I'm going to answer a slightly different question - mostly because I have no idea what product is least likely to melt under those conditions.
Because I believe chainfire protection is best derived from a properly fitting projectile, I think the chamber mouth grease should be one that is most effective in reducing or softening fouling. Bore Butter is high on the preferred list for that function. There are a number of homemade recipes here on the forum that also perform that task admirably. The fact that it might unseal is of secondary importance.
Because I believe chainfire protection is best derived from a properly fitting projectile, I think the chamber mouth grease should be one that is most effective in reducing or softening fouling. Bore Butter is high on the preferred list for that function. There are a number of homemade recipes here on the forum that also perform that task admirably. The fact that it might unseal is of secondary importance.