Max GPR load

[CWC]

The lyman manual that came with my .54 GPR had a table of maximum loads for PRB. For FFFg it listed 80 grains as the MAXIMUM charge, and 90 grains for FFg. I know I've seen people listing their favorite loads, and many were above the factory recomended max load. So, is the factory publishing very conservative figures to satisfy their lawyers, or is there a real danger in going above 80 grains? What is the highest charge you guys regularly shoot?

 

[jtmattison]

Are you looking at the Lyman manual or the manual from the manufacturer Investarms?
The Investarms manual lists smaller maximum charges than the Lyman manual.
For .54 roundball it is 120 grains 2f and 100 grains 3f.
For conicals it is 110 grains 2f and 90 grains 3f.

HD

 

I used 90 grains of 3f on a deer and it was over kill.Ive dropped my load to 80 3f.

 

[renovato]

I think the Lyman and Investarms manuals are being extremely conservative. Those guns are patent breech and made very well. Even my Traditions manual lists 125 gr. FF and 120 gr. FFF as max loads in .54 and the Traditions guns have drums, and I would assume they aren't as well made.

 

[WV_Hillbilly]

100gr of FFg or 90gr of FFFg is what I consider maximum for the .54 GPR. It is pretty accurate at that maximum also, but if I should increase it beyond that level, the groups tend to open up and I am not getting any appreciable gains in velocity either. A chronograph is cheap enough anymore that even I can afford a "Shooting Chrony"

Despite the maximum listings disagreenment between Investarms and Lyman, I would tend to believe that the gun's manufacturer would be the one to follow. I'm sure though that Lyman has been absolutely thorough (and honest) in their own testing; and has proven to themselves (AND to their lawyers!), that their values for maximum charges are acceptable and safe to use.

So it's not that I'm afraid to go higher with the powder charge. I just don't gain enough to warrant the increase and the accuracy is not as good. I frequently am shooting only 40gr FFFg as a plinking & target load in that .54 GPR also.

While it's good that you want to see what others are doing with their GPR's. You are the one who has to shoulder that rifle (and the responsibility) if something should go wrong from too heavy a charge of powder. What if a bystander gets injured and you were shooting more than the mfrs maximum? It's just a supposition I know... but we also need to remember what kind of image are we portraying to those who don't yet shoot or to those are totally against the shooting sports? Something to think about next time you load up...

Regards, and safe shooting,
WV_Hillbilly

 

[shmrck1]

CWC,
My Lyman manual shows 120 grs 2FF and 100 3fff.
I use but 80grs of 3fff because that is the load
I am most accurate with. Its plenty enough for
the ranges I will shoot at when hunting deer.
snake-eyes :hmm:

 

[Mad Professor]

This came up in another thread concerning Investarms barrels.

Since both Lyman and Investarms barrels are made by Investarms they must be proofed by Investarms. An Australian gentleman, Bernie, mentioned that one of the earlier Lyman BP manuals had the proof standards for both Italian and Spanish rifles in it. His copy was on loaner, anyone else have this manual and/or data?

It would be interesting to compare this proof load with the maximum recommended by both Investarms and Lyman, and then compare these with some stout loads listed in the loading data for pressures.

Also does anyone know if Lyman re-proofs (and/or re-tests) any of the barrels it sells but does not manufacture?

My old Lyman barrels only have the Investarms proof marks.........

 

[jtmattison]

Also does anyone know if Lyman re-proofs (and/or re-tests) any of the barrels it sells but does not manufacture?

I Emailed Lyman about this topic and they said they tested the barrels themselves and came up with their maximum loads. They said the Investarms recomendations were very conservative.

HD