Gibby, there's a whale of a lot I don't know about internal ballistics, but the question to me isn't so much whether or not it can be done, but if it can be done well. Entirely a guess on my part, but it is quite possible the loads above are indicators of where I need to be headed. 180 grains of lead (183.5 actually) is a fair bit up the SD scale from the referenced bullet. Transferring data across a wide gap like that may generate some surprises I don't want.
Another point of minor import is the alloy they used versus what I'm using. 30:1 is around BHN 9 which is just slightly harder than bullets found in .22 RF ammo. Their ref. MAP is around 26K PSI and that's a fairly good reference for the max I can use with this alloy.
OTOH, I will need a minimum pressure of about 13 KPSI to promote obturation, so somewhere in the upper middle to max will get me where I need to be for best performance of the alloy, and by extension, the bullet. To my eye that's one of two critical elements in finding the consistency I'm looking for. The second is load density. I imagine I'll find success with something in the 75% or higher range of that. Of course I could be full of crap and find something out in left field that works splendidly.
For all the "research" I've done there are still things to be learned. For example, it came to my attention this eve that WW540 has a lot slower burn rate than I'd been led to believe based on data from one source contradicted by several others. Stuff happens. It explains my findings from the range visit detailed above. In fact, of the 3 powders used to date, they almost perfectly illustrate the range of burn rates I'll be playing with, that being Bullseye to 2400. If I don't find nirvana there I'll step outside the box just a bit. One thing I'm not short of is a variety of powders to play with.
What needs to come next is to find out what velocity range I'm in, at least in my imagination that's it.
Bristoe, as far as picking a velocity, the range listed (800-1,000) is adequate for my purposes. One of the things I've learned about cans of late, is that the low transonic velocity range ups the noise footprint substantially with velocity increase and that bullet form has a lot to do with that. I will be subsonic when all is said and done, but the degree is an open question. I'll be preferring precision at 750 fps to larger groups at say, 950 fps. Is an ingrained preference picked up from popping pigs with CB shorts with the same frame pictured above. The "desire" is MOA @ 100 yards. The practical requirement is a pig brain sized group at 50, 100% of the time with enough snap to put it there, thru the bone structure with any reasonable aspect to the shot.
Yeah, it's an odd looking thing for sure. If you google around for the .30 Badger/.30 Reece you'll find something similar. Difference is primarily in neck length for my round which is near 1/2" and a case capacity intended to drive a particular bullet subsonic rather than a variety of bullets supersonic.
What led me to the .357 case was it's untapered form, SAAMI spec MP and rim which is quite amenable to the Contender. Believe me, I looked at a lot of alternatives. Some that were close runner ups were bypassed mostly due to a lack of brass or other aggravating circumstances.
I had some lengthy discussions with Dave Manson and Bullberry regarding the project and once they understood the parameters and platform they were thumbs up. In the balance of my life it will shoot that one bullet at subsonic velocities yet to be determined even though the range of velocity is fairly well defined. I do have experience with other guns w/cans (.22RF, .22 WMR, .357, .44 Mag, all rifles) and the variety of characteristics/baggage which shaped this project. It's doable, but will take a little time.
I doubt that the most consistent propellant at 700 fps is going to be the most consistent propellant at 1000 fps.
I agree with that. Question is, which is best and where?
