Enfield-Rifles.com Homepage
Forum Home Forum Home > Reloading > Reloading .303 British
  New Posts New Posts RSS Feed - Reloading for the 7.62x51mm Enfields, or...
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Reloading for the 7.62x51mm Enfields, or...
 Post Reply Post Reply
Author
Message
  Topic Search Topic Search  Topic Options Topic Options
Goosic View Drop Down
Senior Member
Senior Member
Avatar

Joined: September 12 2017
Location: Phoenix Arizona
Status: Offline
Points: 8842 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Topic: Reloading for the 7.62x51mm Enfields, or...
    Posted: April 07 2020 at 7:04pm
...One to grow on...
I have been researching this topic for God knows how long and have finally found a military NATO round that will work for both the 2A1 and No4 7.62mm Enfield rifle, as well as your commercial .308Win chambered rifle. The cartridge in question here is the U.S. military 7.62mm Special Ball LR Mk316 MOD O. It uses Federal Match cases,is primed with Federal Gold Match primers which are magnum primed and loaded with IMR4064 powder to a specific 41.745grn (2.7g). The bullet is a Sierra MK 175gr BTHP and seated to a C.O.L. of 2.800" . The test barrel is just that, a test barrel with a 1-10" twist rate. The pressure is rated at just over 46,000+ using the Copper Units of Pressure.  The 2A1 and 7.62mm No4 rifles are proofed to 19 tons per square inch.  Remembering that the 303 chambered rifles are proofed to 18.5 tons per square inch and has a CUP rating of 45,000. It is fairly safe to say that this round would be safe to use in the 7.62mm Enfield rifle as well without cause for concern. If you reload,you can duplicate this load without trying to locate it for sale from a ammunition supplier. 
Back to Top
britrifles View Drop Down
Senior Member
Senior Member
Avatar

Joined: February 03 2018
Location: Georgia, USA
Status: Offline
Points: 8404 		Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: April 08 2020 at 5:13am
I would agree Goosic.  And you can bet it is a very accurate load.  Certainly fine for some limited test firing, I would have no issues shooting a box or two and then reload the brass. 

I think the LE proof tests were measured as bolt thrust pressure.  18.5 tones per sq in is only 41,440 lbs per sq in and doesn’t correspond to the cartridge rating of 45,000 CUP.  In proofing the action, a oiled proof cartridge was used.  So I’m not exactly sure how the proof load on the action was measured.  It’s probably described somewhere in Reynolds book but I haven’t looked for it yet. 
Back to Top
Shamu View Drop Down
Admin Group
Admin Group
Avatar
Logo Designer / Donating Member

Joined: April 25 2007
Location: MD, USA.
Status: Offline
Points: 20510 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: April 08 2020 at 6:54am
It isn't "tons" in the usual sense of the word. I believe it comes from a table converting copper pill crusher tests from a "pressure figure" in CUP.
Pre-metrication British chamber pressures are:
1. Based on the long ton of 2240 lbs,
2, Measured with an axial crusher gauge with element in a modified bolt head, not a radial gauge with hole in barrel.

These combine for lower numerical readings than US radial crusher gun CUP and lots lower than piezo psi.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
Back to Top
britrifles View Drop Down
Senior Member
Senior Member
Avatar

Joined: February 03 2018
Location: Georgia, USA
Status: Offline
Points: 8404 		Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: April 08 2020 at 9:18am
Thanks Sham.  Any idea how much higher the proof test was above the service cartridge maximum?  Seems the two may not be relatable at all.  
Back to Top
Goosic View Drop Down
Senior Member
Senior Member
Avatar

Joined: September 12 2017
Location: Phoenix Arizona
Status: Offline
Points: 8842 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: April 08 2020 at 9:37am
Although no truly accurate conversion formulas are possible for converting between true piezo pressure readings and indicated crusher readings. Linearized approximated conversion equations do exist.

