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No4 & No5 Bolt Head Sizes (Update)

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Alan de Enfield View Drop Down
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Post Options Post Options   Thanks (2) Thanks(2)   Quote Alan de Enfield Quote  Post ReplyReply Direct Link To This Post Topic: No4 & No5 Bolt Head Sizes (Update)
    Posted: February 07 2012 at 5:11am

As some of you may remember I have been compiling a spreadsheet of bolt head sizes for a few years now, and, now having the dimensions for 220 bolt heads I thought it was time for an update.

As you will see (and has been stated on numerous occasions) it is no use at all simply saying "I need a Number 3 bolt head" when (for example) a 0.632" up to 0.636" bolt head can be a number 0, a number 1, a number 2 or a number 3.

Tradition has it that the bolt head  "numbers" fall within the following dimensions :
0 - .620 to .625 in.
1 - .625 to .630 in.
2 - .630 to .635 in.
3 - .635 to .640 in.

I hope you can see from the spreadsheet that this is not necessarily correct.

Note : I use the term "NUMBER" and not  "SIZE".

Disclaimer - these bolt heads have been measured by several people using different measuring 'tools'. There is no way that these statistics would be taken as 'accurate' for QC purposes but I believe they show enough guidelines for us to be very careful when we are buying a 'new' bolt head.

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A square 10 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote A square 10 Quote  Post ReplyReply Direct Link To This Post Posted: February 07 2012 at 5:37am
interesting data , see your point , to what  do you attribute this ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alan de Enfield Quote  Post ReplyReply Direct Link To This Post Posted: February 07 2012 at 7:08pm
Originally posted by A square 10 A square 10 wrote:

interesting data , see your point , to what  do you attribute this ?
 
I cannot answer the question
All of the 'official' doumentation I have does not show a 'starting size' and simply states "No1 to No3 increase in length by increments of 0.003"
 
I can only guess (assume) that each manufacturer started their 'base line' (number 0) from a different point.
 
It may be an interesting exercise (if anyone has enough bolt heads) to repeat the exercise with bolt heads from a single manufacturer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck Quote  Post ReplyReply Direct Link To This Post Posted: February 08 2012 at 2:27am
So, if I were looking for the proper range of bolt head sizes for my guns at a gun show I would need to bring along a caliper gauge to measure each and every one, assuming the bolt heads I do have were not giving me proper head spacing?
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: February 08 2012 at 5:18am
There has been a suggestion that there was indeed a fixed dimension (+/- tolerances) for the # heads from the factory(s), but that field expedient fitting by unit armorers caused the surviving fitted heads to have a wide range of dimensions.
Somewhere I have the documentation on the exact lengths of the various #'d heads as the factory supplied them & this seems to suggest the field modifying is a plausible version. If I can dig it up I'll post the info here.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Alan de Enfield View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Alan de Enfield Quote  Post ReplyReply Direct Link To This Post Posted: February 08 2012 at 7:14am
Originally posted by Shamu Shamu wrote:

There has been a suggestion that there was indeed a fixed dimension (+/- tolerances) for the # heads from the factory(s), but that field expedient fitting by unit armorers caused the surviving fitted heads to have a wide range of dimensions.
Somewhere I have the documentation on the exact lengths of the various #'d heads as the factory supplied them & this seems to suggest the field modifying is a plausible version. If I can dig it up I'll post the info here.
 
Thanks for the offer. Peter Laidler has today looked up the 'specification' given to the manufacturers and has informed me as follows :
 
No 0 = 0.629" +0 / -0.002"
No 1 = 0.632" +0 / -0.002"
No 2 = 0.635" +0 / -0.002"
No 3 = 0.638" +0 / -0.002"
 
What does confuse me is that there are many, many examples ABOVE the sizes quoted. I would have expected that any "field expedient fitted" ( ie ground down to fit) would have been BELOW the minimum size.
 
It would be interesting to see if your documented dimensions are the sames as Peter's
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Post Options Post Options   Thanks (0) Thanks(0)   Quote A square 10 Quote  Post ReplyReply Direct Link To This Post Posted: February 09 2012 at 11:13am
it does give pause to the thought that each mfgr had their own standards , but , that flys in the face of the LOC but i can see where you arive at that conclusion based on your accumulated data , i do not have access to near enough samples to dispute your results , and welcome any info
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck Quote  Post ReplyReply Direct Link To This Post Posted: February 09 2012 at 12:10pm
Is there an available listing for the manufacturers and their marks?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alan de Enfield Quote  Post ReplyReply Direct Link To This Post Posted: February 09 2012 at 4:32pm
Originally posted by Canuck Canuck wrote:

Is there an available listing for the manufacturers and their marks?
 
