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Same bolt / bolt head?

Printed From: Enfield-Rifles.com
Category: Enfields
Forum Name: 7.62 Enfield
Forum Description: All things to do with the 7.62 Enfield
URL: http://www.enfield-rifles.com/forum_posts.asp?TID=13455
Printed Date: March 26 2026 at 3:48pm
Software Version: Web Wiz Forums 12.07 - https://www.webwizforums.com


Topic: Same bolt / bolt head?
Posted By: bceverly
Subject: Same bolt / bolt head?
Date Posted: August 02 2024 at 12:31am
Hi,

I’m thinking about converting my SMLE No 1 Mk 3* to 7.62 and I am pretty certain the receiver and barrel, along with the extractor and extractor spring are unique to 7.62. What I’m wondering however is this. Is the bolt common between the .303 rifle and the 7.62?  Same with the bolt head?

Essentially if I put a barreled receiver from a 7.62 in my stock and reused my bolt (replacing the extractor and spring with the correct 7.62 one) would I be good?

Thanks in advance!



Replies:
Posted By: Shamu
Date Posted: August 02 2024 at 10:18am
You could, but!
you'd have to get a bolt head that would:
Headspace correctly with your bolt body.
Overclock the right amount or less with your bolt body.
Provide the correct firing pin protrusion with your bolt body.
In short it can be done, but its far from plug 'n play.



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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)


Posted By: britrifles
Date Posted: August 02 2024 at 11:50am
And would the locking lugs make even contact to the action body lug recesses?  

Did not not get a bolt with the 7.62 barreled action? 




Posted By: Shamu
Date Posted: August 02 2024 at 1:36pm
I thought he was using the original bolt body?
He's thinking about converting a .303 to a 7.62, so I assume he had the original .303 bolt?


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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)


Posted By: britrifles
Date Posted: August 02 2024 at 2:00pm
He said he was going to reuse his bolt. 


Posted By: paddyofurniture
Date Posted: August 02 2024 at 3:14pm
Originally posted by britrifles britrifles wrote:

And would the locking lugs make even contact to the action body lug recesses?  

Did not not get a bolt with the 7.62 barreled action? 

I think getting a 7.62 barreled action like the Indian Enfield No1 MKIII with barrel. There is a difference in a 308 action and a 303 action in steel used / proof test.


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Always looking for military manuals, Dodge M37 items,books on Berlin Germany, old atlases ( before 1946) , military maps of Scotland. English and Canadian gun parts.


Posted By: britrifles
Date Posted: August 02 2024 at 5:18pm
I think the myth that Ishapore used a superior steel for 2A production has been debunked. But, Ishapore had used a lower grade steel than the UK used in SMLE production, so the myth began that the 2A was made with a stronger steel (true if comparing a Ishapore SMLE to a Ishapore 2A). 

This forum contains numerous posts on this including findings from metallurgical tests by Peter Laidler showing the composition and hardness of 2A action bodies compared closely to British SMLE production.  





Posted By: Moosm14
Date Posted: August 05 2024 at 7:35am
Britrifles - very succinctly said sir. The misinformation on Ishapore metallurgy abounds almost as much as Rock Island 1903’s
Please correct me if I am wrong but the bolt heads on all 762x51 Enfields in England were required to be a greater proof test than .303 ?


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There is room for all of gods creatures ... right next to the mashed potatoes


Posted By: britrifles
Date Posted: August 05 2024 at 9:38am
Originally posted by Moosm14 Moosm14 wrote:

Please correct me if I am wrong but the bolt heads on all 762x51 Enfields in England were required to be a greater proof test than .303 ?

Yes, any "official" conversion such as the L8 and DCRA No. 4 type rifles and the later L39, L42, Envoy, Enforcer (may be a few others) would have been subject to the 7.62 NATO Proof cartridge.  Both my DCRA 7.62 conversions show Long Branch proof stamp markings on the bolt handle, barrel and action body.  




