GM3 Loads for 357 and 38 Special

newbie69

Well-Known Member
#1
Hi
Does anyone have any experience of reloading using GM3 powder in 357 and 38 Special in a lever actio rifle?

I got a tub and about to start working up loads and curious where to start at.
 

EMcC

Well-Known Member
#2
Wow, I didn't know GM3 was still available. I used to use that when reloading my 9mm Browning pistol.
As far as I can remember the bullet was 120gn and the load I used was 6gns, I think.
Not helpful for your calibre but it may give you some idea of what to expect.
 

Shootist

Well-Known Member
#3
My test data.

Testing GM3 shotgun powder in a Marlin .357 lever action rifle.


  1. Object of test
    1. To test the velocity and grouping of various weights of bullets in front of various weights of GM3 powder.
  2. Method
    1. Groups shot at 50 metres through a chronograph using a bench rest to maintain reasonable accuracy.
    2. Hand loaded rounds.
  3. Equipment
    1. Marlin .357 Cowboy Limited with 24” octagonal barrel
    2. Prochrono Chronograph
    3. Lyman electronic powder measure
    4. GM hard cast lead truncated cone bullets
    5. PPU new brass cases.
    6. Federal primers
  4. Results
©SRF 2015

[TABLE="width: 35"]
[TR]
[TD="align: right"] GM3 Sheet.jpg
[/TD]
[/TR]
[/TABLE]
 

dodgyrog

Well-Known Member
#4
Nice to see the job done properly.
You might get better results (group wise) with softer boolits but that means casting your own.
 

Shootist

Well-Known Member
#5
Nice to see the job done properly.
You might get better results (group wise) with softer boolits but that means casting your own.
Thanks for the kind words. I cast my own bullets for a number of calibres but not .357 or .44, mainly because I'm up to my armpits in GM hardcast. Do you have any mould recommendations for either calibre?
 

newbie69

Well-Known Member
#6
Wow thanks thats great information and more than I could ever ahve hoped for so quickly. Fantastic this definetly helps a lot and will save me time. Now to do some test laods with 158g and 180g GM heads
 

Shootist

Well-Known Member
#7
A word of advice should you wish to try out some jacketed bullets. The loads shown in the chart are for target shooting with lead bullets. Increase the load by a half grain at least. I've put a ring in a barrel precisely because I wasn't paying attention enough to make sure the bullet came out of the barrel. Don't go too low.
 

newbie69

Well-Known Member
#8
Hi
Thanks again, io only looking for target shooting with GM heads just now so it looks like this will give me a very good idea of what to expect.
 

phaedra

Well-Known Member
#9
Where did you get your GM3?, last tubs I got were from Peter Lawman and that was a few years ago so I'm running out!.
 

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