243AI

[Dfish1247]

Having a bartlein 8 twist that’s currently a 6br Remington on a 40x turned into a 243AI.

Before you panic, I have a couple 6br Normas. Problem is the brass from the Remington chamber will not fit the Norma chamber. That’s only an issue if I were to sell the gun, I’d have brass I couldn’t use in another 6br. I did neck the brass down and run through a small base body die to fit my 22br. Took 2 firings to get a normal bolt close. Plus, this gun was just sitting due to no interest, so might as well do something with it.

Have dies and brass from years ago when I had a ruger 77 in 243ai, plus I have new 243 brass I can form if needed. Barrel is being made to shoot 90-105gr. I will try a few in the 80-90gr range as well. This barrel grouped well, .250” was a given, only has about 75 rounds through it, so plenty of life left. Not a big sample obviously, but that’s plenty for me.


It’s been a while since I fooled with this, but is it still true I’d start at max 243 Winchester data and inch my way up till I find something? After accuracy not velocity, never had anything that grouped well with sticky extraction and blown primers.

 

[std7mag]

In theory, yes.
In practice, not so much with the cartridges based off the 308.
You don't gain as much volume as say a 250 Savage or 257 Roberts (or 6mm Rem).
While the AI does push the shoulder forward some, there isn't a lot of taper to the body.

Having done the AI route with the 7mm-08, I was only able to increase powder capacity by about 1gr.
I picked up 50fps with most powders. (I am shooting a 22" barrel. Most reloading manuals are using a 24" barrel so I got back the speed due to the loss of 2") 2,832fps with most powders.
RL17 was the speed demon at 2,916fps. That with a 140gr bullet.

 

[longbow59]

waiting to hear more. I just had ER Shaw put a 1 and 7 twist, 21 inch barrel on an Interarms Mark X in 243AI

 

[NZ_Fclass]

Use the 243 loads with slower powders for your start point. Mine shot with N165/565 and H2213SC and H1000. It was awhile ago and had a 10 twist for 80g Lapuas going fairly quick. You will probably end up with around 43.5 of 2213 with 107's. Velocity should be in the 3000+s'

 

[spaniel]

As to your question on where to start yes, I've always started at top end 243Win loads and have a good amount to go up from there. From a 24in barrel I can push the most popular slow powders for 105s to 3200fps, which is a good taste over 243Win.

 

[Dfish1247]

Thank you all. Greatly appreciate it.

Probably be the dead of winter when it comes back, so I’ll be freezing trying it out.