Cartridge to utilize new 131 ace

[OldManOwen]

With the SST will I need to replace the bolt to accept the larger diameter cartridge or is it just machined to fit? If I understand correctly the 25-260AI would not require any bolt work, just a barrel blank machined for the cartridge properly installed by a smith?

 

[MudRunner2005]

Thank you all for the wealth of information! Just spent some time looking at the 25 SST and I love the fact that brass is available (or will be soon) and they have reamer rentals. On the other hand a lightweight build in 25-260AI sounds like a handy rifle. Does anyone have an educated guess on how fast I could safely push the 131 in the 25-260AI? It looks like Lapua makes 243 and 260 brass, I'm assuming necking down to .257 from 260 brass would be the way to go? Leaning towards the Sherman just because the brass is already done for me, but who knows, maybe I just need to jump in and learn.

Based on neck-constriction for .257, and comparing it to a .260 AI with a 130, I don't see why you couldn't hit upwards of 3,100 FPS MV with a 26" barrel...Maybe even faster??? Just have to build it and find out. That's the magic of wildcatting. That's what makes it fun.

Yes, using standard .260 Rem brass would work fine, but to ensure proper brass length after forming (case necks shrink .020" during fire-forming to AI chamber), you might be best to use Lapua .308 Win palma (small primer) rifle brass. Buy a .277 neck bushing for the dies, neck the .308 brass to .277, then neck down to .257. And then from there, trim your brass .020" too long. Load your fire-forming loads (about 5 grains lower than book starting loads) with cheap Hornady Interlocks to where they are pushing into the lands & holding the cartridge head firmly on the bolt face (slight bolt resistance when you close the bolt). And finally, the fun part... Shoot to form. Out pops proper-length .25-260 AI brass.

 

[MudRunner2005]

With the SST will I need to replace the bolt to accept the larger diameter cartridge or is it just machined to fit? If I understand correctly the 25-260AI would not require any bolt work, just a barrel blank machined for the cartridge properly installed by a smith?

Yes, the SST (magnum bolt face) would require opening up the bolt face by a gunsmith.

Yes, the .25-260 AI would just be a barrel swap, and will not require any bolt modification.

 

[RandyinVa]

Since you have a short action .473 bolt face my first thought is a 25-260 Remington Ackley Improved.
You can gat Lapua brass ( big plus). And possibly a bushing die set for 260AI with the appropriate bushing for 25 cal bullets.

This is an easy choice for me since I have the .260 Ackley now!

 

[tbrice23]

Based on neck-constriction for .257, and comparing it to a .260 AI with a 130, I don't see why you couldn't hit upwards of 3,100 FPS MV with a 26" barrel...Maybe even faster??? Just have to build it and find out. That's the magic of wildcatting. That's what makes it fun.

Yes, using standard .260 Rem brass would work fine, but to ensure proper brass length after forming (case necks shrink .020" during fire-forming to AI chamber), you might be best to use Lapua .308 Win palma (small primer) rifle brass. Buy a .277 neck bushing for the dies, neck the .308 brass to .277, then neck down to .257. And then from there, trim your brass .020" too long. Load your fire-forming loads (about 5 grains lower than book starting loads) with cheap Hornady Interlocks to where they are pushing into the lands & holding the cartridge head firmly on the bolt face (slight bolt resistance when you close the bolt). And finally, the fun part... Shoot to form. Out pops proper-length .25-260 AI brass.

If I'm not mistaken 260 brass is longer than 308 win brass.

 

[COBrad]

following

 

[MudRunner2005]

If I'm not mistaken 260 brass is longer than 308 win brass.

It is 0.020" longer... That being said, it's going to lose that 0.020" when it fire-forms to an AI chamber. And when you neck-down the .308 brass will get longer and should give you some extra length. Necking-down makes the brass longer, because the extra brass has to go somewhere... Just like necking-up makes the necks shorter.

Now, I don't know the exact amount of extra length you'll gain from necking-down .308 Win brass, but it should get you enough to make it all workout right.

 

[tbrice23]

Not .020" worth brother.

 

[tbrice23]

Ive had few AI cartridges, they only loose about .005" to .008 after fire forming.

 

[MudRunner2005]

Not .020" worth brother.

I get a fair bit of extra just from necking-down .270 Win brass to form for my .25-06 AI... I don't have any .308 Win size bushing dies to try this with, with one of my old pieces of .308 brass... But I wonder if someone could try to find out. Measure before and record length, run the .277 bushing, measure & record length, then run the .257 bushing and measure and record. I would be interested to see.

 

[MudRunner2005]

Ive had few AI cartridges, they only loose about .005" after fire forming.

I've got 3 currently, and they all lost .020" after forming, except for my .300 Ackley, it seems to stay about the same (but not so much growth as shoulder shape change for it)

 

[257 Blackjack]

With the current bolt you have, 25 Creed (2975-3070 fps) in 26" is an easy and flat shooting option. It basically does more than what long barreled 260 AI's used to do.

Going 25-260 AI is optimal for 3200 fps and would be suboptimal in 2.880" magazines. If you have an internal magazine, BDL style rifle, or can run 2.960" 257-260 or AI will be hard to beat.

If you swap to magnum bolt face, 25 SST is the way to go. 3300 fps with a true short action setup and no boat tail invasion to the case capacity.

Once guys shoot 25 Creedmoor at 1000-1300 yards compared to their match setups they realize that bit of performance they have been missing.

The extra 130 fps between a 26" 25 Creed and a magnum won't make much difference to a deer, goat, or elk if a marksman is behind the wheel.

We just received our Clymer Reamers yesterday and have 25 Creed in stock which always sell out fast.

25 SAUM, 25 PRC, and 25x284 reamers are due in the next few weeks. 25 SAUM is getting 3320-3380 fps.

I think you'd be happy with any of these mentioned, 25 Creed, 25-260, 25-260 AI, or 25 SST. They are more than capable of any ethical hunting situation for medium game and more than capable for match shooting to over 3/4 mile.

 

[Michael O'Connor]

You'll have a few more/ better options in a LA. The weatherby comes to mind.
The Sherman short keep coming up, but I have some reservations about the long term availability of them (or any other new cartridge).
Not sure if it's an option, but what about necking down a 270 wsm case? The 270 wsm is here to stay and would an easy wildcat.

There will always be brass for any Sherman. The Sherman LA works very well with .270 win. RWS brass (good, tough brass). The Sherman Shorts can be used with Norma, ADG (Atlas), and Bertram SAUM and others too.

 

[Felt 223]

Have you thought about 25/284?