Ran the SLPs for about 2 years and they are a solid and reliable platform. For light birdshot, the recoil spring is a bit much for the first 1000 rounds or so. You can leave it locked open in the safe for a few months and that will help.
A few tricks...
Radius the shell extractor notch and chamber edge on the barrel, especially if you weld up the lifter.
Be gentle with the trigger pins as they can tend to open up a bit with many ins and outs.
Check for over-insertion of the magazine tube. If there is a sharp lip, then you can use a dremel to smooth it up.
Don't do the Surecycle. Beats up the gun too much after broken in and just overcomes the initial issue of the strong recoil spring. After 2K rounds or so, all of our SLPs would run light target 100%.
Sight acquisition and weight improvement by hacking off the rail if you don't want to run an optic.
Not better or worse than the M2, just different. However, the M4 and Versa-Max are at the top of the food chain.
Good Shooting, MarkCO
.40 S&W Club #1, 1911 Club #1067
NRA Life Member and Certified Instructor