Let's talk freebore... Weatherby and others..

300WSM

Handloader
Dec 24, 2011
839
470
As the title says...
Freebore

I know over the years many o' fellow would thumb their nose at a Weatherby due to the extra freebore.

It got me thinking...
Back when I was deep in the industry I almost bought a USRAC Winchester 70 Classic pre64 action in .270 Weatherby. We carried that model as a wholesaler and many afternoons I stared at that thing in inventory. 🤔

One of the other managers was a conpetitive bench rest guy and said call Winchester and ask if that rifle had the same free bore as the Weatherby rifles.
The answer was no. It did NOT have as much free bore that Weatherby uses.

I'm not sure that is true...
🤷‍♂️🤷‍♂️🤷‍♂️🤷‍♂️🤷‍♂️

That freebore is there due to pressure

I've also heard that Remington was using extra freebore in the ULTRA MAGS...
Can anyone confirm this?

Was just curious about this as thr freebore doesn't mattrr one bit to me. In other words I know that freebore is in my future as the 30 Kong in either Accumark or Weathermark will have it....

But I was curious on the Winchester chambered in a Weatherby if it really could have had less freebore and does Remington really use that in their ULTRA's
 
I can confirm that! I have a model 70 Classic stainless made in New Haven in 300WBY and it does have the classic WBY freebore
 
Short answer, no.
SAAMI specifications call for the freebore. As a SAAMI-compliant manufacturer Winchester would have included it just as Remington does in its Weatherby chamberings.
That's what I thought but wanted it verified...

What about the ultra mags from Remington.
I can confirm that! I have a model 70 Classic stainless made in New Haven in 300WBY and it does have the classic WBY freebore
Exactly what I wanted...

Thx for verifying.

What about the Ultra Mags from Remington?
 
I have no direct experience with the RUM, however my understanding is that they are built with a healthy amount of freebore. That is what I have read from several gunsmiths.
 
The RUM does not has as long a freebore as a Weatherby, (RUM=0.11, WBY=0.36)
SAAMI Chamber spec
300 RUM
1680905354387.png
300 WBY
1680905395603.png
300 WIN just to compare
1680905439055.png
 
The RUMs have freebore. I rebarreled my 338 RUM without the freebore, life is grand.

JD338
 
My 300 RUMs absolutely do not have weatherby freebore. I'm seating. 020" off the lands.

Almost all Weatherby cartridges freebore is .375". !!!! I think a couple have .285" or something.
 
The RUM does not has as long a freebore as a Weatherby, (RUM=0.11, WBY=0.36)
SAAMI Chamber spec
300 RUM
View attachment 19597
300 WBY
View attachment 19598
300 WIN just to compare
View attachment 19599
On the Weatherby blueprint I see some dimensions with a plus symbol...


Example..
From base to neck it
2.844 plus twelve thousandths..
I see that in a few other spots as well.

I only see that in one other spot on the 300wm drawing.
Plus ten thousandths half way up the neck.

The RUM shows no + symbol I can see
 
I have had a Christensen Arms 300 RUM and currently have a M70 and I can say they have a fair amount of freebore, not like the few 300 Wby's I have monkeyed with, but quite alot where it's pointless to try and get near the lands with them. Even with the CA rifle, I had a 3.750 magazine and couldn't touch most all shorter than 200 grain bullets.

The next 300 RUM will have reduced freebore in the M70 for that reason.

But, if the freebore is done just over bullet diameter I haven't heard of many of the new Wby's with issues shooting really well.
 
The next 300 RUM will have reduced freebore in the M70 for that reason.

But, if the freebore is done just over bullet diameter I haven't heard of many of the new Wby's with issues shooting really well.

I definitely wouldn't shorten the Mighty RUM. I'd install a Wyatt's extended mag box.

If you are going to neuter a 300 rum just get a 30 Nosler.
 

I definitely wouldn't shorten the Mighty RUM. I'd install a Wyatt's extended mag box.

If you are going to neuter a 300 rum just get a 30 Nosler.
You removed the spacer by drilling out the tack welds and get a .375H&H follower. I am not sure if the one on Brownless is longer. You will still need a follower, can use the .375H&H
 
I plan to lengthen the mag box but I’m still going to reduce the freebore some to .070. I want something a little more suitable to the bullets I use.
 
You removed the spacer by drilling out the tack welds and get a .375H&H follower. Gives you I think about 3.7"
The M70 will only handle about 3.6 in any form. A smith needs to mill the receiver pretty good to get out to 3.82.
 
The M70 will only handle about 3.6 in any form. A smith needs to mill the receiver pretty good to get out to 3.82.
I know a friend of mine did it, and I was planning to do it with mine. He gave me a magbox. He got a new 375 H&H follower, he said the new FN M70 works. The other thing, is the ejector on the CRF needs to be replaced with a shorter one.
Scotty, you know M70's better than I do, I will have to check with my friend what his max length is.
 
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