Am I being silly?

Kevin Peacocke

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I am at a loss as to why your rifle is opening on firing. This seems to be much more than a headspace issue. I agree with others, do not fire or alter it further until VC weighs in. Have you tagged them on this post? They are on the site but may not have happened on this post. Given your location difficulties, they may concede to work with a local smith to rectify the problem.
I have contacted them formally through their agent in Johannesburg where I bought the gun. They have not had a reply back, but that is fair and reasonable given the time of year.
As to why it is opening, my take is that in a normal firing the explosion is directed forward and the reaction is backwards. In a split case near the base, with a little head space thrown in, the separated base in effect becomes a bullet and accelerates backwards violently. So you not only have the force due to the pressure of the escaping gasses right near the base, but an additional impulse like a hammer blow. Clearly the combined effect is massive as it has opened the breach every single time. Imagine the forces involved!
I agree with all of you, this is far too dangerous to fire the rifle again and as an engineer I am now absolutely convinced that any excess head space on a pivoting design with locking at 90 degrees to the firing plane is bound to fail.
 

M McDindi

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Expanding/magnifying the photo is interesting. Looks like the case wall on the sectioned case has a thin spot maybe just forward of where the crack is on the other case. Couple of random thoughts.....

1. Wondering what caused that thinned area? a) Could it be a defect in the manufacturing process of that batch of brass? b) is the bit longer headspace allowing the case to move back far enough that when combined with the slight taper of the chamber/cartridge and the heat of firing, causing the brass to "flow" in just that area to fill the void?

2. If it was an error in the quality control by VC and unless the action opened up on them during the regulation testing and if they only used factory loaded ammo, the cracks in the brass may have not been seen. It would be strange too, that VC would not have at least used a feeler gauge to confirm headspace during manufacturing or at least at final QC check before shipping.

3. I'm sure your smith there checked this but is it possible the chamber cut just a little too. When the action is closed, it may "appear" to be tight but, the cartridge heads are actually seating a few 1000's deeper below the breach face?

4, Just call me "Captain Obvious" but, did you try a different brand of factory ammo. I've heard/read of instances where the thickness of the case heads/rims can vary a bit between case manufactures.

Sorry if I'm just thinking out loud and you've already explored these things. Just hate to see someone go through long process of sorting out a difficulty with any "dream" purchase - especially with your added logistical problems and long delays. It really takes the shine off of what should be something special.

Michael

Edited to add - Have you tried to see if or how much the cases are stretching before and after firing?
 

IvW

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Not sure how folks want to fix this with all sorts off reloading suggestions. It is a 375 Flanged Magnum, it therefore uses the rim for proper headspace. The chambers apear to be cut too deep so the rim is loose in the recess, in fact think of it this way chamber is too long, recess for rim is too deep so when the cartridge is in the chamber the whole thing is loose. When the trigger is pulled all sort of nasty things are going on cartridge probably goes forward and then when fired slams back as the rim is not against the breach face(there is play), this causes pressure etc. Which forces the breach open. This also causes the thinning of the brass on first firing and subsequent split in second reloaded firing.

Pull the bullet from an unfired cartridge, de prime and then cut it open length wise and I bet it will be normal. Do the same for once fired and check.

Cartridges that headspace on the shoulder can be manipulated by only neck sizing etc. With rimmed cartridges if the rim recess is too deep you are stuffed.

Whatever you want to do measure check cut open cartridges etc. But please please please stop firing that rifle in the current condition.....
 

Kevin Peacocke

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Not sure how folks want to fix this with all sorts off reloading suggestions. It is a 375 Flanged Magnum, it therefore uses the rim for proper headspace. The chambers apear to be cut too deep so the rim is loose in the recess, in fact think of it this way chamber is too long, recess for rim is too deep so when the cartridge is in the chamber the whole thing is loose. When the trigger is pulled all sort of nasty things are going on cartridge probably goes forward and then when fired slams back as the rim is not against the breach face(there is play), this causes pressure etc. Which forces the breach open. This also causes the thinning of the brass on first firing and subsequent split in second reloaded firing.

Pull the bullet from an unfired cartridge, de prime and then cut it open length wise and I bet it will be normal. Do the same for once fired and check.

Cartridges that headspace on the shoulder can be manipulated by only neck sizing etc. With rimmed cartridges if the rim recess is too deep you are stuffed.

Whatever you want to do measure check cut open cartridges etc. But please please please stop firing that rifle in the current condition.....
No, no more firing! You are spot on with your analysis IvW. So i got out my calculator and did some first year maths, here is the story:
1. The broken off back piece of the cartridge weighs 7.9grams, or about 150 grains.
2. The diameter of the shell at that point is 12.9mm or 0.51 inch.
3. The force on that back piece by ratio of area is about 1.8 times the force on the back of the 375 bullet.
4. Assuming the pressure to be 47000psi, the force on that piece is 9536 pounds force, or about 4.4 tonnes.
5. The shell stretches and then suddenly parts and accelerates backwards. This is more violent than the bullet heading up the barrel as it experiences smoother acceleration.
6. The back piece now parted from the case slams into the breach face with a blast of escaped gas to add to the force.
7. This whole event happens, if my calcs are correct, in about 6 one hundred thousandths of a second.
the impulse force of hitting the breach face is a function of the head space. No head space, and it is just the 9536 pounds, as in a close fitting breach. The more the head space, the more the impact due to velocity. For example, gently nudge your truck up against a wall until it is touching. Floor the accelerator and all you will get is smoked tyres. Back off a metre however and ram the thing and the wall will fall over.
8. Bottom line, head space is bad news. Head space and a split case is far worse, potentially catastrophic in fact.
 

