No. 3 375 Winchester Bore Diameter

[9mmTed]

Just started the process of working up some loads and finishing my brass to reload my new-to-me .375 No. 3. Prior to ordering bullets I slugged the bore just to make sure, and came up with a .377 bore diameter. I slugged again to make sure, and it is definitely .377. This makes me wonder, did the Ruger engineers do this on purpose to allow the gun to be fired with 38-55 lead bullets widely available, or is there variation in the bore diameters of the No. 3s in this caliber? Any one else have any experience with this?

 

[9mmTed]

Just wanted to add a bit of info- I had reached out to a friend who also has a No. 3 in 375. He called last night to tell me he slugged his bore and it measured .377 also. So, with this limited group of 2 it appears the bores from the factory were .377. Interesting, and since I plan to shoot cast bullets this really don't bother me at all.

 

[Rumrunner]

I have a 12" Contender in 375 Win. I shoot 200 grain Sierra JFP bullets in it. My reloads pretty much duplicate the Winchester Factory loads in it.

 

[aphelion]

Groove diameter on my early '80s 375 H&H No 1 is .378. Every Ruger rifle barrel groove diameter I have measured from that era was oversized with long and fat throats.