Is this a helicoil?

Discussion in 'Percussion Rifles' started by longcruise, Sep 13, 2019.

Help Support Muzzle Loading Forum by donating:

  1. Sep 13, 2019 #1

    longcruise

    longcruise

    longcruise

    70 Cal.

    Joined:
    Mar 1, 2005
    Messages:
    4,720
    Likes Received:
    57
    Cleaning a GM drop in barrel today and saw this. It looks like a stainless steel helicoil in the nipple threads. The crossways piece in the bottom seems to be from the helicoil having turned itself in beyond the threads that hold it. I've had this barrel for a long time now and today was the first time this appeared. It's not something I previously overlooked. It's too obvious when you go to reinstall the nipple.

    I have heard of helicoil problems in the past with GM barrels but I thought they were used on the breech plug threads. :eek:

    What do you all think?
    20190913_154625-800x600.jpg
    20190913_154635-800x600.jpg
     
  2. Sep 14, 2019 at 12:03 AM #2

    hawkeye2

    hawkeye2

    hawkeye2

    58 Cal.

    Joined:
    Apr 13, 2004
    Messages:
    2,935
    Likes Received:
    216
    Location:
    Winchester, VA
    Looks like one to me.
     
  3. Sep 14, 2019 at 12:05 AM #3

    sawyer04

    sawyer04

    sawyer04

    40 cal - b MLF Supporter

    Joined:
    Feb 3, 2013
    Messages:
    330
    Likes Received:
    131
    Location:
    missouri
    Yep, looks like a helicoil to me too.
     
  4. Sep 14, 2019 at 12:23 AM #4

    Jaegermeister

    Jaegermeister

    Jaegermeister

    36 Cal.

    Joined:
    Sep 24, 2008
    Messages:
    105
    Likes Received:
    2
  5. Sep 14, 2019 at 2:16 AM #5

    Zonie

    Zonie

    Zonie

    Moderator Staff Member MLF Supporter

    Joined:
    Oct 4, 2003
    Messages:
    28,733
    Likes Received:
    1,361
    Location:
    Phoenix, AZ
    As far as I know, no one has ever used a Helicoil for a breech plug thread repair but yes, that is a Helicoil in the nipple hole. It's a pretty common fix. As I recall, both Green Mountain and Thompson Center have used this repair when the threads the factory machined into the barrel didn't meet spec.

    The thing you see at the bottom of the Helicoil is the tang that is used along with a special driver to screw the Helicoil in. It is supposed to be broken off and removed after the insert is in place.

    You might want to make sure the Helicoil isn't blocking off the flame channel that goes from the bottom of the nipple hole to the breech.
    Helicoils are sometimes too long for the installation and if they are, the reliability of getting the gun to fire can be reduced.
     
    Nyckname likes this.
  6. Sep 14, 2019 at 3:48 AM #6

    longcruise

    longcruise

    longcruise

    70 Cal.

    Joined:
    Mar 1, 2005
    Messages:
    4,720
    Likes Received:
    57
    In this case it looks like the helicoil has been turned deeper into the threads until it was pushed beyond the threads in the bottom. Likewise, there are threads exposed at the top that the helicoil has been turned in deeper than.

    My explanation of this is lacking.

    I'm going to call GM on Monday and see what they say about it.

    I bought it new and never did any mods to it so it must be factory. The better fix would be to drill and tap for an oversize nipple but in Terms of meeting specs in order to sell it they probably have to make a .250x28 fit.

    I'll follow up on the forum.
     
    Okie Hog and Kansas Kid like this.
  7. Sep 14, 2019 at 12:04 PM #7

    Carbon 6

    Carbon 6

    Carbon 6

    58 Cal.

    Joined:
    Nov 3, 2018
    Messages:
    2,268
    Likes Received:
    832
    The story goes something like this.
    GM installed metric nipple holes. As a fix GM, drilled out the metric holes, put 1/4-28 Heli-Coils in, and installed the proper nipple. That did not fly because was folks did not want new barrels with Heli-Coils. As a result GM replaced a bunch of breech plugs.


    From GM.


    Notice to Owners of our Black Powder "Drop-In" Barrels:
    There is a possibility that the nipple on your rifle is defective. Metric threaded nipples were inadvertently installed in some barrels instead of the proper 1/4-28 threaded nipples. The serial number range in question if for percussion barrels # 030672 - 031352. Do not fire this rifle. Please contact us at 603-447-1095 x18 or ksmith@gmriflebarrel.com to arrange return shipping. The barrels will be inspected and if found compliant returned. If they are discrepant the breach plugs will need to be replaced so bear with us as this may take a while to complete. We apologize for the inconvenience.
     
    Nyckname and jdw276 like this.
  8. Sep 14, 2019 at 5:55 PM #8

    longcruise

    longcruise

    longcruise

    70 Cal.

    Joined:
    Mar 1, 2005
    Messages:
    4,720
    Likes Received:
    57
    hmmmm. Mine doesn't fall in that sn range.

    Wondering what to expect from GM?
     
  9. Sep 14, 2019 at 6:08 PM #9

    hawkeye2

    hawkeye2

    hawkeye2

    58 Cal.

    Joined:
    Apr 13, 2004
    Messages:
    2,935
    Likes Received:
    216
    Location:
    Winchester, VA
    It's possible a previous owner damaged the threads and repaired it before you got it.

    "In this case it looks like the helicoil has been turned deeper into the threads until it was pushed beyond the threads in the bottom. Likewise, there are threads exposed at the top that the helicoil has been turned in deeper than."

