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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 (0) Thanks(0)   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 (0) Thanks(0)   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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Post Options Post Options   Thanks (0) Thanks(0)   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 (0) Thanks(0)   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
Tom Kivlehan
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