Wby Throat ?

Handloading Weatherby's in a custom chamber without freebore requires that you throttle back the loads unless you like replacing cases often. The same factory speeds can be obtained but with reduced loads, do not try to get to the book maximums unless you have a saami chamber.
bigbull
 
Weatherby freebore does reduce pressure. It does not increase velocity. A short throated Weatherby will usually be a little hot with factory loads.
The freebore may or may not affect accuracy. In general, if the freebore is within .0005" (one half of one thousandth) over bullet diameter, accuracy will still be good. Often more than good. The problem with the earlier Weatherbys was that the throat was often 3 or 4 tousandths over bullet diameter.
An illustration. I once chambered a 300 Weatherby for a friend and throated it conventionally. He was loading 200 grain Noslers and was able to obtain just slightly over 3000 fps before pressures became too high. He brought the rifle in and requested that I increase the freebore. I did so, extending the throat by 3/8 inch. The throat was cut at exactly .3080 diameter. The same load now produced about 2930fps. He increased the load to maximum and it topped out, once again, at just over 3000fps. Accuracy was unchanged and was very good. My current Weatherby reamers have throats which are Weatherby length but all are .0005" over nominal bullet diameter. Accuracy is excellent and factory loads are OK. Regards, Bill.
 
freebore should behave much like moly, if I understand it properly. Add freebore (or moly) and pressures and thereby velocities increase. By the time your pressures are back up to normal, you're a few percent over 'maximum' load data, and a few FPS about standard as well.

For what it's worth, I have a 243 with a lot of 'freebore' - really, it's just a washed out throat :p. The rifling doesn't start to engage much before the bullet has had to jump a good 1/2". It requires a full two grains more powder to maintain the same velocities that it had when new. Accuracy is not what it was when new, though I can still bust clays at 500 yards with regularity.
 
As freebore reduces pressure, you can pour more powder in to get the pressures back up (or slightly higher, which is what Wby does). Keep in mind that Wby (at least thier European made) ammo runs pretty high pressures to begin with. I would not be comfortable firing say, Norma made Wby ammo in a custom cut chamber with no freebore, pressures would be very high.
 
dan is 100% right here guys! there loaded to 65000 psi before lands contact and running wby sammi free bore.
I still today have no frigging Idea what powder they use but i sure cant match there velocities! that is factory wby ammo
 
I'd wager they're using their equivalents of our 'reloader' series. Weatherby ammo is loaded by Norma. Norma sells their own line of powders, which are available here as the 'reloader' series. Whether the exact powders they use are canister grade or not is debatable
 
Ya I am not sure I bougth a 20 box of wby ammo and pulled one apart and for the life of me could not say it looked like RL-22 but close, I loaded to max and a few above max with my 300 and checked the velocities, i was 120 fps behind the wby ammo with multiple bullet combos, I dont know what they put in for powder but RL 22 at there charge wieght cant remeber off the top of my head I am away this week, but the same wirght in RL-22 was 150-180 behind in velocity!
Accuracy sucked with RL-22 so i went back to 4350
 
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