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Old January 10, 2012, 09:55 AM   #1
mwal
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powder residue from cylinder GP100

I have a GP100 .357 6 inch barrel. I get powder spray hitting my hand or face 1 out 30 shots with the following load. 15.5 gr of H110 spm primer 158 grain XTP. I am using a heavy crimp into cannelure using trimmed bass. Oal matches Hogdon load recommendation. I show no pressure signs. Any other loads such as 38 spcl or factory 158 gr loads do not do this. 15.5 gr is not quite midway to the recommended max of 16.7. Any theories or suggestions?. The residue is powder not copper.

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Old January 10, 2012, 10:44 AM   #2
SL1
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Two thoughts

1. H-110 does not burn well at low pressures, so the "residue" that is sometimes hitting you in the face might be unburned powder from the occasional load that stops burning too soon. Your 15.5 grain load is about 7% below max, and there have been warnings to not reduce H-110/WW-296 (same powder) by more than 3% below max. But, on the other hand, when SAAMI changed the .357 Magnum pressure standard from 46,000 CUP to 35,000 psi, some manual revisions showed the new max charge weight to be more than 3% below the old max. So, it is hard to figure.

2. You made a point about the residue NOT being copper. So, I am guessing that you are familiar with the issues involved with the cylinder not being aligned properly when the round is fired. Still, it might pay to take note of which chambers of the cylinder are giving you the residue. One or more of your chambers might be larger than the others, resulting in slightly lower pressure when the cartridge in it was fired. And, don't rule-out alignment issues until you have carefully checked. I had an experience with a Security Six where the cylinder was not being locked when I was mid-way through a cylinder-full of loads. At that point, the weight of the unfired bullets was all on the side that needed to go up as the gun was cocked, and the imbalance, along with a too-thin cylinder pawl, was failing to get the cylinder notch to the locking "bolt" when I SLOWLY pulled the trigger in double action to test ammo. So, alignment was off and part of the jacket was shaved. So, I suggest that you pay attention to which round in a series spits residue, also.

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Old January 10, 2012, 11:09 AM   #3
mwal
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SL1

I weigh every few charges and have to occasionally trickle because of light charges. I may try going up to 16 gr. And will weigh all charges. No other loads .357 or 38 have sprayed like these have.

Mwal
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Old January 10, 2012, 12:46 PM   #4
mrawesome22
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Quickload predicts that even with a max charge, only 75% of the powder is going to get burnt.
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Old January 10, 2012, 01:36 PM   #5
Blind Dog Jake
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wrong spot --sorry
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Old January 10, 2012, 10:26 PM   #6
GP100man
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Try IMR800x , it`s kinda big flake powder but 7.5-8grs will burn real clean.

Herco is another forgotten performer in straight walled cases.

But be prepared these powders are large flaked & usually don`t play well with powder measures .

2400 works well & will clean up at magnum pressures , if ya drop it it`ll leave little yellow kernels which will fight for position under the ejector star .

I call what your experinceing the H-110 sand blasting .

Sounds as if the face of your cyl. is`nt EXACTLY square & the cyl gap opens a bit more on 1 of the holes.
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Last edited by GP100man; January 10, 2012 at 10:32 PM.
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Old January 11, 2012, 09:56 AM   #7
mwal
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GP100man

H110 sandblasting is the perfect description. Should I try another powder as i don't have this issue with any other load? Or send to ruger to get checked out?

Mwal
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Old January 11, 2012, 02:00 PM   #8
Poodleshooter
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Your load is too light for that powder. Unlike other powders, H110 and its twin W296 should only be reduced 3% from maximum loads, per Hodgdon. It has a very narrow pressure window for good burning characteristics.
Lighter loads will leave you with golden grains of partially burned powder strewn throughout the action.
If the max is 16.7, try a load of 16.2gr, with the same heavy crimp and seating length. You should see a much cleaner burn.
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