Advice needed ... bolt opens on firing!

[gsimmons]

You clock molester.....




Sorry I had to say it, I'm a watchmaker .

[spentprimer]

You clock molester.....

When I was a little boy, I am guessing here, but, maybe 8 or 9 years old, my birthday present was a box full of old clocks that didn't work. The local watchmaker and my Grandfather were lodge brothers and I am certain the box would have been tossed out with the trash if he had not claimed them. I think there were 13 or 14 of them. A couple were the same so i was able to steal parts from one to service another and got one working out of that box full of tickerless tickers. I guess I have alway loved puzzles, and those clocks and this rifle issue fits into that catagory. The clocks were great experience and gift! After all these years, I still think the escape mechanism is truely a great invention.

THEY SAY CURIOSITY KILLED THE CAT, and perhaps one day it will get me, too. So far, the conventional wisdom of don't do anything stupid that you will regret later has kept me out of trouble and still on the green side. However, this old adage DNA to wimmen.

[303Guy]

I am still going to measure the CHS on this rifle just to satisfy my curiosity.

And that is the whole point. Curiosity and understanding. Just saying it's knackered doesn't really say much at all. I want to know the mechanics of the bolt unlocking itself. Call it a post mortem if you will.

Just out of curiosity (here's that word again), here's a pic of a bolt with a heap of bolthead lift.



So here's that photo. See the clearance? Too much? Am I seeing things regarding the bolt bearing faces?

Looking closer one also sees what appears to me to be peening of both locking surfaces yet this rifle "has no problems", i.e. the bolt handle does not rotate on firing, probably because the locking lugs have beaten a depression on the thrust faces. I don't know, I just wonder. Thing is, had spentprimer not had his issue and had we not 'beat on the dead horse' I wouldn't have picked up on it and suggested to the owner that he gets his rifle checked over. I like to learn stuff and this discussion has been both interesting and informative for me. I've learned more about Lee Enfield issues, so much so that I have checked and condemned two of my own rifles. Condemning a rifle is not dangerous and can be done by a layman - taking a chance on it being OK could be risky. I'll get a Lee Enfield expert to have a look before I consider using them but I'm pretty sure of what he'll say. I have another bolt or two that needs looking at too.

I'm wondering whether the bolt has set back and the excess headspace has been corrected but not the striker stop. If it has then that action may be past it's use by date. Anyway, I've suggested that the owner gets it checked out by an expert just to be safe.

So you see, it's not just flogging a dead horse - not to us anyway, it's gaining knowledge and respect for the old war horse.

[jmoore]

THEY SAY CURIOSITY KILLED THE CAT, and perhaps one day it will get me, too. So far, the conventional wisdom of don't do anything stupid that you will regret later has kept me out of trouble and still on the green side.

Well, we've gone from "it's impossible, can't happen" to "pitch it in the rubbish, it's obviously worn out" in remarkably short order. All from folk that haven't laid hands on the thing.

There's several avenues of investigation left, and the rifle might be anything from easily cured with a mere cocking piece change, to beyond any sort of reasonable hope of repair. At this point I can only advise that further live firing should be done remotely. Lash the rifle to a bench in a manner that suits you and fire it by attaching a string to the trigger (or equivalent) whilst you are in a safe location should the thing decide to let go under pressure.

Probably best to leave the forestock assembly installed, but the butt could go.

If it were a front locking action you could do something along these lines, but it's just not practical with this system:



(Test rig seeing if the web of a .303 British case would remain intact in a grossly oversized chamber. It did, but the .30-30 was a bit small to survive! Yah, that's a fired .303 case, just shortened a bit to get into a 7,62x54r chamber...)

[Peter Laidler]

303 guy. I see the point that you are making, but I'll cut to the quick if I may. There are some REAL experts with bags more experience out there who will disagree but I'll say my piece all the same and be done with it. I don't need to tell you that the bolt closing of the rifle is via a simple double-lug, in effect interrupted 30 degree or so screw thread. Don't believe me? Well just look while you CLOSE the bolt. Look carefully and the bolt WILL cam slightly forwards. Neither you nor anyone else can fight against this inward screw threading. You don't need a degree in Engineering principles to understand it. It is a screw thread.

