Anyone have any experience with the 300 Jarrett? It is like a lot of the hot overbore 300s such as 300 Ackley, 308 Baer, 30 Goodling, 30 Spencer, ect... I am looking to use better brass than 8 mm Remington, and wondered if anyone had tried using 300 Weatherby for this purpose? I suspect the necks might be just a little short, but not sure if it is even a possibility. Any help would be appreciated, and any info on your experience with this cartridge is entertaining. Thanks!

Hey

You can use 300 WBY cases and fire form them once. Mr Jarrett claims that this is not the way to go. I know people who had 300 Jarret rifles and used Wby cases. I would have bought a 300 Wby or 300 RUM instead, better aftermarket value, easier to find ammo, reloading dies and data.

I have a lot of experience with 300 Jarrett. This is ballistics twin of 300 Weatherby, but it is more accurate and efficient, probably because of short freebore.My Weatherby Mark V before converted in 300 Jarrett grouped in 1 MOA with best load: 200 grain Sierra, 80 grain MRP, Federal 215 primers. Velocity was about 3000 ft/s. Same rifle with 300 Jarrett barrel grouped 0.3 MOA with 200 grain Sierra,76 grain MRP, same primers and velocity is same. Three shot group, powder was from same can. I used fireformed Weatherby cases with no problem at all.

I'm also a 300 Jarrett user and think a lot of the cartridge. It is basically a 300Wby with square shoulder and better throat dimensions. I've never fireformed 300Wby brass so can't comment on how that works. I just do as Kenny suggested and run the 8mm Rem. brass through the re-sizer die. Fireforming blows out the shoulder, etc but I find that my sized brass does just as well accuracy wise and velocity wise.

Just wanted to add a little. I have used this round quite a bit and think it is one of the best things going in 30 Cal. It is far more accurate than any other factory loadings, and I find it efficient too. I have a gun with a heavy Hart Stainless cut at 271/2" and I get an honest 3350 FPS with a 180 Grain Barnes X boat tail shooting into 1/2 MOA for as far as you want to check it. Cant do much better than that for a hunting round. Just curious where everyone else starts cause I can pick any 300 Weatherby load and just go up from there. I find it is a good deal faster than a Weatherby though. Would love to hear pet loads and such. I just would like the option of using Norma, Laupa, or others who make better brass. No one said if the necks wind up short or not? I would bet, though I havent tried it, that I could probably fire normal 300 Weatherby rounds in it and it would work. Comments?

When fireformed Weatherby brass I got somewhat shorter cases ( about 71.7-71.8 mm).
If you use 8 Rem. Mag. brass, fireformed cases would be about 72.1 mm length. I think this is not significant difference. I mentioned my pet load, only for serious hunting 200 Nosler can be used. H-1000 and H-4831 might be good choice,and 300 Weatherby starting loads should be safe.
It is interesting to mention that 200 grain Noslers and Sierras are perfectly stabilized with 1:12 twist that is usually used in Jarrrett barrels.