shot these out of my knight mk-85 100 grain pyrodex rs with a 250 grain xtp and a horady sabot winchester 209.........this is the first time i'
ve tried the 209's

gun shot very well,at 50 yards i didn't clean the bore because i forgot my patches at home....but i didn't think the primers would look like these the 3rd shot the primer popped out alittle the top one is my first shot bottom one my last

I wouldnt call that over pressure, just a typical slam fire type of rifle that doesnt hold the primer in place very snug. Some break actions today have loose " head space" and shoot the primer back into the action and they get stuck.

If this just started I would check the flame hole in the BP for size, they do burn out and will cause more pressure on the primer.

On Ebay, I saw a replacement Knight breech plug that I think was said to be a 2nd generation breech plug that was vented for the earlier model Knight rifles.
I was looking because I just picked up a Knight that also uses those full plastic jackets.

oh ok i just switched from the 11 cap to the 209 so the bp is new , my other 209 guns is a black diamond and it's got a very different nipple and i got a knight disk and i didn't remember the primers looking popped out......hope to shoot the mk-85 at 100 yards tomorrow. I'll remember my patches i hope this time lol

i had to take the trigger off to get the tool in to take the breach plug out. the last shot the primer part got stuck in the top of the trigger part that has to lower to get the tool in.

i got some federal 209a primers i'll try a few of them there a hotter primer than the win 209's