And the SAME principle works when you open the bolt too. But this time, it is the FRONT face of the left hand locking lug acting against its opposing UNLOCKING cam face inside the left side of the body that WILL draw the bolt very slightly rearwards - as in a screw thread. This action is called PRIMARY EXTRACTION but I won't go into that any further.

Now do you understand fully that the bolt locks and unlocks on a screw threaded principle?

Now, another fundemental point about firearms is this. And if you don't believe it or wish to dispute it, then DO NOT READ ANY FURTHER because all will be lost on you. It is quite important - some say VERY important - that at the moment of firing and until the mechanical safety margin of time has taken place, that the bolt or other breech closure device remains firmly in place. Otherwise, there's a very real chance that you will get a headfull and certainly an eyeful of hot bolt. Don't believe it? Just ask Tankie or Skippy to relate the sad saga of the L96 trials when not ONE, or TWO, but THREE people got the chop when the bolts failed.

When recoil takes place against the 2x flat locking surfaces of the bolt working against the 2x flat working surfaces of the body, both bearing equally against eachother (that's why we fit bolts and test/check and number them to the rifle.....) then all is well when recoil takes place. Nothing can move. But if the surfaces are worn and angled, even slightly, then guess what's going to happen? Yep, the rearward force will act on both surfaces and cause one to rotate.

In fact this rotating action by the bolt in this crap, totally worn out knackered rifle is so great that it had overcome the torque (ok, very slight I agree.....) of the striker spring AND had also compressed the striker spring at the same time by withdrawing the striker into the bolt AND shifting the safety stud on the cocking piece OUT of the long cam groove, over the hump between it and the short cam groove AND then allowed the safety stud to sit down into the short cam groove.

At this point the BOLT IS UNLOCKED and that is a very dangerous sutuation to be in. Don't believe me? Then tell him again Tankie and Skippy!

Now a question for you 303Guy. Can you tell me of any other force or load or whatever else, be it white mans magic or a call from the heavens, that made this bolt rotate to this dangerous situation? Nope

I bet the last time you went to the dentist you didn't go waffling on to him about knowing the how's, why's and wherefores of the abcess in your molar did you. Or the Vet about your dogs gut after eating the chocolates you left handy. I've just told you some of the zillions of things that I've learned, sometimes the hard way, through experience inthe small arms business over 50 years. I'll leave it at that. But one final word. You're a Kiwi........ If this bolt opening shxxe was something that was safe and to be expected, why do you think Charlton and Brunn wasted all that time and energy making their guns remain LOCKED when they fired?

[spentprimer]

Well, we've gone from "it's impossible, can't happen" to "pitch it in the rubbish, it's obviously worn out" in remarkably short order. All from folk that haven't laid hands on the thing.

There's several avenues of investigation left, and the rifle might be anything from easily cured with a mere cocking piece change, to beyond any sort of reasonable hope of repair. At this point I can only advise that further live firing should be done remotely. Lash the rifle to a bench in a manner that suits you and fire it by attaching a string to the trigger (or equivalent) whilst you are in a safe location should the thing decide to let go under pressure.

Probably best to leave the forestock assembly installed, but the butt could go.

If it were a front locking action you could do something along these lines, but it's just not practical with this system:

https://www.milsurps.com/images/impo...12010040-1.jpg

(Test rig seeing if the web of a .303 British case would remain intact in a grossly oversized chamber. It did, but the .30-30 was a bit small to survive! Yah, that's a fired .303 case, just shortened a bit to get into a 7,62x54r chamber...)

Many years ago a friend acquired a French Lebel, I told him it looked like a pregnant Guppy. Like me, he is a bit suspicious of old mil-surps that have been in unknown hands and had unknown things done to them. He had 160 acres out in the country that we would go out and shoot imaginary Alligators and charging Rhinos, etc. When the Lebel came on scene we headed out to the farm and lashed the rifle to the crash bumper of his Land Rover and with the aid of a long string test fired it once from the safety of an old granery. Neither of us had brought a ramrod ... extractor didn't work so it was a single shot that day. After he pulled the string and it went bang, I said, you know this wasn't the smartest thing we have done today. If that rifle would have come apart and taken out the radiator, it would have been a long walk back into town. Needless to say, we didn't do that again.

