Home Forums Hunting & Shooting Ask The Gunwriters 260 Remington Ackley Improved

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.