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Shot gun proofing question


manthing
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How does one know to what standard their gun is proofed?

I ask because I've just picked up a box of

Gamebore Special Load

12g, BB, 36gms 70mm.

And before I use them I need to satisfy myself the gun is up to the 3.25 tons psi that they generate.

I found the proofing marks on the underside of the barrel block but can't find a specific proof Mark fro the pleasure quoted.

The gun is a Lincoln no2 btw

Any help would be appreciated

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I will try and post a photo of the proof marks later.

 

Yes I got a box as I've seen a fox moving from land I have permission on into the pens in some woodland I don't have permission on and was just trying to do the keeper a favour, no ulterior motives at all,,, honest.

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  On 13/08/2017 at 22:06, manthing said:

How does one know to what standard their gun is proofed?

I ask because I've just picked up a box of

Gamebore Special Load

12g, BB, 36gms 70mm.

And before I use them I need to satisfy myself the gun is up to the 3.25 tons psi that they generate.

I found the proofing marks on the underside of the barrel block but can't find a specific proof Mark fro the pleasure quoted.

The gun is a Lincoln no2 btw

Any help would be appreciated

Purely for info as you already have the answer. 3.25 tons per square inch. PSI is pounds per sqare inch. Never seen them but you might just find that the 3.25 is the required proof pressure for the gun in which they are to be used and not that which the cartridge develops.

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  On 14/08/2017 at 07:44, Scully said:

No, you're not.

 

+1.

 

If it's a 70mm chamber, it'll fire 70mm commercial cartridges safely.

 

If it wasn't going to be capable of that, it would have gone bang by now. A gun is a pressure-bearing device operating well within the limits of the steel of which it is made. This is why firing a couple of proof cartridges and measuring the chamber / inspecting for cracks is actually sufficient to determine safety. Because metal only deforms / cracks when it's Young's modulus is exceeded (I think its Young's and not Hooke's), any force which doesn't exceed its tensile limit will be successfully resisted. This doesn't change with age - it's a property of the metal itself - so provided the gun isn't allowed to rust / degrade, a gun that safely fired 2¾" nitro cartridges in 1922 - for example - will safely fire them today.

 

You'll also probably find that a good number of "high speed" clay cartridges produce pressures as high as (or higher than) many hunting loads. 36g isn't much shot on slow powder in a 12ga - you can load it with plenty of wiggle-room, pressure-wise.

Edited by neutron619
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I know I have some shells which are 70mm that my SxS's can't handle pressure wise but were fine in the SA when I had it.

 

But they were labelled magnum loads.

 

I think from memory my shotguns had 900kg? marked on them but the shells had 1500kg? was a while ago now so my numbers could be out

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I can't seem to get a photo to pick up the marks....

I asked the question purely because it's the only time I've seen such a warning on the box, to be honest it put the willies up me a bit.

Supplementary nubie question. Lol

The gun is marked at 76mm so does that mean it will take 3" magnum shells

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  On 14/08/2017 at 21:09, scotslad said:

I think from memory my shotguns had 900kg? marked on them but the shells had 1500kg? was a while ago now so my numbers could be out

 

I don't think there have ever been any shotguns proofed at 1500 kg/cm² or 1500 bar (close, but not quite the same pressure), but you may have seen cartridges indicating 1200kg or 1320kg for maximum individual pressure or equivalent proof pressure for the loading.

 

The tables used by the CIP are here:

 

http://www.cip-bobp.org/homologation/en/tdcc_public?page=1&cartridge_type_id=7

 

You can see - apart from all the pressure values associated with the different gauges and chamber lengths, that there is such a thing as a 3" 28-gauge cartridge, a 3½" 20-gauge cartridge and that they still, occasionally, encounter 14-gauge guns. :hmm:

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  On 15/08/2017 at 10:04, manthing said:

I can't seem to get a photo to pick up the marks....

