Testing a barrel to see if it's safe to shoot?

Hello! Like a lot of folks on here, I'm looking into doing a restoration on an IMA Nepal Cache weapon. I'm currently looking at an 1853 Enfield. While I decide which direction I want to go, I'm researching everything I'll need to know to do a good, proper, restoration to (hopefully) shootable condition. I understand the barrels on these usually come with some significant pitting and have heard people mention testing the weapons to make sure they are safe to shoot.

Question I have is: Whats the best/proper way to do that, other than just loading it and firing it with a shoestring?

Wagnam: No idea if it's applicable to one of the Nepali-manufactured "P53" type rifles but Roads ("The British Soldiers's Firearm", pg 70) summarizes the P53 proofing as follows: First proof: tightly fitting 730 grn bullet with 7.5 dr. powder; Second proof: ("less severe......very rarely, indeed, burst the barrel") used 5 dr. of powder. The standard charge of 70 grn powder is 2.5 dr. If you aren't already, you might consider joining the British Militaria forum on which there is lots of discussion of the IMA guns (and the shooting of them).

Ridolpho

Hmmmm? I think it's all a bit sleepy at the moment. Too much good living. Time to stir it up a bit.

Shall I try to put it poilitely?

IMOH, using 3 times the service charge of powder to test a 160-year old barrel is pushing yout luck. Plus the additional pressure rise resulting from the inertia of the extra-heavy bullet, and you are creating an overpressure, compared with the service load, of SEVERAL HUNDRED PERCENT.

If the barrel wasn't knackered before, it probably will be afterwards. If it doesn't burst, it may have been strained beyond the elastic limit of the steel. Meaning that its capability to resist pressure has been sharply reduced. So it has in fact been rendered more dangerous, and the "test to see if it's safe to shoot" is, again putting it politely, counter-productive.

Ignoring gunnery for the moment, think about the motor of your automobile. The rev-counter is red-lined at, say, 6000 rpm. The manufacturer will have conducted destructive testing, and sets a safety reserve, having established that a typical example will take, say, 7000 rpm for a few seconds. But somewhere between the red-line and the 7000 rpm is a point at which, although the user does not immediately notice it, the damage to the bearings is sufficient to cause an early failure. So would you test your motor by revving it up to 3x the normal limit - 18000 rpm? I think not.

OK, I know i'm being disingenuous, because (if my memory serves me right) the pressure on the bearing increases as the square of the rpm, so 10000 rpm is sufficient to produce a disastrous 300 % load.

Or a simpler example without dynamic complexities: The floors in your house will have been designed for a maximum static load of something like 1 ton per square metre (depends on your local building regulations, of course). Would you let someone interested in buying it apply a load of 3 tons /m² to see if the house is safe for occupation? I think not.

Or apply 3x the rated supply voltage to your electrical equipment, to see if it is "safe to use"?

Of course, in industrial mass production, samples are tested to the point where damge becomes apparent. But this is in order to establish the safety margin for normal use, and such samples will no longer be marketable after testing.

Now lets get back to gun barrels. The CIP Pmax with the copper-crusing method as about 4800 bar. Try 3x that, 14400 bar, and the barrel will shatter. I understand that modern proof levels are of the order of +30% of the maximum. (Once again, anyone wh knows bettershould please correct me). 300% would be a pointless destructive testing.

The proof-testing of gun barrels was introduced before modern methods of metallurgical investigation for cracks etc were available. It was the only way to sort out the duds . with the concomittenteffect of possibly weakening examples that would otherwise have had a longer working life. But the test was applied before the barrel was put iinto service. To repeat it after 160 years is, I have to put it bluntly, NOT A GOOD IDEA.

Patrick: I believe the general idea of "proofing" is to subject the barrel or barrel plus action to a pressure overload to increase the odds of a defective example failing and I think it's useful to see what the original practices were. I guess in the case of older antiques, the question is: does "proofing" with a normal load prove safety? Does one firing at normal stresses prove it's safe. Could shot number 3 or 23 be the one where it lets go? Would an overload establish some margin of safety or, as you suggest, is it just as likely to induce a failure later? I don't proof test my P53's, Sniders or Martini's, I just inspect them very closely and watch very carefully for any signs of problems after the first few normal rounds. However, I have an 1811 EIC Windus musket I'm toying with the idea of firing and am interested in hearing how others with more experience at this would go about evaluating it for safety. And getting back to the OP, these Nepali P53's are known to be metallurgically inferior to the English product. Is some sort of mild overload/ proof a worthwhile thing for the owner to try? Regards.

