Quote:
Originally Posted by spentprimer
I've never heard of headspace being adjusted that way...
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Quote:
Originally Posted by spentprimer
I've never heard of headspace being adjusted that way...
"Increasing" headspace by removing metal from the front of the bolthead can introduce another "issue": excessive striker protrusion.
If you ever get to measure a bunch of different "number" No4 bolt heads, you will find that the overall length is VERY similar across the board.
This is because striker protrusion is set by the relative lengths of the front-end of the striker (forward of the collar) and the OVERALL length of the bolthead.
Given that SMLE and No4 boltheads, (and their associated bolt bodies), have indexed threads, the mathematics and sequence of manufacture must have been quite interesting.
The "back-thrust" of the cartridge is NOT supposed to be transferred via the threads, but via the tiny flat surfaces on the back of the main body of the bolthead and on the front of the bolt body. Extreme caution is advised before fooling with either of these surfaces. The bolthead thread is "beefy" because it takes ALL of the tensile load during extraction, especially primary extraction. A delicate "UNEF" pattern would not last very long in service. (And coarse threads are harder to "cross-thread' than fine ones: i.e. more "soldier-proof").
My friend is a retired mechanical engineer that has a complete machine shop in his basement. I knew he had this grinding attachment for his lathe and it works quite well. I figured it would be best if the surface was square with the world and flat as well. A small collar was made to hold the bolthead and the rest was quite easy. On the first pass of the grinder we found that the face of the bolthead was not very flat. Predictable if it was sanded down by hand. The grinder was removing about a thou per pass while the bolthead rotated quite slowly in the lathe. I will try to post pictures of the boltface this week.Quote:
Originally Posted by browningautorifle
When he lived here, it was his equipment and skills we used to build the replica of the Selous elephant gun some ten or twelve years ago, a four bore firing a one inch round ball with a four ounce black powder charge and a musket sized cap to ignite.
I measured the firing pin (oops, striker) protrution and it is .044", my Winchester Signal Cannon extends .047" and will occasionally pierce a primer. I don't know what the spec. is on the firing pin protrution, but, I would rather make it shorter if I need to before the string goes on the trigger.Quote:
Originally Posted by Bruce_in_Oz
The bolthead measured .636" before removing about .005".
This has sure been a learning experience and I really appreciate everyone's input and insight on this project.
If I remember correctly the striker protrusion specifications are:
0.040" minimum
0.042" maximum
D. :cheers:
From:
Inspectorate
Provisional Standard
REME Central
File No: 7/IW/Gen
Issue 1, 1957
Striker protrusion:
Gauge, Armourers, No. SM 143
In post WW2 Oz, this (or its locally made equivalent) had the NSN of 5220-99-961-9944.
Max: 0.050",Min 0.040"
Viz:
"f. Striker protrusion is within the limits of 0.050 inch high, 0.040 inch low and the point is radiused 0.038 inch.
Note: Adjust by stoning the point of striker if too high, ensuring radius of 0.038 inch is maintained. Stone tenon of bolt head if low, ensuring face of tenon is kept square and that “lift” of cocking piece is within limits of sub-paragraph 2.e, otherwise, exchange striker."
Note the second sentence of that "Note":
If you are going to adjust anything, stone the REAR of the threaded tenon, NOT the face of the bolthead. There are two reasons for this:
Firstly, removing metal from the front face WILL enlarge the headspace.
Secondly, because the mating hole for the striker is TAPERED; "adjusting" the face will effectively enlarge the hole by a whisker AND it will remove some of the VERY thin hard skin.
The finished radius of the tip of the striker is important. You do not want a "truncated cone" like the tip of an SKS striker, unless you have a fetish for ruptured primers.
The bit about maintaining the "lift of the cocking piece" is kinda important, too
But then from:
"Instructions for Armourers",
Published by the War office 30 Sept, 1931. Document No. 40/W.O./8743
Section 4.— Repairs, Modifications and Adjustments,
7. To fit new bolt-head to Rifles No. l.—(Spare part bolt- heads, marked “S” on the top, are longer at the front.) Assemble the bolt-head to the bolt, insert it in the body, and test with .064-inch No. 1 gauge; should the bolt not close over the gauge, remove the bolt-head from the bolt, and having placed a piece of emery cloth (No. F) on a flat surface, rub the face of the bolt-head on the emery cloth, maintaining a circular motion in order to preserve a flat surface, until sufficient metal has been removed to enable the assembled bolt to close over the gauge. The bolt should not close over the .074-inch No. 1 gauge. Care should be taken to keep the-face of the bolt-head flat and square. After fitting and adjusting, the top front edge of the face of the bolt-head is to be rounded to a radius not exceeding .02-inch.
