How many TPI for the 5/8" breech plug?

[Busta]

Could someone with a 5/8" breech plug tell me how many threads per inch for your plug? The 7/8" plug has 20 TPI. Does the 5/8" plug have 18 or 20 TPI? If you can post a pic of the breech plug and give me a length measurement I would appreciate it. I am working on finding some 209 replacement plugs and just want to know the length and TPI for the 5/8" as well. Thanks.

[Underclocked]

Busta, mine is 7/8" also.  Hope you succeed and find someone to make them at a reasonable price - would love to have a couple.

[OBXPilgrim]

Form my Huntsman barrel:
Looks to be 18 TPI.  OAL is 1.400".  The shoulder thickness at the base is .325".  Hope the photo comes through ok.

That's the H&R 7/8" plug from a Sidekick next to it.

[Busta]

Thanks OBXPilgrim, that is exactly what I was looking for.    Just wish you knew for sure if it was a 18 tpi, it does look a little coarser than the 20 tpi 7/8 net to it though. Could you check it for sure, amybe see if the threads mesh with each other or not?  Thanks!

[OBXPilgrim]

No Problem.

Hope this one shows it all. 

[Busta]

Thanks, it is 18 tpi as I suspected.

[Underclocked]

Busta, any progress with this effort? 

[kody]

 Are the grooves at the forward end of the 5/8" plug recessed to hold an 0-ring or are they taller than the portion right behind them? Ken

[Busta]

Are the grooves at the forward end of the 5/8" plug recessed to hold an 0-ring or are they taller than the portion right behind them? Ken

No, that is where they relieved the threads. I think they must have found out later that they needed the extra meat on the face of the plug, there sure isn't much meat to make a seal against the back of the bore. The plug measures .566" at the end, .550" between that and the threads. I think they deceided to flare that out to help prevent some blowback. The nominal bore is supposed to be .501" land to land, and .510 groove to groove. That only leaves .566" - .510" = .056" / 2 = .028" seal. That sure isn't much, but Knight does the same thing with their 5/8" plugs, and they only measure .555" at the face. That would only be .0225" of seal.