Tikka .243 AI

[eric1115]

Looks like she's gonna be a shooter.

No pressure signs, going to load a few at 50.0 to make sure groups hold up, but looks like the 108 load is done.

106 is less impressive, but going to try 51, 51.5 if I can stuff that much in, to see if I hit pressure, then probably try 50.5 or 51 to see how it groups.

 

[SloppyJ]

Looks like she's gonna be a shooter.

No pressure signs, going to load a few at 50.0 to make sure groups hold up, but looks like the 108 load is done.

106 is less impressive, but going to try 51, 51.5 if I can stuff that much in, to see if I hit pressure, then probably try 50.5 or 51 to see how it groups.

So you did a 18" barrel? I've been really wanting a 6mm in an 18" barrel right at 3kfps. I have damn near just talked myself into being reasonable and doing a 6 creed but damn if this didn't reignite the spark....

What powder were you running?

 

[eric1115]

So you did a 18" barrel? I've been really wanting a 6mm in an 18" barrel right at 3kfps. I have damn near just talked myself into being reasonable and doing a 6 creed but damn if this didn't reignite the spark....

What powder were you running?

That's a 19" barrel running H1000.

I 100% get the practical appeal of a 6CM, and going this route probably cost me an extra $200-300 in brass, dies, gunsmithing compared to a profit 6CM. I probably lose 500+ rounds of barrel life. But I do like to tinker.

 

[eric1115]

I'm super stoked by these results. I was hoping for a "goldilocks" between 6CM (2700ish in an 18-20") and 6UM (3300ish with terrible barrel life, more recoil, higher startup cost). This (3000ish, moderate startup cost, hopefully decent barrel life) seems to be a winner.

6-284 would be the next step up (same startup cost, more MV/recoil, less barrel life) in my mind. Brass is same (or easier, since no fire forming needed), dies same or easier, rechamber factory fast twist .243 and keep factory bolt face same as .243AI.

 

[SloppyJ]

That's a 19" barrel running H1000.

I 100% get the practical appeal of a 6CM, and going this route probably cost me an extra $200-300 in brass, dies, gunsmithing compared to a profit 6CM. I probably lose 500+ rounds of barrel life. But I do like to tinker.

Well I love to tinker too and I'm in the same exact boat but I'll be building this one to match my 300prc I just finished with a zermatt and a McMillan but I'm going bdl on this one. Kind of like a big/little brother type deal. Want it short because it will be suppressed and want it screaming. Dammit if that's not exactly what I'm looking for. Thank you for posting all of this. Down the rabbit hole I go! I imagine with a little hotter powder and an inch less barrel that 3k is achievable.

 

[pods8 (Rugged Stitching)]

Did you do the flared end threading to 5/8"?

 

[eric1115]

Did you do the flared end threading to 5/8"?

Yes, came out great.

 

[wyosam]

You could, but it'd probably cost you more than new dies.

And yes per everyone above, the "proper" way to do an AI'd case is to set the shoulder back, but it isn't like you can't work around it if the barrel isn't set back. You'd just want to control headspace on the initial firing a different way, ie false shoulder or a solid bullet jamb.

Not sure why you put quotes around proper. Setting the barrel back is the proper way to do it. Doing anything else is not an Ackley Improved chamber, as headspacing off the neck shoulder junction of parent case brass is a key concept of the design.


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[wyosam]

From what I've read, if done correctly, it doesn't have to be set back.

Wrong, can’t be done correctly on a chamber already chambered to spec as a 243 win without setting it back.


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[pods8 (Rugged Stitching)]

Yes, came out great.

Lets see it!

 

[eric1115]

Lets see it!

Did you just ask for a picture of my flared end?

 

[pods8 (Rugged Stitching)]

Did you just ask for a picture of my flared end?

19" you say? ericTHEHORSE1115....

 

[eric1115]

19" you say? ericTHEHORSE1115....

It's not a sendero contour though... just want to manage expectations.

 

[Tom-D]

With the fire forming of this cartridge does it matter the quality of the brass? Does it need to be a harder brass, what issues could occur with fire forming cheaper brass?

 

[wind gypsy]

I'm super stoked by these results. I was hoping for a "goldilocks" between 6CM (2700ish in an 18-20") and 6UM (3300ish with terrible barrel life, more recoil, higher startup cost). This (3000ish, moderate startup cost, hopefully decent barrel life) seems to be a winner.

6-284 would be the next step up (same startup cost, more MV/recoil, less barrel life) in my mind. Brass is same (or easier, since no fire forming needed), dies same or easier, rechamber factory fast twist .243 and keep factory bolt face same as .243AI.

43.0 grains of n555 (0.7 grain under viht published max) behind a 108 in an 18” creed seems to be pushing 2900 FPS. But , I haven’t been able to justify buying a pile of n555 yet because I’m up to my eyeballs in 4350.

 

[eric1115]

With the fire forming of this cartridge does it matter the quality of the brass? Does it need to be a harder brass, what issues could occur with fire forming cheaper brass?

My (limited) understanding is that softer brass should still fire form just fine, but you're likely not going to get as many firings so you'll be burning more barrel life forming additional pieces of brass.

Disclaimer, this is my first foray into Lapua brass (I've run Hornady and Nosler brass in the past for the most part), but I've done a fair amount of reading.

 

[wind gypsy]

“Hard” is good on case heads. Not so much on necks/shoulders. Good thing is I don’t believe hard case head means the necks have to be hard.

 

[Axlrod]

With the fire forming of this cartridge does it matter the quality of the brass? Does it need to be a harder brass, what issues could occur with fire forming cheaper brass?

I have used Horn. & Lapua brass in 243 AI's. The Horn. works pretty good and only gives up a couple of firings (primer pockets) over Lapua- and Lapua is my first choice on a lot of different cartridges that I reload.
On powder I have had the best accuracy and velo. with H4831sc.

 

[eric1115]

Lets see it!

 

[Mulyhuntr]

Looks like she's gonna be a shooter.

No pressure signs, going to load a few at 50.0 to make sure groups hold up, but looks like the 108 load is done.

106 is less impressive, but going to try 51, 51.5 if I can stuff that much in, to see if I hit pressure, then probably try 50.5 or 51 to see how it groups.

H4350 is more accurate for me with the 108, but about 75fps+\- slower in a standard 243 chamber. 3000fps+ would be cool, but makes no real practical difference than the 2916fps at 41.3 h4350.