MP 359-125 versus Lyman 356402

[Charlie Two Tracks]

I know that these two molds are not the same size or weight but here is my question. Neither of these two boolits have a crimp groove. I have been using the MP 359-125 in 38 cases and using light loads for my wife to shoot. It works well for her. I was looking at the 4th edition Lyman CB handbook and noticed the 356402 loads for a .357. It shows using up to 8.3 grains of Bullseye getting 1390 fps. It just seemed strange that without a crimp groove, you could get speeds and pressures like that. Using 9.4 grains of Unique you get 1482 fps and 41,300 CUP. Do you just put a taper crimp on? My MP 359125 is dropping boolits about 127 to 129 grains depending on the alloy. The Lyman info is for a 120 grain boolit and I have been using the max load for the 120 grain as an example. I would start out less of course but was just wondering about the crimp and if anyone has used the 359-125 in their .357:?::?:

[Charlie Two Tracks]

bump-

[cbrick]

It just seemed strange that without a crimp groove, you could get speeds and pressures like that.

Not in the least strange. The crimp has little to do with the load "working". The crimp helps hold the bullet in place under recoil. The load will build pressure & burn correctly from neck tension. I tested the effects of crimp in a high end 357 load a few years back including loads with different types of crimp, different amounts of crimp and no crimp at all. The test rounds used H-110 which absolutely HAS to get burning to work at all. The result was no change at all in the SD or average velocity among any of the test rounds.

I have posted those results on the forum several times but this morning I am on a brand new computer and have none of my documents on this machine. A search of "crimp tests" may bring it up.

Rick

EDIT: Here ya go, post 15 has the results of the crimp testing.

http://castboolits.gunloads.com/showthread.php?174458-Position-of-crimp-in-crimp-groove&highlight=crimp+tests

Hope this helps.

[Charlie Two Tracks]

Thank you cbrik. That was very understandable information.