Converting standard .280 Rem to .280 AI

[TheNatureBoy]

I'm snowed in and bored outta my mind and I started thinking about a conversation I had on the way back home from the shooting range a few weeks ago. My partner suggested that I have my Interarms .280 Rem. converted to a .280 AI. We talked about it for a few minutes before moving on to something else. I took a look at a few reloading manuals that I have and noted the improvement from a velocity stand point, made comparisons ref powders that I have and use, read testimonials as to its accuracy and energy, etc. From what I gather as it stands now a standard .280 is very close to a .270. Converting it to a .280 AI puts it closer to a 7mm Rem Mag. My question is how does a gunsmith go about such a conversion? Whats involved?

 

[knight0334]

The barrel needs to be turned back a .003" to .004" to have the proper Ackley Improved crush fit. Then you reamer the chamber.

If you use barrel mounted sights you'll have to turn the barrel back 1 complete turn to maintain a top-dead-center alignment. Which may require having the barrel turned/cut on the chamber end due to clearances with the bolt.

 

[fisherman66]

Just a related side note. One of the greater benefits to AI is extended brass life. That would mean more to me if I were a handloader than the extra 100 or so FPS. If you are killing game inside 250 yards with very few exceptions there is little real world gain. If you like to tinker then by all means go fer it. How long is yer barrel?

 

[FrankenMauser]

The barrel needs to be turned back a .003" to .004" to have the proper Ackley Improved crush fit. Then you reamer the chamber.

This is critical.

If a gunsmith offers you a "no turn" AI chamber reaming... Don't do it. To achieve proper headspace, AI cartridges must have a slight crush-fit for factory ammo. After the first firing, the AI resizing die bumps the shoulder, and takes care of future head spacing concerns.

As for sights and other barrel-mounted items - there's always a chance the 'full turn' won't be perfectly top-dead-center. If the gunsmith won't stand behind his work, you may end up having to pay to have the barrel redrilled and tapped for sights, as well as a bluing touch up (where they used to be).

 

[GeauxTide]

Another view

Nosler 5&6 have good comparisons on both. After that, I ordered a 26" barreled 280 and had it fluted to trim the weight. I don't get the extended case life claim because I neck size after the first load anyway. My 280 shot best at about 85% throttle (140s@3027 in clover leaf groups). If you want the 100 fps, get the 26" barrel and you won't have to buy dies and fool with fire-forming. BTW - The four 7mm Mags that I've loaded for all preferred 145-160gr bullets and the AI will only approach the 7s with 140s.

 

[fisherman66]

I don't get the extended case life claim because I neck size after the first load anyway.

You might be right due to the only very slight taper (as opposed to a 7x57 or other "conical" cartridges). The shoulder angle is already severe enough to stop brass much migration.

 

[TheNatureBoy]

26 inch barrel Fisherman. I was just curious as to what a gunsmith would do to convert from one to another. I'm very happy with the rifle as is. The guy that suggested I convert it traded it to me about two years ago for a pistol (XD-45) and has wanted it back ever since. Its a custom job. Boyds stock, ruger action, douglas 26" barrel...a really beautiful/accurate rifle that I'm very happy with.

Thanks for the response

 

[Jimro]

Don't bother with the AI process for the 280 Rem.

You can load the 280 Rem hotter than factory ammo without going through the AI process. Remington did this and called it the "7mm Express".

The 280 was originally a lower pressure round because of the older pump action rifles lacked the camming action on extraction that a bolt action rifle has.

Jimro