Have a few boxes worth of PMC FMJ 6.5X55. Looks like 160 grain bullets. I tried firing them in my Tweed and after two attempts the primers were severly dented but no bang. Just tried this on two cartridges and then quit. Other commercial ammo fires fine. What can I do with this ammo short of throwing it in the ditch? Thanks in advance.

Pull it down, reprime the cases, fire away.

Try one or two more rounds. Looks like a defective lot. You can pull the bullets. dump the powder, then snap all the primers in your rifle. Once you have done that, reload with fresh primers and the same powder and charge weight. I hesitate to recommend decapping live primers. If you do, be sure to wear safety glasses.