predator rifle

[Long Time Long Ranger]

For best results you would need to twist it for either the light bullet or the heavy bullet. If not then you have to twist for the heavy 107 and the 75 will still shoot in it. My rifles shooting the 107 are the 240 gibbs, 240 wby and the 243 AI. With the velocities of those I can stabilize the 107 with a 1-10 twist but most like a 1-8 or 1-9 if they shoot the 107 exclusively. With the 243 I think you will need to go with at least a 1-9 for best results in that velocity range. Some of the 243 experts would need to come in here and answer that one for you.

I have one of my 243 AI's set up with a 1-12 twist for the light noslers and am shooting the 55 grain varmint bullet 4200 fps into under 1" at 300 yards. They average around 5/8"-3/4" for a three shot group at 300 yards. It is pure he!! on varmints out to 500 yards. The wind takes that little bullet for a ride though on long distance shots.

 

[partisan1911]

Like top cat said this is going to be heavier than I thought it would be. I got a decent deal on a surgeon 591 action. I didn't realize it was chromoly. I plan on going for a McM HTG stock with edge fill. Badger bottom metal, jewell trigger, broughton 5c barrel. Chamber in regular .243 to shoot bullets around 70gr. I don't want to mess with fire forming brass since I have never done that. Not real sure if it would be worth the extra fps for me. I havent decided exactly what twist. Looking at broughton barrels there are two options on the "A" contour. Which of the "A" do I need. 1.20" or 1.25"? Length will be 25" plus brake. I am guessing recoil won't be an issue with this weight.

Long Time Long Ranger- what barrel lengths and contours are you using for your two rifles.

 

[Long Time Long Ranger]

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.

 

[partisan1911]

Thanks for the great post. I guess I really need to figure out which bullet weight I want to use. I can't have the best of both worlds. I will probably go with a 1-10 so I can shoot around 80 grain. It always confuses me as to what bullets a certain twist can shoot. Will a 1-10 allow me to shoot say an 80gr and everything heavier but definately not 75gr? Or will a 1-12 allow me to shoot 77gr and everything lighter? Or will say the 1-12 allow me to shoot 77gr down to 60 grain and the 55gr will not shoot at all. I see a certain bullet weight for a certain twist but is there a range of bullets that can be shot for each twist?

I also read that barrel life is about 1500 rounds with a 243. This is the reason I wanted to stick with a regular 243. I figure if I have to fireform brass this will cut my barrel life down even more? I am not sure if I am correct in this thinking? I have visited the 6mmbr forum as well but I am still not 100% on these questions.

 

[Chas1]

The 1:10 will pretty much stabilize any of those bullets you mentioned in your previous post.

 

[partisan1911]

so a 1:10 will allow me to shoot the 55gr and an 87gr?

 

[Chas1]

I've shot 55gr up to 95gr with good results in a 1:10.

 

[roninflag]

i have shot up to 88 in my 12 twist hart. i have not tried the 95 berger yet. that said they shoot everything through 6br 1 in 8 barrels from 55 to 107 they all shoot less than 1/2 inch see the 6mmbr web site . for hunting you don't need more that 100 grAIN out of a .243 . the 105 and 107 are target bullets. so i say a 1 in 10.

 

[Long Time Long Ranger]

chas1 and roninflag are right on. The 1-10 will shoot all those well. I don't know that there would be much barrel life difference between the 243 and the 243AI. The AI shoots fine with standard 243 ammo so your not really waisting a shot. You wouldn't want to do it shooting competition but at predators fine. You will enjoy either. Good luck with it.