Different size nipples on my Piettas?

[oldracer]

I bought two of the Pietta 1858 Remington Bison models with the 12 inch barrels. I also have a pair if ASM with the shorter barrels and all shoot very good. Yesterday I practiced with the two bison models and also a spare Pietta cylinder I bought few months ago. Usually I clean one gun at a time with includes one cylinder at a time but yesterday I pulled the cylinders and then nipples from both guns and the spare cylinder too. I kept the cylinder with each associated gun and the spare separate. After cleaning the cylinders then nipples, including brushing the threads I went to reinstall the nipples (with 1800 degree anti seize on the threads) the first nipple did not go in? Soooooo I looked closely at each nipples and there are 6 with slightly larger diameter threads than the other 12. I checked the thread diameter and the large ones are 0.229 inches or 5.8166MM diameter and smaller ones are 0.212 inches or 5.3848MM diameter. The larger ones are in one of the Pietta's the smaller ones are in the other and the spare cylinder? I checked the threads by holding the large and small nipple together and the threads meshed exactly so I never measured threads per inch. I have a couple thread gauges but after that I figured the actual number of threads per inch didn't matter? Maybe the larger ones are an "oversize" which I saw on a couple websites?

I should have mentioned the date code also, the larger nipples are code "AT" for 1988 and regular nipples are "CT" for 2018 and the newer one was sold "as new" and it appeared that way. The older one has a slightly different frame with a full length groove in front of the rear sight and several dimples in the bottom of the frame in the grip area. Maybe that was what they were doing back then?

Note that I use #10 CCI caps on all 3 cylinders with no issues.

I searched and did not find these same sizes any where although I may have been searching wrong? Has anyone seen this and what nipple comes standard in the Pietta's if anyone knows? Thanks for the help.
Any help is greatly appreciated.
John

[frogleg]

Track of the wolf shows 6-.75 mm Metric Thread for the current Pietta Revolvers I pulled one of mine and measured it and
it is 5.91 mm or 0.232 inch mine is kinda New within the last year.

[rancher1913]

several sizes to work with, even #12 for the colt walkers, but they hard to find.

[oldracer]

Thank you for checking your Pietta for me. My newer on has the same size which I have found are "real" 6mm x .75 threads. I also looked at that catalog page and it appears my old ones have what are called 5.5mm x .75 threads, My extra cylinder, older Buffalo gun and both short barreled 1998 have the smaller thread size. I went to a terrific supply store and they had never heard of 5.5MM threads! So I'll shoot them until they get too worn and then open up the thread size for the 6mm nipples as I have one set and will buy a few more as time and $$$ permit.

[frogleg]

I did a little more looking (this stuff interests me) and in the Track of the Wolf catalog they list a( 12-28 aka 5.5-.9 ) for some older revolvers. So as Rancher1913 mentioned 12-28 might be the size they are listed under. I know that T/C used that thread size on their Seneca and Cherokee Barrels and Patriot pistol.