No4 Mk1 Firing pin Protrusion
If one changes or adjusts the bolt head on the No.4s how do you adjust the FP protrusion?
12-31-2010 08:49 PM
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If the bolt heads vary by .003 to .005", then there's every chance that you won't need to alter the FPP that is between .040" and .050". If it's too long, then just stone it down making sure that you maintain the radius of the tip. If it's too short, then take the appropriate amount off the face of the bolt head tenon or skim said amount of the beating face of the striker.
But before you do any of this, make sure that what you are going to do doesn't affect the lift of the cocking piece and the overturn of the bolt head when you change it. The bolt MUST be looked at as a whole unit, accurately set up and not just the sum of a load of parts screwed together.
I'd suggest you read an article about setting up bolts, published here some time ago.............................
Thank You to Peter Laidler For This Useful Post:
Must the strikers beating face strike and sit on the rear of the cocking piece tennon to be set up right? ie. is it the case that the striker should move forward even slightly when the bolt head is unscrewed?
NO Tbone. The beating face of the striker must sit on the rear of the bolt head tenon (the screwed part of the bolt head that screws into the bolt) when the bolt is in the fired position - that is with the cam stud of the cocking piece aligned with the long cam groove of the bolt.. I don't understand what you mean by the cocking piece tenon............. This position controls the firing pin protrusion. When the firing pin is in this 'FIRED' position, there must be a gap of between .016" and .060" between the cocking piece and the rear of the bolt. That is called 'lift'
The beating face of the striker is the collar/ring you use to remove it and this collar prevents further movement forwards. Hence the term beating face
As Peter mentioned, click on the index link at the bottom of any of his posts and see if what you need is there …
Index of Peter Laidler's series of formal Knowledge Library articles and selected archived posts ... (click here)
I'd start with the article titled "Fitting Rifle Bolts - CHS and Boltheads" ...
Sorry, had meant bolthead tennon
But you get the point TBone. In THEORY, a simple change of bolthead might only change the CHS and therefore the FPP by .003" or so. On the other hand, in reality, it could alter it by .010" knowing what we do about the variables.
Peter: Thank you very much. Im "new" to Enfields and have read your articles on these rifles. Ive had my LB since the late 70's when I bought it from a neighbor for the sum of $28. He didnt know what he was selling ( a all matching including magazine Bubba rifle) and I didnt know what I was buying. After I cleaned it , I shot it a few times. I reloaded it and got the usual case separation. Being young and not knowing much about these rifles (way pre internet info where you can now find info easily) I decided to set the barrel back one turn and recut the chamber. I removed the barrel (dont remember how), had a machinist friend remove materail from the barrel in an amount that I had "calculated" to be one turn (minus what I again "calculated" to provide tension) and reinstalled the barrel. 30 years ago when I did this I now remember that when I screwed the barrel back onto the receiver (I understand its called a body) I found that the barrel would contact the body about 15 or so degrees before the front sight came to the 12 oclock position. If I remember correctly (30 years ago) I was concerned that this would not provide enought "torque" when I tightend the barrel so that when the front sight was at the 12 oclock position and the extractor alined to the extractor cut out on the breech end. From what I NOW understand, 15 to 20 degrees under would provide acceptable "torque" once the barrel was tightened so that the front sight came to the 12 oclock position.
Using a Cylmer finishing reamer I hand cut the chamber, which per the casting I made of the "new " chamber was a just a few thousands larger than the diameter of the chamber specs BUT about 20 thousands longer in the shoulder area. Im now "worried" that in my youth I cut the chamber to deep.
This brought me to the next "issue" which at the time (30 years ago) caused me to put the rifle into my gun safe and "forget" about it.
I used a .'064 HS gage and a .....I think a .074" HS gage to check the HS. I found that the bolt would easliy close on the .074 gage.
Not knowing what to do I "elected" to weld up the face of the bolt and file it down. Doing so the bolt still easily closed on the .064 gage but would not close on the .074 gage.
I put the gun into the safe after trying my hand at reparkerizing it (which IMHO came out a real nice greenish color, not knowing what was correct) and installed a full military stock.
I dragged the rifle out of the safe last week after finding out that the CMP was going to be conducting a new match called the Vintage Sniper Rifle match. Ive thought that perhaps I could fabricate a "fake" T rifle with what I have instead of finding a Mosin or something else (wife said she loves me but another rifle is um...not really something I need) BUT the headspace "issue" is now something I have to deal with.
I now realize that welding the bolt head has ruined it and that "clocking" the bolt head (which is way past what I understand is the limit) is also something that is important. Also FP protrusion is a issue as the current the pin only sticks out .020 or so.
I really dont know what to do. Im thinking that I will purchase 2 or 3 "0" bolt heads and first get the "clocking" issue resolved ( I hope its not a body "issue"). Then get a stainless shim silver soldered to the bolt head face and machined it to provide minimum HS. BUT I dont know what to do about the firing pin protrusion. I dont know if the current pin can be "adjusted" to provide additional lentgh or if a "new" pin would "fix" the issue.
From what I have now read on the internet you are a, as we Yanks call it, "a go to guy" when it comes to the Enfields. I wish you were in the the States as Ild be asking you if I could get you to give it a once over and perhaps "fix" my gunsmithing attempts.
I'ld appreciate any input as I would like to shoot this ol gal again and perhaps use it in these new matches that will be fired at 300 and 600 yards.
Could I get your thoughts on "fixing" these "issues"?