I have a Browning model 71 I would like to rechamber to .348AI. My local gunsmith didn't want to do the work as he says it's pretty involved and not a simple rechambering job but that the barrel has to be set back, etc. Does anyone have any experience with what it takes and recommend someone they know can do the work? I appreciate the comments or thoughts.

Can't speak to the process... but JES does barrel boring so maybe also does chamber work like that.

Why do you want to rechamber? What do you think the .348AI can do that the basic .348 can't?

-Chris

You're lucky that your local smith doesn't have time, because the barrel does NOT need to be set back. He's obviously an idiot.

I can understand AI'ing the case, but I wouldn't and won't with mine. The 348 is reported to be hard on cases due to stretching. I think the 348, as it is, may likely be much easier to feed. If you are likely to come across big bears, the need for good feeding of cases outweighs the stretching of the brass, in my opinion.
BTW: The chances of me running across big bears much lower than someone in the last frontier. The only animals around here that might hurt are occasional wolves and mountain lions, neither of which would need the power of a 348 to dispatch them, IMO. I suppose if I were elk hunting in the mountains it's possible to come across grizzlies as I did once near the Selway river and I have seen them at a distance in Colorado.

I appreciate the response. I thought it wasn't an overly complex matter and will look for another smith.

Most that i've read about or chatted with were very happy with the performance of the AI over the standard 348, both from brass life as well as increased performance. I was reading P.O.'s book and he states its likely one of the most "improved" cartridges and his data suggest 300+fps gains if i remember correctly. It struck me as not just a 100 fps increase like you may see with others.
Will the 348 in its current state work, absolutely, but i'm intrigued i guess by the improved efficiency gain.

I didn't think about JES. He's done a couple rebores for me and they worked out well.

My AI feeds just fine. I cannot tell the difference between standard and AI in that department.

If you think you will shoot 250gr bullets, the AI can get you over 2,400 easily (mine is a 24").

The only thing that disappointed me about the AI was I HAD to trim cases back to the stated AI length to get them to feed through the gate, due to that fat shoulder.

I was hoping I could leave the necks a little longer. I am kind of a long neck guy.

So I took .0005" off the expander and use a Lee Factory Crimp die (I had to modify it to work on the shorter AI case). I also anneal the Starline cases prior to fireforming.

I have even been thinking about doing the AI treatment to a 26" barreled 30-30...but I have other 30 cal for that hot rod stuff! lol

300 FPS increase... hmmmm....

My M71 is a family inheritance, and I guess I don't see changes worthwhile... influenced by nothing around here that needs shooting with a .348 anyway. Doubly influenced by if there was, I have a family M70 in .338 WM too. Triply influenced by having a boatload of .348 bullets, 6 different brands/weights/styles I think, so I already have plenty of fodder for handloading experiments, without needing to change the case too.

Good luck with your project!

-Chris

I looked up what I read. The standard 348 with max load with 4064 of 58gr and 150gr bullet yielded 2835fps. AI chamber with max load of 67 gr 4064 with 150gr bullet was 3175.
The 250gr bullet went from 2150 fps to 2530. pretty substantial difference.

Those extra 300+ FPS are bought with much higher pressures not case shape or case capacity. What percentage larger case capacity it the AI version? I think that you might divide that percentage by 4 and that would be the percentage extra velocity you could get at the same pressure level.

I'd love to hear how it works out if you go that route.

Sounds right to me. I consider my M71 a 40,000 CUP (or whatever it was) system. 46K PSI, something like that? Don't really want to hot-rod the cartridge because of the rifle limitations.

Peaceman, what were pressures at those AI velocities?

-Chris

The book doesn't list pressures so I don't know.

OK, just for grins I did a quick check using QuickLoad and the two 150-grain loads you mention.

.348 MAP = 46,412 PSI

.348, 58 grains IMR 4064 with 150 grain bullet = max 41,669 PSI (well within MAP).

.348AI, 67 grain IMR 4064 with 150 grain bullet = max 55,891 PSI.

This was all fairly rudimentary, since I didn't have bullet info other than weight... so real info might give slightly more accurate results. (And I'm not a whiz with QL, anyway.) I didn't do the same check for the 250-grain bullets, only because I didn't have your powder charge weights.

-Chris