Some years later we built a 4 gauge musket type Elephant Gun following an old photo of the weapon Selous used in his early outings in Africa. Our proof load was 1/2 pound black powder and 1/2 pound of lead shot lashed to a 4"x 12' red elm plank and triggered by some cannon fuse in the touch hole. This was placed against another plank of the same type that was placed against a barn foundation wall on a winter day that was -15 degrees F. When it went bang, it left a 3/4" deep dent in the plank. The barrel weight was about 9 1/2 pounds. Thankfully, at 61 years old, I am not wasting my youth.

While I have been know to troll when out fishing for large Northern Pike, it is not in my nature to do so on the internet. I am glad Scott was able to catch the culprit on a video recording trying to steal my integrity.

[303Guy]

Thanks Peter, yes I am familiar with the camming operation of the bolt. We are on the same page here.

Now don't get me wrong here, I'm not saying rifle is not knackered. There is clearly something wrong with it and whatever that might be it should not be fired.

What I speculated in an earlier post was that the bolt may have rotational free play which under vibration allows the bolt to rotate far enough to actually reach the cam faces were the angled cam faces might provide the rotational force to cam the striker. Is it likely? Only examining the rifle can answer that.

I am quite aware that the lugs and recesses may have worn to an angle. For all we know someone may have stoned the outer face to fit the bolt and introduced an angle! I have an action body with only the inner recess worn so fitting a replacement bolt puts the load on the outer lug. It is quite conceivable that someone might stone one or both outer bearing faces to get the inner lug to bear and getting the faces square is not easy and most cannot do it.

Now a question for you 303Guy. Can you tell me of any other force or load or whatever else, be it white mans magic or a call from the heavens, that made this bolt rotate to this dangerous situation? Nope

Yes, I believe I can. Not negating what you have said - just speculating on possible mechanisms.


The bolt body will be lifted in the action by the sear then on firing shock waves passing down the bolt and receiver could be causing the bolt body to to move down violently, levering up the bolt handle giving it enough momentum to unlock the bolt. It doesn't always do this for whatever reason - differences in shock wave patterns or pressure of the bolt handle on the socket?

However, frictional forces under the load of a firing cartridge is very high and even if lubed, will prevent bolt rotation in the early stages of firing. But add vibrational forces and it might well turn!

Even it the locking faces are angled, the angle required for the sliding forces to overcome friction forces is greater than what one might think. Interrupted thread breach locking mechanisms don't turn on their own and they have angled locking faces. Frictional forces outweigh any angular sliding force vectors that may exist. However, what could conceivably happen is that if the locking faces are angled from wear then during initial stages of firing the rearward forces would lock the bearing faces under force of friction, then as the pressure drops the friction reduces to the point that it will slide and unlock the bolt under vibrational forces.



In the above photo one can see the cocking piece clearance. Now here I would suggest the bolt could rotate right into the cam faces yet it doesn't lift on firing. So that alone is likely not be the problem. It may have nothing to do with it but it then it may be a contributing factor.

So supposing one of the contributing factors is removed and the bolt doesn't lift most of the time, how would one know there is a potential problem lurking?

[Amatikulu]

I want to congratulate everyone that has participated in this thread about the way in which you have conducted yourself. Knowing the "thin skinned" nature of some of the members of the human race, you have had a very healthy discussion which so easily could have turned "nasty. " Having followed this thread from the beginning, I just felt that I needed to make this comment, and you all should know, I'm not the touchy feely type - I'm just truly impressed with the way in which this has been openly discussed. It makes me proud to be a member. Enough said!

[spentprimer]

Well, a new bolt arrived today and it looks to be in much better condition than the one we have been discussing. Since I do not have the proper equipment, know-how, etc., etc., etc., does anyone know of a qualified SMLE gunsmith in the Upper Mid-West of the USA that I could get to do a proper install, set CHS and safety check? I am in Southern Minnesota and am not opposed to driving a few hundred miles or shipping it.

Having compared the two bolt assemblies, the original bolt body seems to be quite worn in multiple places.

[303Guy]

I take it then that the lug recess faces are not worn into an angle? I've mentioned my action with a worn inner face. No replacement bolt will fix that one as it would bear only on the outer face. I don't recall whether you said the old bolt had matching numbers?

Peter Laidler has a write up on fitting a replacement bolt. It's an interesting read.