I asked the question purely because it's the only time I've seen such a warning on the box, to be honest it put the willies up me a bit.

Supplementary nubie question. Lol

The gun is marked at 76mm so does that mean it will take 3" magnum shells

Unless those were made for the USA market, I'm surprised that there aren't additional figures for suitable proof given in addition to the older UK tons.

Re the 3" magnums - possibly but not necessarily. Have a closer look at the proof marks. Beware though, the gun is Italian so there will be a barrel weight stamped on there and it is possible that this can be confused with a proof pressure given in Kgs/cm2

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Also beware that there are (Italian) guns out there which have 3-inch chambers and "Superior Proof" to 1000kgs, which is not equivalent to modern 1200bar "Magnum" proof.

 

These were guns intended for use with home-loaded or other special types of ammunition. They're usually marked with "provisional proof", "final proof" and "supplementary nitro proof" marks, along with the number of kg/cm² (i.e. 1000).

 

In practice, you'd probably get away with it, but it may be worth bearing in mind.

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  On 15/08/2017 at 11:58, neutron619 said:

Also beware that there are (Italian) guns out there which have 3-inch chambers and "Superior Proof" to 1000kgs, which is not equivalent to modern 1200bar "Magnum" proof.

 

These were guns intended for use with home-loaded or other special types of ammunition. They're usually marked with "provisional proof", "final proof" and "supplementary nitro proof" marks, along with the number of kg/cm² (i.e. 1000).

 

In practice, you'd probably get away with it, but it may be worth bearing in mind.

This highlights my point above nicely. One is barrel weight and the other, proof.

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  On 15/08/2017 at 13:39, manthing said:

You lot are just doing me nut in now...

Going to have to find a better light to photograph it in and you can then advise as appropriate.

 

Ok - we'll take a look if you think it's worth uploading the pictures. However, if you can find the numbers "12-70" anywhere on it, probably inside a diamond, or if the second number is larger, you are unequivocally good to go.

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  On 15/08/2017 at 13:39, manthing said:

You lot are just doing me nut in now...

Going to have to find a better light to photograph it in and you can then advise as appropriate.

:lol:

Don't panic. You've got the chamber length sorted so just look for the figures as mentioned. Just one thing, the weight is in kgs so you might just see - dependent upon how neat the stamping is - a comma (or whatever) which is actually a decimal point. Ie, 1.200kgs. Two stars each inside a 'cog' side by side would be good.

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On the top barrel it's stamped 76mm and 18.4

The bottom barrel is stamped KG1.550 and 18.4

This should be a photo of the block

DSC_0543.jpg

 

Top line is serial number and what looks like makers stamp, bottom is I'm assuming the proof marks

Edited by manthing
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OK you have the 2 stars we were after.

 

Before you have a look here: http://www.shotguns.se/html/italy.html a brief explanation. When you scroll down to the 2 stars, you'll see a figure for PSI. When you divide this by 14.5 to convert it into Bars, it won't be quite right. This is because a while back some bright boffins at the SI (SI Units) - possibly to simply justify their existance - decided to change its value for some - not all - applications of which our needs fell into one such category. Consequently, if you use the value which was used at the relevant time - 14.7 - it makes perfect sense and you'll realise that you have a superior or magnum (lead) proofed gun.

 

Edit: Oops, didn't see Post #20, there's the barrel weight as described.

Edited by wymberley
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  On 16/08/2017 at 09:18, manthing said:

So I don't need to worry, I can load anything upto and including 3" magnum in lead shot?

 

Yes - the 17637psi pressure indicated by the marking exceeds 1200 bar which is magnum proof pressure. You're quite safe.

 

However, the gun isn't steel proofed, on the basis of anything you've said so far. You meet the pressure requirements, which is the main issue, but the proof houses do other inspections / tests for a specific steel proof mark to be applied. Once again, you'll probably have no issues, but it's really up to you.

Edited by neutron619
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