Shoot it and enjoy it. Life is too short to "save" it because it "might" be worth something in the future. Enjoy it now!   

My son and I had an outing yesterday. I wanted to put my Thunderbolt and some newer guns through their paces. First off the newer guns, which consisted of a brace of 1872 Uberti Colts which performed without flaw and my new Fred Dodge/ Wyatt Earp replica. I totally enjoyed all three of them.
Then came the Thunderbolt. I am happy to announce that after an initial bobble (no fault of the Thunderbolt) it performed flawlessly as well. I had a ball with it, and was quite impressed with it's accuracy. The only regret, I forgot to bring my camera. Oh well, next time. Then we went and had breakfast in our favorite cafe in Florence. All in all, a very good day.

Sorry, I made another post not long ago about getting a new-to-me Chaparral 1876 rifle.

Yes, the Jamison case rim is larger than the Winchester brass 45-70 cases I cut down to the 45-60 length. The Winchester 45-70 case rim is .600 and the Jamison 45-60 case rim is around .680. They are Ten X rounds made for the 45-60 WCF. I would think they should chamber if they are made specifically for the 1876 rifle in 45-60 caliber.

I have trimmed the case rims on the Jamison rounds I shot to the same size as the Winchester 45-70 cases but have not yet loaded them or tried to chamber one.

Buckaroo Lou,
First off, I have a Chaparral 45-60 and use 45-70 trimmed cases.  I have never encounter Ten X or Jamison brass.  The rim diameter that the Chaparral pamphlet lists is the same as the original Winchester -- 0.629".  That Jamison rim diameter is totally off or out of spec, if the 0.680" diameter is correct. If it is correct, then I can understand why your bolt and guide tab is making those dents.

You stated that you reduced the Jamison to the 45-70 diameter.  I hope you did not do all of them.  It would be nice to see if a piece cut to the proper 0.629 or slightly smaller, would function and eject better, than the extremely small diameter of the 45-70 brass.

My biggest issue with the Chaparral rifle, I bought/received was excessive extractor to bolt face gap.  I corrected that by installing a WinchesterBob 1876 extractor that resulted in a correct 0.060" gap.  But the ejection of brass was still weak because the tab was not pushing of the bottom on the rim.  As an experiment, I was able to extrude the rim diameter to 0.620" before the rim thickness of Winchester/Remington 45-70 brass got too thin.  These attempts still resulted in weak ejection from the rifle.  As I stated above, it would be nice to see if a piece cut to the proper 0.629 would function better.

While I was typing this reply it came to me -- Could your 'bolt guide tab' have been 'welded up' to give better contact, for use with the standard 45-70 rim diameter?  This would cause the dents in the Jamison brass even if the rim diameter was close to the original 0.629".  (EDITTED --- Sorry missed DJ posting comments before typing this line.)

Good luck with your rifle.  It sounds like it is a good shooter so far.

Updated furniture

Abilene, I was using the Mav Dutchman bullet with lambfat/beeswax lube sized to .429". It carries plenty of lube. I checked my notes and I was using a reduced charge of 27 grains of 2F Goex black powder plus Cream of Wheat filler. The group was 6" at 25 yards fired from a sandbag rest. Not quite as bad as I remember but still pretty bad.

That was last week. I have just got back from the range today and I have much better news. First of all I got a Marbles tang peep sight. Secondly I tried a stouter load. Same Mav Dutchman bullet sized to .429" and lubed with lambfat/beeswax but now with 38 grains by volume of Schuetzen 3F and no filler. With this load I got a fantastic 3 shot group of 3/4" at 25 yards off a sandbag rest. I wanted to take it to 50 yards but it was raining off and on and becoming unpleasant.

I think the peep sight helped a lot but I did find it a bit awkward being located on the tang and so close to my eyes. There is more to report, I also shot a Pedersoli Lightning .44-40 today, eventually I will post some targets. For now suffice it to say I am quite pleased with the Miroku-Winchester as a black powder shooter. Now it is time to clean some guns.

I have found similar results with Uberti rifles. Had horrible accuracy using reduced loads with cream of wheat in  all guns. Mav44 using full house BP loads will drive tacks in the same guns.