Just how much freebore does a Mark V have?

[DNADave]

I was starting a load for a .300 Wby Mag I have in a SS Japanese made Mark V when I noticed two things.

1) When measuring CBTO using 175gr Barnes TTSX bullets, the base of the bullet (which is quite long) has only the boat tail in the neck when the ogive is in touching the lands.
2) I am 0.25" off the lands when I get enough bullet seated in the case. That seems like a lot.

So, just how much freebore is expected in a Mark V?

 

[cohunt]

shouldn't matter what rifle it's in as the chamber is based off of the saami specs and tolerances--weatherby's are known to have long freebore dimensions
here is a chamber drawing with tolerances

 

[cape cove]

FAQs - Weatherby, Inc.

SEE FAQs

weatherby.com

9'th question down

 

[cohunt]

FAQs - Weatherby, Inc.

SEE FAQs

weatherby.com

9'th question down

Exactly what the saami spec sheet shows

 

[DNADave]

Thanks, guys. Didn't think to check if this was in an FAQ on their website.

 

[David Emerson]

about 3/8,s of an inch

 

[Dr. Vette]

FYI, there are no Japan-made stainless Mark V rifles.
If yours is made in Japan and it's silver colored, it's an Alaskan model which is actually nickel plated.

 

[DNADave]

FYI, there are no Japan-made stainless Mark V rifles.
If yours is made in Japan and it's silver colored, it's an Alaskan model which is actually nickel plated.

Wow. I'm just batting a thousand today. My Mark V is indeed made in Japan and is silver colored. This is a recent acquisition and obviously I'm not the original owner. So, it's an Alaskan model? How does the nickel plate hold up to extreme weather? Most of my elk hunting is for Roosevelts on the Olympic peninsula, so in extreme wet weather.

Some context to my original question. I knew the amount of freebore in a Weatherby was long, but just didn't expect this much. I'm reading all of these posts about seating depth and seeing values of 0.020 off the lands as a starting point. I'm reading this and thinking "There's no way I could ever get close to this close".

Right now, I'm wondering if I really have enough of the bullet seated at 0.250 off the lands.

 

[cohunt]

Loose rule of thumb is at least the bullet diameter of full diameter In the neck but others may know better -- some bullets work very well with lots of jump you just have to find the right bullet/powder combo. If you cant reach the lands i generally load to max mag box length to start with, i find my powder charge then if my groups dont satisfy me i start shortening the coal untill i find my accurate load.
Might be good to read up on the berger bullet jump method of reloading- even if you arent using berger bullets their method works with other bullets too.

 

[HARPERC]

A friend had one, long time ago, so maybe it's changed, but we never could get to the rifling. Loaded an old school Barnes Original 250 grain .308 and seated as far out as possible. Anyway someplace over 4"'s.

 

[rsnell]

Forget about how far to seat off the lands for a Weatherby caliber. Since you are using a Barnes bullet, follow the Barnes loading manual for overall length.

 

[nicholasjohn]

You might look at the 200-grain Barnes bullets, since you like that design. They are going to be a bit longer, and may get you closer to the lands with enough shank still in the neck of the cartridge case. You should get good velocity with the hiver bullet in the large case of the 300 Weatherby. Like someone already stated, though, magazine length may determine your COAL for you, and it's quite likely that there will still be some jump to the lands. Good luck.

 

[DavidleeCole]

Mine .300 Whby mag had factory jump and shot great with Berger's hunter 185gr. With 85.7 gr H1000. I had it rebarreled and my smith put a sammi chamber in it and it does have less free bore now. I shoot 210 Nosler LR with H1000 and she shoots great.u load at mag length for my Box and have no issues.

 

[R100RS]

Hi, I also have a 300WBY (made in Japan) when I do load development I either start a 3.700 max length that fits in magazine or whatever loading manual suggests. Once I find a promising load I retest the load at different AOL's using .030 differences between 3.560 and 3.700 to see if anything is a clear winner. Good Luck