outdoorfan
03-25-2009, 10:50 PM
Here's the deal. I have a Savage bolt action with a McGowen 1-10 twist barrel that I want to start shooting cast in. In preparation to having a mold made, I slugged my barrel and made a casting of the throat. Turns out that McGowen does not chamber these with any reasonable amount of throat. There is virtually almost no freebore. The rifling starts pretty much right where the case mouth ends within .020 or so.
The rifling is tapered from where the case mouth ends, where it is about .310-.311, to no more than about .110 further down where I'm measuring a full .308 (groove diameter).
I want to shoot a 180 grain (or so) spitzer, and from what I've been learning it's good to have at least two caliber's width in bearing surface. Seeing that the bottom of the bullet should not be extending much below the bottom of the neck, that leaves me with less than .5 inch of bearing surface without having the bullet jammed into the lands.
So, it seems to me that in order to get .6-.7 bearing surface I'll need to create an actual throat and some freebore.
Does this make sense, or am I missing something? I could use some confirmation that I'm on the right track (or not).
The rifling is tapered from where the case mouth ends, where it is about .310-.311, to no more than about .110 further down where I'm measuring a full .308 (groove diameter).
I want to shoot a 180 grain (or so) spitzer, and from what I've been learning it's good to have at least two caliber's width in bearing surface. Seeing that the bottom of the bullet should not be extending much below the bottom of the neck, that leaves me with less than .5 inch of bearing surface without having the bullet jammed into the lands.
So, it seems to me that in order to get .6-.7 bearing surface I'll need to create an actual throat and some freebore.
Does this make sense, or am I missing something? I could use some confirmation that I'm on the right track (or not).