I am thinking about building another long range custom varmint rifle for shooting woodchucks at 500 to 800 yards. I can't decide on the 6x284 or 25x284. Any suggestions? Does anyone shoot one of these calibers?

agreed, i was thinking 6mm/284 over the .257/284, and if not then a 6.5mm-284

so either 6mm/284 or 6.5mm/284

Which one have you had built?

I jumped on the 6.5X284 Band wagon about a year ago. Myself along with two friends bought one for the exact same purpose you are proposing(long range ground hogs out to 600 yards). We found the cartridge to be very finicky. I could not get mine to shoot. Now I know it could just be my problem with my rifle(I am sure it was). But all three were finicky. We did get one to really shoot wit N-165 and a 140 grain pill, but that is a large bullet for a ground hog. He uses his for 1,000 yard shooting at our 1,000 yard club, and he does well with it.

I have not used the 6X284, but I have read good reviews. I have also heard it is a bit finicky, but that could be hear say. It has to be approaching overbore.

Do you want to see impacts?? You will not be able to see impacts with these rifles, unless the GH's are a long way off.

Have you looked at the 22 caliber 75 grain bullets. Check out the BC of the Hornady A-Max 75 grain bullet. This bullet IMO exceeds the 6mm bullets in comparable weight, and yields the same velocities. You just need a 1in8 twist. Tom.

You know I have alot of friends with the 6.5-285, and they can't get the velocity once thought. In a good quality barrel, its darn accurate, but no better than 6mm-BR's but not as fast