The Firing Line Forums

Go Back   The Firing Line Forums > The North Corral > Black Powder and Cowboy Action Shooting

Reply
 
Thread Tools
Old February 16, 2012, 10:41 PM   #1
deerslayer303
Senior Member
 
Join Date: January 10, 2011
Location: Leesville SC
Posts: 1,134
Uhh why is there a ledge in my GPR Barrel?

Ok so I was cleaning the GPR and I kept noticing the patch would get really tight about 3 inches from the base (breech) of the barrel. So I'm thinking man this barrel probably has a ton of rust in there. So I peak down it with the bore light and it shines like new penny. So I take a small brass cleaning rod and run it down the barrel keeping in contact with the side of the barrel. And yep about 3 inches from the end I hear a *tink* then I move the rod just a tad toward the center of the barrel and it will travel the rest of the way to the end. What in the world??????? Do I have a defective barrel? I have never seen such a thing. Its clean as a whistle. thoughts? These things should have a removable cap on the base of the barrel.
deerslayer303 is offline  
Old February 17, 2012, 06:49 AM   #2
mykeal
Senior Member
 
Join Date: October 8, 2006
Location: Northern Michigan
Posts: 2,758
GPR barrels have what's called a patent breech, or Nock's breech. It's actually a smaller diameter combustion chamber in the breech end. That's probably what you are feeling. Here's a drawing of the concept (this is not a scale drawing of the detailed GPR design, and it's not my drawing; unfortunately I've lost the source reference):
mykeal is offline  
Old February 17, 2012, 09:44 AM   #3
ScottRiqui
Senior Member
 
Join Date: January 27, 2010
Location: Norfolk, VA
Posts: 2,905
That's really strange - is the "step" present all the way around the inner circumference of the barrel? And is it nice and sharp, like it was machined that way?
ScottRiqui is offline  
Old February 17, 2012, 11:17 AM   #4
shortwave
Senior Member
 
Join Date: December 17, 2007
Location: SOUTHEAST, OHIO
Posts: 5,932
Very interesting mykeal,

Thanks for the info.

Wouldn't you say the Nochs was designed to help lessen blow-by?
shortwave is offline  
Old February 17, 2012, 12:07 PM   #5
mykeal
Senior Member
 
Join Date: October 8, 2006
Location: Northern Michigan
Posts: 2,758
Quote:
Wouldn't you say the Nochs was designed to help lessen blow-by?
I honestly have no idea.
mykeal is offline  
Old February 18, 2012, 02:05 AM   #6
prof marvel
Member
 
Join Date: March 9, 2011
Location: over the hills and far away
Posts: 15
this link should answer your question:

http://www.trackofthewolf.com/catego...tnum=plan-nock

yhs
prof marvel
__________________
Professor Marvel's Traveling Apothecary and Fortune Telling Emporium
Purveyor of Patent Remedies, Snake Oil, Cleaning Supplies, Dry Goods, and Picture Postcards
Supplying useless advise for All Occasions
prof marvel is offline  
Old February 18, 2012, 07:58 AM   #7
shortwave
Senior Member
 
Join Date: December 17, 2007
Location: SOUTHEAST, OHIO
Posts: 5,932
sorry...

...DP.

Last edited by shortwave; February 18, 2012 at 08:04 AM.
shortwave is offline  
Old February 18, 2012, 08:03 AM   #8
shortwave
Senior Member
 
Join Date: December 17, 2007
Location: SOUTHEAST, OHIO
Posts: 5,932
..."improved ignition and increased velocity.

Thanks prof marvel.
shortwave is offline  
Old February 18, 2012, 11:02 AM   #9
deerslayer303
Senior Member
 
Join Date: January 10, 2011
Location: Leesville SC
Posts: 1,134
Thank you everyone. I was dumbfounded when I found it. Thats very interesting thank you for posting up that info.
deerslayer303 is offline  
Old February 18, 2012, 05:17 PM   #10
prof marvel
Member
 
Join Date: March 9, 2011
Location: over the hills and far away
Posts: 15
If one browses about one finds that the Nock Patent breech was highly recommended for fowlers as well as the large bore rifles represented by American Hawkens and British Percussion Sporting Rifles. It seems the larger bores "need" a smaller "chamber" to achieve better consistency and efficiency.

Happy to be of service -

yhs
prof marvel
__________________
Professor Marvel's Traveling Apothecary and Fortune Telling Emporium
Purveyor of Patent Remedies, Snake Oil, Cleaning Supplies, Dry Goods, and Picture Postcards
Supplying useless advise for All Occasions
prof marvel is offline  
Old February 20, 2012, 07:14 PM   #11
deerslayer303
Senior Member
 
Join Date: January 10, 2011
Location: Leesville SC
Posts: 1,134
So in essence you have to put enough powder in to fill up this smaller chamber? That or when the ball is rammed all the way down, there will be an air pocket otherwise. Am I correct in thinking this way. The Lyman manual only gives a "max" load for the .54cal they don't give a starting load.
deerslayer303 is offline  
Old February 20, 2012, 08:41 PM   #12
Beagle333
Senior Member
 
Join Date: January 7, 2012
Location: Auburn, AL.
Posts: 1,369
The Nock's breech

I was reading about it here, and it pretty much tells why it's there and what it's supposed to do. It's on page 117 and page 118 of this pdf. It's exactly as Prof Marvel said. I can't find a drawing that actually has a scale on the same picture, but I'm bettin this little chamber only holds a smaller charge than you would ever play with (in reference to worrying about not filling it up). But, that's just me looking at it. I didn't scale it into my cad program. It was interesting, but not that interesting.

http://books.google.com/books?id=obx...ech%22&f=false
Beagle333 is offline  
Old February 21, 2012, 12:33 PM   #13
Poodleshooter
Senior Member
 
Join Date: August 7, 2000
Location: Floating down the James River in VA
Posts: 2,539
You also have to be more careful swabbing the bore with the GPR patent breech since it doesn't clean out particularly well when using a full width jag and patch. I use a regular rifle cleaning rod with a slotted patch holder to clean that portion out. Otherwise rammed down fouling and excess cleaning patch lube/solvent builds up in there and can cause ignition problems. It's handy for keep you from ramming a ball down to the breech w/o powder, but other than that, it's a hassle for cleaning with a normal BP rifle kit.
Poodleshooter is offline  
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 04:54 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2014 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Contact Us
Page generated in 0.08214 seconds with 7 queries