Reloading for Oversized Bores

C

Cantthinkofaname

New member
Rating - 100%
1   0   0
Location
Edmonton, AB
Fairly new reloader here (only done 260Rem and 35Whelen for a couple of years). I have found myself in new territory and I'm hoping to use the knowledge on this forum.
I bought a Winchester model 1910 at auction. I'm in the process of collecting all the items need to start reloading. I slugged the barrel last night and discovered that it measures between 0.409-0.410". I'm a machinist so I trust my measuring skills. I even took the slug to work and double-checked on the profile projector and those grooves are not very deep.
So my understanding is that I need to fill up that groove diameter to get any sort of accuracy. So I should be looking into 0.410" bullet diameters. I don't cast my own boolits at the present moment, but someday I might.
I also read that I have to ensure the cases will chamber correctly. An increase in bullet diameter can interfere with the chamber neck correct?
I do have access to QuickLoad so I'll be playing with some numbers to make sure I don't over-pressure anything but I'm not 100% of myself when it comes to that program. It also appears QuickLoads info for the 401 WSL is incorrect: they were listing case length as 2.0" and overall length as 2.5". So I can't trust the programs number for case capacity until I measure my own.
Realistically I'm not looking for super performance or perfect MOA. I'm just hoping to make something safe, works reliable, and hopefully within 3-4 MOA.
 
Sounds like you have a lot of it figured out. A good check, and about only thing that really counts, is what is going on in your chamber. Often done with a cerrosafe cast - follow the directions and you will get decently accurate numbers 60 minutes after making the cast. That, among other things, will tell you what is the diameter of the neck portion of your chamber. Typically, you want your loaded round to be several thousandths smaller there - with the bullet in the case's neck - might be able to find your cartridge in the SAAMI standards on line and see what "standard" clearance would be - no telling about your chamber until you measure. Then comes the "ball seat" area, or "free-bore", or couple other names - that section ahead of your chamber but before the rifling starts. I have an older 9.3x57 here that is close to half inch - so you want your ideal bullet to be about that diameter or a thou smaller - nice snug fit, so that it can not get sideways as it leaves the case mouth but before it hits the rifling. The better you can do your own measurements, the better choices that you can make - there are numbers in books and articles, but you will not know if they apply to you, until you measure your chamber.

Just an observation - as with some revolvers, it is possible that your rifle has a groove diameter larger than what your chamber neck can chamber - some revolvers are known to have throats in their cylinders that are smaller than the barrel groove. Sometimes were addressed by hollow base cast bullets that would "swell up" once they passed through the cylinder - not certain how that is dealt with on a rifle, other than having that neck portion / throat portion of the chamber opened up?
 
Last edited:
If it was my rifle I would be looking for lead bullets of around .412"

A cast bullet is large and gets sized and lubed to the desired diameter.

When I need "fat" bullets I just get unsized/unlubed bullets from the guy that casts them and then just tumble lube them with Lee Alox.

I would ask the cast to send you 2 or 3 unsized bullets so you can see if the cases will chamber a loaded bullet that fat. It may not work.
 
You must log in or register to reply here.
Back
Top Bottom