To be clear, your bullets are not sticking in the rifling, they are sticking in the chamber throat?
In an AR type rifle.
A gas operated rifle designed to shoot jacketed bullets....
And, you're doing what the books say you should do with lead bullets, .001" over bore diameter, so the rifling gets a good grip.
And your bullets stick in the chamber...
Is that about right?
the first thing to try is to use smaller diameter bullets. Jacketed .458 is what its made for. Lead and coated or plated probably can be used, but some adjustment to the normal loading practices due to your rifle's characteristics may be needed.
Just did some checking with a friend who had a .458 SOCOM upper (though not the brand you mention) and he recalls that the owner's manual said it wasn't a good idea to use cast bullets. The didn't expressly prohibit them, but they recommended they not be used.
These guns are made for jacketed bullets and because of that they are "tight". It's normal. Also, ARs are not very cast bullet friendly. Extra care and inspection is needed to ensure they don't clog the gas system.
Also, full Socom speeds are in the upper range of cast bullet speed, not the very top end but in the range where extra care is needed to ensure the proper alloy and sizing for the 18-1900fps speed. Get something just a bit "off" and you can get leading, and/or poor accuracy from bullets stripping in the rifling. reduced loads can solve some of that, but then you have issues with the rifle cycling. Its a balancing act between several different factors. Get things right, they work, but get one thing a little off, and you'll probably be unhappy with the results.
I'd shoot jacketed bullets in that gun. If you're determined to use the cast bullets you have, I'd size some to .458 and then see if they perform properly or have issues before doing all of them up as loaded ammo.
Be aware that there are some combinations that just won't work well together no matter what you do, and be open to selling or trading stuff that proves it just won't work as well as you want. Someone else, doing something else will be happy to be able to get what you can't use.