GM3 and 357 Mag reloading
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All handloading data posted on Full-Bore UK from 23/2/2021 must reference the published pressure tested data it was sourced from, posts without such verification will be removed.
Any existing data without such a reference should be treated as suspect and not used.
Use reloading information posted here at your own risk. This forum (http://www.full-bore.co.uk) is not responsible for any property damage or personal injury as a consequence of using reloading data posted here, the information is individual members findings and observations only. Always verify the load data and be absolutely sure your firearm can handle the load, especially older ones. If in doubt start low and work your way up.
GM3 and 357 Mag reloading
I was at the range for a local competition today and it turned out the vast majority of shooters have been moving to GM3 powder and they seemed to be doing OK. DOes anyone here have any experience of GM3 specifically for the .357Mag with 158 grn cast bullets?
- bradaz11
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Re: GM3 and 357 Mag reloading
Not 357. But for 44 I've moved over to a1 as it's the same price and same weight but so much more consistent
When guns are outlawed, only Outlaws will have guns
Re: GM3 and 357 Mag reloading
It is GBP23.00 a tub (500g?) at the range so has to be worth a look
- phaedra1106
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Re: GM3 and 357 Mag reloading
I've been using it in my 44's for quite few years, originally about £20/lb from Peter Lawman but I picked up 5Kg at £42/Kg (£19/lb) last year from a very nice man in Carlisle.
We had one of those "I'll meet you at 1pm under the train station clock" meetings, a bit like Brief Encounter but without the tea and tears :) I live an exciting life sometimes
Another powder to look out for is Maxam CSB-1, not found anyone in the UK selling it yet though. Load data is reported to be the same as Universal powder.
We had one of those "I'll meet you at 1pm under the train station clock" meetings, a bit like Brief Encounter but without the tea and tears :) I live an exciting life sometimes

Another powder to look out for is Maxam CSB-1, not found anyone in the UK selling it yet though. Load data is reported to be the same as Universal powder.
There's room for all Gods creatures, next to the mash and gravy :)
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Re: GM3 and 357 Mag reloading
Ovenpaa wrote:I was at the range for a local competition today and it turned out the vast majority of shooters have been moving to GM3 powder and they seemed to be doing OK. DOes anyone here have any experience of GM3 specifically for the .357Mag with 158 grn cast bullets?
I no longer load .357, but got excellent results with my .357 Rossi lever action, with 5.8gn of GM3 behind a 158gn RNFP GM commercial cast bullet from Kranks.
The current owner of my rifle still uses this load and does very well with it.
I also use GM3 for my 44-40 Spencer carbine and 45 Colt Rossi lever action.
Disclaimer
This load worked well in my rifle but, use this load data at your own risk.
ukrifleman.
- bradaz11
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Re: GM3 and 357 Mag reloading
what sort of charge do you use for the 44-40 and 45lc?
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Re: GM3 and 357 Mag reloading
I've used it for 38 Spl loads but not magnum loads.
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All round good guy and VERY grumpy old man.
All round good guy and VERY grumpy old man.
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Re: GM3 and 357 Mag reloading
For the 44-40 I use 6.5gn GM3 with a .427 commercial cast 200gn RNFP bullet.bradaz11 wrote:what sort of charge do you use for the 44-40 and 45lc?
For the 45 Colt, I use 6.5gn GM3 with a .454 commercial cast 250gn RNFP bullet.
Disclaimer as previous, use this load data at your own risk.
ukrifleman.
Re: GM3 and 357 Mag reloading
I use GM3 in my Rossi carbine, Uberti 1873 and Taurus revolver (all chambered in .357).
As much as I like Unique the alternative is so much cheaper and the net result is the same.
As much as I like Unique the alternative is so much cheaper and the net result is the same.
Re: GM3 and 357 Mag reloading
I've used a lot of GM£ over the years It is exceptionally clean burning and well mannered. I put over 4 kilos through my .45; of course that was when law abiding subjects were trusted to legally own such nasty things. My main use now is for sub 2000 fps target loads in my .375 H&H.
There is loading data out there but you you have to go to continental practical shooting sites, specifically Italian.
There is loading data out there but you you have to go to continental practical shooting sites, specifically Italian.
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If liberty means anything at all, it means the right to tell people what they do not want to hear. George Orwell.
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