Curious to know what you all think of the 260AI. I have always been a 6.5 shooter 6.5x55, 260 Rem, 6.5-06 and 6.5x284. I have a 260 rem Sako 85 that has been become a bit of a safe queen it has lot's of room in the magazine and I'm thinking re-barrel or re-chamber.

With the 260 rem I believe that 24 is minimum bbl length with the AI I am not sure. I like the handling of the 85 as is but not sure about 22.5".

What's your opinion/s?

Thanks in advance.

Bob

It's a cool cartridge but I don't think I'd rechamber a rifle just to AI it . Fact I know I wouldn't .

Your FPS gain would probably be 100FPS - guessing/ballpark ..

I'd sure consider the 260AI for a build or rebarrel though .

Another guess.on barrel length - 20-25FPS per inch is a pretty good estimate .260R w/a 22.5'' barrel is perfectly fine , especially with heavier bullets .

An extreme velocity cartridge or what is considered an overbore cartridge will get far better velocity gains in a long barrel than a short barrel .
Example a 26'' barreled 22-250 shooting a 32gr. v-max bullet would lose a lot more velocity if you cut 4'' off the barrel compared to the same rifle shooting a 70gr. bullet load -then cut 4'' off barrel .
The 32gr. load might lose 75FPS per inch of cut off barrel . Guessing there again .

Of coarse do what you want and have fun with your Sako 260 .

The 260 won’t benefit from it all that much.

I’m having a new barrel put on now and decided not to do it based on research and the advice of a very good gunsmith.

Now my 280 on the other hand....

I think it's a waste of time. If you need a case fatter than the standard .260, go with 6.5x.284. That's like an AI and a half!

I think that you could expect a maximum of 10% more case capacity and that would probably get you between 75 and 100 more fps of velocity.

I have bounce the idea of converting a 260 to 260AI multiple times over the past 20 years, but every time that I run the numbers, the cost to set the barrel back, cut a new chamber, and buy a set of dies make those additional 75 to 100 more fps less interesting.

If you want more velocity then you're getting from the 260, would your Sako be a good candidate for conversion to 6.5 SAUM?

The 260 AI isn't a bad round by any means but the standard 260 Rem is just fine. Like was mentioned above the 6.5x284 on a different gun would be a great idea. In the end only you need to be happy with what you decide. If I ever thought my 260 wasn't enough the 6.5x284 or possibly the new 6.5 PRC would be intriguing.

Comparing case capacities and using Mule Deer's "Rules", the gain is likely to be maybe 50 fps depending on bass capacity, or the equivalent of around 2" of barrel length. So a 24" 260 should run with a 22" 260 AI, when loaded to similar pressures.

260 AI oughtta be about equal to both of em huh?

I have 2 very similar 260 AI's One with 22' Brux and one with a 23" Rock. They are a couple of my favorite rifles. I shoot the same load in each and shoot 123 Scenar's or 123 SST's at 3087 and 3090 fps.Great cartridge in my opinion.


I think goat called it pretty close but I have a standard 260 with a 24" barrel and about the best I can do with that rifle is 3K with a 120 BT. For the life of me I can't really tell ANY difference in the field but I like AI's and these were custom barrels, It cost no more to cut that chamber rather than Saami chambers.

On a positive note I have not had to trim a case fired out of either of the AI's yet

I don't have an opinion, but I do have first hand experience with both the 260 Ackley and the 6.5x284.

If you have the the magazine length I would go with the 284 case and depending on twist,
1/9 I am guessing, then shoot 130's.

140 VLD's didn't fly that great in the 1/9 twist but 140 Partitions did just fine.

The Ackley will get you 3,000 with the 130 and the 284 case will get you 3,100 with 130's

140's at 2,900 and 3,000 mv.

You can get those speeds with a 22" barrel in either cartridge if you decide to just re chamber.

I think it's worth it to go with 284 case, going Ackley not so much unless you just have to have one.


I personally would open up the bolt face and go 6.5 RPC and a 1/7 twist to shoot 147's at I would suspect 2,950.
24" barrel.

One of the problems with almost AI cases is there's no real pressure-tested data for any of them--except the .280 Ackley Improved, which was thoroughly tested when approved by SAAMI.

