I picked up a 26" Douglas factory chambered .340 Weatherby barrel to put on a Mark X action. It is all headspaced, and bedded into the stock, so now on to load work up. However......

I asked what the throat length was, and was told whatever a standard reamer produces. Not much help. I cast the chamber and the throat is cut to 0.25". So, short compared to the Weatherby spec of 0.373" given on their website.

I would prefer not to lengthen it.

What should I expect reloading for this one? I plan to start at the min book load and work up, checking for pressure signs.

Is 2900fps realistic with a 250gr bullet? What are your experiences with a custom Weatherby chamber?

Thanks guys.

Jeremy

quote:

Is 2900fps realistic with a 250gr bullet

Assuming you will need to seat the bullet shorter than the normal because of the shorter throat I would think 2900 would be very optimistic. Just a quick look at QL says you are in the 64,000 psi range to get 2900 and even then with very few loads.

Norma brass (Weatherby) is notorious for being a little soft. If you use a harder brass and load to the capability of the brass you might see some improvement in FPS. However a load at 2700 (think 30-06 using hot 180 grain loads) is nothing to be unhappy with.

quote:

Norma brass (Weatherby) is notorious for being a little soft.

Heck Weatherby only list 2940 for the 250 with their generous freebore and measurement.

I haven't done that much Weatherby loading but have found it difficult to get what they list for their factory ammo.

There are a few 2900fps+ loads listed in my manuals using 7828, RL22 and RL25.

If I can't get there, so be it.

Mostly, I am after what others have experienced with non-standard Weatherby chambers. Given how some benchrest shooters load into the lands and don't blow up their rifles, I am wondering if the long throat thing is that critical.

The slow powders we have today weren't available in Roy's day. Maybe the long throat was needed with faster powders? Obviously, a lot of care has to be taken to test that theory.

As for brass, I have a small batch of Remington .300 Weatherby brass that I will neck up to start. I don't have bullets yet, so I don't know what the OAL will be to the lands. I suspect it will be 3.6" or longer, though. Looking at trying out the 250gr Accubonds, and CEB 252gr MTH.

Thanks for the replies.

Jeremy

quote:

Given how some benchrest shooters load into the lands and don't blow up their rifles, I am wondering if the long throat thing is that critical.

It isn't critical as long as you start low and work up to the pressure limit for YOUR CHAMBER.

If you work up a load at max for a long freebore then stick it in a short throated chamber and jam the bullet into the lands you are asking for trouble. Will it blow the gun up I doubt it. Blow the primer maybe.

If 2750-2800 won't kill it I doubt 2900 would either.

If I understand you correctly, your chamber has .25" of unrifled space in front of the cartridge mouth. This is a lot of space, and, while perhaps a tad short of what Weatherby uses, amounts to significant freebore. You won't likely be able to reach the lands with bullets seated deep enough to fit into the magazine, therefore you'll have some freebore with any load.

I have a friend who has a .338/8mm Rem Mag (.338 bullet in an 8mm RM case). The internal capacity of this round is very similar to your .340 WBY. His rifle has no problem making 2900 fps with a 250 grainer; the barrel is a factory rechambered Rem 700 .338 Win 24" in length. I suspect that with the right powder (think slow -- I'd try IMR 7828 SSC) you'll have little problem making 2900 fps within sustainable pressures. For comparison, my .338 Win does 2900 with 225 grain bullets (again, think slow powders!)

Stonecreek, yes, that is the measurement of the unrifled portion and good point. It is still long relative to similar cartridges. Part of why I don't want to lengthen it to Weatherby specs.

I just have no experience with Weatherby cartridges and all of my manuals have a disclaimer about custom rifles. So, I figured I would ask and see what others have seen.

I have a good selection of slow powders:7828, RL22, RL25, Magnum, H870. One of those should work.

Interesting to hear your friends results. In a 24" tube, no less.

Ramrod/SR4759, yes 2700fps and a 250gr bullet will flatten my quarry. That said, 2900fps is just more fun even if it is meaningless in practice. I can poke fun at my .338 RUM shooting friends.

Jeremy

What do you do when a .338-.378 shooter shows up?
Oneupsmanship can work in many different ways.

quote:

Originally posted by farbedo:
Stonecreek, yes, that is the measurement of the unrifled portion and good point. It is still long relative to similar cartridges. Part of why I don't want to lengthen it to Weatherby specs.

I just have no experience with Weatherby cartridges and all of my manuals have a disclaimer about custom rifles. So, I figured I would ask and see what others have seen.

I have a good selection of slow powders:7828, RL22, RL25, Magnum, H870. One of those should work.

Interesting to hear your friends results. In a 24" tube, no less.

Ramrod/SR4759, yes 2700fps and a 250gr bullet will flatten my quarry. That said, 2900fps is just more fun even if it is meaningless in practice. I can poke fun at my .338 RUM shooting friends.

Jeremy

Stand well back to get out of the blast of the muzzle brake.

My friends with the RUM's will just pull out their 300gr loads and knock the wind out of my sails anyway.

Jeremy

I agree with Stonecreek - start with a relatively slow burning powder (Re25, Retumbo, H1000, and the like) and work-up. You'll likely be able to achieve 2900 fps with a 250 bullet.

Freebore is massively over rated. In fact, it can lead to accuracy problems, because you can't play with getting the bullet seated close to the lands, if needed to maximize accuracy.

In the guns I have built, I deliberately avoid freebore and still achieve high performance equivalent (if not greater) than Weatherby claims to get from freebore. And, my guns are accurate (MOA) guns.

That is what I am hoping for with the shorter throat. Seems like it is over rated given other cartridges of similar capacity/performance.

I did get a box of CEB 252gr MTH bullets and a box of Berger 250 Elite Hunters. We'll see this weekend how they do.

Starting loads are with RL25 and IMR-7828 using the starting charges out of the Sierra manual. Once I see how those chrono, I can start the real work.

Thanks for the help, everyone.

Jeremy

quote:

Originally posted by farbedo:
That is what I am hoping for with the shorter throat. Seems like it is over rated given other cartridges of similar capacity/performance.

I did get a box of CEB 252gr MTH bullets and a box of Berger 250 Elite Hunters. We'll see this weekend how they do.

Starting loads are with RL25 and IMR-7828 using the starting charges out of the Sierra manual. Once I see how those chrono, I can start the real work.

Thanks for the help, everyone.

Jeremy

I had my latest 270Wby build without the Wby freebore.

I'm suprise that barrel wasn't mark pretty big liability on seller part if something happen.

most reloading manauals don't put warning about custom throating anymore for the Wby. What you do is start appr 10% under start load and you should be at start velocity. Without the Wby freebore your going to use less powder but get same velocity. My 270Wby I'm 3gr under max @ max velocity and pretty accurate load also.

I just checked and Speer manual 14 on 300Wby page 540 gives warning about custom throating without the freebore and reduced loads.

Well good luck

I've had Kevin Weaver short throat 340 Wby for nearly 10 years. No pressure issues. If anything having a shorter COAL has helped the cartridges fit well in my Pre War Mod 70 box. I have been able to work up loads at near max without any issues.