misfires

[BillH]

I have a Marlin 81-DL (probably 1940's vintage, based on stock design) and a Glenfield model 25 (1977). Both are accurate shooting rifles and in good shape. The problem with both is falure to fire at times, more so with the 81, about 3 out of 10 ftf with modern ammo. I have tried three different firing pins and a new striker. The mainspring is strong. I am beginning to think that it may be that maybe something has changed with .22 ammo over the years, possibly the type of metal used in the cases. I have some boxes of Remington ammo that my dad bought back in the late 1960's (he used to write the year on the boxes), and that seems to be much more consistant in firing, and shows deeper firing pin indentation. The only problem is that the supply of the old stuff is getting limited. Has anyone else had similar experience, and if so, what modern ammo seems to be the best in the older rifles?