Twist Rate for 243 AI

[601handryan]

guys, i am planning a new rifle project. i am realy leaning towards the 243 AI. i plan on shooting the 105-115 grain bergers from this rifle. it will mainly be for target shooting with the occasional deer hunt. what is a good twist rate for these bullets? barrel groove selection? also, would there be any benefit of building this on a long action reciever?

 

[ATH]

I've heard 1:8 is the minimal twist for the 115 Bergers, and 1:7.5 is really needed. I've also heard of people being able to push them fast enough in a 1:8 in a 243AI to blow them up. So I don't know is say rachet rifling or something similar may allow you to shoot them faster or not; I have no experience personally with the bullet and am relaying 2nd/3rd hand information.

I went through all the options myself and decided on the 105 AMAX and 1:8 ratchet rifled Shilen. I started out wanting to shoot the 115s and changed my mind after doing the research.

 

[azsugarbear]

Sounds about right. My 243 rifle has a 1 in 8 twist ans stabilizes the 105 gr. Bergers very well.

 

[AZShooter]

Three of us built three different 6mms to shoot the 115 DTACs. A 6mm Dasher, 6 SLC and a 6mm-284. All were 1 in 7.5 twist 5R bartlein barrels. We had read extensively that a 7.5 twist was necessary to stabilize the 115. Unfortunately the bulk box of 115s we bought didn't shoot. The 6 dasher and 6 SLC shooters were 1000 BR guys and they did every tweak possible but found nothing they would shoot in competition. We all gave up on the 115s.

There was a great deal of information on the net regarding my choice of the 6mm-284 suggesting that the 7.5 twist would unravel the 115 Berger VLD. That left us with no 115s to shoot.

We all moved to the 107 Sierra MatchKing which shot well in all three rifles. So much for getting that faster twist.

Enter the 105 Berger hybrid with a BC that is higher than Berger's 115 VLD! (.547 vs .545)
The bullet has been launched up to a tad over 3500 fps from my 6mm-284 with no issues.

I have a second Bartlein 5R I will be using as a 6 BR. This time I opted for a 1 in 8 twist. I KNOW it will stabilize the 105 Bergers.

I would suggest you go with a 1 in 8 twist and not bother with the 115s. Even if you go with the 115 DTAC the small gain in BC over the 105 Berger hybrid will not overcome the advantage due to higher velocity.

FYI the 105 Berger kills coues wt just fine.

 

[Joel Russo]

My experience mirrors what AZShooter just explained...

 

[Outlaw6.0]

Do yourself a favor & run the 1-8" twist & don't go any slower. I'm still kicking myself for building a slow twist 6mmAI. It hammer's 85grainers like no other but toss in a boat tail & watch the frustrations grow as the bullet hits your target sideways...

The 1-8" will stabilize the 105-107's very well & it should be just about optimal bullet weight for your AI. While I don't agree a 40point increase in BC is marginal, I too have read the DTAC's can be finicky. If you want to run a heavy, I believe Matrix makes a 117grn VLD. If they shoot like other heavy Matrix VLDs, they would be well worth looking at.



t

 

[601handryan]

thanks guys. also this will be my first ackley rifle. ive never fireformed brass before. is there a particular way that is not damaging to the barrel that you guys like to use? ive read the cream of wheat method using fast burning pistol powder. is that the best way? or should i just buy regular 243 win bullets and fire them?

 

[Outlaw6.0]

I load COW for my father's 6.5-06AI, it works fine but is kind of a PITA. for my 243ai & 6mmai I loaded a bullet long to where they jam in the lands hard & fire a stout load, it seems to form the cases a little better & is usually accurate enough to do some plinking.

If you can afford lapua cases, please do so, you will thank yourself later.


t

 

[601handryan]

just wondering, have any of you guys seen the hydraulic forming die made by hornady? supposed to form your brass without fireforming. But for dang near $200 i can buy enough powder to form a lot of brass and COW is cheap. that being said, if it works like advertised, it would be nice to have.

 

[ATH]

just wondering, have any of you guys seen the hydraulic forming die made by hornady? supposed to form your brass without fireforming. But for dang near $200 i can buy enough powder to form a lot of brass and COW is cheap. that being said, if it works like advertised, it would be nice to have.

I have heard of it and that it works well. But for an AI it seems overkill.

I got my 243AI Shilen barrel today and installed it. Headspaced correctly, a regular 243Win case will be a slight crush fit. So seat close up at the lands, load a high end normal 243 Winchester load, and get in some plinking. I've got 200 Lapua cases, I'll probably end up fireforming most of them shooting at prairie dogs next fall.

 

[tobacco road]

I have a 243 ai with a 28" shilen barrel 1-8 twist shooting berger 105gr. Vld and I get great velocity and accuracy. Fireforming is kind of a pain but I just loaded up a bunch of 80grainers and shot a bunch of squirrels to fireform.

 

[601handryan]

I have heard of it and that it works well. But for an AI it seems overkill.

I got my 243AI Shilen barrel today and installed it. Headspaced correctly, a regular 243Win case will be a slight crush fit. So seat close up at the lands, load a high end normal 243 Winchester load, and get in some plinking. I've got 200 Lapua cases, I'll probably end up fireforming most of them shooting at prairie dogs next fall.

Are you installing your own barrel? Is it a savage pre fit from shilen? Would like to hear some feedback on those barrels.

 

[westcliffe01]

Here is my Savage 12 with a 26" Varmint contour Shilen 243 AI 1:8 twist barrel

It has served me very well, I have not yet missed a coyote since I put the new barrel on and started shooting the 95gr Bergers. The factory (1:9.25) barrel would not group the 95gr Bergers better than 2 or 3MOA. Right now I am still in the fireforming stage and will start with 105gr load development when I have 100 shells prepped. So far, for coyotes the 95gr Bergers have been devastating and the ballistics a massive improvement over the 223 I hunted with before.

I have heard negative comments about Shilen from gunsmiths, but every barrel I have except my 6.5x284 is a Shilen and I have been very happy with them. For some reason, there was a huge problem with yield on 6.5mm blanks the year I was building mine and after waiting a year I caved and got a CBI. I do think that gunsmiths scorn prefit barrels since it takes them out of the manufacturer / customer relationship and I have fitted all of my barrels myself.

 

[601handryan]

thanks. i have a custom built rifle but i think it would be pretty cool to build one on my own. when taing that route, savage seems to be the way to go. sweet looking rifle by the way. what kind ove groups were you getting with the 95 gr bergers?