About half the reason for the .280 AI's velocity advantage over the standard .280 Remington is its higher SAAMI Maximum Average Pressure of 65,000 PSI, while the .280's MAP is 60,000 PSI. Higher pressure is also the reason for probably AT LEAST half of velocity gains in any Ackley Improved round. Since there isn't any pressure-tested data for most, handloaders primarily use the old stand-by method of adding powder until "pressure signs" appear, then backing off a little.

The trouble with this method is pressure signs often don't appear until around 70,000 PSI, and sometimes not even then. Now, many handloaders have used this method for decades without any problems, but SAAMI prefers to err on the safe side, the reason the highest MAP for any round they list if 65,000 PSI. This is because pressures are NOT constant; instead they can vary due to more than one factor, but most especially temperature.

Working up loads in an AI round without any real knowledge of what the pressure might be not only tends to result in much higher velocity gains than would result IF pressures were the same as the "parent" cartridge, but can result in surprises in warmer temperatures.

I know this partly through the help of a couple of piezo pressure labs (not some handloader who owns a strain-gauge set-up), and partly because I've owned a number of AI rifles. In every instance I was able to come within less than 100 fps of the velocities of the AI round when loading the standard round via "pressure signs"

The least amount of powder capacity gain in AI rounds is with cartridges that have little taper to the case body, because other than the shoulder there's no much to be blown out. Probably the most useless common Ackley Improved Round is the .35 Whelen AI, because the shoulder is so small it only gains about 6% in powder room--meaning about 1.5% in potential velocity when loaded to the same pressure. With 250-grain bullets this amount to less than 40 fps. Yet .35 Whelen AI fans often report gains of 100-150 fps. Guess why?

Back when I shot a .257 Roberts Ackley Improved for a few years, my standard loads got around 3300 fps with 100-grain bullets and 3100 with 115's, from a 24" barrel, both about 100 fps faster than the standard .257 loaded warmly in a 24" barrel. I couldn't notice any trajectory difference in the field over the standard .257, and of course none in "killing power." Now, this was back before we started twirling elevation knobs and all the associated stuff, so I rarely shot anything beyond 400 yards, but at 400 another 100 fps of muzzle velocity results in a trajectory 2 inches flatter at 400 with the 115 Partition.

The sharper shoulder did result in just about zero case-stretching, which is the only real advantage I've seen in any AI case. The biggest disadvantage was reduced resale value of rifles, partly because I usually had to throw in the dies, which sometimes (though not always) cost more than standard dies for the parent case.

Of course, some shooters just prefer having a rifle chambered for a non-standard round. If that, plus less case stretch, works for you, then by all means go for it. Hell, despite the unimpressive gains I've seen from improved cases, I still own two rifles chambered for improved rounds, a .22 K-Hornet and .280 AI. They go bang a kill stuff, but I do know the gains aren't significant over the parent rounds.

Cynic!

;-)

This answered all my questions about AI'd cartridges and in a few paragraphs to boot!

I've never really understood the "less trimming" argument. Some guys will spend weeks at their reloading bench, making the perfectly tuned load, and when they're not reloading they're talking about reloading, whether on the internet or in real life. Then when it comes time to trim brass and spend a little more time at a hobby they obviously enjoy, the task suddenly becomes a lot of work and they'd rather be anywhere else.

This may get me run off the board, but I kind of enjoy trimming brass. With a round I'm loading in low quantity, the twenty minutes once every two years I spend trimming brass isn't going to cut too heavily into my schedule. Sure it sucks when I've got 1000 cases to trim for a varmint rifle, but the rest of the steps to load 1000 cases get monotonous as well, not just trimming. So I break it down and do a percentage of the total at a time, and don't try to overwhelm myself by doing them all at once. Also with cartridges I load in bulk, a WFT Trimmer really cuts down on the time spent trimming.

IMO it's less of an argument than an oft-repeated chestnut.

Get thee gone and never darken this forum again!




With new tools like the WFT trimming isn't quite the chore it used to be, but be that as it may the lack of trimming for AI rounds is a reality. I recently retired a batch of .243 AI brass which had been fired 25 times. I had trimmed them at 1X to .01" under max length and 24 firings later they had only stretched about .005" on average, about .004-.006 actual measurements. i.e. they never needed trimming over their useful life. OTOH I have some .25-06 brass trimmed to 2.484" after the first firing, but with that 17 degree shoulder after 9 more firings they had stretched to about 2.504 - 2.509", some .01 to .015" OVER the max length which was a real negligent boo-boo on my part. But interpolating from that one can assume they had stretched to max length in about 4-5 firings, and that was with neck-sizing only and bumping the shoulder .002" once.

