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Jonathon Browning Mountain Rifle Mainspring

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My second post (just joined) was going to be about those springs. I have a JBMR on the way, and I will need to take it apart to remediate some rust. I ordered one of those springs, and I see the seller has some other JBMR parts as well.

How is the quality of the spring? Would it be worth taking the original off, putting the repro on for shooting and keeping the original for a "rainy day"? What's the best way to remove/replace the mainspring to not damage the spring?
 
My second post (just joined) was going to be about those springs. I have a JBMR on the way, and I will need to take it apart to remediate some rust. I ordered one of those springs, and I see the seller has some other JBMR parts as well.

How is the quality of the spring? Would it be worth taking the original off, putting the repro on for shooting and keeping the original for a "rainy day"? What's the best way to remove/replace the mainspring to not damage the spring?
They look good. I think they may be new old stock.

BI
 
I really like that rifle. Have two, a .50 and a 54 cal. The .50 was purchased this year, unfired! It's not unfired anymore! :)

BI

Mine is a .50, what loading do you shoot? I have some Pyrodex RS but no round balls or patches (I bought a coworker's inline Knights and it came with Pyrodex pellets, RS, and sabots) - so I need some balls and patches. How about conicals?
 
Mine is a .50, what loading do you shoot? I have some Pyrodex RS but no round balls or patches (I bought a coworker's inline Knights and it came with Pyrodex pellets, RS, and sabots) - so I need some balls and patches. How about conicals?
The Pyrodex will work, I most often use 2 FG Black or T 7. It probably won't be the best with conicals. It has a slow round ball twist but it won't hurt to try. My .50 is very accurate with 70 grains of Black 2FG. a over powder wad, and a patched .490 RB with a 15 thousandths patch. A .495 and a 10 thousandths patch works too. The over powder wad makes a big difference in accuracy.

BI
 
The rifle has a patent breach so you need to make sure you clean the breach channel too after shooting. I use a .30 cal brush with a patch on it. This is a less than bore diameter channel in the breach.

BI
JBMR Lock.jpg

Picture from the auction, there is rust from lack of cleaning around the nipple and drum. The screw looks like it hasn't been removed before, so I may have to take the nipple out and put some Kroil in there for a little while. I have some Birchwood Casey Plum Brown, so I think it will cover any bare metal that I end up with after cleaning this mess up.
 
View attachment 257750
Picture from the auction, there is rust from lack of cleaning around the nipple and drum. The screw looks like it hasn't been removed before, so I may have to take the nipple out and put some Kroil in there for a little while. I have some Birchwood Casey Plum Brown, so I think it will cover any bare metal that I end up with after cleaning this mess up.
The bore probably needs some work too by the looks of the nipple and drum. I would give the bore a good cleaning with Ballistol and a brass brush then patches and more Ballistol.

BI
 
Mine is a .50, what loading do you shoot? I have some Pyrodex RS but no round balls or patches (I bought a coworker's inline Knights and it came with Pyrodex pellets, RS, and sabots) - so I need some balls and patches. How about conicals?
Don't frustrate yourself trying to use pellets in a side lock. Tried it once on a TC Hawken. Didn't work well. Didn't work on the Scout inline either.
 
Don't frustrate yourself trying to use pellets in a side lock. Tried it once on a TC Hawken. Didn't work well. Didn't work on the Scout inline either.
I can see that being an issue on a sidelock. The 44 caliber ones work great in my Remington NMW clone because it is a short direct path from the cap to the hollow center of the pellet.
 
Thanks, I ordered a couple. If you dry fire a JBMR, the spring will break, sometimes.
I don't dry fire...
Definitely not a good idea to dry fire any percussion gun. I once had a ASM Walker clone that had never been shot but obviously "played with" as the nipple was flattened out and the hammer had a ring worn into it.
 
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.
 
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