cast bullet bore chamber relationships

[al27023]

Would like some comments on the subject - the question is brought about by slugging a reasonably new 686-6 and checking chambers in same. (Also by 44 spl/mag barrel chambers measured.)
686 barrel measures about 0.3586 groove and 0.3466 bore. Chambers will just pass 0.357 - 0.3569 with some tapping. Everything I am familiar with would indicate the groove should be close to but not over the chamber mouth. This is the only revolver I have experienced with this size relation. Everything else (2 M14's, 36's, a couple Colts and Rugers - all 38/357) follows the above theory.
Also have read the earlier 44 discussions, and would like to note that my 29 and 24 chambers both run .433 with barrel grooves around .430. Have loaded some rounds with .433 as cast and hand lubed with better results.
Thanks for any info you can provide.
Al

 

[al27023]

Would like some comments on the subject - the question is brought about by slugging a reasonably new 686-6 and checking chambers in same. (Also by 44 spl/mag barrel chambers measured.)
686 barrel measures about 0.3586 groove and 0.3466 bore. Chambers will just pass 0.357 - 0.3569 with some tapping. Everything I am familiar with would indicate the groove should be close to but not over the chamber mouth. This is the only revolver I have experienced with this size relation. Everything else (2 M14's, 36's, a couple Colts and Rugers - all 38/357) follows the above theory.
Also have read the earlier 44 discussions, and would like to note that my 29 and 24 chambers both run .433 with barrel grooves around .430. Have loaded some rounds with .433 as cast and hand lubed with better results.
Thanks for any info you can provide.
Al

 

[cp1969]

I wouldn't worry about the .357. When the bullets hit the rifling, the metal displaced by the rifling grooves cut into the bullet has to go somewhere...it's gonna fill the bore.

I have had much worse results when chamber mouths are bigger than bore diameter (.45 Colt Blackhawk). It wouldn't shoot into a bucket and leaded like crazy.