What are the advantages and disadvantages??

I am having a .260AI put together. I'll post results & we'll see. The only real down side is no factory ammo. To any handloader, that's really a none issue. There is also no factory brass, but again, not really a problem. Brass life is supposed to be extended & you may get a bit more vel. & accuracy from the Imp. case.

I have read many times that AI'ing many of the more modern cartridges (308 family being one example) is not really worth it. I have no experience either way but it seems that when you read about the Ackley cartridges that show the most improvement, they are the ones that were originally loaded to lower pressures, so when you load them a little hotter they show significant gains. Examples would be the 250 Savage and 257 Roberts. Both are factory loaded to substantially lower pressures than more modern cartrudges, in order to protect the weaker actions they may be chambered in like Savage 99s and Spanish Mausers. Even the 30-06 is loaded to lower pressure than the 308 because of the Early Springfields still around. Sean

Most guys I know who shoot an AI in almost any caliber, that also have a NON AI rifle in the same caliber say that the velocity gain is not really all that great. At least the truthful ones. I do think there can be some acceptions like the 257 Roberts AI, but since the Roberts was so downloaded by the factory, dramatic increase in performance is not real hard.

As a person who shoots several 260s, 6.5 x 55s and 6.5 x 57s, I also fail to see the reason with any practicality. If you just want to impress your buddies by having something different, or are just the type that have to have something different, then it may be of personal value to you.

In the field, or at the range, a 100 fps or so will be your only real yield and that will not really show up any different on targets or on game.

Practical or Impractical, follow your heart!

heider,
To answer your question, there are advantages and disadvantages.

Disadvantages:

1)After spending the money to have your barrel removed, turned down a thread, rechambered, and refitted, you still have a factory barrel leaving a lot to be desired, more often than not.

2)Dies cost more than standard offerings.

3)If you sell your rifle, you may not find as many takers, since it's only an advantage to a handloader.

4)Fireforming brass wastes primers, powder, and bullets.

5)Velocity gain is only minimal most of the time, unless pressure is also increased.

The other side of the coin:

1)If you're starting out by rebarrelling or starting from scratch with a custom, it costs the same to chamber for an Ackley cartridge as it does for a standard cartridge.

2)The difference in the cost of dies over the life of a rifle is miniscule.

3)Why sell a rifle once acquired unless you're trading up, in which case, who cares about resale?

4)Fireforming loads doesn't "waste" primers, powder, and bullets. I've developed some pretty accurate fireforming loads that I use for practice (hardly a waste of anything if you take shooting seriously), varminting, and general plinking (I enjoy shooting).

5)When done properly, Ackley chambers can safely handle slightly higher pressure than standard cartridges, contributing to the added velocity along with the small gain in powder capacity. The reduced case wall taper lends itself to better grip of the side walls during case expansion, resulting in less bolt thrust. Less bolt thrust means less peening of the bolt lug recesses. Headspace doesn't "grow" as quickly as it does with standard cartridges. Since most Ackley Improved rifles are done by competent gunsmiths, headspace is no longer an issue for the shooter. Even though velocity gains are not that significant (whatever that means), I'll take the extra 50-100fps if it's there for the taking.

6)Case life is extended with improved cartridges. Brass doesn't flow forward like it does with standard cartridges. Trimming cases is almost non-existent.

7)The sharper shoulder makes for more positive headspacing and a better "feel" when resizing or chambering.

8)A properly cut and polished Ackley chamber makes for easier extraction.

9)It's not necessarily an ego trip, but it's kinda nice to have an exotic flavor when everybody else is stuck with vanilla.

10)An Ackley improved cartridge is a sexy looking number.

Thanks for the input guys