Author Topic: 1/2 x 20 Breech Plug  (Read 3393 times)

Offline 44-henry

  • Hero Member
  • *****
  • Posts: 1113
1/2 x 20 Breech Plug
« on: March 24, 2015, 10:22:08 PM »
Kind of an odd question, but what are your opinions on a 1/2-20 breechplug thread on a pistol barrel? If the caliber was small, say 32, would a well fitted plug be considered safe if 1/2" deep?

Offline okawbow

  • Hero Member
  • *****
  • Posts: 807
Re: 1/2 x 20 Breech Plug
« Reply #1 on: March 25, 2015, 12:00:01 AM »
Yes. A 1/2" breech plug would likely work at 1/4" if fitted properly. That would give you 4 or 5 good threads.  So, at 1/2" long, you would have9-10 good threads. With a 32 cal. You would still have a good shoulder left to seal the plug.
As in life; it’s the journey, not the destination. How you get there matters most.

Offline Bob Roller

  • Hero Member
  • *****
  • Posts: 9301
Re: 1/2 x 20 Breech Plug
« Reply #2 on: March 25, 2015, 01:14:07 AM »
Kind of an odd question, but what are your opinions on a 1/2-20 breechplug thread on a pistol barrel? If the caliber was small, say 32, would a well fitted plug be considered safe if 1/2" deep?
I would have no qualms abut a 1/2x20 thread in a 32 caliber pistol.With loads used in those little calibers I wouldn't be afraid of a 7/16x20.Small bore caplock pistols are common in Germany and use about 10 grains of powder so the chance of a blow up is zero.

Bob Roller

Offline 44-henry

  • Hero Member
  • *****
  • Posts: 1113
Re: 1/2 x 20 Breech Plug
« Reply #3 on: March 27, 2015, 05:55:16 AM »
Thanks for the info, didn't figure it would pose any problems with light loads, I'll definitely proof it if I go that route. I did the calculations on shear area compared to a 9/16 -18 thread and it was substantially different.

Regards,

Alex Johnson

Offline gunmaker

  • Hero Member
  • *****
  • Posts: 691
  • the old dog gunmaker
Re: 1/2 x 20 Breech Plug
« Reply #4 on: March 27, 2015, 11:40:23 PM »
A 1/2"-20 tpi is much bigger than a 1/4"-28 vent liner some of those only have 3-4 threads.  Why wouldn't 1/2" work well on a 36 or smaller bore rifle or pistol as a plug ?   Just asking,  if one of the metal eng. knows yes/no--just like to find out ?  ...Tom