What is the service life of a 1917 barrel? 5,000 rounds? 10,000 rounds?
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What is the service life of a 1917 barrel? 5,000 rounds? 10,000 rounds?
Until it starts to throw groups all over the place. I have found some shot out early while others keep going. depends on how they are cleaned or what type of ammo.
Few people ever shoot that much, except serious shooting competition. In the military usually only machine guns.
So, depending on the ammunition you're using, you might find that your rifle is fine with one combination of bullet and propellent but atrocious with others. Those rifles were intended for military issue ammunition but even then some would be very accurate and others not.
Experiment until you find the right ammunition combination and keep to it, then keep shooting until the groups open up too much, then start experimenting again.
Short answer, there are too many factors influencing barrel life in a military firearm to say for sure, because nobody keeps track of the number of rounds fired through them. Read the books about the P14/M1917, somewhere it may mention what they found when testing the rifles before final acceptance,, that might be for the P14 only. Although I doubt the USA worried too much about that when they decided to change the P14 to 30-06 as it was 'available' and 'tested'.
It would have been designed around the issue ball .30-06 ammo of the day (1917), which of course is .30 M-1 ball, introduced, unsurprisingly in 1906, as a rapid response to the German introduction of THEIR ground-breaking, 150 (ish) grain, flat-based spitzer bullet that essentially rendered all other contemporary military rifle bullets obsolete.
Interestingly, the .30-06 "barrel spec" retained the 1:10" twist requirement from the ".30-03" with its original LONG, heavy, round-nosed bullet.
Conveniently, the P-14 in .303 has a 1"10" twist, so that was one less set of production tools to modify or replace on the shed-full of Pratt and Whitney sine-bar rifling machines.
As long-range machine-gunning became a serious battlefield tactic, a heavier, spitzer bullet was introduced, the "M2". The Germans had done the same thing with their 7.92 x 57 sS round several years earlier. See also the British development of the mighty .303 Mk 7 and the Swiss for their superlative GP-11 cartridge with its extra-slinky boat-tailed bullet. (A "battle" bullet designed and made by watchmakers).
Thus, the service .30-06 barrel in all manner of platforms retained the 1:10" twist of the original .30-03, whether it needed it or not.
Note that the subsequent 7.62 NATO went with a 1:12" twist, because it was sort-of standardized with a 147gn boat-tailed FMJ that would happily stabilize in that twist, at all temperatures and elevations. Initially, if I recall correctly, Britain and Australia went with a 144gn BTFMJ and a slightly different loading (L2A2) that was "outside the NATO spec." and thus did not have the little "cross in a circle" stamp on the head.
I know the expected number of rounds of M1906 ball out of a Springfield barrel were supposed to be around 6000 rounds back in the pre WWI period. This is with a .30o bore and .004 grooves, which makes the grove diameter .308 nominal, .3085
That said the M1917 used the Enfield like 5 grove with the lands being .005 dep, Bore .300, so in theory it should last a wee bit longer.
While it should last 8,000 or so there are other factors.
One of the good measurement to have is TE (throat erosion). It tells you how much its been shot though its not a guarantee of accuracy. A guy by the name of Steven Mathews makes what he is called a TE/MW (muizzle wear) for an interested buyer of 1903/1917 (caveat) If you have MW you are going to have more TE so the TE is more informative.
As corrosive ammo was used back in the 1917s day, a few thousand rounds and then not cleaned out cold leave the barrel a disaster. Lyman makes a low cost boroscope to check it out (you have to understand what can look awful is fine as Button Rifling and no lapping leaves a very ugly looking surface that works for a military gun just fine)
The following is from Shilen website. As you can see, while the 1-10 was for the 220, it means it will stabilize UP to 220. The 308 for military purposes was never going to load past the 150 so they sped it up. You can shoot 1-10 twist down to 125 gr with good results, sometimes very good.
Versatility is the 1-10 and is used in a lot of 30 caliber rifles and lower ones for that reason.Quote:
.308
- 7" * for heavy VLD bullets and/or subsonic ammo.
- 8" for bullets heavier than 220 gr.
- 8" Ratchet rifled 4 groove
- 10" for bullets up to 220 gr.
- 10" * Ratchet rifled 4 groove
- 12" for bullets up to 170 gr.
- 13" * Ratchet rifled 4 groove
- 14" * for bullets up to 168gr.
- 15" * for bullets up to 150 gr.
- 17" * for bullets up to 125 gr.
If you go back to Greenhill and his calculations, the critical factors are Length of bullet and the density of the air.
That second one was a prominent arguing point with the adoption of the M-16 and the M193, 55gn bullet. Original twist was 1: 14" twist. The 'Arctic" tests in cold, DENSER air indicated quite strongly that a change to 1:12" twist would be a good idea.
The 55gn, boat-tailed bullet at the "standardized" muzzle velocity was adequately stabilized in a 1:14" twist barrel everywhere except the deep arctic. The "adequate" stabilization IN AIR meant that as soon as that fast-moving bullet entered a different medium, ( like a big bag of red, oxygenated salt water), there was a radical change in the mathematical calculations and at the rotation provided by the 1:14" twist, the spin rate was insufficient to maintain stability after entering the 'new medium". THAT is the reason for the reports of "spectacular" wounds generated by the nascent M-16. Basically, the bullet started to YAW and in doing so, would start to tumble and / or break in two.
