In the 308 Copper Bullets in 318 Mauser thread, I ended up fiddling around with paper-patched JBoos and paper-patched Copper-Boos in my Model 1896 Swedish Mauser (6.5x55). I got them to work okay, and learned some interesting lessons. This thread is a PPCBoo follow-up to what I learned and shared in that thread.
I polished out the mouth of my 0.259" diameter Lee push-thru die a bit further and found that it would size down the long 160 grain NEI 6.5mm CBoo after all (it had given me trouble, initially), but that CBoo is right on the very edge of having its butt expand too quickly to get through the die ~~~> use good lube, add on a GC, and process through with a very fast stroke and it WILL got through fine, but still just barely. There are so very many things, I'm finding, that put the 6.5 CBoo and PPCBoo work into that real = a VERY narrow window where you can get it to work. This issue is not as heavily manifested in most chamberins, but these wide-shoulder/narrow-neck things magnify this problem. I need to find a better bulk filler.
Here is the CBoo (unsized) and the finished PPCBoo, after adding a GC, sizing to 0.259, giving them a way-hard oven HT, and patching up to 0.269" with a 2X16# patch.
I shot these without sizing-down the as-wrapped PPatch, as my rifle's groove diameter is 0.269", or perhaps a bit larger (it is a military barrel and I last checked its groove diameter perhaps a decade ago, but this is what I recall). I tried 40-to-50 Kpsi loads with AA-4350 and got mostly the abusual (for 6.5x55) large-patterns-not-groups.
I then moved down to what would be a ~29 Kpsi load (w/o corn meal), added corn meal, and got the first group of the day. At 1.8" at 50 yards 2200 fps MV), it was not a belch-ringer, but far better than I expectorated.
I went up to what would be a 38 Kpsi load (w/o corn meal), added the corn meal, and maxed out on the pressure (Russian Wolf primer just barely started to crater), so the corn meal was really boosting the pressure in this fat-body/small-diameter-neck case ~~~> be CAREFUL in this chanbering when using bulky fillers! It gave 2360 fps, and 7 of 8 shots went into 1.0". A second group of the same load gave 1.5", but that is still doing okay, under my own rather different-from-others' PPCBoo experience.
I tried backing off the powder quite a bit further and using the corn meal. It still gave slight cratering of the primer. Therefore, the corn meal, although it does seal against gas leakage, takes up LOTS of room even when compressed. So, the less powder you use (therefore, you add more corn meal), the smaller is your effective case capacity. This makes it VERY difficult to adjust the maximum pressure!
This stiff pressure was causing the cases to expand more than in my usual loads, so I had to quit using the Lee Collet Neck Sizer die and run the brass through a full length sizer. This caused the light grip that I had used on the PPCBoos to be replaced by the normal JBoo way-death-grip. I reshot the "good" load with the FL sized cases, and got a 2.15" group, but the cartridges DID go in and out of the rifle easier.
Conclusions
- The hard CBoo seemed to help, but this one was so hard that I could barely get a load hot enough to obturate the CBoo core. So, I need to try a slightly softer CBoo core.
- Without the corn meal, gas leakage eats your lunch. If the CBoo is hard enough to take the fast twist, then it is almost too hard to obturate, so you need a bulk filler to give gas sealing. This may be the main reaon we have had so much trouble with the 6.5: the performance window width is so very narrow as to be extremely difficult to find!
- If I want to stick with the AA-4350, rather than buy a special-use-only slower powder, I will need to find a fluffier bulk filler, so will try 303Guy's idea of using bran. A fluffier filler will not make such a profound decrease in the effective case capacity, so should allow one to adjust the max pressure by lowering the powder charge.
- PPCBoos like a rather light grip by the neck.
- I need to order a 270Win Lee full length sizer ejector/neck-expander assembly, then grind the expander button down to ~0.268", so that I can USE my FL sizer die without having to put up with a way-death-grip on the poor long-suffering little PPCBoo.
So, I'll try this same CBoo core again and with this same PPatch, but using an alloy hardness of around 20 Bh (i.e., I'll soak the Boos at ~430 F, prior to quenching, rather than the 450F that I used on this batch). I'll get back to you all on how the results come out.
The 6.5x55 is tricky! This load used a way-long CBoo core, which helps get the rear end of the Boo to obturate and seal. A lighter CBoo core would be even more difficult, in this regard!
Regards, Zeek