I am considering having a 1911 built. Can anyone speak to the relative merits/demerits of the 40cal/357sig in the 1911 frame. I own two 1911s now both in the traditional 45cal. Any help would be appreiated.
Either one should work fine, especially in a custom built 1911. 10mm, .40S&W and .357 Sig are all interchangeable on 1911s built for any of the three with a barrel swap (and heavier spring for 10mm). I think the magazine is the same for all 3 too. In my experience 10mm and .357 Sig seem to be somewhat more accurate than .40S&W, though I won't pretend to have a good explanation for this.
From a 5" barrel any of the 3 will have good ballistics, though of course 10mm has potentially the best. .40S&W will be the most economical of the 3 ammo-wise, but the difference isn't that big if you shop around. Recoil should be no drama for any of them; even a 10mm Delta Elite has quite reasonable recoil. For self-defense against people all 3 are as good as anything else, but the 10mm also has loads better suited to hunting.
My choice would be to go with the 10mm and load it down to .40 *&* velocity. That way you always have the possibility of using the very potent full power 10mm ammo in case of bear attack or some other nasty situation.
The only negative is that you won't find free 10mm brass lying on the ground at your range unless you are very lucky.
If you're going to build it, I figure one has the $$$. Get all three barrels. The 40 will work in the 10mm, but if I recall, I have seen 40 cal 1911 mags advertised, so there is a difference.
Don't download too much in the 10mm case. If there isn't enough power, there might be an accident.
If one is looking for 10mm brass, I've seen some on Gunbroker.com and ebang.com. Check under the user name: unique_reloader
I've bought some brass from this person, 100rnds for under 10 shipped. I could have spent 6 more to get new brass (16.00 @ my local shop).
I've heard that full power 10mm loads in the 1911 will have bad effects over time. Something about cracks forming iswhat I read before (might have been here too.) Pressures a 10mm operate at are much higher then the old war horse 45 ACP.