I would think that ANY "muzzle loading rifle" could shoot a patched round rifle ball... be it a side-lock or an in-line.
Both of my sons hunt with in-lines, but like most of you in-liners, they've never attempted to use a patched round ball either. Their regular "deer load" is a 295 grain sabotted bullet driven by
three 50-grain powder "pellets" (total = 150 grains) which yields a chronographed muzzle velocity of over 2,000 fps together with a very "
robust" recoil!
BTW, you don't need a 300 grain bullet to kill a deer. The swaged .50 caliber patched, round lead rifle ball weighs 177 to 188 grains and kills deer with relative ease... often shooting THROUGH a whitetail at ranges less than 100 yards.
Then, too... you don't need those HUGE powder charges to drive a patched, round rifle ball at a respectable velocity. I use just 65 grains (by volume, not weight) of Swiss FFFg behind my .50 caliber patched round lead in my older CVA percussion cap Hawken Carbine with a 24" barrel. With a weight of only 6� lbs, I'd hate to load and shoot a 100 grains of powder in it... plus it's not necessary.
And this doesn't even mention the much lighter, more pleasant recoil of the smaller powder charges needed for the patched, round ball as opposed to those "monster" powder charges (up to 150 grains or it's equivalent) it takes to move those 300 grain sabotted bullets out at of your in-line rifles at a reasonable muzzle velocity.
Since most deer are taken at considerably LESS than 100 yards which is well WITHIN the effective range of a patched round ball of .45 caliber or greater in any "front-stuffer", you in-line guys may be missing a good "bet" by not trying out the old "solution" in projectiles for muzzle-loading black powder rifles.
It would not only be a whole lot less expensive shooting, but it would be a lot more "sporting" to "throttle back" your in-lines to a patched round ball and 70 or 80 or even 90 grains of REAL black powder or a loose powder substitute charge like Pyrodex... and if you think of it, it would completely eliminate ALL the traditional muzzle loader shooter's "objections" against the modern in-line muzzle loading rifles.
It's just my 2�... but it really is something to consider, eh?
Strength & Honor...
Ron T.