Minimum Charge for lyman GPR with patent chamber

[BigBoreBLR]

Whats the minimum charge for a great plains rifle.

The patent chamber has a certain volume that should be filled up. Once that's filled the extra volume of powder is snuggly pushed against the roundball.

I got the 54 cal model. I used to feed it 90 grains. I find using 50 grains to be much better. I did read on a forum 60 is the minmum, but can't verify that with the lyman book for the gun.

I'm going to call them in a few days to verify.

 

[azmntman]

Minimum? maybe 5 grains? whatever is enough to get the ball all the way outta the barrel! :haha:

When me lil boy was like 3-4 I would load a few rifles with 5-10 grains so he could shoot. Once he actually hit a pepsi can, ball went in but not out! Somewhere i got video of him as a late 2 yr old shooting my roa with just over cap only loads. He kilt his first BP buck last Oct with a .54 great plains. INCREDIBLE destructive wound (entrance worse than exit!) Course now he is 6'3" and weighs 230 so he was shooting 70 grains.

 

[BigBoreBLR]

That is true of common muzzleloaders.

But, the GPR has a patent chamber.

At then end of the 54 caliber 33" barrel is a 1" or so long and roughly 36 cal bore area before it end up to the flash hole. They call it a patent chamber.

Putting 5 grains in let say a 50 grain volume spot would be like pushing the ball with a 1 inch gap.

Maybe it's OK, maybe it not.

General knowledge is to push the ball all the way down to eliminate the gap.

 

[AZbpBurner]

Once upon a time (actually twice) I seated a .54 cal. PRB over dead air.

I've got a ball puller, but couldn't get a good enough grip on it or leverage to pull it out, so I removed the vent liner and poured in around 5-6 grains (from empty .17 rimfire brass). When fired, the ball made it almost out to 100 yards before it hit the ground and skipped into a dirt backstop.

While I don't recommend such a light charge on a routine basis, it was an eyeopener to see that it performed a lot better than just spitting outta the barrel and landing out on the ground some 30 feet downrange.

While my typical load is 75-80 gr., I've had pretty good up-close (25 yard) accuracy with a 35-40 gr. load.

 

[ravenousfishing]

30 grains in my 50 cal GPR leaves the ramrod more exposed than when empty, so the patent breech holds less than that.

 

[ohio ramrod]

Since many people "shootout" dry balls by working a little powder in to the flash hole (or under the nipple in a cap gun) I don't think you have a thing to worry about as to minimum charge. Now a "light " charge and a short started ball is another story. If you have any doubts put in a light charge then some corn meal to fill any gaps. :idunno:

 

[Lonegun1894]

I have used 20grs 3F in my .54 with good small game performance out to 50yds, with obvious elevation adjustments, so wouldn't hesitate to use that. Have used the same load with a .50 CVA too, with that goofy breech design, with good results also. I have no doubt as to the safety of a load that light in my guns, so unless your patent breech is much deeper than mine and has a larger volume, I would think they should be safe on your GPR also.

 

[roundball]

FWIW, based on the one's I've owned, I think the powder chambers in T/C 4x & 5x caliber Patent Breeches are the same size...and having a couple spare breechplugs, I measured their powder holding volume one day...averaged 22-23grns of powder.

 

[Jim Evans]

From the Lyman Loading Manual.
Minimum for a .54 cal on a 32" barrel 1/32 twist is 60gr.
Minimum for a .54 cal on a 32" barrel 1/60 twist is 40gr.

 

[BrownBear]

I've dinked around a lot with the question because I own GPRs in both 50 and 54, and because I use them lots for head bopping snowshoe hare. My interest has been in how much was needed for trajectory at less than 50 yards, and how well the loads worked with no change in the sights.

It's boiled down to 30-35 grains of 3f.

Accurate as a snake bite with no change in sights, flat enough for shots out to 50 yards, reliable power for head mushing with no excess damage to fine eating meat.

I do a whole lot of small game shooting and field plinking, and that charge gives a little over 200 shots per pound of powder.

Good enuff for me.

 

[FPDoc]

I've used as low as 30gr of 2F or 3F in my .54 GPR flinter when bunny hunting or plinking and it has worked well for me.