INQUISITIVE MIND CAUSES A CONCERN

[Ralph in Mn]

I have a new muzzleloader that, this morning, I decided to do some measurements on. In checking the breechplug I found that the top of the threads only touch approx .003 of the mated thread in the barrel and the rear sealing surface only touches on aprox .005. I am not sure if anyone else has ever checked this on their muzzleloader. It seems like the threads should be tighter to me.
I am just looking for info and not trying to cause anyone else a concern.
Thanks
Ralph

 

[Bucker]

threads

Okay, I'll bite and get the ball rolling! What kind, caliber and make? I do not beleive i have ever seen on this site other than length.

 

[Ralph in Mn]

Ok, it is a .50. I hesitate to print the make because I do not want to start a flame against a manufacturer. I,ll just say it was not made in the U.S.A.

 

[Swampman]

According to a new article I was reading this morning, improperly fitted breechplugs are pretty common.

 

[Underclocked]

I've no ready means to measure the barrel threads. Could you explain how that is done?

 

[Ralph in Mn]

I am also am a long range benchrest shooter, mostly 600 yd. and some 1000 yd. We measure everything. Measuring and wieghing is what shoots small groups at long distances.
I have moved back to my home state of MN. and have started hunting again, I bought a muzzleloader to extend my season. I probably have read to much information and am concerned about the safety of my gun, also my wife does not want to be refered to as the widow of.

 

[Grouse]

If your measurements are correct, you have a big concern. Please take a pic of the plug, and the barrel.

Measuring bullets and powder by weight, will increase down range accuracy with Muzzleloaders as well.

Not to confuse anyone, Black Powder still get weighed by volume. Then you take the measured by volume and dump it on a scale. Now you can use that weight to weigh out your charges to be more accurate.

 

[Underclocked]

Understand your concern, Ralph, but HOW do you measure those internal threads? I'm not challenging you, I just want to know how to do it.

 

[Busta]

Ralph,

DO NOT SHOOT THAT RIFLE! At least until you get this resolved. I have heard of a few tapered breech plugs, and that is definitely not enough thread engagement. If your rifle has a standing breech, that is one thing, but if it has a drop/swing/rolling block or a plunger action that is very dangerous. DO NOT SHOOT IT either way. Contact the manufacturer ASAP!

 

[Underclocked]

Busta, can you make such measurements? How do you do that? Am I the only one that would like to know (or the only one that doesn't know)?

 

[dphobby]

I'm with you U. C. Don't quite understand :?: :?:

 

[Swampman]

When I worked in quality assurance at a Jet Engine repair facility, we would have used wax impressions. An optical comparator or dial calipers + a little math will provide the info you need. I'm not sure what is an acceptable fit.

 

[greatbasin]

Should'a bought American.

 

[Ralph in Mn]

I cleaned the breech insert threads and the breech plug threads. I then took a Sharpie and covered the the threads, then I screwed it in to make contact on the threads. I then measured what was rubbed off with a caliper. I know that is not an exact measurement so I said approx.

 

[RogerDailey]

I may have to check mine. Thanks for explaining how to do it.

 

[frontier gander]

thats a very rough and inaccurate way to do it IMO. I like swampmans way of using wax mold.

 

[frontier gander]

Ok i tried the magic marker trick except i dont have an inline so i used my nipple off of a cva mountain rifle. I colored the threads black and installed it tightly, removed it and it was still all black with no color missing.

I guess the nipple isnt engaging the drum threads?

I am going to try some whiteout next.

 

[ewald]

They make special micrometers just for measuring threads, that would be the only way I know of that proper measurments could be taken.

I think you need to talk to the manufacturer about this before you shoot the gun. If indeed there is only 0.003" of engagement you may have a problem. Why chance your health and life, call the factory.

 

[Underclocked]

Well, I think we should all know what constitutes an accurate method for measuring such things, at a minimum, before we go screaming about the sky falling. I know that I've encountered plugs from several manufacturers where the plug fit was obviously different from one to the next. I think manufacturing tolerances are such that one should not expect otherwise.

I also think knowing how to interpret such results against an acceptable standard would be needed info. It seems to me that total length of threads, pitch, angle of engagement, and yield strength of both the barrel and plug materials would be needed and analyzed to reach any sort of reasonable conclusion.

And I don't think there is any practical method for the average guy to measure or know such things. Maybe someone could make go/no-go thread testers for the myriad of plugs on the market.

ewald, could you point me to an example of those micrometers?

 

[Underclocked]

Go/NoGo thread gauge

Those things come in various sizes, pitches, and tolerances.

I've had input from two very competent individuals about this. The easiest test that one suggested was quite simple - if the plug is wrapped with a single layer of teflon tape and still screws in VERY easily - look out.

The other was quite sure that a measurement of .003" in the manner obtained was not at all an accurate indication of thread engagement.

So I would say wrap that plug in some white teflon and then thread it in. If it goes in with nearly no effort, you might have cause for concern.