Do some research, there was a batch of about 10K H&R's about 3-4 years ago that had this issue. It's pretty widely publicized.
I will say, I've run two boxes of ammo on my .35 and it hasn't experienced any of it, same for the 45/70 I bought in 2011. However, my dad had a 45/70 buffalo a few years ago that had to be sent back right out the box.
re: Problem with a 444 Marlin not firing?(Posted by gmshooter on 12/7/12 at 8:19 am to Junior23)
bad hammer springs. like some have said before there were some bad batches that were installed. i have had them come back in the .35,.444,and 45/70. Call h&r (remington) and have them send you a ups label to return it. i have had these guns go thru a couple of boxes of shells before they started misfiring.