Alas, that is so not true. One of the ideosyncracies of the M14 platform is that USGI barrels are way long in headspace. 7.62-MM ammunition has the same cartridge headspace dimension as SAAMI .308 Winchester, but USGI mlitary 7.62-MM chambers can be waaay longer than SAAMI .308 No-Go. So, what's a poor commercial M14-type receiver manfacturer to do? Alter the receiver face location so as to acommodate USGI barrels? But, that will allow the bolt to interfere with the rear of the barrel?at least in many cases.I'll assume that at the point it clocks right it also head spaces
With a commercial barrel the procedure is this. First, lap in the bolt lugs so that both are bearing evenly and completely. Next, install a short-chambered barrel that will clock at 7:00-7:30 (the position of the web between the feed ramps at the bottom of the chamber) when hand-tight. Torque the barrel to alignment. Finally, finish headspace. This will ensure that the bolt, receiver, and barrel are in the proper longitudinal positional relationships, with "good" headspace.
(For those who wonder how to final-chamber with the barrel installed, there are pull-through reamers. Even better, in the books below we show how to finish ream for proper headspace with the barrel off the receiver such that when you install, torque & align you have "good" headspace. It's a neat trick.)
Please consider this: we want the barrel to be in the design position with regard to the receiver, regardless of how we get there. The procedure that has stood the test of time is peening/rolling, as what we're really doing is getting the "crush" back (or creating some if we never had it). We end up with the barrel in the place God & Garand intended.
When you're starting with a USGI barrel and commercial receiver, UGH! Commercial receivers vary widely in their face positions, even from the same manufacturer over time (S, Inc. is notorious for tool creep). Even the best non-GI receivers currently available, from Norinco/Polytech rifles, have an oddball bolt-barrel relationship. Generally you need to replace the barrel when you replace the bolt (the bolts are not serviceable and must be replaced), because the Norinco/Polytech barrel was dimensioned for the oddbal N/P bolt. If you can manage to fit a USGI bolt with the N/P barrel, you generally end up with short headspace. The N/P barrels are chrome lined, so you aren't going to finish-ream them. Unlike the Garand, you're not dealing with a military standard when you're working with M14-type barrels. We aren't working on our own receiver just for the fun of it. Doing it ourselves is the only way we can get consistenly good recievers on which to build rifles.
To reiterate, it may just be possible to get away with shimming the barrel. I don't think so. I'm just intent on doing my best to help folks understand the ramifications of going that direction so that they can make informed choices. Believe me, if shimming were the way to go, USGI and civilian armorers would have been doing it for the last fifty years instead of getting out the hammer. Shimming would have been so much easier.