Posted By: Zed
Date Posted: August 06 2024 at 4:16am
Original L39 and L42's were proofed to 19 tons per square inch; compared to 18 tons for .303
However if proofed for .308 instead of 7.62; it should be 20 tons ( in UK).
Personally, I stick with loading up to the NATO 7.62 spec'; even when using.308 components for reloading.


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It's nice to be important, but it's more important to be nice!


Posted By: britrifles
Date Posted: August 06 2024 at 6:24am
Here is a good website with details of British Service Cartridges

https://sites.google.com/site/britmilammo/home" rel="nofollow - https://sites.google.com/site/britmilammo/home

Cartridge         Mean Service Pressure       Proof Round Pressure
.303 Mk 7 Ball        19.5 tsi                                25 - 26 tsi
.303 Mk 8z Ball       20.0 - 21.0 tsi                           "
7.62 L2A1 Ball        20.5 - 21.5 tsi                      27 - 29 tsi
7.62 L2A2 Ball        22.3 tsi                                     "

Proof pressure and service cartridge pressure tests were done with the cartridge case well oiled to maximize bolt thrust loads.  

Edited to add Mk 8z ball service pressures.  

Interesting to note here that Mk 8 ammunition produced very similar service pressures as 7.62 NATO.  The Mk 8z round was permitted to be fired in the No. 4 rifles "in an emergency".  It would obviously result in a higher point of impact at the same rear sight elevation setting (probably out past 200 yards) and that may be why it was for "emergency use".  

Also note that these pressures are not directly comparable to SAAMI or CIP standards, the Brits used a completely different method of measuring chamber pressure using an oiled cartridge case that acts on an axial piston in place of the bolt in a specially made breach mechanism.   Don't try to convert these figures to psi as they are not relatable to any other standard method of pressure measurement.  

Lot acceptance testing of service ammunition is an interesting subject.  The "Mean Service Pressure" above relates to the maximum average pressure that is permitted for that specific cartridge.  It is expected that there will be a variation of this pressure in individual rounds across the lot giving rise to the muzzle velocity deviations permitted by the cartridge specification.  The proof round is set higher than this maximum average pressure of service ammunition in part to account for this but also to prove the action has a strength margin above the highest pressure expected to occur with service ammunition.  On top of this, the proof round used for proofing all rifles was oiled, which significantly increases bolt thrust loads over a dry round fired in service.  





Posted By: paddyofurniture
Date Posted: August 06 2024 at 7:20am
Thanks!

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Always looking for military manuals, Dodge M37 items,books on Berlin Germany, old atlases ( before 1946) , military maps of Scotland. English and Canadian gun parts.


Posted By: thespooz
Date Posted: April 29 2025 at 1:27pm
Could you use a 308 bolt in a 303? i have a mk3 ishapore that im dying to shoot but the only thing missing is the bolt. My friend has a 308 mk3 intact. the headspacing looks proper but i dont know if its safe to shoot with it.


Posted By: A square 10
Date Posted: April 29 2025 at 6:42pm
there is a distinct difference between an ishapore mk 3 and ishapores 2A and 2A1 , it makes no sense to take a chance of injury when its simple enough to just buy the one you want or get correct replacement parts for what you have 


Posted By: britrifles
Date Posted: April 30 2025 at 9:30am
Good advice from A square 10; always seek the correct replacement parts.  

I can't speak for the Ishapore No. 1 and 2A/2A1 rifles, but I do know that the No. 4 .303 and 7.62 conversions used the same action, just a different barrel.  The DCRA conversions only changed the barrel.  Enfield and other conversions also replaced the extractor and magazine.  The rifle was then re-proofed to the 7.62 NATO pressures.  So, other than checking for bolt locking lug bearing contact, headspace and striker protrusion, there would be no issues doing this with the No. 4 rifle.  

You might argue that the bolt in a No. 4 7.62 conversion should not be swapped for a bolt removed from a No. 4 .303 rifle, as it's not been proofed to the higher pressures that the 7.62 conversion was. 









Posted By: thespooz
Date Posted: May 06 2025 at 1:34pm
Thank you for the input, went ahead and got the proper bolt ordered.



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