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Nipple bore diameter.

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Grantmac

32 Cal
Joined
Dec 12, 2021
Messages
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I have an older Investarms Ransom .50 which was my first BP.
The nipple that came on it was worn out, blowing back to half cock with a pretty mild charge and the accuracy left much to be desired.
Changed for a new Ox-yoke stainless, groups much improved (1-1.5" at 50) but ignition is inconsistent at best. The bore on the new nipple is smaller than any of my other BP guns. When snapping a cap it won't produce any sort of report at the muzzle. Even a loose patch placed there won't move. When I can off other guns they'll knock the patch out no problem.

I have precision number drills. Should I take the diameter out a bit? Cone the bottom?
 
I have an older Investarms Ransom .50 which was my first BP.
The nipple that came on it was worn out, blowing back to half cock with a pretty mild charge and the accuracy left much to be desired.
Changed for a new Ox-yoke stainless, groups much improved (1-1.5" at 50) but ignition is inconsistent at best. The bore on the new nipple is smaller than any of my other BP guns. When snapping a cap it won't produce any sort of report at the muzzle. Even a loose patch placed there won't move. When I can off other guns they'll knock the patch out no problem.

I have precision number drills. Should I take the diameter out a bit? Cone the bottom?
Are you sure the flame channel through the breech is clean, clear and DRY? You may want to put a patch over your clean jag and run it all way down the bore, then fire off a cap. When you remove the patch, you should see evidence whether or not the fire channel is open.

You mention that the orifice in the new nipple is smaller than any of your other BP gun’s nipples. Are you using blackpowder or a sub? Subs are more difficult to ignite than blackpowder, and there are a couple of nipple designs out there to help with the subs. I have found that a .028” diameter to about .036” max works best for me shooting paperpatched conicals over blackpowder before accuracy starts to go away.
 
I'm confident that the channel is clear since I was able to pass a pipe cleaner through it. I haven't tried removing the clean out screw on this breach yet, it's a tiny setscrew that I don't want to strip.

Using Goex 2F and switching to 3F once that jug is gone. PRB .490 with a 0.12 patch using either spit or windshield washer fluid.
 
Take the nipple off and hold it up to the light, you should be able to see daylight. If not, get a nipple pick or small pin to clear the nipple.
 
Compare the length of the thread journal to the original to make sure the new one is not getting too close to bottom of channel.
Depending on grade of metal you may find it difficult to drill with such a tiny bit.
If the thread journal length is good you might but if the metal is too hard you might try a welding tip cleaner and lap it. But just getting another saves a lot of hassle.
Know the issues with ff. Had periodic issues with Pyrodex RS. Switched to Pyrodex P and it went away.
 
Pipe cleaner runs into the bore no problem and nipple has the same threaded length as the breach as close as I can measure.

This rifle is rough near the breach end so it might be holding moisture in those pits. I'll run some isopropyl and a dry patch before shooting next time (usually just dry patch). Then try dribbling a little powder in before capping it off for the day.
 
Do you have access to a borescope? May help you figure out what is going on.

To me, from what has been stated, first guess would be a buildup of oil and powder residue in the breech and/or fire channel. Ignite blackpowder in the presence of any gun oil and the product is a hard tar like substance that is tough to clean and will build up over time. Eventually it will start to cause ignition problems and only gets worse over time if not resolved. I have seen this play out more than once. If you have to put powder under the nipple you are just working around the problem, not correcting it.
 
I've had an automotive scope down it, that's how I found it's quite pitted on the breach end. Can't see around corners with that though.
Maybe I'll see if I can get the clean out screw free.
 
I've had an automotive scope down it, that's how I found it's quite pitted on the breach end. Can't see around corners with that though.
Maybe I'll see if I can get the clean out screw free.
Here are a few photographs from an Investarm breech I took a while back. Basically a hard 90° turn from the sub-bore chamber to the fire channel, as opposed to the angled fire channel found on TC guns. Idea works, but any obstruction in the fire channel keeps powder separated from the percussion cap blast.
1640146559797.jpeg
1640146581977.jpeg

The so called ‘clean out’ screw is really there as part of the manufacturing process, and not really designed or intended to be a clean out. There are plenty of buggered up ‘clean out’ screws, particularly if not frequently removed as part of a maintenance regiment. Just do a search on the forum if interested in reading about.
 
I have precision number drills. Should I take the diameter out a bit? Cone the bottom?
Just sharing,
In my experience. "Modifying" a nipple (any factory nipple) by it's design renders mute results.
Those things are designed in tube diameter/shape and orifice size for a particular reason, be-it patent issues or a "new improved" characteristic.

You can Drill, shape and cut, anyway you want, but doing that comes with the knowledge that you did modify it.
I have found that experimenting with different manufacturers nipple, and finding one that suits my individual loading technique and load combo has been more successful than jimmying-up an over the counter design.
That said, I haven't touched an Ox-Yoke nipple for any gun for decades.
Knight Red Hot, rules!!
 
I'm confident that the channel is clear since I was able to pass a pipe cleaner through it. I haven't tried removing the clean out screw on this breach yet, it's a tiny setscrew that I don't want to strip.

Using Goex 2F and switching to 3F once that jug is gone. PRB .490 with a 0.12 patch using either spit or windshield washer fluid.
3F will help a lot in the calibers 54 and under.
Another thing that will help (a lot) is to give the gun a couple of thumps with the heal of your hand in the lock area to "shake" the powder into the flame channel.
Seems silly, but it works!
 
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