My father-in-law gave me a cva staghorn that he has not shot since 2000. I can't get the breech plug to move need suggestions on removing it and where to get new bolt/striker

Welcome to the forum.

You can do a search as this topic has come up many times and there is lot's of advice in previous threads.

My first start ( after making sure it's not loaded ) would be to submerge it in boiling water, heat it up and then, place it in a vise for a good twist.

Welcome to the forum.

Take the barrel out of the stock. On the bottom is the lug that supports the barrel. As mentioned.. put the breech plug in boiling water (not loaded) and get it real hot. A little dish soap in the water will help. Wear leather gloves as this barrel will get hot.

With the correct breech plug removal tool (My Staghorn had the slot head) when the barrel is hot, put that lug in a vice, it does not hurt to wrap that in leather or something to protect it from the jaws of the vice. Then with the tool in place and a pry mechanisom, tap that plug tool a little to shock the breech plug. Then apply steady pressure and normally they will turn out.

If that fails, take a spent 209 primer and put that in the plug. Then tape over that 209 and fill the barrel deeper then the plug with penetrating oil such as Marvel, Liquid Wrench, Kroll Oil, and let it sit... Normally over night.

The next morning dump the oil first to avoid a mess and again, with the vice, the tool, a some tapping, and steady pressure. When you get it loose, be very sure to check and clean the threads of the plug and the rifle with a good brush.

If its been in that long and what Cayugad suggested does not work then pour the barrel full of Evapo Rust [available at the auto parts store] and leave it for 24 hours.
If the problem is from 777 or Pyrodex the hot water may be all you need but if it is rust in it may be that you have to alternate the treatments.

Is it threaded clockwise or counterclockwise

the breechplug is a "bolt" and the rear of the barrel is the nut. Righty tighty, lefty loosey.

Or, when viewed from behind, turning it clockwise tightens, counterclockwise loosens.

Here are a couple of the others..

http://www.huntingnet.com/forum/blac...-any-help.html

http://www.huntingnet.com/forum/blac...eech-plug.html

...............get you some pb blaster spray and pray it down the barrel wait 5 minites then try to get it out.......when you put it back in get you some breech plug grease and put on threads and just snug it up dont over do it.