H4895 = 2400 fps
25.0gr H4895 = 2463 fps
25.5gr H4895 = 2505 fps
75 gr Hornaday V-Max (16 inch 1:10 twist barrel
25.5gr H4895 = 2560 fps
26.0gr H4895 = 2600 fps
26.5gr H4895 = 2678 fps
27.0gr H4895 = 2728 fps
27.5gr H4895 = 2803 fps
I think that H4895 is a bit too slow of a powder for this cartridge. Also there is no way that I can get anything close to the amount of powder in this cartridge as that listed for the 257 Kimber. I have some IMR 3031 around to try but from the data posted by Kurtz on his 25/40mm I think that 1680 may be the best powder.
We will find out.