Barrel Choke Point & Nipple Threads

[bkisel]

Hi Guys,

Finally got to shoot my T/C PA Hunter yesterday and now have two questions to ask you ...

1) After starting my bullets they would ram smoothly down the bore until about an inch or two before seating on the powder where they would meet some additional resistance. I'm refering to this as a choke point, it wasn't a lot either in terms of resitance or length but was definately noticable. Felt it for both PRB and the Hornady PA Hunter slow twist conicals (short 240 grain 1/2 conicals simular to Buffalo Ball-ets)that I was loading. Groups seemed OK to me for first time out with a BP rifle. Is this barrel choke point normal? Is it part of the barrel design or do I have some sort of problem. Choke point was not noticeable when just running cleaning patches down the bore.

2) When replacing the nipple after cleaning the rifle should I be putting something on the nipple threads or is leaving them dry OK.

Thanks ...

 

[thewho66]

I had the same problem with a T/C hawkin in .50, but mine started about 3 inchs from the muzzle. It shot great never really had a problem. As to what it is someone at my club thinks that the rifling cutter was changes and that made the bore tighter there hope someone else has another idea. As far as the nipples go I put a little bore butter on the threads, It will make it easier to remove if needed. another way to look at it is another club member didnt put anything on and it took him 30 minutes to get it off when he dry balled it.

John

 

[paulvallandigham]

Last first:

When replaceing the nipple, put a small drop of oil on the threads inside the bolster, or breech, and another small drop on the threads of the nipple. That keeps them moving well against each other, rather than galling or rubbing together to wear the threads.

The choke is not normal. I am suspecting that there is some lead or crud build-up where you are seating the PRB and the lubed conicals. Use a good lead solvent on the barrel, AFTER first cleaning it with soap and water to remove any water soluable residue. Then go at it with a brush, ( bore brush) and cleaning patches over the brush, dipped in solvent.

Consider this. Most replica BP revolvers have two choke points: The first is at the front of each chamber, where the diameter of the throat of the chamber may be much smaller than the bore diameter of the barrel. This means that the ball leaving the chamber is smaller than the bore diameter of the barrel, and will be rattling down the barrel, instead of grabbing the lands a grooves to be properly spun before it leaves the short barrel. The other choke point is at the rear of the barrel, where the barrel is screwed into the frame, or the forward portion of the frame. Often those points will be tighter, or measure smaller than the Bore diameter. So, even if the chamber throats are reamed out to a proper matching diameter, if this constriction where the barrel is threaded into the frame is not removed, the ball has to be squeezed down to get through that tight spot, and THEN rattles down the barrel, with gases blowing by, cutting the lead, or melting part of the ball, all contributing to inaccuracy.

When you put a constricted area at the Rear of the Barrel, you are creating the same condition in a rifle or smoothbore.

Target shooters often choke the front of their muzzles, and taper the bores from large to small- a difference of only a few thousandths of an inch over the length of the barrel-- to improve accuracy. The theory is that as the ball moves out the barrel, the choking taper keeps increasing pressure on the Patch and ball so that gases don't blow by, or in conical barrels, the lead that is slowly rubbed off is off-set by the smaller diameter of the barrel along the length of the barrel.

 

[roundball]

Hi Guys,

Finally got to shoot my T/C PA Hunter yesterday and now have two questions to ask you ...

1) After starting my bullets they would ram smoothly down the bore until about an inch or two before seating on the powder where they would meet some additional resistance. I'm refering to this as a choke point, it wasn't a lot either in terms of resitance or length but was definately noticable. Felt it for both PRB and the Hornady PA Hunter slow twist conicals (short 240 grain 1/2 conicals simular to Buffalo Ball-ets)that I was loading. Groups seemed OK to me for first time out with a BP rifle. Is this barrel choke point normal? Is it part of the barrel design or do I have some sort of problem. Choke point was not noticeable when just running cleaning patches down the bore.

First seating in a clean bore or after being fired? Sounds like a crud ring buildup where the powder ignition occurs.
What kind of powder & lube are you using?

2) When replacing the nipple after cleaning the rifle should I be putting something on the nipple threads or is leaving them dry OK.

I believe something should always be used...I always just packed the nipple threads with Natural Lube 1000 before screwing them back in...now I do the same thing with vent liners on my Flintlocks...

 

[roundball]

"...someone at my club thinks that the rifling cutter was changes and that made the bore tighter there..."

Actually, TC barrels are "button rifled"...a bore size steel slug (button) with raised studs around it is pushed through the barrel with a hydraulic ram and the studs actually compress the steel to make the grooves...doubt seriously they would stop and change the 'button' in the middle of a pass through a barrel.

 

[mykeal]

Paul and Roundball hit the tack, right in the middle on both points. I use Gorilla Grease as an anti-seize on all gun threads; the material isn't as important as just using something other than leaving the threads dry.

 

[Jerry Coffee]

I too use Gorilla Grease but very sparingly especially on the nipple threads and other threads as well. I don't know for sure what the composition of GG is but it is likely graphite-moly lube. GG comes in a small tin about the size of a silver dollar and even that small amount will last a long time.

You don't need to tighten the nipple in the bolster only a little more than finger tight or you can strip the threads in the bolster. Nipples are notorious about not fitting the threads properly. They have either too much threads or not enough threads to seat properly.

I was looking for some spare steel nipples for my P53 Enfield rifle musket and it took me a half-dozen 5/16"-18 nipple purchases from six different suppliers until I found one that fit correctly. I found the correct nipple at Dixie Gun Works. I purchased six DGW NP1430 5/16"-18 spares.

 

[Leatherbark]

T.C used to advertise their round ball barrels as "Cut Rifled". I always assumed the grooves were cut one at at time?

 

[bkisel]

Fellows,

Thanks for your timely replies. I'll be certain to use something on the nipple thread.

One of you asked about the choke being felt with the first load. I just don't remember but that is something I'll take note of next time out.

BTW, found the gun a real joy to shoot with 80 grains behind both PRB (180 grains?) and 240 grain 1/2 conical. At 100 grains, with the conicals, the recoil was a bit uncomfortable but not unbearable. Wouldn't enjoy a long shooting session with the conicals but figure my practice could be mostly PRB and just a few shots with the conicals ifin that turns out to be my settled on hunting load.

Thanks again ...

 

[roundball]

T.C used to advertise their round ball barrels as "Cut Rifled". I always assumed the grooves were cut one at at time?

Unless I missed it, the poster didn't specify RB barrel so I assumed he was talking about a standard barrel (with .006" button rifled grooves)

 

[bkisel]

Don't know much about the barrel except that it is a 31" T/C 1:66 barrel. The gun is a percussion T/C Pennsylvania Hunter in .50 cal. Guess I could count the lands and grooves if that is of interest to you.

Take care ...

 

[roundball]

Don't know much about the barrel except that it is a 31" T/C 1:66 barrel. The gun is a percussion T/C Pennsylvania Hunter in .50 cal.

Wasn't aware it was a round ball barrel when I commented on the "button rifling"...one thing's for sure, TC has a real lifetime warranty second to none...if you have a problem with the barrel, just send it back and they'll make it right at no charge.

 

[Rat Trapper]

I take the nipple out every time I clean the rifle. Do not tighten nipples or breech plugs (on inlines) harder than two finger tight. I always recommend lube on breech plugs and maybe a drop of oil for nipples. Clean out screws also need a little lube and must be taken out every time you clean the rifle.