Well folks, I've been reading for a long time how Marlin should get their act together and give the 38-55 a proper bore size. Digging out my original copy (1979) of Ken Waters “Pet Loads” to read what this well respected researcher had to say on the subject, I wasn't surprised to find the following.
When he wrote the original article for the May 1976 issue of “Handloader” Mr. Waters used three rifles, a Ballard No. 9 to represent weaker actions, a Winchester High Wall representing moderate strength actions, and a Winchester M 94 representing the stronger actions. Point is, he had two more 38-55 rifles than most of us have to work with.
Now, on to bullet diameter. Mr. Waters wrote “A most important consideration is bullet diameter, this being quite a variable factor among the different .38-55 caliber rifles. An oft-committed error in some of the older publications was the listing of .38-55's as taking bullets of only .375 diameter. I have yet to see a .38-55 with a barrel groove diameter that small, or even close to it! Both of our Winchester test rifles have .3785-.379 inch groove diameters, and the Ballard “Union Hill” slugs-and-mikes at a whopping .383 inch. Obviously, if cast bullets are to be spun for proper stability, especially with smokeless powder, they must be of a size to fill the bore to the bottoms of the grooves.”
From reading this, I believe we can assume that Marlin is indeed using the proper specs and holding them pretty close too, judging from what I've seen written about .378-.379 bores on almost all 336 CB's.
I'm going to post this on a few other forums too and would be interested to see your responses to the above.