The rifle manufacters generally made their own bolt heads so the markings are the usual (Savage) S, (Longbranch) LB etc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: February 09 2012 at 9:37pm
I got the same info as he did.
The only thing I can say is that to carry weight a theory must explain all the facts. This leads to the inevitable conclusion that either  the specs are incorrectly quoted somewhere & the wrong info just keeps getting repeated as fact, or someone wasn't doing good QC, or that some were built up & ground back down.

I subscribe to the "Once you have eliminated all that is not possible, what remains is truth, no matter how unlikely!" school of thought.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote guntek2112 Quote  Post ReplyReply Direct Link To This Post Posted: January 27 2016 at 4:48am
what is a U stamped bolt head designate, my measurement is a .634 with a micrometer, I did not see any in the chart and cannot remember where I saw it, maybe in gunsmithing school 38 years ago!
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Post Options Post Options   Thanks (1) Thanks(1)   Quote maxwell smart Quote  Post ReplyReply Direct Link To This Post Posted: January 27 2016 at 8:16am
I think that the "U" relates to the type of material that the bolthead is made of. All that I have seen with this mark are for No 1 rifles; it is not related to size/length of bolthead.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote guntek2112 Quote  Post ReplyReply Direct Link To This Post Posted: January 27 2016 at 8:25am
OK, thanx
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerrit Quote  Post ReplyReply Direct Link To This Post Posted: April 07 2019 at 11:35am
I have recently converted my No4 Mk1 to an EPPS.  Before the conversion I only used old factory PMP ammunition in my rifle without any problem. Since the conversion to EPPS I also started reloading new cases from Hornady. As the orignal intention of the EPPS was to increase case life, I did not expect case seperation due to a head space problem. The old PMP cases never indicated any problem. By the way, I have a #2 bolt head on my rifle. Fortunately I still had some of the old PMP cases with me. After a quick measurement of the Hornady and old PMP rim thicknesses, I realised that the old PMP case rim is 0.13 mm thicker than the Hornady rim. Looking at the different bolt head sizes discussed and the difference between the #2 and #3 heads for the max. 8 samples taken, calculate to 0.127 mm, more or less confirm why my PMP does not have a problem. So I ran off to my local dealer to get some new PMP cases to solve my problem. Before actually buying the PMP cases I also had its rim measured, only to find out its the same as the Hornady. Problem not solved. I have not actually measured my #2 bolt head, but now I know I need a #3, 0.13 mm longer than my #2 head. I need to be very specific when replacing my bolt head.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: April 07 2019 at 5:29pm
Gerrit. Welcome from Phoenix. Your first line states that you just had the rifle converted to Epps. Is this a newly manufactured barrel chambered to fire the Epps round? Or,did they re-rifle and re-ream the chamber area of the original  barrel? You first need to have the headspace checked by a professional gunsmith who is familiar with the No4Mk1 Enfield before you make an assumption that you need a new bolthead. Case separation could be due in part to an overly enlarged chamber. The No4 chamber is originally designed with a generous chamber area to allow for battlefield conditions and re-reaming it just makes it that much more generous. The case can only expand so far before it bursts. Alot of people claim headspace this or headspace that so I'll just swap out the #0 for a #1 and all will be good. Have you fired a round and then tried to extract it slowly, checking for any resistance? Where is the case separating at? Is it splitting the case laterally  or is it splitting the case a 1/4" above the rim line? Here's another one Gerrit. How many times have the reworked cases  been reloaded? The six questions I have a asked of you need to be addressed before you decide to buy a #3 bolthead only to find out your cases are still separating. Just an FYI Gerrit. The Epps was found to work better in a P-14 due to an increase in velocities and pressure. A reduced powder charge for the Lee Enfield action was mandated by Epps himself. When a chamber is reamed out for the Epps cartridge sometimes more metal gets removed then anticipated.  The combined reshaped chamber and case itself wil tend to initially get you a few case separations before it gets better.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Gerrit Quote  Post ReplyReply Direct Link To This Post Posted: April 08 2019 at 1:29pm
Thanx Phoenix.
My rifle is still the original 1942 Lee Enfield No4 Mk1, same barrel and just rechambered to epps by a good gunsmith. I am aware that the Lee Enfield cannot be loaded to the extent of the P14, so I am realisticaly conservative when loading. My seperation is about a 1/4 inch from the rim, and only occur after about 4 to 5 firings from the cases. I can only compare the old PMP cases fired from the same rifle with the modern cases, which indicate to me there is a difference in rim thickness. The bolt head and rim combined must be a good fit to eliminate the head space problem. Even when I fire form the old PMP cases to the epps shape, I do not see any deformation on the cases where I get seperation on the new stuff. The slightly thicker rim of the older PMP cases are definitely better.
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