I usually use Kroil or (horrors!) WD-40 on machinery but happened on a mostly empty can of PB Blaster. Worked better than I thought it would. Can emptied before I got much experience but worth a try. Have had occasional luck with VonGruff's tap method. And on rare occasions torque in the tighten direction first to break the threads loose.
And think pure thoughts - good vibes you know.
marko - I heat wherever the torch reaches. Just want it warm enough to assist the penetrating oil to penetrate and soften any threadlocker which, in the case of a Springfield, might be linseed oil. Like to 200F or so which won't affect temper on any steel. Any steel not exotic of whatever temper can handle 400F or so without changing its structure. The hot wrench technique is to heat the hole part really hot to expand that part enough to break rust and loosen the fit a bit. For big stuff unaffected by red heat.
