Reloading for the 7.62x51mm Enfields, or...
Printed From: Enfield-Rifles.com
Category: Reloading
Forum Name: Reloading .303 British
Forum Description: Enfield-Rifles.com accepts NO responsibility for any loads that may be used by persons reading this forum. USE CAUTION WHEN TRYING ANY NEW LOADS!!! ANY DATA DEEMED UNSAFE WILL BE REMOVED!!!
URL: http://www.enfield-rifles.com/forum_posts.asp?TID=10487
Printed Date: March 26 2026 at 5:14pm
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Topic: Reloading for the 7.62x51mm Enfields, or...
Posted By: Goosic
Subject: Reloading for the 7.62x51mm Enfields, or...
Date Posted: April 07 2020 at 7:04pm
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...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.
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Replies:
Posted By: britrifles
Date Posted: April 08 2020 at 5:13am
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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. |
Posted By: Shamu
Date Posted: April 08 2020 at 6:54am
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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) |
Posted By: britrifles
Date 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. |
Posted By: Goosic
Date Posted: April 08 2020 at 9:37am
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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 |
Posted By: Goosic
Date Posted: April 08 2020 at 11:46am
The 7.62 rifles were tested to above 20 tonnes or 1.5 tonnes over the original 18.5 tonnes of the 303B.
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britrifles wrote:Posted By: Shamu
Date Posted: April 08 2020 at 12:12pm
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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) |
Posted By: britrifles
Date Posted: April 08 2020 at 6:36pm
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? |
Posted By: Shamu
Date Posted: April 09 2020 at 7:17am
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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) |
Posted By: Goosic
Date Posted: April 09 2020 at 7:24am
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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....
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Posted By: Goosic
Date Posted: April 09 2020 at 7:34am
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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.
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Posted By: britrifles
Date 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. |