This phenomenon is not unknown in other "service" bullets, like the Mk7 ,303, for instance, where impact with bone would cause serious bone damage AND what is generally called "tumbling" as it kept on going.
An aside on matters of weight (mass):
For some years, competitors in the US military used "modified" M-16(A1) platforms in the "Match Rifle" division. One of the best bullets "across the course" was the Sierra 63gn SP spitzer, a slightly "dumpy-looking" flat-based bullet that is pretty much the same OAL as the M-193 bullet. Perfectly stable in a 1:12" barrel, unlike the one grain LIGHTER M-855 / SS-109 bullet. Why? the M-855 is LONGER for weight because it has a boat-tail and a long ogive AND has a composite lead / steel core. The M-16A2 went to a 1:7" twist. The M-855 will cheerfully stabilize in a 20 inch, 1:10" barrel, so why 1:7"?
The "experts" could not design a tracer that was of any real use until they came up with the FN L-110 / M856 tracer bullet which is VERY long, just because it has to contain enough trace compound to be still burning and visible, over 600M downrange. On the two-way rifle-range, riflemen often use tracer for target indication, hence the "necessity" of the fast twist in the standard service rifle.
If you look at "match rifles" in .308Win, you will find that many are running slightly tighter twists than the "standard 1:12". The slinky "Very Low Drag" bullets are "slinky" because, for their weight, they have longer ogives and boat-tails to maintain aerodynamic performance EXTREME range. A long bullet with a short bearing surface is a tricky thing to stabilize.
Bruce: Well done as you are correct for marginally stable bullets of which the M-16 ala 5.56 in its original speed, bullet size (barrel length of 20 inches) small diameter was one.,
Bullet design can create the ability to tumble as well (303)
The ones we are talking about are well stabilized ones.
When you can shoot anywhere from 125 gr to 220 grain you have a nice slot of stability to work with.
Bruce in OZ
Your information concerning the ammunition for the M1917 when it was adopted is incorrect. The correct nomenclature is: .30 caliber ball cartridge, Model of 1906. Below is an excerpt from the manual of The U.S. Rifle, Caliber .30 M1917. Issued by the War Department on October 8 1917, revised January 1918:
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As indicated, the cartridge fired a 150 grain, flat based , cupro-nickle jacketed bullet at ~2700 fps and had a published maximum range of ~4800 yards.
When the AEF entered combat in WWI, the US army had few if any Machine Guns so they borrowed British Vickers British MG’s firing the various marks of the .303 British cartridges and the French Hotchkiss MG’s using the famous Balle D bullet. When the US Browning MG s ,firing the .30 M1906 cartridge, arrived in France and were put in use, it was discovered that the maximum range was far short of the published 4800 yards (somewhere in the range of 3400 yards) and the US MG’s could not lay down long range covering fire as that had with the Allied MG’s. This caused a great fervor in the US Ordnance Corps which undertook to develop a satisfactory .30 caliber round.
Work began on a long range .30 caliber cartridge, but was not completed until after WWI ended. Development continued into the 1920’s and resulted in the development of the .30 Caliber M1 Ball round. This round fired a 174 grain, nine degree boat tailed, spitzer bullet with a gilding metal jacket at ~2640 fps which was adopted in circa 1926. Maximum range was ~5600 yards. The US Army had as lot of WWI ammo left and it was policy to use up older ammo first; therefore, the M1 Ball did not come into general use until ~ 1936. At that time it was found that the M1 Ball round would out range the safety zones of many rifle ranges. The National Guard Bureau requested that the Ordnance Department develop and furnish a round similar to the old 30 M1906 round. Thus was born the .30 caliber M2 Ball Ammo. It fired a 150 grain, flat based, spitzer bullet with a gilding metal jacket at ~2800 fps (Several different numbers are quoted in various sources as to the actual velocity. This became standard issue in ~1940 and thee M1 Ball was declared obsolete circa 1942 .
During WWII, the long range MG fire requirement was fulfilled by the .50 caliber MG. Because there was a lot of metal on the battlefield , the M2 Ball was generally superseded by the 30M2 AP round and 30 M2 Ball was relegated to training ammo . Since you do not identify which M2 round ( M2 Ball or M2 AP) you are referring to I cannot comment on it.
FWIW
So, of the "standard" infantry round was the 1906 Ball with its 150gn bullet, it would have been the one for the M-17.
The catch is that at .30-06 velocities that 150 gn bullet would EASILY be stabilized in a 1:10" twist barrel. That 1:10" twist was originally required for the /03 bullet which was somewhat longer. It seems that the relatively short /06 bullet performed well in that twist, even though not actually requiring it, and the rest is history.
The twist in an M-17 barrel is, indeed 1:10". The further "twist" is that the rifling is five-grooved and "left-handed", as per the .303 P-14. Thus it is quite different from the 03 /06 "Springfield" barrel.
What I was getting at was that it would have taken very little "re-engineering" to go from making P-14 barrels to making M-17 barrels; same twist rate, same twist direction, same number of grooves. The only differences are in the nominal starting bore diameters (.303 / .300) and the allowable groove depths, (VERY different). Probably more work in redesigning the mag follower, extractor and sight calibrations; any feature specifically related to cartridge loading, feeding, extraction/ejection related, etc..