Can I just unscrew one and screw another on if I want one rifle to cover two s/a calibres. 243/308.
Can you please tell me the pitfalls in such an idea? I would only envisage swapping them twice a year or so.

It can be done providing both barrel headspace correctly for your action. If you are talking factory barrels then it is a little more difficult if you want the sights/caliber designation in the correct spot. Plus you will need a action wrench, barrel vise, and either a pinned recoil lug or something to hold it straight when the barrel is tightened (they make tools for this). Other than not being able to use both at the same time and having to rezero after the change there isn't any other pitfalls that I can think of.

Thanks for the reassurance. What's a pinned recoil lug ? Should I keep a recoil lug in position on each barrel?-is that a pinned lug? If it's a new Rem. factory barrel, and I'm not concerned about calibre stamp or final position of any sight screws. I can just screw it on tight and headspace will be OK? (in all probability)

With a pinned recoil lug what they do is drill through the recoil lug and into the action. Then a tight fitting pin is put in the hole. This effectively keeps the recoil lug in the same place every time a barrel is remove and then replaced.

Not all barrels will headspace correctly on all actions but I would guess the odds of one headspacing correctly is close to 80% (At least that has been my experience).

Based on Precision Shooting articles and follow-up phone calls to discuss...

Norman Johnson has been playing with Remington 700 and Remington 40X actions and Remington barrels for over twenty years. Think he has done over a hundred factory barrels so far. So far, every barrel has been within go/no-go gauges headspace tolerances.

Hammer

And you don't need to pin your barrel, especially if your gun is glass-bedded.

Sit the action and recoil lug in the stock. Then hand screw the barrel in 'til its shoulder stops against the recoil lug. Then remove now-barreled action from stock and tighten to the extent you believe necessary. Personally, I use 23 foot pounds. Nothing special about that figure...it is just the weight of one "pig" of linotype hung on the end of the 1-foot long action wrench handle.

I have 7 different switch-barrel rifles, and this process works on all of them.

Incidentally, one of them I put a factory take-off sporter barrel in 7 m/m WBY Mag on, and put it in a factory take-off composite sporter stock. Barrel and stock cost me $50 each, new. It is capable of shooting genuine half-inch 100-yard 5-shot groups from the bench with Hornady 162 gr. match bullets. Not every group, but often enough to please me. Action is a first-year-of-production goodie, originally in 7 m/m Rem Mag (which wouldn't shoot anywhere near even 1" groups...go figger...)

AC