DG Gunsmith

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No, no more firing! You are spot on with your analysis IvW. So i got out my calculator and did some first year maths, here is the story:
1. The broken off back piece of the cartridge weighs 7.9grams, or about 150 grains.
2. The diameter of the shell at that point is 12.9mm or 0.51 inch.
3. The force on that back piece by ratio of area is about 1.8 times the force on the back of the 375 bullet.
4. Assuming the pressure to be 47000psi, the force on that piece is 9536 pounds force, or about 4.4 tonnes.
5. The shell stretches and then suddenly parts and accelerates backwards. This is more violent than the bullet heading up the barrel as it experiences smoother acceleration.
6. The back piece now parted from the case slams into the breach face with a blast of escaped gas to add to the force.
7. This whole event happens, if my calcs are correct, in about 6 one hundred thousandths of a second
the impulse force of hitting the breach face is a function of the head space. No head space, and it is just the 9536 pounds, as in a close fitting breach. The more the head space, the more the impact due to velocity. For example, gently nudge your truck up against a wall until it is touching. Floor the accelerator and all you will get is smoked tyres. Back off a metre however and ram the thing and the wall will fall over.
8. Bottom line, head space is bad news. Head space and a split case is far worse, potentially catastrophic in fact.
Right on the money, Mate! Most people don't understand just how critical Headspace is... Too much Headspace, and you'll end up with a ruptured casing, which could cost you an Eye, or worse...
 

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You may have seen on various posts and replies I have made that I bought a new Verney Carron 375 Flanged Magnum O/U. This is/was my dream rifle, it fits perfectly, it is well regulated and I shoot it well. Nice wood, light, finnesseful. Problem is it has excess head spacing, the top barrel more than the bottom one, 24 thou and 12 thou respectively. The net result is that it shoots fine with new cases, but splits reloads, both top and bottom barrel, on the first or second reload. So all ammo must be new, which is not easy in Zimbabwe, but nevertheless doable.
The question - should I accept this situation and keep the Verney, or write it off and start dreaming of a Heym 89B? Is this a fatal flaw, or just an annoyance that I am over-reacting to? What would you do?
@Kevin Peacocke
I would personally opt for a Heym Model 89B , if I were you . The shell casings ( of reloaded ammunition ) splitting and the action opening , are major deal breakers for me . I would also highly recommend a Krieghoff double rifle , unless you are particularly fixated on the Heym .
 

DG Gunsmith

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@Kevin Peacocke
I would personally opt for a Heym Model 89B , if I were you . The shell casings ( of reloaded ammunition ) splitting and the action opening , are major deal breakers for me . I would also highly recommend a Krieghoff double rifle , unless you are particularly fixated on the Heym .
Krieghoff is the Holland & Holland o' Germany...
 

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Hi Kevin. Thanks for the photo. That clears it up a lot. What you have is a classic "case head separation". Its caused by the case stretching to fill the chamber. Its a different problem to "splitting" which generally refers to longitudinal splits in the case neck or shoulder caused by work hardening due to excessively resizing the shoulder/neck area.

In the sectioned case you can see the ring on the inside of the case just in front of the case head. Again a classic symptom. Some people use a bent piece of wire to feel for the ring before reloading a case. I've never had any luck with that technique. Also sometimes you can see a ring of lighter coloured brass on the outside of the case in the matching position.

Obviously the proper solution to the issue is to have VC examine the rifle and provide a solution. An alternative method is to start with new brass, fireform to chamber size. Then either only neck size or minimally resize the case using the method described by @Phoenix-Phil (or similar process using Hornady Comparator kit).
 

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How do you only want to neck size on a cartridge that relies on the rim for headspace when the rim recess is too deep?.....this is a 375 Flanged Magnum....the rim is the headspace determiner......not the shoulder....
 

PHOENIX PHIL

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How do you only want to neck size on a cartridge that relies on the rim for headspace when the rim recess is too deep?.....this is a 375 Flanged Magnum....the rim is the headspace determiner......not the shoulder....

Are the now once fired cases in Kevin’s rifle not fire formed to his chambers? I believe they are. If so then neck sizing or the procedure I mentioned above would reduce case stretch on subsequent firings and eliminate the case head separation issue.

At least in theory......
 

IvW

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NO!!! How do the rims fireform when recesses for them have been machined too deep? The rim is the back part of the case ....
Yes the case body will form to the chamber size but nit the rim...
 

IvW

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The differance between cartridges that rely on headspace on the shoulder vs cartridges that headspace on the rim needs to be understood... if the rim headspace section is cut too deep that is it you need new chambers which in the case of a double O/U or SXS means new barrels....simple as that....
 

degoins

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Again, I wouldn't judge or change anything based on Bertram rim thickness. I would use what it was regulated for. If I had problems with that, then it would be on VC to handle it one way or another.
 

PHOENIX PHIL

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NO!!! How do the rims fireform when recesses for them have been machined too deep? The rim is the back part of the case ....
Yes the case body will form to the chamber size but nit the rim...

Yah, you’re right on that of course. And if most of the stretch is coming in the rearward direction due to the excessive cut in the recesses.....well my idea won’t help much if any.
 

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Kevin, do you know anyone else that reloads for this caliber? If so, trying some of their reloads would sort out a couple things. If their reloads work just fine, the issue is probably your reloads. If they show the same failures, you have no choice but to get the rifle repaired by the manufacturer or one of their designees, at their expense of course.
With the existing problems I wouldn't chance putting a round of anything in that thing, factory or reload. Seems to me the more you shoot it the more the problems increase therefore increasing the danger of a catastrophy.
 

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Gentlemen , I'm not a gunsmith. lets hear what Verney has to say. Surely the new barrels have to be regulated with the rifle and cannot be just sent seperately ? Double gunsmiths could advise here.
 

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