300WM freebore

[belizejet]

I'm installing a replacement rem/age barrel on my 300WM. I got new bottom metal for the ACIS 3.85" mags so I want to freebore the barrel. Plan is to load the longer bullets with better BC and take advantage of them with switching to the 300PRC. Before I freebore the barrel what would you all recommend? I'm not trying to sling huge bullets just a bit bigger than 200grn like 212 ELDX and 208 LRX. I'm thinking 0.10".

 

[MagnumManiac]

Take the longest bullet you intend to use, make a dummy round with the heal of the bullet below the neck/shoulder juncture and measure. You may find you have to compromise on that measurement due to it not fitting your mag but works across several boattail bullets.
This is is how I have always measured my throat, sometimes it works exactly for the intended bullet, like running 142g or 150g pills in the 264WM with a 3.7" mag, or sometimes, like the 7STW or 6.5-300 Weatherby, it doesn't and you cut the difference…
The 300WM requires at least .220" throat for a 210g VLD bullet, my A191 chambers are cut .240" for 215's & 230's, neither bullet is exactly at that point though.

Cheers.

 

[belizejet]

Take the longest bullet you intend to use, make a dummy round with the heal of the bullet below the neck/shoulder juncture and measure. You may find you have to compromise on that measurement due to it not fitting your mag but works across several boattail bullets.
This is is how I have always measured my throat, sometimes it works exactly for the intended bullet, like running 142g or 150g pills in the 264WM with a 3.7" mag, or sometimes, like the 7STW or 6.5-300 Weatherby, it doesn't and you cut the difference…
The 300WM requires at least .220" throat for a 210g VLD bullet, my A191 chambers are cut .240" for 215's & 230's, neither bullet is exactly at that point though.

Cheers.

Thanks. I'll probably do that. In my mind I'm limited in mag length to 3.85" vs 3.7" so I can go out to .15". From what I've read in the past most people will do freebore of .1 to .15" max on the 300WM. I don't have the barrel length to get the velocity I would want or twist to stabilize .308 over 230grn. It's a 24" barrel with 1:9 twist.

 

[bergara0256]

.195 freebore is what I have on my 300 winmag. I shoot 215 bergers with it.

 

[MagnumManiac]

As I stated, minimum throat length is .188", a throat of .200" is the starting point with long bullets running longer than a max OAL of 3.4".
I don't know where you're getting a .100"-.150" throat as standard, it is far longer than this and most chambers used in a 3.4" mag cannot get anywhere near the rifling. Look at the SAAMI print, 2.97" is standard throat length with a 1°26'37" taper.

Cheers.

 

[belizejet]

As I stated, minimum throat length is .188", a throat of .200" is the starting point with long bullets running longer than a max OAL of 3.4".
I don't know where you're getting a .100"-.150" throat as standard, it is far longer than this and most chambers used in a 3.4" mag cannot get anywhere near the rifling. Look at the SAAMI print, 2.97" is standard throat length with a 1°26'37" taper.

Cheers.

The 0.1 to 0.15 comes from magazine length difference. I get what you are saying. Thanks for the input.