Note.—When it is found that the bolts of several rifles turn over the 074-inch No. 1 gauge, the bolt-heads should be ex- changed among such rifles, as, owing to the varying lengths of bodies and bolts, bolt-heads which are too short in one rifle may be serviceable in another. Bolt-heads that have been replaced in rifles by longer ones, should be kept by the armourer and used whenever possible in rifles requiring the bolt-head replaced, so as to avoid unnecessary use of new spare part bolt-heads. Part-worn bolt-heads held as required by armourers in accordance with the foregoing need not be accounted for as part of the annual allowance of new spare parts.
Soooo, does anyone have any tech data on the "S" marked replacement bolt heads that can be "adjusted" for headspace at the front end???? Lithgow made a run of specially marked No1 type boltheads that came in incremental lengths like the No4 series.
They are marked thusly:
DSN Length of Bolt Head Size No.
1005-66-056-1292 0.635 in 5
1005-66-056-1293 0.636 in 6
1005-66-056-1294 0.637 in 7
1005-66-056-1295 0.639 in 9
1005-66-056-1296 0.640 in 0
A "standard" bolthead has the following critical dimensions:
Length of main body: 0.635" Accept, 0.632" Reject.
Length of threaded tenon: 0.694" Accept, 0.692" Reject.
Diameter of striker hole: 0.077" Accept, 0.078" Reject.
Diameter of main body (front bit): 0.585" Accept, 0.582" Reject
"The face and "hook" of the bolthead are to be case-hardened to a depth of 0.010"."
See also:
A.I.D 1529 and R.S.A.F. 3095(1)
Cheers!
Bruce,
Question, I have this tool and I thought that the .04 and .042 were to measure the min and max striker protrusion!
What does the tool measure?
Is the rounded recess to the right of the .042 used to check the striker profile or what?
Any info you have will be greatly appreciated!
D. :cheers:
Does it have any other part numbers on the other side? Ive never seen this before or any pics....interesting...Nagant's have such a tool but simpler. Is it an armourer's tool? or third party?Quote:
Originally Posted by Dad
40 to 50thou is the protrusion spec for a no4 anyway, though 38 to 56thou seem OK...my no4s all vary a bit....
regards
On the introduction of Mk7 ammo, the FPP for ALL .303" rifles and MG's was set at .040 - .050", regardless. This meant that even if your particular unit or station was using up stocks of Mk6, the FPP was standardised thereafter for all .303" firing guns
Good question.
By the designation on the tool itself, it looks fairly early.
I have a lot of weird and wonderful stuff in my toybox, but I don't actually have a genuine SMLE "multi-tool"; all I can go from is the data in the original manuals and use my new headspace gauges along with digital calipers or micrometers etc. as suitable. Bear in mind that ALL metrology equipment for "serious" use is supposed to be re-certified at regular intervals; gauges, despite being fairly tough, can actually wear. Rust is an absolute killer.
Maybe I should start a new collecting line!:sos:
Bruce, sorry, I cannot add anything regards your request for S marked bolthead info, but I think it is worth mentioning (for clarity) that the procedure for adjusting headspace right up until the end of the service life of the SMLE remained the same from it's introduction. Select a bolthead that was either correct (and leave it) or slightly over length and stone the face back to achieve headspace. The sized boltheads in your post came about only with the EMEI for maintaining the No1 MkIII*HT when it was brought back into service almost 20 years later. By that time, I believe the "art" of our trade began to be lost to cost and time saving methods of precision mass production and component exchange, removing the need for the skilled hand of the craftsmen of previous eras. That chart appears in the EMEI dated Sept 76.Quote:
Originally Posted by Bruce_in_Oz
Well I sat here through 12 pages of funny things and serious things some good advice other well circumspect one thing I have learned here is to keep ones yap closed and only offer advice when it is 110% correct as I fell foul of relying on my grey matter which turned out to be greyer than I thought with not advice but quoting from what I had read in an Amourers Perspective and was only 80% correct, to wit Mr Peter Laidler corrected me on "got the solder bit right, not the silver bit!".(my italics)
So I have read stuff on ammo, lathes, grindings, FPP, races, camming, watched a person shoot a rifle with obvious issues (2 trains of thought there!).
