Stuck nipple

[LRP]

Purchased a used .50 caliber Lyman Great Plains.  The previous owner said to replace the nipple.  Purchased a nipple wrench, well he attempted to remove the nipple and it was so tight he rounded off one corner on the nipple.  The nipple is really tight.  Any suggestions on getting the nipple out.  The cleanout plug is also seized in place. 
LRP

[JimmyHoffa]

break free, torch, vice grips.  Maybe even drill out the old nipple.

[kerrdog]

even if you can't get the nipple out of the breech plug, you can still get a new breech plug with a new nipple. (I love that word. )  Use a socket wrench to remove it.  My breech plugs both use a 7/16 socket.  You can remove the barrel from the stock and run hot water over the breech end of it for a while; it will get nice and hot. You can do it! 

[ICEMAN]

Kroil.

[duckmen1]

Kroil.

That's what I use on anything stuck. That stuff is like magic

[Sagebrushwilly]

even if you can't get the nipple out of the breech plug, you can still get a new breech plug with a new nipple. (I love that word. )  Use a socket wrench to remove it.  My breech plugs both use a 7/16 socket.  You can remove the barrel from the stock and run hot water over the breech end of it for a while; it will get nice and hot. You can do it! 

The Lyman Great Plains is a side-lock rifle.  The nipple does not go into
the breech plug.  If you're going to offer advice, please know what you're
talking about.

[ICEMAN]

even if you can't get the nipple out of the breech plug, you can still get a new breech plug with a new nipple. (I love that word. )  Use a socket wrench to remove it.  My breech plugs both use a 7/16 socket.  You can remove the barrel from the stock and run hot water over the breech end of it for a while; it will get nice and hot. You can do it! 

The Lyman Great Plains is a side-lock rifle.  The nipple does not go into
the breech plug.  If you're going to offer advice, please know what you're
talking about.

Why get nasty? Ease up, folks are trying to help.

[Heredoggydoggy]

break free, torch, vice grips.  Maybe even drill out the old nipple.

Those nipples are really hard, so drilling it out might be difficult.  We had a hex-head cap screw that was so tight that the hex socket rounded out, so we ended up cutting a slot in the head with a Dremel, and using a straight screwdriver bit in an impact driver to get it loose.  Even then, it was a real bear to get loose... Kroil or Free on it overnight will do the most good.     I always remove the nipple(s) when I clean a blackpowder gun, and coat the threads on the nipples with automotive anti-sieze grease before reinstalling them.  It may sound like overkill, but it's not!

[scotty1969]

did you get it out?if not just take the barrel off heat the nipple up good and hot with a (brunson burner) that will make it grow then let it cool down slowly then try nipple wrench.when it cools it will shrink and should come outafter it cools you can even put lube on it.

[LRP]

Thank you much.  Will give it a try.  Sounds like heat and penetrating oils.   
LRP

[kerrdog]

even if you can't get the nipple out of the breech plug, you can still get a new breech plug with a new nipple. (I love that word. )  Use a socket wrench to remove it.  My breech plugs both use a 7/16 socket.  You can remove the barrel from the stock and run hot water over the breech end of it for a while; it will get nice and hot. You can do it! 

The Lyman Great Plains is a side-lock rifle.  The nipple does not go into
the breech plug.  If you're going to offer advice, please know what you're
talking about.

  You're obviously much more knowledgeable and intelligent than me.  Forgive me.

[usmc74]

The nipple on a GPR is metric .75 x 6 mm.  Harder to find than a 1.0 x 6 that a CVA uses

Kroil is great stuff!

[LRP]

Had not heard of Kroil.  Buying it now, have replacement nipples.  They came with the muzzleloader.
Thank you all,  much appreciated.
LRP