OK, I'll bite.
Dave Tooley, biffj, and others covered the technical part quite well already. The following should concisely sum it all up (including practical recommendations), I hope.
I like the idea of picking up a rifle that's ready to fire at the distance I sighted it in at. The switch barrel feature means re-adjusting the scope for zero whenever you change calibers.
Yes. Each barrel has its own zero - so while you don't need to re-zero, you have to adjust the scope or keep track of the difference. I'm doing this, and it's not a big deal for me.
If it is for you - stay away from switch barrel systems.
And there's just no way a switch barrel system will hold its zero the way a fixed barrel rifle will.
Correct. However the difference (in good systems like AX and DTA) is far smaller than a good shooter could observe or be affected by. In other words, this difference does not cross from the realm of theory to the real world (where the rifle itself prints inside 0.5 MOA, not inside 0.01 MOA), and does not affect the
practical accuracy (as observed and reported by good shooters here on SH).
I haven't seen you shoot, but it is unlikely that in this life you'd outshoot either AX or DTA accuracy-wise, switch-barrel or not. On the other hand, if a sub-half-MOA switch barrel isn't accurate enough for you - by all means go buy or build a more precise rifle that's not a switch barrel system.
The total cost for the chassis with two different barrels really isn't that much less than 2 rifles.
Depends on the rifles. Do they have to be reliable and able to function in tough environments, like AX? If so, it would cost you extra. I seem to recall you asking about AR-30 in 338LM, and got back the cost of TRG42 around $3500, AWSM around $4000-$5000, AX 338 around $6850... Now double or triple this, and tell me that one chassis and two or three barrels "aren't much less" than $8000-$15000 (two or three systems). And we haven't addressed the scope issue yet - how many scopes are you planning to put on your multiple rifles, and how much would each of them cost? If your goal is "exacting accuracy" you can't settle for a cheap junk-scope, and good glass costs an arm and a leg, as I'm sure you know. If you plan to move one good scope between the rifles and re-zero (for your own logic assures/asserts that nothing can maintain its zero when moved
), then why is it any better than the absolute worst case with switch barrel (when for whatever reason you have to re-zero)?
In any case, to each his own. If you'd rather deal with several rifles each in its own caliber, and think it wouldn't cost much more dough that way - it suits me just fine. Go for it. Here's another advantage of keeping multiple rifles: you can lend one to your neighbor and still have something to shoot with.
Its a neat gadget, but doesn't lend itself to the reason I buy a rifle - extreme, exacting repeatable accuracy on the spot.
"Extreme, exacting, repeatable accuracy on the spot" is exactly what I am getting from my DTA. I concede that switch barrel or not - I cannot outshoot it.
But you convinced me - you don't need a switch barrel rifle. Go and buy a set of individual chassis for each caliber and barrel length you want to use.
My intended application would be 6.5CM (out to 1000, zeroed at 200) and 338 ( out to 1 mile, zeroed at 500)
My ballistic calculator says at 500 there's over 5" difference in drop btwn the 338 and 6.5CM. At 1000, its 2 feet. Knowing me, I'd forget which barrel I got the scope dialed for, and being 5" to 2 feet off is too much for me. I'm a simple man...
In that case absolutely stay away from switch barrel systems, they are bound to be too complicated for you.
I shudder to think what it must take to keep track of the dope for each load in each caliber for each rifle.
Of course for those of us who thrive on difficulties, scope adjustment is a part of the caliber switch procedure: replace the bolt, replace the barrel, re-torque the holding screws, adjust the scope for the new caliber. Like a checklist: a new barrel gets in - the scope gets adjusted, right then and there.
