PDA

View Full Version : Riddle me this, boolit man (primers and WC820)



rbstern
05-17-2006, 02:08 PM
I shot two, similar 357 magnum loads recently, and trying to interpret differences in pressure signs. Gun used for both loads was S&W Model 66 with 4" barrel, starting with a clean barrel in both cases.

Load 1:

Lyman 358477 SWC 158 grain wheel weight alloy, pan lubed (3 parts candle wax, 1 part kerosne, 1 part Dexron ATF), sized .358
12.0 grains WC820 (hi-tech/"H110" speed)
1.577" COL
Remington 1 1/2 primer

Good accuracy, fairly clean barrel, primers flattened

Load 2:

Lee 358158 round nose, 158 grain wheel weight alloy, tumble lubed with Lee Alox, unsized at .359 +/- .0005"
12.0 grains WC820 (hi-tech/"H110" speed)
1.600" COL
Remington 5 1/2 primer

Fair accuracy, moderate leading, primers well rounded

It's the primers that have me scratching my head. While these are not apples to apples loads, they are close. Bullet shape and lube are the only difference.

I expected more pressure signs in the load with magnum primers, and got exactly the opposite. Any thoughts?

felix
05-17-2006, 02:20 PM
Go back to your pistol primer, and up the load to 13 grains. If that works much better, then try 13.5-14.5 grains, and look for a downturn in accuracy at a 0.5 increment. If so, back off a half grain. That will be your 820 load with that boolit and primer. If you have a chrono, pick the powder amount where the curve STARTS to flatten. Best spot for the various 820 formulations. ... felix

rbstern
05-17-2006, 05:00 PM
Go back to your pistol primer, and up the load to 13 grains. If that works much better, then try 13.5-14.5 grains, and look for a downturn in accuracy at a 0.5 increment. If so, back off a half grain. That will be your 820 load with that boolit and primer. If you have a chrono, pick the powder amount where the curve STARTS to flatten. Best spot for the various 820 formulations. ... felix

Sorry, Felix, you've confused me:

Both loads used pistol primers, one regular (Load 1), one magnum (Load 2).

I'm not going to increase the charge for the load where I got flattened primers...too dicey.

Are you suggesting I increase the charge for the magnum primer version, i.e., "Load 2"?

Lloyd Smale
05-17-2006, 05:18 PM
;mag primers probably have a tougher cup.

StarMetal
05-17-2006, 08:14 PM
With alot of revolvers and semi-auto pistols having a minimal firing pin strike, I personally would doubt that pistol mag primers have tougher cup...I really feel they just have either more or a different primer mixture compound.

Joe

David R
05-17-2006, 09:29 PM
I have found mag primers are much harder. I can flatten a winchester small peestol primer in my 38 with 4.9 grains of 231. This should be around 16 to 18 thousand PSI. 357 shoots at 37 thousand PSI with a magnum primer.

Hope I answered your question.