Jonathon Browning Mountain Rifle Mainspring

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What’s the going rate for one of these rifles?
I have the opportunity to grab one but $675 seems a little high.
 
Probably the best factory made ML you can own. Well worth $675
The only drawback is they are slightly heavier than most others
 
Great Rifles, they set standard when they were introduced. My iron mounted .50 is the heaviest rifle I my collection.
 
I got my extra mainspring in last week, and my JBMR finally made it in today. I took it as far down as I could (the nipple is seized, going to get my Kroil and let it soak) - the mainspring is very thick and hefty on this gun. Looking at the two springs, the replacement is identical to the original down to a pressed indention on the side.

I fired two caps, and the channel is clear as it will blow a pile of leaves on the ground away. There was a little more corrosion around the drum than the picture shows but I spent the afternoon polishing up the brass, taking the lock apart and cleaning/lubricating it, and going through everything. I have two stainless 1/4-28 nipples on the way.
I would heat up the nipple after the Kroil works for a while. It should come out then. :)
 
I would heat up the nipple after the Kroil works for a while. It should come out then. :)

Three days of Kroil and it came out without a hitch. The channel and bore are clear. I took a file and worked on the flats followed by 240 grit sand paper, and plum browned where I had bright metal. It turned out pretty good
IMG_20231014_174849068.jpg
 
Here is the before picture, someone had tried to take the breech plug out not knowing it was silver soldered in. This picture was somewhat flattering, the rounding looked worse in person.
JBMRlock.jpg
 
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