That line about the sight adjustment sure sounds like what I heard on "Gringo Pistollero" - although I seem to recall that the shot was uphill, rather than down. I tried searching for "Gringo Pistollero" on several engines, with no results. Not surprised, as this was a pretty obscure song and certainly non-PC. I'm not yet convinced that we're not talking the same song, here.".. Wasn't the '06 an earlier Mauser style rifle?.."
The Springfield M-1903 rifle "borrowed heavily" in design from the ledgendary Mod. 98 Mauser. So much so that the US Government actually had to pay a penalty for patent infringement to the German Mauser Verkes prior to WW-I. The U.S. historically has never been above "appropriating" a good idea when it sees one, especially when it comes to ordnance. Our first flintlocks were essentially clones of the French .69 cal.Charleville, and we took "heavy inspiration" from the French in Artillery and small-arms throughout the black-powder era. After flirting with the Danes with the Krag-Jorgensen, we seemed to have taken a fancy to German technology. Good thing, too; they were really good at it! The US 90MM cannon which was used from WW-II up through VietNam (I'm not sure but what they are still in use somewhere) is little more than the notorious German 88MM with minor modifications.
"... The "Enfield" design picked up by USA was the British P14, being made in USA for Britain,..." I could look this up, but off the top of my virus-infested head, it seems that the British 7MM system was in development with the British ordnance dept. around 1912-13 in anticipation of having a problem with the Hun. This too was a development of the Mauser system, but considerably "beefed up" to handle the higher pressures of the special round. this new round was way ahead of it's time, essentially equivelent to the modern 7MM Magnum. The P-14/17 family of actions are highly desireable by Gunsmiths as the basis of custom-built high-power big-game rifles, as they are probably one of the strongest actions ever built. I sold an old '14 recently to a friend who had it re-barreled to .45-70 (since the '14 was designed to feed rimmed cartridges) and it is well known that this cartridge in such an action can be loaded up to darned near .457 Winchester Magnum ballistics; ergo; "Elephant gun"! The rear sight "ears" are ground off, a scope mounted, and they make up to a pretty slick sporting rifle.
"...in (~) .276" or 7 mm. This was always a bit too hot for the ordnance steel of the day and the Yanks had the sense to rebore it for their .30" '06 round when they adopted it as the M17 (in 1917)."
Strength of the action or quality of steel was not the issue...
Unfortunately, WW-I happened before the 7MM project really got off the ground. Not enough P-14's could be produced to justify an Empire-wide ammunition conversion, so they decided to stick with the .303 British, and Remington contracted with the Brits to produce the P-14 in .303. Before long, the Brits were dealing with Dunkirk and running out of money, so defaulted on their contract; production of the P-14 ceaced. Now along came 1917, and the U.S. realized that it could no longer sit out WW-I. Problem was, Springfield could not keep up with production demand for a World War, and National Arsenals did not have enough '03s on hand to go around. Recognizing the fact that Remington and other US manufacturers were all tooled up to crank out the P-14 and that it was a passing-fair Battle Rifle, they hit on the bright idea of converting it to the US standard .30-06 and issuing it to US Troops; Viola'; the P-17! It seems that more US "Doughboys" actually went into action with the P-17s than Springfields in WW-I.
Apparantly British soldiers referred to the P-17 erroniously as the "Springfield", since it was made in the U.S., while Doughboys were fond of calling it an "Enfield" due to it's British design and distinctive combless buttstock and "hook" pistol-grip. It was neither, really.
The reputation for "burning out barrels" your Granddad alluded to is more likely to be a function of the early "cordite" propellant and corrosive mercuric priming than any fault of the rifle. Sgt. YORK captured an entire German Company with his P-17; with it's 17" sword-bayonet, it is a formidable weapon. Somewhat heavier than the '03, it was not as popular with Infantrymen - but could hold it's own in most cases on the Battlefield or target range. The P-17 was produced at the Remington Arms facility as well as Winchester and Eddystone Arsenal.
"...Rifle #1 mk. III* ... We Australians had that model in both World Wars ... and they were still on issue to the Cadet Corps when I was at High School - '50s/'60s!
Shucks; I might have the rifle you drilled with down cellar! (pretty long shot). It is a Lithgow Arsenal 1915 SMLE No.1 Mk III. I bought it cheap as a "Drill-Purposes" demil, but with a new firing pin and extractor, it was brought back into service. It had such a "cherry" "HP" ("High Power" WW II replacement) barrel, shucks; I had to! I even put a WW-I magazine cut-off plate on it, as well as a nifty little grenade-launcher. It just so happens that an Australian WW-I hand-grenade is just the same caliber as an American 20th-Century tennis ball... and what fun that is!
The old SMLE's were not a particularly strong or stable/accurate action, but they perfomed well under battlefield conditions and were probably one of the fastest bolt-actions ever issued. They earned their reputation well.
If you want to "talk guns", drop me a PM and we can take it to another forum perhaps more appropriate to that topic, and where there are folks a lot more qualified than I to bounce it around with. There are some "political" issues around the rights of private Citizens to keep and bear arms I'd like to discuss with the Victims of police-state "disarmament" programs - like Australians - as well... but probably not here.
Later, Mate!