243 AI or 6mm AI

[Bulseyetom]

I am about to order a barrel for an antelope and deer hunting rifle and am looking toward the 243AI in a 10 twist 26" long #5 contour barrel. The rifle is a falling block so oal is not an issue. I compared 6mm AI and 243 AI loads using quickload and there is not much difference, surely not enough for an animal to know. I can get Wilson seating dies for either as well as Redding bushing fl dies. I am leaning toward the 243 version as Lapua brass is available. What are anybodies thoughts? I have a handfull of larger calibers so I don't need advice to go with a 30-378 Weatherby! Thanks. Tom

 

[40X Guy]

I have had both, and currently own 2 6MM AI's, (both 8 twist) I like the 6AI because of the longer neck, and you can shoot that heavier bullet better at least in my experience. My 243 AI was a 10 twist that shot light bullets very very fast, but I firmly believe you can do more with the 6AI, especially with heavy bullets for class. Both are inherently accurate, both you have to take the time to fireform, and either one will make the critters dead. Yes the Lapua brass is available for the .243, but you can also buy Norma 7X57 Mauser brass and neck down to 6MM and fireform, then you have the benefit of the good brass in the 6AI. Which is what I did for my rifles. Mine are more long range paper punchers then hunting rifles, but I would love to have a lightweight walking rifle in 6AI. I guess FWIW either one will get er done for you and they both are hi intensity cartridges. It may come down to what your smith has as far as a chambering reamer also. I am not quite sold on the velocities being about the same either. Real world tells me my 6AI is almost approaching 6-284 speeds with 105 Lapuas. I can't disprove or prove that a .243 AI will get em going that fast. This will be a good thread to follow as members chime in. Best of luck and keep us posted.

Frank

 

[Bulseyetom]

This project started out (and might still end up) a 6mm based on the swift case but when I called CPA rifles they have perfected an extractor for the Stevens 44 1/2 action that will work on rimless cartridges. The cost of match grade dies for the 240 Cobra is pretty stiff compared to the 243 or 6mm improved and there is a loss of 150 fps compared to the 6mm improved at the same pressure levels. I ran a comparison between the 6mm AI and the 6-284 and the gain from the 6-284 is not worth it in my opinion. I have also considered the 6mm Krag Improved long and I am sure I would be the only man on the block to own one of them! From a practical standpoint the difference between brass for a hunting rifle is probably going to be of no consequence. I am currently shooting 85 and 105 grain Speer hunting bullets in a 6x47 Lapua with a 10 twist and accuracy is great. I have killed several antelope with the 85 grain bullet with one shot through the lungs and am really happy with the bullet. I hoarded up a few boxes of the 105 grain Hot-core when they quit making them and had all intentions of hunting with them this season but ended up with the lighter bullet again.

 

[WyleWD]

This won't be very popular, but in my experience with the ones you mention.... I'd go with the 6-284. It is a lot more simple, No fireforming, any brass you'd like to try, accurate, and all the potential you need for hunting. I've had 2 of the 6-284's now and would not go back to the 243ai nor the 6ai for a hunting rifle. Just my humble input based on experience. WD

 

[LWolken]

I've had/have three 243AI's what I like is the Lapua brass, speed is very good have driven 107's to 3350fps but were not accurate there. The 243AI is the 6mmbr of the bigger cases. Once you go bigger you don't get much if anything in return. It does everything the bigger cases can with less powder, less heat, less wear, shorter action, cheaper brass. I only wish it had a slightly longer neck. I might try the 6mm SLR next.

Lance

 

[1000yardstare]

A couple of years ago I was debating .243AI or 6AI for F Class competition. Looking around for info is how I found AccurateShooter.com, the only forum I belong to.

Went with the 6AI because I wanted the extra velocity with 107 SMKs at 1000 yds. May only be 100 fps but I need all the help I can get. Also my best varmint rifle over the years has been a custom 6mm Rem built on a M98 action and 26 inch McGowen barrel. I have always had a soft spot for the 6mm Rem. My favourite deer rifle for years was a Rem 700 BDL in 6mm Rem. Too bad Rem screwed up the marketing of that fine cartridge.

So I had Rob MacLennon blueprint a Rem 722 action and install a 30 inch 8 twist 6AI barrel. He had the reamer for local coyote hunters who favour the reach of that cartridge. He just had to throat it for the heavier bullet. Won second place in the 1000 yd F Class match at the 2009 Ontario Championships with that combo.

Barrel is shot out now. Doesn`t take long - 1800 rounds. Getting a new one.

 

[MarkS]

Bulseyetom,

I have had both. 243AI for Lapua Brass.

Mark Schronce