So I recently picked up a Tikka CTR in 260AI. I have never worked with anything AI Before.

Question 1: fire forming brass. Should just be load and shoot correct? Was planning on using something on the bottom end of 260 data? Should fire form all right?

Question 2: I was recommended to use H4350 as the go to powder for 260 AI. But I having trouble finding 260 AI load data. Anyone have any load data sources or powder recommendations.

Comments, this rifle is gonna be the bees knees.

Scott

Don't have that specific one but...

just start load development as you fire form.  The diff with formed brass is very subtle.

If you're short on data, start with regular 260 data realizing you'll have a little more leeway at the max end.

I'm shooting a 280 AI.  Its not the same obviously, but the principles are identical.

For the 280 AI, the Nosler instructions are listed in their online data.  In short, use a light load of relatively fast powder (relative to the cartridge.  I use IMR4895) from the regular, non-improved data.  IN my case, regular 280 Data.  Nosler 280 AI instructions and notes

Seat the bullet really long.  I use a cheap no frills 140 7mm Speer for this.  Long enough that it seats firmly into the lands on loading.  Loading will actually drive the bullet deeper into the case.  This ensures the case head is pressed back against the bolt.  On firing, you get a nice Ackley Improved case.  These will likely have to be loaded one at a time, and will not fit in  the magazine.

Some people use the Cream of Wheat method.  Its only personal preference, but I worry that the firing pin strike can still push the case forward on firing, causing more case stretching once the case expands.  Apparently, I am not the only one with these concerns.   Cream of wheat issues with 260 AI  I like the idea of the bullet firmly in the lands to help keep the case head hard up against the bolt face for maximum 'holding power'.  I want the shoulders filled in, and the case taper straightened, not the case head stretched.  I could be wrong.  But its working for me.

I found that the actual starting loads for IMR4895 and regular 280 Rem data (as per nosler instructions for 280 AI) weren't quite enough to fill in the case shoulders completely. The fired cases looked more like Weatherby cases, with rounded shoulders instead of nice clean tapered bottle neck.  I bumped it up by a grain or two and they fill in  very nicely.

IF, again IF, the conversion was done correctly, the gunsmith removed the barrel, cut one thread off the threaded area, and then rechambered to 260 AI.  IN this case you can just chamber a regular .260 Rem cartridge, fire, and end up with a 260 AI case.  If the smith was lazy, didn't set it back one thread, and simply ran a new 260 AI reamer in the existing barrel, your 260 is probably "longer" than its supposed to be and has some excessive headspace if you chamber and fire a regular 260.

After firing, I anneal the case neck and shoulder.  Its been worked pretty hard.  A little 750 degree tempilaq inside the neck, a cordless drill and a 13mm socket together with a small butane torch.  It takes about 6-7 seconds per case.  Annealing at this point means the case necks don't split as readily.  I simply neck size future loadings...

The conversion was done right. the factorty tube was taken of and replaced with a bartlin blank chambered in 260 AI. I still have the old 260 CTR barrel.

Scott

Then you should be entirely good to go...

Load 260 Rem cartridges and squeeze the trigger.  Its now a 260 AI case.  Or load new virgin brass with a light load as described, and squeeze the trigger.  Either way, those cases are costing you the cost of a cartridge, or a new case plus powder, primer, bullet.  The fireforming isn't cheap.  So extend the life of that hard-worked brass:  Anneal the neck and shoulder...

Enjoy.  the 6.5mm's are awesome.  And my CTR  is a winner too (but in 6.5 Creed)

No source for data.  Which isn't unusual for a wild cat.  You'll be able to exceed 260 Rem data of course.  By how much?  I dunno.  I'd use powders on the slower end of the 260 data you have, and then work up to and beyond 260 data.  Watch for pressure signs.  I have no hard and fast guidance for you.  Check your chronograph.  If you safely get 100-125fps faster speeds with the same bullet and no pressure signs, I'd call it good and quit.  I'd be happy with 2900 and a 140 out of the 260 Ai and a 24" tube....

I have some 100 Lapua cases that came with the rifle. 35 still need fire formed. I just don't wanna blow up my gun or end up with rounded shoulders. 2900-2950 with 140s is my goal. Nothing to hot. Should be a fun gun to shoot. Imma play around with some other powders and see if it likes anything else

Scott

Some things I do when forming Ackley cartridges.

Neck up the case with a tapered expander one caliber over and then resize enough of the neck until the bolt can just barely close.  Its called the false shoulder method.  I do that for cream of wheat or live ammo.  Keeps the brass against the bolt face.

I have also done hydraulic forming with water.  Works pretty good.  Gets the shoulder 90% of the way formed to where it looks like a Weatherby shoulder.

For reloading data, start with max loads for the parent cartridge.

You can also try 6br.com

The Hide has some data for the 260 AI as well.