357 magnum question

D

Davidf

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Location
Milton, Ontario
I bough myself a Ruger GP100 for Christmas and so far I'm delighted.

I noticed something odd at the range on Sunday though. I had made up reloads with small pistol primers (not magnum), 11 grs of Blue Dot and a West Coast Copper plated 158 gr SWC. I hand weigh each powder charge just as I would with my rifle rounds. When firing at the range about every third round or so had a noticeably greater muzzle blast. Looking at the brass at home I noticed that most of the primers look fine but some are completely flattened and look smeared against the base of the brass.

Obviously, I'll be backing off on the powder next time but why only some over pressure and others fine? Is there any chance the chambers are not all the same size in the cylinder?
 
Is there a chance you double charged some of your rounds? or there is a problem with your scale? I have been shooting a Ruger GP100 for over 15 yrs .. never had this issue..
I reload on a Lee progrssive press and the auto disk dispenses the powder by volume vice weight.
I have never used magnum primers, all my 38s and .357 are made with Winchester small pistol primers.
I also stick to Bullseye or Winchester 231 powder.
 
Of course it's not impossible that I double charged but it is extremely unlikely. Theoretically I could double charge one cartridge but not a third of them. Plus I suspect that a double charge would be far more dramatic than the moderate increase in muzzle flash I noticed.

I'm using a Lyman T-Mag II turret press.
 
I would measure the bullet diameter. Some might be oversized bullets (actually not sized). You might be getting excessive pressure if the bullets are too large.
 
There may be a variation in the chambers, but what about the brass--is it all the same make and lot? Are the cases trimmed to the same length--if not, the crimp will vary from case to case. Blue dot can sometimes be a bit fickle when loading it it can give excellent accuracy if you find the right combo--usually always gives a brilliant muzzle-flash.

44Bore
 
11.0 grains of Bluedot is slightly above max recommended for a 158gr jacketed. You would have no doubt if any were double charged.;) This from the alliant powder website. They also recommend F200 primers. Small pistol primers are somewhat softer and coupled with a load that is "getting up there" , may show irratic pressure signs.

If it was me, I would try a magnum primer and back the load off and work back up. The mag primer may also provide more consistant ignition.
 
DOH! Joe is just too fast for me.. I was also going to suggest what he states.
Alliant show a recc max of 10.7gr but then again that is the lawyerized version and reccommended load, not necessarily maximum load. They also reccommend magnum primers to ensure proper ignition.
Good luck
dB:)
 
Thanks everyone!

I have a brick of magnum primers now so, I'll use them and work back up towards the optimal charge with Blue Dot.

I hadn't considered measuring the bullets but that could easily have been causing the problem too. I was using West Coast Copper Plated SWC's. They looked good but I only measure a few when I opened the box then just loaded up the rest. The box is empty now anyway, but I'll check more carefully when I get more.
 
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