ok - I'm new at muzzleloading but I thought I'd share what I learned. I'll do my best to get the terminology correct...just want to give back a little for all the help I've rec'd here. I apologize for any misuse of words & the length of the post.
1. It seemed that placing a small folded patch or piece of foam under the barrel, near the breech end provided enough lift/resistance so that I'd have to push down on the barrel slightly to get the wedge pin in, and it would stay...this worked, but I anticipate using the stock barrel sometimes for round balls and I just wasn't happy not knowing exactly what the cause was...
2. I do not have (yet) and extra wedge pin - and I did not want to start bending the one I have, since it works fine with the stock barrel....and I really wanted to eliminate the loose fit.
So....
3. I removed the tang and took time to really understand what the difference was between the green mountain barrel and the stock lyman barrel. It was immediately clear why the green mointain barrel would just drop into the stock with no resistance whatsoever.
On the stock lyman barrel the hooked breech fits the tang almost perfect..once it's in, the hook sits immediately behind the tang...no play...and when the barrel is flush with the tang, the barrel is angled up slightly, relative to the stock...thus, some pressure must be applied to the barrel to get it to line up with the wedge. I noticed it actally puts some lifting pressure on the back of the tang, which would normally be screwed in the stock.
But the GM barrel had a good 1/8 play between the hook and the tang AND there is space between the top of the hook and the tang...so when the barrel breech hook is installed into the tang, there is enough play, so there is no resistance - barrel just falls into place.
I ended up heating the hooked breech with a MAPP torch and slowly hammering it back towards the barrel...almost bending it in...and filing the top of the hook, and then bending it a bit more...essentially reducing the space between the barrel breech and base of the hook, to match the width of the tang.
did this till when installed in the tang (which I had to remove initially to keep measuring), fit as the stock barrel did...no play back and forth.
put back the tang, and the new barrel fits in like the lyman stock barrel now...a bit of pressure needed to seat the barrel in the stock, and enough "up pressure" by the barrel to hold the pin in.
what was frustrating is there is so much play in the GM breech hook to tang fit...and the green mountain barrel has a very narrow hook compared to the lyman hook....also quite a bit thicker which required filing on each side to even get it in the tang. But the thin hook on the gm barrel means you do not have much material to work with as you are bending it back towards the barrel...
I've used drop in barrels before on rifles & pistols that say you must do some fitting...but these barrels are meant to fit a variety of rifles...but the GM manual is real clear about not doing anything to the barrel at all as it is made to drop in....but right away I could see visual differences between the breech hooks of the two barrels. The specs are way off.
I'm glad I got the fix done, but if the GM barrel for the trade rifle requires this much tweaking, as the specs are so off, they really should state what you should do...