The less-trimming argument is often made by guys who use the .223 AI for prairie dog shooting.

The .17 Hornet and .204 Ruger are the two centerfires I so mostly of my PD shooting with anymore, though usually throw in several other rifles anyway, like my Ruger 1B .22 Hornet, a fast-twist .223, or whatever else needs shooting. (This year it was a heavyweight 6XC.) The .17 Hornet .204 don't stretch much either when neck-sized, and when they do need a little trim I used a Gracey power trimmer that trims and chamfers in one operation, at a rate of 15-20 cases a minute, depending on how much I want to hurry. Which means I can do 1000 in about an hour.

I think it's most often used by guys on the internet to promote the church of the almighty Ackley Improved.

"No trimming" is the AI church's mantra.

built one about 14 yrs ago.....Pac Nor on a Salvage action......

dies then were a PIA.....had Lee build me a set then.......have since sold.....

my LR is now a 6.5x55......Pac Nor/Salvage......the new Hornady 6.5PRC

looks interesting.......

http://bulletin.accurateshooter.com/2017/10/new-hornady-6-5-prc-precision-rifle-cartridge/

MD pretty well summed up the AI thing. I am still tempted to do a 6.5x55 AI as this is one that gains about 10-12 percent over the parent case but the 6.5x284 is more practical and there are many others in the mid to magnum range to consider too. Just did a 6mm AI because I was starting from scratch and it is another case with a fair amount of taper. But my loads are usually only one to three grains more powder than the standard for about 100-130 fps gains. Best reason to go AI is if you like to tinker with rifles and want to shoot more. Fire forming is just more practice to me so not a chore.

I think that, for the most part, the AI concept appeals to guys who have read POA's books, embrace his words as gospel, and are desperately seeking the last fps of velocity that they can squeeze out of a cartridge that they like. Otherwise, why would guys go to the trouble of putting together a 257AI on a long action bolt gun when they could much more easily get as much, or more, fps from the 25-06?

When I was in my 20's, I was that guy and AI'd multiple rifles for multiple AI'd cartridges. Now that I'm in my 60's, I'm much more likely to take the path of least resistance than I am to go out of my way to duplicate the performance of an existing commercial cartridge with a wildcat. The biggest exception for me is the 256 Newton, 'cause although isn't enough different, performance wise, from the 6.5x55 and 270 to make it "better", it is that rare cartridge with a "cool factor" that appeals to me and that makes the extra effort required to shoot it worth it to me.

I find it curious that nobody seems to order a reamer with a longer neck so they don't have to trim their brass all the time.....

The reason you don't want to be trimming is that brass you are grinding off comes from where you need it most- it is weakening the web/body junction.
I love my lightweight 22 inch 260AI.

Friends,

I worked extensively with the .260 Ackley Improved and wrote an article on the cartridge in Varmint Hunter Mag Issue #39, July 2001.

Hey, it is a decent round and one worthy of consideration, especially if building a custom rilfe.

Possibly, you might read the article before condemning the .260 Ackley Improved 40º totally ... or maybe not.

In the end, each of us make our own decisions, so it ain't my problem ... not at all

God Bless,

Steve

IMO that's the most useless AI conversion ever. At least the Whelen benefits from straightening out the case body and a better shoulder to control headspace.
Have you calculated the volume gain in an AI conversion of the 223 case?

Hey Steve is that article available on the internet, I would like to read it.

Yondering,

I fooled around with the .223 AI several years ago, just to see what the fuss was about. Bought a slightly used Remington 700 barrel and screwed it onto an action, finding cases formed perfectly without adjusting the headspace.

The case capacity comparison was done with water, using fired cases of the same brand filled with a 50-grain Sierra hollow-point seated to standard SAAMI overall length.The "unimproved" cases held and average of 28.1 grains, and the "improved" 29.5. That's a gain of just about exactly 5%, which with the 4-to-1 Rule means a potential velocity gain of 1.25%, or about 35-45 fps, depending on bullet weight.