Anyways we skipped here and dashed there and all advice was offered, but I will offer this one bit of advice and I am not a technical nor trained in the great art of weapon armoury but this is what I reckon;
On average you are with the SMLE No1 Mk III looking at around 42,000 psi pressure some inches in front of your beak, and to have a bolt fly up like that even for 1 shot would have me getting that puppy looked at and rectified if possible or turn it into a wall hanger it is just not worth it guys dont egg poor ol spentprimer on a path of she'll be right cobber it will work one day, next there will be advice to put a washer behind the bolt head after they shave to much off the face.
I may also be wrong but I thought you were better off inserting a single round into the mag rather than slamming it shut on a chambered round seem to recall something about it could break the extractor claw but then again I myself may have been miss informed. :confused:
Lets have a pause and remind ourselves of the benifit of years of training and experience contained within the site as I would certainly adhere to what the most learned of pelicans offer us mere trigger grippers (just made that up cool....) they have probably done more in their chosen careers than we the average shooter will do in 4 lifetimes, love the site and all it has to offer a mere sometimes I hit it and sometimes not shooter but I do love the smell of burnt gunpowder.
All the best to all thoroughly top site this. :super:
Given that, I will leave well enough alone and see what happens at .044". Thanks!Quote:
Originally Posted by Bruce_in_Oz
I think Cinders is right. And I think that the moderators ought to step in and close these foolhardy notions and ideas that really have no place in a common sense led and sensible discussion that now seems to be bordering on the farcical. Not because of any censorship issues but to be honest, safety and what I call 'the bleedin obvious.......'
Just my common sense approach based on a couple of years on the bench
Hello gentlemen,
I just thought a short report to let you know that I appreciate your well wishes and concerns for my health. Unforunately, my mental health is the same as usual, fast cars, fast motorcycles, fast rifle (.220 Swift), etc., etc., etc.
I suspect Scott will post a video sometime this weekend of the proceedings of the day that I can link to so you can see the set-up.
A little smoke was placed on the locking lugs and the bolt closed several times to see if both locking lugs were bearing equally, no changes were made. Satisfied with that, off to the range it went. The rifle was placed on a machine type rest from the local Wal-Mart store and clamped in place, then a 1 inch wide nylon cargo strap secured the rifle and rest to the shooting bench top. A loop of paracord was tied through the trigger guard to actuate the trigger. The magazine was loaded one at a time and six rounds were fired in that manner from twenty feet away with the paracord. Scott recorded this part of the shooting session. No case head separations, no hard extractions, all went normal as I had hoped. The rifle was removed from the rest and I fired ten more rounds from my shoulder while seated without incident. I do not have a source for any proof loads or I would acquire some and see what happens. The bolt did not jump up or even move with this test firing today. No punctured primers were observed.
Afterthoughts: The bolt body that came with the rifle is very badly worn. The bolt that was just fitted to the rifle shows some signs of blueing finish wear, but, no material wear. When pushing down at the rear of a closed bolt with the striker forward, the old bolt moved more than 1/8", the "new" bolt shows no visually discernable up/down movement. After grinding the boltface, the dimension from the boltface to the shoulder of the bolt head is .631". The method of chucking the bolt in the lathe and grinding the boltface has the boltface flat and square to the world. Plastigage on a fired case is a useable method of determining headspace. The ammo used today was a mix of BG 1944 VII surplus, HXP 75 surplus and reloads utilizing WRA 1943, Federal Cartridge, REM-UMC, Dominion, R-P, 1942 DC G IV Z and Superspeed brass. All cases chambered without an issue.
This has been a very interesting learning experience and everyone's input here on this thread have been very much appreciated. Your concerns for my safety have been much appreciated as well:bash:. I have a thick skull you know. This rifle will probably be shot once or twice every few years just see if it still goes bang with my own lower pressure reloads. A big THANK YOU to all of you.
I will post a link to Scott's video when it is uploaded on U-tube.
Can anyone tell me which end the pointy bit comes out of? :madsmile:
Oops sorry for the mirth but I just wanted to get the last hoorah on this rather long saga which could have been cured on the first bolt lift.
I am :clap: for spentprimer now his rifle will not hurt anyone also all the knowledge and info I gained in trolling through theis mammoth saga of ?
"Smelly lifts bolt, thousands bemused by this happening" Keep the faith have fun and enjoy a rifle that has such a long history and really is an induvidual to each other one!!
Cinders :dancingbanana:
Hi guys, I'm very glad that this thread has remained civil that everyone has participated relatively constructively. However I believe that the subject of this post has been exhausted at this stage and that we are very unlikely to see anything further that is constructive come out of it. That is why I'm closing it.
I appreciate the views of many of the participant posters, and I encourage your ongoing engagement and discussion within this forum.
Cheers
Tom