Re: predator rifle
Go to Dan Lilja's (Lilja barrels) website and browse through there for twist info and such. He has a chart that is very accurate concerning bullet weight and twist. Dan has done much research and developement and is a good guy. His info is straight forward and not biased. He pretty much tells it like it is. Just remember for optimum performance you want just enough twist to do the job and not overtwist the bullet. Particularly when dealing with the light fragile varmint bullets you want to shoot. They have a tendency to come apart at high velocities when trying to shoot them through rifles with to much twist. This is hard to do because velocity plays a role in there and that just takes a lot of experience when playing on the edge of performance. That is why most just say do a 1-10 because it will pretty much stabilize anything unless you get into long heavy vld specialty bullets. But if it were me and trying to play right on the edge of performance and knowing it was a varmint rifle all the way shooting only bullets 55-70 grains I might try the 1-12 twist. If you want to be safe the 1-10 will work great and allow you to go a little higher in bullet weight if you chose to later on. The 25" barrel is fine with this cartridge. The contour just depends on how much weight you want to carry. heavier the barrel, better it will shoot typically. If it is a carry rifle a 25" #3 in 6mm caliber has enough metal around it to shoot extremely good and still light enough to carry around. Plus it will give the gun enough weight that combined with a brake you can stay right on target and watch the hits.
I have 243 AI's in barrels from 20" lightweight contours to 28" straight bull barrels with no taper at all. The reason I like the 243 AI so much is that it is very efficient performing great in short or long barrels. Really no need to go beyond 28" in it. The 4100 fps I mentioned with 5/8" 300 yard group with 55 grain bullet was the 28" no taper barrel. With the AI there is no problem fireforming. You just buy a box of 243 ammo, shoot it, and you have 243 AI. You can buy dies for it just the same so it is no difference than loading for the standard 243. You just get a good bit more performance putting it near a 240 wby. The 243 is a great cartridge on it's own so don't get me wrong. I am just saying the extra performance is there for you with no extra work. The 243 AI has been for many years as accurate a round as there is on the 1000 yard circuit and has held several world records. 5 shot groups in the 4" range at 1000 yards are fairly common with this round. It and the 6.5-284 are two of the most accurate cartridges ever developed.
Predictions are difficult, especially when they involve the future