Antique Firearm collecting

[edbear2]

[QUOTE=barryeye;3745827]

Ah. Now that could be the answer. I too have seen similar rifles including Martinis. However I was talking to a fellow collector today and he was of the opinion that steel goes "off" with age and that 150 year old rifle barrel will not be as strong as when it was made no matter if it has been well cared for and never fired. I'm still not sure about this but confess that it is out of my personal exterience to answer.
I own a number of Martinis and up until now have had no doubts about any of them that have been checked by a gunsmith or have come from a prevous collector that has shot them. I now have doubts.
Barry

Hi Barry........This theory of your friends ......There is no scientific basis for it......Known and tested alloy steel compositions which have a "proof" or "yield" load done on test pieces as specimens, and where this data has been recorded, and the said pieces have been retested, have all shown no change in their original properties even after many years.......The problems are that; The methods used in the days when a lot of these old guns were produced were not as accurate as since the early 1900's (and actually in the 1950's, the Linz-Donawitz process of oxygen control).This is the main problem....A tube may pass the proof load, but there were no x-rays or ndt testing in those days!...on many old guns also there is no way, apart from obvious bulging or visible indications, of overloading, or excessive stress cycles which are leading to failure, The other comment of a close grained, grey appearance on a break only gives an indication of a fairly hard, and possibly brittle composition....It may be that the piece was not tempered properly, and so was susceptible to breakage, or it may have been a correctly designed part, taking a high load, that just failed due to excessive strain...(it would be interesting to break a similar part that was of recent manufacture to compare the grain structure)..a bit like a cast iron part....will take huge compression, and steady loading, but wack it somewhere where it is thin with a hammer.......see what I mean?

The older stuff I have shot, and seen used, is normally loaded light in deference not so much as to it's age, but to it's unknown state.....at the end of the day, you are dealing with high pressures on parts that you do not know the history of, do not know if they were made from the exact design and composition of metal intended etc....The craftsmen and barrel makers had great skills in those days, but the results varied a huge amount compared to what we have learnt in the last century.

Just to give a tiny idea of the science of basic carbon steels;

http://steel.keytometals.com/Articles/Art62.htm

Note the huge changes in properties given by the addition of just 0.1 -3 % of different alloying elements, and therefore the result of getting it very, very, slightly wrong!.....For sure, you could have done basic hardness, ductility, toughness tests back in the days when some of the older guns were made....but in no way could you be as 100% confident in the final product as in recent times.

ie.......the difference between a horse shoe, and a differential gear is about 0.6% carbon content!..scary!