Lil'Gun damages your forcing cone:
Bob Baker’s, from Freedom Arms, comment from a quote in an older post from the Ruger Forum.
https://www.rugerforum.net/threads/lil-gun-erosion-in-rifles.360363/
Direct links seem to all be dead.
"We have seen numerous barrels damaged by using Lil Gun. According to customers, some had as few as 30 rounds using Lil Gun through them, some had several hundred. Before we figured out what was happening one customer had sent his gun in for a new barrel. Then 600 rounds later it came back for another new barrel.
A couple years ago we did a test with a M83, .357 Mag. using Hornady 180 gr. bullets. We loaded 50 rds. of three different loads. One was a heavy H-110 load and the other two both used Lil Gun in different quantities.
We fired the H-110 loads first, then cut off the threaded end of the barrel. Rethreaded the barrel and shot one of the Lil Gun loads then rethreaded the barrel and shot the last Lil Gun load.
We found even the light load of Lil Gun caused the gun to get extremely hot. The heavy Lil Gun load had the gun so hot the only place we could touch the gun was on the grips and they were very hot.
Under magnification the surface appeared to have heated to a point of flowing using the Lil Gun loads and the heavy load was worse than the light load. This is probably due to Lil Gun having about 10% more nitro glycerin in it than H-110.
Yes it applies to the .475 also. I intentionally ran the tests with a cartridge that is less pressure than the 454 just to make sure.
I have also heard of problems with rifles but I haven't tried to verify it by running my own tests."