Buddy bought Baer frames from Brownell's. A standard 1911 mainspring will not line up with the pin hole in the frame. What is going on here. Has Baer modied his frame so only a Baer mainspring housing will work?
I put an S&A arched msh in my Monolith. It had a bit too much metal that I had to smooth down to get a perfect fit. I think some of the drop in parts may have a bit too much metal and benefit from a bit of cleaning up.
I think Baer uses a little tighter tolerances on everything. I have noticed this in nearly all parts. I didn't care for the aggressive checkering on the TRS msh, so went to a EB chainlink. I had to do more than a little fitting on a part that is almost always "drop in". The same for the mag release. I like the slightly extended EB unit that I put on all of my guns. I have never had to substantially fit this part either. The Baer frame cutout is significantly smaller than the mil-spec. Sight dovetails a few thous smaller, too, as is documented. His guns are known to be tight, and I think he probably squeezes the tolerances on all the dimensions a bit.
All of the components on LBC pistols are fit together by hand. This includes the Mainspring housing. After the housing is fit into the frame the bottom of the housing and the frame are matched together for a flush fit. I think you will always have trouble fitting "Drop in Parts" to custom guns no matter the Manufacturer. Also be sure to check the Mainspring Housing, it may be the problem not the frame.
The mainspring housing in question fits Colt and Wilson 1911s... I am looking forward to seeing the Baer frames in question myself. The gunsmith is literally disgusted with the overall condition of the frames. Says that there isn't a pin hole in the frame that doesn't have a burr....
I've installed Wilson mainspring housings in 2 of my 3 Baer's. In both cases, I had to do quite of fitting to get them on. I like the Wilson 20 X 30 mainspring housings and have installed them on most of my 1911's. The Baers are the only guns where they haven't been a drop in fit.