HELP! GPR won't group

[stevelyn]

I have a Lyman GPR in .54 caliber I got for Christmas this past year. I'm having problems getting to group. At first I thought it might be due to a metal burr I discovered in the notch of the rear sight preventing me from getting a clear sight picture. A little filing solved the sight problem.
Now performance is so inconsistent I'm about to give up on it.
I'm working on an accurate hunting load. I've been using Hodgdon Triple 7 for propellent and my starting loads were 90grs and I've gone up to 110 grs. I can't seem to find the right combination of patch thickness and charge.
Here is what I've found so far. A .535 ball with a .010 patch is too tight requiring both hands wrapped around the ramrod and one leg around the rifle to seat the ball. A .530 ball with a .010 to .015 muslin patch is too loose. Pillow ticking patches from .015 to .016 is inconsistent and the rifling dosen't always cut the patch. Pillow ticking patches of .018 is again too tight with the .530 ball requiring the two-handed, one legged balancing and cussing act.
Sometimes the patch is intact with an even, dark ring around it and no or very few rifling cuts. Others are completely shredded into a pile of little fibers.
One guy told me that perhaps I should consider ordering a custom ball mould at .531 or a little larger (definitly less than .535).
Do rifling cuts need to be evident on the patches? Is it possible due to T-7's increased energy and velocity, the ball/patch could be skipping over the rifling?
Other factors to consider is lubes consist of T/C Bore Butter or a home grown recipe of Crisco, olive oil, lemon oil and beeswax cooked on the kitchen range. One is not used exclusively over the other. Patches are dipped into the molten lube and set aside to cool. Balls are made by different manufacturers mostly Hornady and Buffalo Bullet. Powder is 2F Triple 7. Is there something I can fix here or do I need to consider purchasing another barrel?

 

[4v50 Gary]

Whoa! 90 to 110 grains of powder?

First, is your barrel for round ball or conical? If round ball, I suggest you start with a lower charge like 50 grains FF and work it up from there. Too much powder isn't conducive to accuracy either.

 

[stevelyn]

Yes, it is specifically for roundball with a 1 in 60" twist.

 

[stevelyn]

It would appear that at least for now 80 grs of T-7 is the magic number.
After I started shooting found a sight adjustment was in order so I tapped the rear sight to the right and the front to the left and and it shifted everything to center. I raised the rear a couple of clicks to get it into the black. Then I fired for effect on three different targets.
All of the shots were within a couple of inches of each other on each target except for one which landed about three inches high from the other two. That one is obviously my fault since the other two shots are touching. Groups are definitely m.o.m.v. (minute of moose vitals).:grin:
I also discovered that it made no decernable difference as to the .015 twill patches verses the .016 pillow ticking patches. Two patches I could find reveal there were tiny separations in the fabric where the rifling grabbed iton its way down range.
It would also appear that the balls from Buffalo Bullet Co are slightly bigger. They seemed to fit a little tighter than the Hornady's and were a little harder to seat.
My results might have been better if it were not for a 10-12 knot wind blowing from behind to quartering from my right.
The distance was 50 long paces in evening light. Targets were 7" diameter bullseyes downloaded from http://www.targetz.com
Since this rifle is going to be used for a moose hunt I guess the next step is to increase the charge until the groups start opening up. Suggestions?
Another discovery, by stacking the used targets on top of each other and superimposing the holes, the overall group is fist sized with one flier.

 

[mec]

you might experiment with pyrodex rs or ffg. I've shot 777 in pistols and found that at full volume charges, it produces much higher velocity than any of the others but is also very erratic over the chronograph. It is both consistent and accurate when I use reduced charges. But it looks like you have gotten a handle on your accuracy problem.

 

[smokemaker]

I had decent luck with roundball guns that didn't group well by using cut denim patches. Don't know why, but guns that shredded linen or ticking patches did well with denim. Also, I use 100 or 110 grains of powder with my GPR, and the faster I push the balls, the better it shoots.

 

[4v50 Gary]

Every gun is different. Generally you start with the lowest recommended group and work up in 5 grain increments. You'll note at some point where the group gets better and then it starts to widen again. That's why load development is so critical for a muzzle loader - just like a modern centerfire cartridge. The rifleman's task is to find that happy combination of ball size & weight, powder charge and patch thickness.

 

[stevelyn]

mec,

My main reason for not using Pyrodex is that I live in a rather stormy marine environment. Corrosive propellent combined with a damp, corrosive atmosphere would make maintenance problematic.

 

[Dave Markowitz]

WHOA!

You DON'T want the patches to be cut. You WANT the patch to remain intact and uncut, and there should be a ring of fouling around it.

A properly functioning patch is acting as a gasket to allow the ball to engage the rifling, yet be small enough to ram home without undue effort. When the patch gets cut the gasket effect is diminished.

My suggestion, based on prior experience with a .54 GPR, is to use a .530 ball, pillow ticking, and something like Wonder Lube or Crisco. I obtained good accuracy with 70 to 90 grains of 2Fg black powder. (Sorry, I've never used 777, and since my rifle was a flinter, didn't use Pyrodex.)

The above loading info let me shoot 50 yard offhand groups that you could cover with your palm.

 

[stevelyn]

Dave,
When I first started shooting it I was recovering patches with a charred ring around them and intact. An aquaintance with a custom rifle told me to stoke it up and said the patches should have cuts in them.
Since I put to use the knowledge gained from this thread and experimented a little, I have a couple of theories.
First, 777 is a lot hotter (about 15%) than Pyrodex and blackpowder charge for charge. Secondly, I believe the custom gun has deeper rifling than mine and the heavier charges were causing the balls to skip over the rifling without stablizing them correctly and possibly deforming them. Which would explain the 70 yard .54 caliber shotgun pattern I was getting on the target board and the shredded patches. Also the custom gun's ideal load is 110 grs of blackpowder by design and BP substitutes have never been fired out of it. It also has a custom ball mould made specifically for it.
Since I've reduced the charges in my rifle my patches aren't really cut. They are more like separations in the strands of fabric. They do have a uniform ring going around them and some slight charring in the middle where the ball was seated against the charge. Now I have to fine tune it. I want to use it for moose season want to be confident that I'll have a reliable 100 yard load capable of adaquately penetrating a moose. A mature bull is the size of your average horse.
Any thoughts?