Enfield-Rifles.com Homepage
Forum Home Forum Home > Reloading > Reloading .303 British
  New Posts New Posts RSS Feed - Bullet size for throat erosion?
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Bullet size for throat erosion?
 Post Reply Post Reply Page  <12
Author
Message
  Topic Search Topic Search  Topic Options Topic Options
Lakemaster View Drop Down
Newbie
Newbie
Avatar

Joined: November 16 2025
Location: Lake Havasu Cit
Status: Offline
Points: 15 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Lakemaster Quote  Post ReplyReply Direct Link To This Post Posted: November 24 2025 at 7:24pm
Cast full of lead with a Lee 200 grain bullet. 

I even put a 160 grain bullet ON TOP OF THAT when I was getting these huge measurements. 

So far, the only person who's confirmed 316 and bigger bullets for this type of 2 groove is Ed Harris
Back to Top
britrifles View Drop Down
Senior Member
Senior Member
Avatar

Joined: February 03 2018
Location: Georgia, USA
Status: Online
Points: 8404 		Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: November 25 2025 at 3:53pm
A .316 groove diameter is not at all unusual for a 2 or 5 groove barrel.  

Manufacturing tolerances, particularly in war time, were quite large.  

The post war new BSA barrel installed on my Fulton Regulated Long Branch Mk I/3 slugged at .315.  Unfortunately, I didn’t record the 6 or 7 other No. 4 barrels I have (not including CBI and Lothar Walther recent production barrels), but IIRC, they are all larger than .314, I think one was .318. 

Keep in mind that the two groove barrel has the same width of cut grooves as the 5 groove, it just eliminates the cutting of the additional 3 grooves. So the mean diameter (average diameter around the circumference) is quite a bit smaller than a 5 groove barrel (just 1/5 of the circumference is at the groove diameter, 4/5ths of the circumference is at bore diameter).  This is why the 2 groove barrels shot .308 jacketed bullets reasonably well. 

Only way to find out what shoots the best is to test bullets of different diameters. I’d probably start at .314 and go up to .317. 
Back to Top
Lakemaster View Drop Down
Newbie
Newbie
Avatar

Joined: November 16 2025
Location: Lake Havasu Cit
Status: Offline
Points: 15 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Lakemaster Quote  Post ReplyReply Direct Link To This Post Posted: November 25 2025 at 6:55pm
I had a heck of a time measuring bore and grove and wrapping my head around how weird the barrel looked. 

The measurements I was getting were so bizarre that I thought it was error. The grooves in front of the throat are 322. That's why I made this post

I also wanted to he how quickly the barrel erosion went down to 310 or 309. 

I've had this rifle since I was a toddler so I'm not fond of blowing it up over not understanding what 2 groove barrels like eating
Back to Top
Lakemaster View Drop Down
Newbie
Newbie
Avatar

Joined: November 16 2025
Location: Lake Havasu Cit
Status: Offline
Points: 15 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Lakemaster Quote  Post ReplyReply Direct Link To This Post Posted: November 26 2025 at 5:39pm
Originally posted by britrifles britrifles wrote:

A .316 groove diameter is not at all unusual for a 2 or 5 groove barrel.  

Manufacturing tolerances, particularly in war time, were quite large.  

The post war new BSA barrel installed on my Fulton Regulated Long Branch Mk I/3 slugged at .315.  Unfortunately, I didn’t record the 6 or 7 other No. 4 barrels I have (not including CBI and Lothar Walther recent production barrels), but IIRC, they are all larger than .314, I think one was .318. 

Keep in mind that the two groove barrel has the same width of cut grooves as the 5 groove, it just eliminates the cutting of the additional 3 grooves. So the mean diameter (average diameter around the circumference) is quite a bit smaller than a 5 groove barrel (just 1/5 of the circumference is at the groove diameter, 4/5ths of the circumference is at bore diameter).  This is why the 2 groove barrels shot .308 jacketed bullets reasonably well. 

Only way to find out what shoots the best is to test bullets of different diameters. I’d probably start at .314 and go up to .317. 



To be honest, I'll probably stop at 317 and start over sizing gas checks. 

Thank you got validating these barrels can be huge and sloppy. The groove area in front of the blasting cone/throat are as high as 324. I sent 3 313 cast bullets down the muzzle to the chamber and they were all 309.5

I was literally clueless as to what to do with those measurements.

Give me a any " normal " barrel and I wouldn't have questioned a thing. But a2 groove? .324 to 309? No way!!! That's why I started researching
Back to Top
 Post Reply Post Reply Page  <12

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.07
Copyright ©2001-2024 Web Wiz Ltd.