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Oh YES - that be loverly, big bitch that she is. she is so nicely proportioned. She has very similar lines to my .69.

The barrel appears longer than 28" - what is the pull, may I ask?

1st thing I would do, is determine if even or odd lands and grooves, then to mike the bore with a good set of dial calipers. Get help if needed, or lock the rifle in a vise.
If odd lands, need to measure from corner to corner of lands as closely as possible.

The bore should be .1052" if true 4bore - but anything from 5 at .977" to 3 at 1.158 is possible. I would not expect anything further out than that, however that is not beyond possible.

The first thing I would do is to scrub the bore with Scotch-Brite on a close fitting jag, with something like WD40 as a lube - must be thin. Depending on the bore's condition, I'd do that for 10 to 40 strokes, then I'd dry out the bore with clean patches - more WD40 and patches until they come out fairly clean.

As to size, with such large bores, finding out what the rate of twists are may or may not help. The twist rate probably doesn't matter - much.

I would use a ball (order the mould from Jeff Tanner) no more than .015" smaller that the bore size - land to land. This should give you a ball that is .020" smaller than the bore, with shrinkage of the lead upon cooling. Hard alloys will cast larger.

The problem with trying to use really thick cloth as patching, is the thicker the cloth, the less supple it is, as in canvas material if the ball is too small.

The thicker the patch material, the more lube it will carry, so please, no cotton panty or handkerchief material - unless of course, you include the gusset - eh larcher.

If the cloth patch is thick enough to cause the lands to engrave slightly on the ball (use a strip, seat a ball flush and pull it back out to examine the ball) it may work, but it may also need some form of groove depth sealing card wad between the powder and patched ball to prevent gas cutting of the patch.

You must prevent gas cutting if you want the guns to shoot as cleanly as possible to allow subsequent loading without having to swab or wipe out the bore.

Ahh - that Hollis is a lovely rifle indeed.

All of this goes for the 6 bore as well, Huvius. Ball about .015" smaller than the bore, .020" at most and only for hardened balls.

Note - I'd even try paper ctgs. boys.

I make mine tapered as they then all sit in the pocket, ball down. I glue with paper glue, all seams. The ctg. is then easily grasped and the small end torn off with the teeth, then stuffed into the muzzle- torn end down. By the time you have the rod out, the powder will have drained into the breech. Then choke up on the rod and shove the whole ctg. down into the bore, then down onto the powder. The paper compressed beneath the ball will act as a gas check. The paper wrap around the ball should make a very snug fit on the lands. I was able in my 14 bore, to fire 10 of these with same accuracy as patched round ball, before a cleaning shot had to be made with a light load and very wet patched ball.

Now, the big thing - powder charge?

10 drams would be 273 grains. 12 drams the 'normal' max charge would be 327 1/2.

I think I would start at about 200 and see how much I liked that, then go from there.

I have shot up to 330 from my 9 1/2 pound 14 bore and that was not fun.

With the heavy weight of the 4 and 6 bores, 200 should actually be easier than my normal hunting charge from the 14.

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Daryl

"a gun without hammers is like a Spaniel without ears" King George V