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Weatherby mag freebore

18 Mar 2021
@ 03:23 pm (GMT)

Rob Bird

I've now got two 257 Wby Mags, one is a brand new Vanguard and the other a custom job based on an M1917 Enfield action. Weatherby states that the freebore on their 257 mags is .378 inches though I only got .285 past the cannelure on a 120 gr Interlock. The Enfield has .500 over the cannelure! Is that excessive? I haven't fired either gun yet.

Side note about the Vanguard, when using the Hornady comparator tool, I had to push a bit hard to get the bullet to push toward the lands, like there was a tight spot or burr in the throat. Might this be because it hasn't been fired yet and hasn't had ammo run through?


20 Mar 2021
@ 09:51 am (GMT)

Nathan Foster

Re: Weatherby mag freebore
Hi Rob, seat your loads around 3.346". Jump will be about .200".

Get a few cases fireformed and get the throat run in (Vanguard). Once you have a handful of cases, you can remeasure the max OAL. A nipped case mouth / dummy round will do (as per the reloading book). No need for the comparator.

Don't mix up the cases for each rifle, keep them well separated.
23 Mar 2021
@ 03:02 am (GMT)

Rob Bird

Re: Weatherby mag freebore
Thank you. I ordered the David Tubb abrasive bullets (Final Finish) to break in the throat and barrel on the Vanguard. Cheaper than blowing through a box or two of factory ammo and hopefully with better results.

I will most definitely keep the brass of the two guns separate after fire forming!
02 Apr 2021
@ 08:49 am (GMT)

Jon Short

Re: Weatherby mag freebore
Hey Rob,

It's really worth investing in Nathan's books if you haven't already. You can get them in an electronic version &/or hard copy so you can view the books right away on purchase electronically.

They contain a wealth of information & are extremely useful reference books as you encounter the various challenges & problems along your journey with your rifles, be them bedding, reloading techniques, breaking in a new barrel, proper shooting form, long range shooting & drop charts, projectile selections etc etc.

The great things about Nathans books & approach is that he shows readers how to do things well but with minimal specialist tools & without half the tools & products that shops try to con you into buying, that in many cases simply aren't needed.

The bullet comparator tool is a good example (in his books) when you can do the same by simply partially neck sizing a fire formed case so that it grips a projectile a little but not enough to stop it sliding back when forced against the lands by closing the bolt. Remove & measure... do that 6 times to check for errors & you have your OACL. Easy with no special tool.

Making do with what you have got is what we call in NZ, the no 8 wire mentality. (you should see some of the things people make to make do using no 8 fencing wire!) And this is where Nathan's advice in his books are extremely useful.

Buys his books if you haven't you'll be stoked you did.

Many of us also donate to Nathan too when we are gaining advice from him. No body should work for nothing & his advice is invaluable saving us so much time & prevents the proverbial f- up occurring. Donating is the least we can do to make it worthwhile for him to lose personal time helping us.

Cheers Rob,

10 Apr 2021
@ 01:24 am (GMT)

Rob Bird

Re: Weatherby mag freebore
I appreciate the advice, Jon. And I'm certainly amenable to making things work with what you have.

I donated to Nathan right off the bat and received a lot of unexpected great information through an email exchange! Very happy with that.



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