    I believe you are correct or it's possible that the installer pulled that thread out of place when they broke the tang off. The tang would have been directly across the hole and not like that piece. I would probably remove and replace that one but if it doesn't bother you or hasn't given any trouble.....
     
  10. Sep 14, 2019 at 7:43 PM #10

    longcruise

    longcruise

    longcruise

    70 Cal.

    Joined:
    Mar 1, 2005
    Messages:
    4,720
    Likes Received:
    57
    I was the original owner so it must have been the factory that did it.

    It it's not satisfactory to me to have a helicoil repair. If GM won't fix it I'll drill and tap for oversize or replace the breech plug.
     
  11. Sep 14, 2019 at 8:37 PM #11

    Carbon 6

    Carbon 6

    Carbon 6

    58 Cal.

    Joined:
    Nov 3, 2018
    Messages:
    2,268
    Likes Received:
    832
    I think GM had two separate recalls and I only posted the one.
    I would still call them.
     
  12. Sep 14, 2019 at 11:08 PM #12

    Zonie

    Zonie

    Zonie

    Moderator Staff Member MLF Supporter

    Joined:
    Oct 4, 2003
    Messages:
    28,733
    Likes Received:
    1,361
    Location:
    Phoenix, AZ
    I would just remove the broken thread at the bottom and use the barrel like it is.

    The thread on the nipple should be a 1/4-28. That is a standard thread size for nipples.
    The Helicoil tap that was used to prepare the hole for the 1/4-28 UNF insert is a .300-28. That is, the major diameter of the thread is .2995 and the thread pitch is .03571.
    Since the major diameter of the threaded hole is only .015 smaller than a 5/16 thread, there isn't enough material to thread the existing hole for a 5/16-24 threaded nipple. That is the next larger size standard nipple thread and it is used on percussion muskets.

    Here is a drawing I made of a 1/4-28 Helicoil with a standard nipple screwed into it. I made it back when this issue of using a Helicoil to repair nipple threads and people were saying Helicoils are used all the time to repair spark plug holes.

    HeliCoil-2.jpg

    Although there is very little sealing surface for a nipple, there are a lot of places where the nipple screws directly into a round drum and in that case, there isn't a real sealing surface either.
    A Helicoil isn't a real good repair but it is stronger than a hole without one and it is totally safe to shoot a gun that has a Helicoil installed for the nipple.
     
  13. Sep 15, 2019 at 4:36 AM #13

    longcruise

    longcruise

    longcruise

    70 Cal.

    Joined:
    Mar 1, 2005
    Messages:
    4,720
    Likes Received:
    57
    Great information, Zonie. Thanks.
     
  14. Sep 16, 2019 at 2:48 AM #14

    SDSmlf

    SDSmlf

    SDSmlf

    40 Cal.

    Joined:
    Nov 4, 2006
    Messages:
    892
    Likes Received:
    302
    Location:
    Western North Carolina
    Within the past week contacted Green Mountain through their website about two barrels, neither ever shot, that were within the serial number range of previous recalls. Concerned about possible Heilcoil use in nipple hole. Received an email within an hour wanting to know package size...

    Go to GM website and contact them. Tell them what you have and what your concerns are. Expect they will quickly respond.

    FYI. Currently have four GM barrels. Three of the so called LRHs and one roundball barrel. No complaints. Great customer support.
     
  15. Sep 18, 2019 at 6:11 AM #15

    Mad Professor

    Mad Professor

    Mad Professor

    50 Cal.

    Joined:
    Aug 20, 2005
    Messages:
    1,357
    Likes Received:
    23

    I had one like that from GM ~ fall 2005. Threads hung down too low and installation helicoil tang in the way too. I wasted a good amount of lead and powder trying to figure out why my new barrel was giving misfires. GM would have replaced the breech plug but I needed the rifle for deer season. I snapped off the bottom few coils that were in the way and no more miss fires. I still contemplate sending it back for a new breech plug, but it's dialed in to shoot now so I've lived with it.
     
  16. Sep 18, 2019 at 2:30 PM #16

    longcruise

    longcruise

    longcruise

    70 Cal.

    Joined:
    Mar 1, 2005
    Messages:
    4,720
    Likes Received:
    57
    Got in touch by phone yesterday. They requested an email with full info which I did late yesterday and included the same pictures from this post. Should hear something soon. They were very helpful.
     
  17. Sep 18, 2019 at 3:55 PM #17

    SDSmlf

    SDSmlf

    SDSmlf

    40 Cal.

    Joined:
    Nov 4, 2006
    Messages:
    892
    Likes Received:
    302
    Location:
    Western North Carolina
    As I mentioned in post #14, GM is very quick getting back to you on inquiries. They responsed to my initial email in less than an hour, and I had the UPS prepaid label to return the barrels by the following morning. And this is for barrels made over 10 years ago.
     
  18. Sep 20, 2019 at 2:29 AM #18

    longcruise

    longcruise

    longcruise

    70 Cal.

    Joined:
    Mar 1, 2005
    Messages:
    4,720
    Likes Received:
    57
    Update. Called them Tuesday afternoon and before the day was out had a return label in my email.
     
  19. Sep 20, 2019 at 3:28 AM #19

    SDSmlf

    SDSmlf

    SDSmlf

    40 Cal.

    Joined:
    Nov 4, 2006
    Messages:
    892
    Likes Received:
    302
    Location:
    Western North Carolina
    Package with both barrels I previously mentioned was delivered today. Based on previous dealings with Green Mountain expect both barrels are checked, repaired if required, and returned by end of next week.
     

Share This Page

arrow_white