Yet a bunch of handloaders reported much higher velocity gains. That was a pretty easy one to resolve, however. The standard SAAMI maximum average pressure for the .223 is only 55,000 PSI, but "pressure signs" (the various indications used by handloaders to supposedly indicate they're loads are "safe in their rifle") usually don't show up until around 70,000 PSI. So there's 15,000 PSI to play with in the .223 AI, along with the slight gain in case capacity.

So I decided to see how much velocity the standard .223 would gain if loaded up to "safe" levels using pressure signs, since that would be roughly equivalent to most .223 AI pressures. Quite a few .223 AI fans like to use 40-grain bullets because they can get 4000 fps, so the experiment was conducted in a 22" barreled Thompson/Center Icon. 40-grain Berger hollow-points were used with TAC powder, because TAC's listed velocities are among the top for 40-grain bullets in the .223, and it's also a compact powder, leaving plenty of room in the case for experimenting. The cases were Winchester, from a batch that had proven to be relatively hard, and I raised the powder charge in half-grain increments, starting at 29.0 grains--a grain over the highest maximum listed in Ramshot's data with any 40-grain bullet.

It turned out the top charge that didn't show any "pressure signs" was 30.5 grains (9% above the Ramshot maximum), which averaged 3946 fps over my Oehler 35P. (31.0 grains resulted in a slightly stiff bolt lift and occasional faint ejector-hole marks on case heads.) I then tried the same load in a Remington 700 with a 26-inch barrel, and got exactly 100 fps more--again without "pressure signs."

Thanks for all the replies you all. I have had a bit of a 6.5 obsession pretty well since Remington standardized the 260. Started there and thought I would try the "higher performing" 6.5x284 norma about 5 years ago purchased a Cooper model 52 and this firearm is as fine as any I own. Bore is beautiful fitment is all quality trigger breaks like glass. It is capable of extreme accuracy and for some unknown reason all at 260 rem velocities this with a 25"bbl.

Tried all the usual suspects H4831, Retumbo, MRP, H1000 and I even tried H414 to see if a faster burn rate would get me to "higher performance". Any where near max and groups open up from the size of a dime to as big as a quarter with at least 3 of those powders mostly with BR2 some with 210M primers. After about 150- 200 rounds I just believe the firearm wants to be a 260 rem.

It would be a no brainer for me to buy another 6.5x284 I have probably 500.00 worth of dies and plenty of lapua brass. I have 3 accurate 260's along with above and the last thing I need is another that performs the same.

I was honestly wondering if the 260 AI is not a better 6.5x284 I like reloading and am not worried about trimming brass. Everything I read says 2950 with 140's 100-150 faster than 260 rem or equivalent to 6.5x284.

My 6.5-06 is definitely higher performing but that comes at a price 25"bbl .800 at the muzzle gets pretty heavy for my types of hunting. I may try lighter than 130's and 140's in my 6.5x284 norma.

Good luck and shoot straight all

Bob

There just isn't enough gain in case capacity when going from 260 to 260AI to equal 6.5-284 velocity if all three cartridges are loaded to equal pressures.

I have 4 6.5-284s, 3 with 24" barrels and 1 with a 22" barrel The rifle with the 22" barrel gets higher velocity with the same exact loads as the other 3 rifles, so either it has a fast barrel or the others have slow barrels. It is a conundrum that bothered me until I came to accept that some things are just the way they are.

So it sounds like the 260ai is equivalent to the the new 6.5prc?

The 260 AI is equivalent to the 260 Remington, loaded hot. GD

Or a longer barrel, but you'd miss the magic cool factor associated with the 40-degree shoulder.

Interesting stuff, and sounds about like my own experiences too. Thanks!

I've loaded for the very similar big brother to the 260 AI, the 7-08AI for about the past 10 years or so. I checked the difference in case capacity using standard WW brass vs fireformed and could get about 2.5-2.8 gr more of W-760 powder in the AI case. About 5%. I think 50 fps over your standard max velocity is about what you should safety expect with 22-24" barrels. Which is negligible, but the hardly ever trimming thing is nice.

Both times Hope has taken elk she has used the 7-08 AI - one at about 315 yds, the second at about 400 yds. It was nice to be able to load for a little more velocity for those two hunts, but the gain over a standard 7-08 is probably not worth it for most folks.