Chappy 1876 45-60 chambering issues

[Baltimore Ed]

I bought a Chappy RCMP 45-60 saddle ring carbine years ago because one of my CAS personas is Sgt Preston. I loved the show when i was growing up. I carry my plush Husky when i dress the part. Ive finally retired and am working on my old projects. This rifle is one of them. Ive been casting 292 gr bullets and trimming old 45-70 brass to 45-60 length. The gun looks great, is stiff to cycle but works ok, my problem with this rifle is that some of my brass will chamber with various amounts of over camming others will not chamber at all. How do i correct this? Can it be fixed or do i need to trim the case heads?  I have 2 '73  ubertis in .45 lc and these run fine. Im more of a 1894 Marlin guy but am willing to learn the ways of the toggle. Thanks ahead of time for the imput. By the way, at 45 yds, my first loads made 2 inch groups and seem to be centered about 3 inches high. The wide notch on the ladder sight might be historically correct but is a pain to use.

[DTS]

If the OAL brass length is correct for your chamber and the cases have been sized in normal dies, then the rims of those cases are probably too thick.  It is best to trim them on a lathe where you can do accurate work. they need to be trimmed, just a couple or few thou normally, from the top edge of the rim, not the base, as cutting from the base would serve to reduce the primer pocket depth and possibly cause protruding primers = not good & possibly dangerous.

[King Medallion]

Better yet, just buy the proper brass.
http://www.captechintl.com/products.php?cat=17&pg=3

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[Baltimore Ed]

Looking up the case dimensions  last night i found that the rim on a .45-70 is .070 thick while the .45-60 is .063. Some of my .45-70 brass is already .063 so i used a feeler gauge to measure the closed bolt on my 76 and came up with it starting to tighten it up at .059 inch which is less than what .45-60 is. Before i start cutting on my brass is there something i can do to my rifle to give me a little more headspace?

[DTS]

Sure - however, not the 76 bolt does not touch the end of the barrel, thus, the depression of the rim cut on the chamber is not full depth.  You can have a gun smith remove the barrel and cut the rim cut-out more deeply, but - big - BUT - it is touchy due to the normal clearance of the bolt & toggle linkage lockup - I'd think, which must be measured against the bottom of the rim cut in the chamber. Pretty easy to make a BIG mistake.

[Baltimore Ed]

My shooting buddy and self taught smith John Chance came by yesterday and gave me a tutorial on the 1876/73 and fixed my Chappy RCMP carbine. He had built a rig to remove some metal from the breach face without removing the bbl but before doing that he checked the toggles. With only the left toggle installed the bolt would close just fine on any piece of brass! But with the right toggle installed nothing chambered. Obviously the rt toggle was too long out of spec. A few minutes using a wore out belt on my belt sander and a needle file and with both toggles installed the bolt closes fine on any thickness rim. Now I need to work up some loads. When I get some good targets I will post them. As Chance says " Work on the cheapest part first". Thanks,

[Pettifogger]

This is sort of an old thread but original .45-60 brass has thinner rims than the .45-70.  A properly chambered or tight 76 will have problems chambering shortened .45-70 brass without encountering the problem described by the OP.