by Bmt85 » Wed Jan 22, 2020 5:08 pm
Have no personal experience with big bore's and poly lowers. I would recommend against it, though.
I do have experience with an NFA poly lower that I bought on sale to play with. It had a tight upper to lower fit that I tried remedying, worked ok. Had a snuggish fit, not tight. Ended up splitting the lower right at the seam (where the 2 molds met) in the front of the mag well. Didn't even put a round through the build. Plus, a lot of people end up snapping the receivers at the back corner when installing buffer tubes.
There are a couple poly lowers I would maybe try for an Ultralight .223 build. Honestly though, it will only save you a few ounces in the end. Comparing lightest poly lower's to lightest, non-magnesium lowers, you have the Tennessee Arms clear "ghost" lower at 3.6 ounces and V7 2055 at 6.4 ounces. So 2.8 ounces. Even though they are lighter and cheaper, I wouldn't say they are worth it, unless you are going all out, and can't strip anymore weight out of the build. Just for reference, the lightest .223 rifle builds I know of are something like 2.8lbs. They are also basically range toys the way they are built. Plus I don't think you would want to shoot 450B that weighs close to that, do you?