Well the weather finally cooperated today and I got out to shoot my sleeved Hawken flinter barrel.
Shot some 250 gr SWs with Harvester blk CR sabots (left target) and some 300 gr Sierra JSP .451" with same sabots.
Loads were 80 gr of FFFg & FFg. Both loads from each bullet were pretty similar. Range was 50 yds. The 2 Sierra groups measured 1.6" and the SWs were 1.7". However with the SWs, I have 4 bullets in that ragged hole on the left target. I need some more time to tweek a load but the barrel does show promise. I had to change flints mid shoot but other than that, had a fun outing,
Note: the 2 holes on the right target at about 8 O'clock were my first 2 shots at 25 yds to see where it was sighted in.

That looks great Bronko, especially without experimenting with other powder charges. What rate of twist did you go with on the sleeve - 1:28 or 1:24?

Semi - I went with the 1:28. I thought the 1:24 might be too fast for the bullets I was planning on using and this twist worked good for me in my GM barrels. One thing that is nice about this barrel sleeve is that I sent hm the bullets I was going to be using and he sized the bore to that particular combo. Use the short starter to start the bullet and once the rifling bit into the sabot, it went down with just a nice smooth push.
And a bit ago I was out in the yard and the neighbor said he saw me pulling up after I was done shooting. He told me he has a muzzleloader, he thinks its a Hawken but he's not sure. He has never fired it. And - he told me it has a long brass scope that goes on it!!!!!!!! I told him I liked MLs and he said he would bring it out for me to look at when he can 'dig it out'. Maybe I have found a little treasure.

You just may have to make him an offer he can't refuse.