Anybody heard of a 6.5mm-300RUM or a 6.5mm Ultra-Cat????

J

jtoews80

Handloader
May 19, 2007
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I've been seeing a wildcat chambering listed on the pac-nor site and 4-d reamer rental's site. It's based on a 300 RUM necked down to 6.5mm. I really like this projectile, not really sure how much of the BIG RUM case would be useable due to that much overbore. With really slow powder, possibly polygonal rifling(never used it, but supposed to be better with big pressure), what would a person expect besides a short barrel life. COuld be a lot of fun.

Just thinking to much probably, but anybody have any knowledge of this wildcat?
 
The Barrel maker Shilen actually has this caliber listed and www.z-hat.com has it listed too based on a 300 or 338 Ultra. I imagine that it would be pretty quick with that huge of a case capacity.
 
I think the 6.5mm is maxed out in the STW case, about max as far as overbore goes. You can build it on a 300 RUM but I expect the barrel will last about 100 shots. :lol: :lol: :lol: :lol: :lol:
 
Yeah, that is what I was thinkin'. It would be fun, but very pricey. There have been 6.5/300wby's for awhile with not bad results, but I think the double radius shoulder may have a lot to do with that being viable. The other thing is that for the added cost of weatherby cases, custom dies etc. it doesn't payoff. A 6.5/284 norma is a production caliber that is extremely accurate, will run 264 wm velocities with half the powder of an odd wildcat. Or just build a nice 264 and use the stuff I already have. Still might run the numbers in quickload to see about what is possible tho.
 
The 6.5-300 RUM would be a screamer but as the others have said, its serious over bore. My geuss is that barrel life would be 800-1000 rounds, provided you keep it clean and cool.

JD338
 
I too briefly looked at this round. Appears some of the lighter bullets 120's and down are haveing a hard time staying together?? Anyone heard that as well?
Not sure why you'd want that light of bullet, but...........
 
Powerstroke":3qpzkg9s said:
I too briefly looked at this round. Appears some of the lighter bullets 120's and down are haveing a hard time staying together?? Anyone heard that as well?
Not sure why you'd want that light of bullet, but...........
Click to expand...

I would think a light bullet would be a 125 gr PT or 130 gr AB. The 140 gr PT's for longer range or bigger critters.

JD338
 
A new barrel every month or so???? Sounds like a wonderful plan, especially for the super high velocity freakos!!!
 
The 6.5WSM is grossly overbored but far more practical than a 300RUM version. It would also fit in a shorter action while still allowing you to use long, high BC bullets that don't have to be seated too deeply in the case.

Just a thought
 
I believe I'll look at a 338 Edge or 338-300 RUM long before I look at anything in a screamin' 6.5mm. The reason being that a 7mm RUM is so close to a 6.5mm RUM that it isn't really practicle to spend an extra 650-1000 dollars on a rebarrel job. On the other hand if I find a RUM caliber with a shot out barrel that I can buy as a donor action and stock for under 400 bucks, seeing as the 700 sps goes for 567 new, and pac-nor has a barrel in 6.5mm that isn't chambered for 180 as they sometimes do on the ready to ship list(ie discount bin) I could do something foolish, like chambering it to 264 to break in the rifleing and then going bigger to the 300wby or rum case with 264 neck. My fear isn't that is will eat barrels, I'm scared of flashing a powder colum because of a 65% density or less with too small of a load. I think that with really slow powders and keeping velocity down to 80-85% of Max velocity the barrel could last substancially better like 1200 rnds. Moly coating is another option, but I have avoided it like a disease on my hunting rifles because of the fouling reputation. It is a cool idea, probably never see the light of day.

The other thing I've found with my 30-378wby is that although it is capable of 3680 fps with sierra 150 grns and Retumbo, it doesn't use all the powder giving a serious puff out of the muzzle brake to the extent that one needs eye protection to fire it prone. Also, Retumbo fell seriously short of the accuracy yielded by IMR 7828 with the same bullet at 3550fps. That rifle prefers heavier bullets, works best with a minimum 180grn bullet. Bullet stability would be a HUGE question at the velocities, a 6.5mm RUM would go and especially if there is a few grains of powder that are not expended by the time the bullet exits the barrel giving really uneven velocities or irregular flight patterns.

Thanks for the input guys, is always fun to see who would be loony enough to build something like this.
 
jtoews80-

Just FYI-

I currently run a 264 WinMag at a very comfortable 3200 fps for an SMK 142 grainer in a 1:8 twist, 28 inch barrel using H50BMG. I know of a 260 Weller (7mm Dakota necked down to 6.5mm) that will do 3400 fps with a 140 grain NP using a 28 inch barrel and AA8700. Also, there is the 264 Thor (8mm RemMag (almost the same as 6.5 STW) necked to 6.5mm) that will do 3400 fps with a 140 grainer. Doing a 6.5mm/7mm RUM or 300 RUM could work with a very heavy 6.5mm bullet and a VERY slow powder given a barrel lengh of 30-32 inches and twist of 1:7 or 1:8. I would not worry about an early barrel burn out as long as you do not over heat it.

I've had trouble finding a good VLD bullet above 142 grains to try. And, I've found that the 140 grain VLD Berger's blowup within 30 yards of the muzzle when pushed above 3100 fps.
 
Big Squeeze":3u6p27aw said:
A new barrel every month or so???? Sounds like a wonderful plan, especially for the super high velocity freakos!!!
Click to expand...

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
 
jtoews80-

Sounds good on the Mauser. However, most 6.5/284's top out around 2950 fsp for a 140/142grainer in a 1:8 twist. Even the 6.5mm WSM will not go much over 3150fps. If you want to go faster, use a larger case.
 
LOL, I ended up going with a Savage 111 and a 31" 1-8.5 Poly rifled Med Palma pacNor barrel in 264 win with a tightneck & short throat. Now that the rifling is broke in and I've got neck turning equipment for 6.5mm the wheels are turning again in my head. I wonder just how crazy I could get with this thing, thing is it shoots very well already. Maybe.....

CC.
 
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