Ridolpho

In the interests of safety caution is the catch cry you surmised by your own statement the inferior metallurgy of the Nepali units is questionable at best so why risk it as the first thing you will come to realize of the imminent failure of the firearm will be when it grenades in your hands.
I mean you could try very reduced loads but how does one surmise the rifles capability NDT test the whole lot call me a wuss but with the known amount of pressure just in front of your beak I would rather keep it & not shoot it, though you could tie it to a tree or bench but that only proves it did not fail that time what about 5-10-15 shots latter.
Nah! not for me but you may wish to walk a tight rope.

I think Patrick has been putting it very eloquently for you.

Thanks for the comments. Just now, I wanted to correct some typos in my contribution, but when I select "edit" the text box comes up blank. Has anyone else had this effect, and is there a solution?

Boothroyd gives the UK provisional proof for .45 as 212gn of Tower Proof Powder (TPPH) and the definitive proof as 170gn, both behind a 640gn bullet. The provisional proof was carried out on a bare plugged barrel fired through a simple touch hole. The issue with proofing a breached action is getting more than the service (85 gn) charge behind the projectile! Both proof firings are carried out remotely.

You need to understand that the UK proofing process involves more than simply firing the charge. The gun is inspected and guaged both before and after the definitive firing to ensure the bore has not been ringed or enlarged. The proof firing must ensure that the metal has not exceed the limits of elasticity. The bore is cleaned and then "viewed" to ensure there is no distortion.. this is the real test and takes a degree of skill..

The gun barrel proofing regime may not have been based on modern material science knowledge, however it does seem to have stood the test of time, and is still relevant. Normal gun barrels do not suffer from metal fatigue as the number of duty cycles never reach the point where stresses reach failure levels. Provided the barrel is not damaged, corroded or heat affected, the bore will wear to the point where accuracy is seriously compromised well before the barrel fails mechanically.

Most gun failures occur because of overloading, incompetent gunsmithing, or bore obstructions..

A final "comment" on the theme of proof-testing of ancient rifles:

http://www.egun.de/market/item.php?id=6773902https://www.milsurps.com/moz-extensi...rGoodImage.pnghttps://www.milsurps.com/moz-extensi...rGoodImage.png


One may assume that the German proof houses are well aware of the aspects noted in the previous post from bombdoc, so I am very surprised that this should have happened. Of course, the unfortunate rifle may have been one of those dubious objects assembled by Hartley & Graham, or Bannermann, from arsenal clear-outs and condemned material.https://www.milsurps.com/moz-extensi...rGoodImage.png

"...the general idea of "proofing" is to subject the barrel..." Yep, except that method uses 19th Century technology on an antique. The BP used in 1853 was vastly different from modern BP.
7.5 drams of FFg Black Powder, that is measured by VOLUME when reloading not mass, is 205.08 grains. Pretty much a guaranteed barrel buster for a valuable antique.
Take the thing to a BP smithy. However, if it's one of the rusted cracked stock, 2003 acquisition of the Nepal Royal Arsenal, rifles, it's waaay too far gone to be financially feasible to restore. Its condition isn't good enough to be a wall hanger.

To get back to the OP- what is the best way to test a Nepali P53 type rifle to prove safety? With a British ordnance issue (or, I suppose a volunteer/commercial equivalent) P53 one knows it was subjected to, and survived, a pair of proof loads. Given that, to my knowledge, iron doesn't "age" in the short time and conditions we're talking about, assuming no intensive corrosion of visible defects, that proof still means something. Based on the little available material on the Nepali "P53's", I don't think it is known that they were even proofed. They may have been forged differently (twist) out of lower quality iron. Does one 70 grain load fired with a string constitute an adequate safety test? Can a "BP smithy" guarantee safety by examination? I would suggest looking for a real P53 made in England/Belgium/USA,etc?, or, possibly, a modern replica, if shooting is in your plans and you don't feel comfortable with your own knowledge of these issues.

edit: add photo. This is a worn out Snider I chopped up. This cut is just above the chamber in this converted 1859 P53. The thickness of the barrel is slightly greater than 0.20" (in the grooves) at this spot. That's a lot of good British iron! No wonder the original proof loads didn't blow up too many.

Ridolpho

O dear! What a sad case - was the muzzle end ruined? I hope you at least recovered some usable parts from the wreckage.

Getting back to the proof question: the old method of applying a near-fatal "dose" and then saying "the patient didn't die, so he must be healthy!" seems a bit primitive. Surely modern methods of metallurgical investigation must be able to offer a better, non-destructive way of testing? Does anyone out there have any insider knowledge?