GM Barrel nipple threads

[Ken Rummer]

I bought a GM 54, 1"x32, 1:70 replacement barrel for my Renegade from Log Cabin Shop, Lodi, OH.

During cleanup following my first range session I discovered the nipple was M6x.75 thread instead of the expected 1/4-28..

The Log Cabin Shop owner checked his stock and found several more with metric nipples. He called Green Mountain and they requested the barrels be returned. This is currently being done.

It is too early to tell what the scope of this situation will be.

Screwing a metric nipple into an English thd hole will go without a lot of extra torgue, will damage both threads and obviously will not be a strong as designed. Only GM engineers can assess the risk and I think this will be a problem for them.

The m6x.75 nipple has a .236 dia thread and has 33.8 threads per inch (my calculation) You can check this without a metric thread gage by using a 32 tpi gage. This is close enough that 3 or 4 threads will fit the gage but not the entire length of the nipple thread.

 

[Mad Professor]

You think they'd have learned from the "helicoil" barrels......

Hmmm..... makes me wonder???? Maybe the helicoil barrels were due to improper threading in a way that was not disclosed as GM described, and the leftover bad plugs got fitted to some new barrels.............

 

[wtilenw]

Wow! that's too bad GM is going through another quality control issue. Sometimes that is all it takes to discontinue a product and I would hate to see the IBS barrels nixed from production.
Idaho PRB

 

[roundball]

It would be interesting to see if your barrel's S/N is in the recall range posted on GM's website...that would tell if it was from the original drilling & tapping screw-up...or if this is yet a new range of D&T screw-ups.

If they didn't learn their lesson the last time, their fix will be to over-drill & retap the nipple seat, then screw in a heli-coil spring, then screw a nipple into the coiled spring, and send it back to you. But surely they learned their lesson from all of THOSE returns the last time and won't try that again.

 

[roundball]

Wow! that's too bad GM is going through another quality control issue. Sometimes that is all it takes to discontinue a product and I would hate to see the IBS barrels nixed from production.
Idaho PRB

I think they'd just as soon walk away from the IBS line as keep it going...it strikes me they're not really paying much attention to it lately

 

[catman]

I guess I'm glad I got a drop-in 50 cal 1:66 for my Renegade from TC, fit and finish is perfect. The only thing I don't like is the !*&^ wood (not hickory)they choose for their ramrods..

 

[jtmattison]

I have the 32 inch .54 15/16" 1:70 and it has the 1/4 x 28 and no heli-coil.

I hope they replace yours without a fuss.

HD

 

[Ken Rummer]

This barrel was not in the group listed for recall on the GM home page. It is a brand new problem.
Knight makes all three nipple sizes so I can see the new guy who screws in the nipples getting a coffee can full of the wrong ones from the storeroom and screwing them in. They will go without a lot of extra effort and look a lot like the 1/4-28.

The heli-coil would be the fix that would allow reuse of the breechplug. Otherwise a new breechplug is required.
In self defense, I don't know if I could identify a properly installed heli-coil by visual inspection. I have read on this forum that heli-coils are identified by the extra length hanging into the flash channel.
The ones I saw used in the business world had a copper wash on the surface to reduce friction during installation and the color contrast was noticable. No copper color and a correct length coil could make it hard to identify.

I hope GM gets the IBS back in the production schedule. When I spoke to a GM rep a few weeks ago the 58cal was scheduled for next spring. They were selling out of inventory and referring customers to local dealers for items that were sold out.

 

[roundball]

I had them convert a caplock .58cal barrel to a Flint and it is outstanding...it was recalled back before they started the helicoil mess and they replaced the breech plug/reblued everything...

 

[Mad Professor]

The helicoils they used were stainless and you could tell they were there with a close look.

I got one of the ones that hung into the flash channel and spent/wasted a good pound of powder before I checked the flash channel through the cleanout screw, it was more than half blocked.

I was blaming a bad lot of caps as it never occurred this could have been the problem on a new barrel.

 

[uncrichie]

I would really hope that they replace your barrel breech with the proper nipple threads as should be and not a helicoil fix. Even though they claim there is enough strength its just not the way it should be. Good luck.

 

[Semisane]

THANKS MUCH FOR THIS POST KV Rummer. :thumbsup:

I bought a GM .54 barrel for my Renegade from Track Of The Wolf last month. I just checked it and, sure enough, it had a M6X75 nipple threaded in the 1/4 x 28 nipple seat. When I started to pull it out there was a definite wobble to the nipple after the first 1/4 turn out - not a healty situation.

I just got finished sending a notice to both TOW and GM.

You Da Man!!!! :bow:

 

[Ken Rummer]

To recap my earlier post, Green Mountain 54 cal 1"x32, 1:70 barrel drop-in barrel I bought from the Log Cabin Shop had a M6x.75 nipple installed in the 1/4-28 threaded hole in the breechplug.

Log Cabin told me this morning that GM told them that this was not a problem and GM would not issue a recall.

I would assume GM feels the mis-threaded combination is not a serious risk of failure but I will probably not buy a GM barrel now.

 

[rafterob]

I have often seen people do it the other way around not knowing they had a metric threaded drum. They are very close to the same size and may not actually pose a big problem-short term. I think I would want to remedy it as soon as it was discovered however.

 

[roundball]

I just got an email reply from Rick Sanborn at GM:


"...Bill, The issue with the nipples is correct, there's no recall because the metric nipple is very close to the 1/4".

If anybody has an issue we'll fix it but so far everything we pulled from stock has either had the correct nipple or if metric, was pulled and replaced without damage after inspection.

We certainly don't want to make folks mad at us or anything but the truth is that there's nothing really wrong with the barrels..."

Thanks
Rick

 

[Ken Rummer]

It looks like the fix is to install the correct nipple and forget about it.

The nipple diameters are close, .247 vs. 236, and the difference is approx .011. Not too bad.
The thread pitch is the issue with me, 28 tpi vs. 33.8 tpi. Screwing them together expands one and crushes the other. Now if you buy a barrel it will have the correct nipple and I am not sure I could visually inspect the threads to determine if it ever had the wrong one installed.

This may be perfectly safe and if GM made a public statement to that effect I would accept it.

 

[R.M.]

Being ever so slightly smaller in diameter, the thread mismatch will be a bit more forgiving. A safety problem, I don't know, but I'd surely want the right nipple installed.

 

[Mad Professor]

I wonder what would happen if one of these nipples (the wrong one they were shipped with) pops out and the shooter looses an eye???

 

[Kentuckywindage]

no nipple problems here. Then again i ordered my .58 barrel from deer creek.

So much for having an American company stand up and make things right:hmm:

 

[roundball]

I'm disappointed with their attitude towards these things...there are two major problems that seem to be evolving at GM lately:

1) Barrel manufacturing quality control failures allowing escapes to the public;

2) Company attitudes towards communicating / resolving the quality defects;

Marginal product quality items should not be manufactured and sold to the public without a clear announcement and warning so the consumer can then make an informed decision to buy or not.

To me, not being proactive in getting the word out about this problem is not a responsibile approach by GM...a cover-up is always worse than an original issue.