CUP × 1.52 - 17138 = PSI                            PSI x 1.21 - 15817 = CUP

303B                                                               303
45000 × 1.52 - 17138 = 50262.                   50262 x 1.21 - 15817 = 45000

.308 Win
52000 × 1.52 - 17138 = 61902
Back to Top
Goosic View Drop Down
Senior Member
Senior Member
Avatar

Joined: September 12 2017
Location: Phoenix Arizona
Status: Offline
Points: 8842 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: April 08 2020 at 11:46am
Originally posted by britrifles britrifles wrote:

Thanks Sham.  Any idea how much higher the proof test was above the service cartridge maximum?  Seems the two may not be relatable at all.  
The 7.62 rifles were tested to above 20 tonnes or 1.5 tonnes over the original 18.5 tonnes of the 303B.
Back to Top
Shamu View Drop Down
Admin Group
Admin Group
Avatar
Logo Designer / Donating Member

Joined: April 25 2007
Location: MD, USA.
Status: Offline
Points: 20510 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: April 08 2020 at 12:12pm
For some reason I remember the "Blur Pill" test loads as being an intentional 5/3 over maximum. Not sure where I remember that from though.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
Back to Top
britrifles View Drop Down
Senior Member
Senior Member
Avatar

Joined: February 03 2018
Location: Georgia, USA
Status: Offline
Points: 8404 		Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: April 08 2020 at 6:36pm
Originally posted by Shamu Shamu wrote:

It isn't "tons" in the usual sense of the word. I believe it comes from a table converting copper pill crusher tests from a "pressure figure" in CUP.
Pre-metrication British chamber pressures are:
1. Based on the long ton of 2240 lbs,
2, Measured with an axial crusher gauge with element in a modified bolt head, not a radial gauge with hole in barrel.

These combine for lower numerical readings than US radial crusher gun CUP and lots lower than piezo psi.

 It wasn’t the maximum cartridge pressure of 45,000 CUP measured the same way?  I.e copper crusher method.  

Proof Pressure to 18.5 tons per sq in = 18.5 x 2240 = 41,440 CUP, no where near what the Mk 7 cartridge is rated for.  It should be much higher.  

Doesn’t add up, what am I missing?  
Back to Top
Shamu View Drop Down
Admin Group
Admin Group
Avatar
Logo Designer / Donating Member

Joined: April 25 2007
Location: MD, USA.
Status: Offline
Points: 20510 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: April 09 2020 at 7:17am
Maybe where it was measured? Radially Vs rearward thrust?
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
Back to Top
Goosic View Drop Down
Senior Member
Senior Member
Avatar

Joined: September 12 2017
Location: Phoenix Arizona
Status: Offline
Points: 8842 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: April 09 2020 at 7:24am
Hey there The Armourer!! You have a wealth of information at your disposal. 
Would you be kind enough to weigh in here with one of your astute answers to britrifles question? The math definitely does not add up here....
Back to Top
Goosic View Drop Down
Senior Member
Senior Member
Avatar

Joined: September 12 2017
Location: Phoenix Arizona
Status: Offline
Points: 8842 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: April 09 2020 at 7:34am
 I had emailed Winchester the other day and asked them what their averaged PSI ratings are for both the commercial 308 and their 7.62 rounds. I got a response back last night.

Thank you for your question.

We are sorry to inform you.
 That is proprietary information and cannot be divulged to the general public. Please feel free to contact us anytime.
Back to Top
britrifles View Drop Down
Senior Member
Senior Member
Avatar

Joined: February 03 2018
Location: Georgia, USA
Status: Offline
Points: 8404 		Post Options Post Options   Thanks (0) Thanks(0)   Quote britrifles Quote  Post ReplyReply Direct Link To This Post Posted: April 09 2020 at 12:25pm
You can bet that all commercial manufacturers have at least one load that is very close to the SAAMI MAP limits, they all want bragging rights on high velocity and energy.  Loads identified as “target” typically are not high pressure.  Some “Match” loads can be hot, especially if intended for long range where supersonic velocity retention is desired.  
Back to Top
 Post Reply Post Reply

Forum Jump Forum Permissions View Drop Down

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