I've tried all kinds of different loads from maxi balls homemade and factory, powerbelts, greatplains and even round balls. Mostly I've shot Triple 7 and Pyrodex through it. 70 to 100 grains.

A first I thought it was my sight picture and not having the same position on the stock. I was convinced enough to buy peep sights to eliminate error to a minimum. Well that wasn't it. It's not sight picture at all and I had a gunsmith match the peep to the globe for height.

One thing I forgot to mention was it's already busted one stock from just firing it. Not that would be a issue but it could be if the barrel is drilled off center. One thing I'm going to try is to shoot it upside down a few times I should get the reverse effect. I'm sure this will get inventive to figure out how I'm going to do just that. I just if it is what I'm thinking it could be then I guess I'll ship the barrel back to Thompson. I'm also going to do what cyugad said and go for the 50yd range first but I believe I did that before new sights were put on it.

The accuracy of it at 100yds is every round with in a 3 inch circle. Considering what it's doing at 50yds I didn't think it was doing too bad at 100yd. I've shot better groups with my Lyman but the issue isn't how well it's grouping but it's radical difference in trajectory.

I've even put wads between the powder charge and the bullet thinking I was losing severe velocity. That doesn't seem to be the case. I've cleaned it and cleaned it and cleaned it. I've ran more loads through one muzzle loader in 10 years and never cleaned it that much.

Alot of good ideas and I'll try a few before letting Thompson have it back. It's became a challenge at this point. Thank you all

The off-center bore notion does not make any sense to me.

As you shoot for testing, if you don't already, use a 6 o'clock sight picture. Get the bullet hitting exactly at the top of your front bead at 50. Then see what it does at 100 with exactly the same aiming point. I cannot see how it will be anything but a couple inches low.

This defies logic and physics. If you are getting a 3 inch group at 100 yards and are 18 inches high at 50 your muzzle velocity has to be about what you would get out of a Daisy BB gun. A slow moving projectile is the only explanation that makes sense.

Have you tried shooting a different powder like Pyrodex RS or Goex?

i have seen this happen using BULLETS THAT DONT WORK WELL.
370 gr in my hawkins .50 is great.
put in a 320/350 gr and it will do things like this.
MAXI-HUNTERS would do things like this.use only MAX-BALL.

get box of 370 gr MAXI-BALLS ,shoot those and see if it happens. use 70/80 grs of GEOX.

let us know..

take care sproul

I SEEN WRONG BULLETS/POWDER defy logic/physics

Sproulman I am sure you are more experienced than I am on this but I am trying to understand it. So with the wrong powder/bullet you can have a wide pattern at 50 yards and then at 100 yards things come together in a tight group?
Art

Quite simply, a bullet shaped projectile of 200 to 500 grain weight moving on a horizontal plane at 1400+ fps can not possibly drop 18 inches over a distance of fifty yards.

more experienced,NO..........just i have ONLY .50 cal hawkins and seen just about everything than can go wrong.usually its BULLET/POWDER that makes this cal shoot crazy.

yes, i have seem WILD things happen with .50 cal hawkins.

just going from a MAXI-BALL to MAXI-HUNTER would shoot all over, drive you nuts.

.50 cal has to shoot right LENGTH bullet to group good.i seen MAXI-HUNTERS put bullet in same hole at 25 yds and miss the target at 100 yds.switch to MAXI-BALL 370 and hit dead on at 100 yds.