Hows this gas port

[CINDERS]

Was looking for information on Fire cracking and throat wear and came across this one of a gas port that has been machined to expose the inside of the barrel I think they said M-16 she is rather sad that barrel.......
Mind you that barrel has oodles of fire cracking.....

2nd pic of some test barrels from the same page now they are really flogged out...................

Information

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[mrclark303]

Barrel Cinders, looks more like my leaf filled gutters, come to think of it my gutters probably have better ballistic properties that that barrel, the newness has certainly worn off!

[browningautorifle]

You can see how it started to erode from the first spot the gasses entered the gas port. Through time it enlarges...to that. Very interesting...

[Peter Laidler]

Yep, certainly very interesting and does illustrate the point. Never saw such a good cutaway example. I bet there were flames whacking down that gas cylinder!

[Aragorn243]

Did it say anywhere how many rounds it took to get to that point? I've watched a few vids on the barrels where they fire full auto almost continuously and it doesn't take long to melt or burst them but the gas port is something different.

[Peter Laidler]

We did a similar test with the Dillon minigun trials where we just fired non stop until............. well...., something broke. And it did, big time. But the gun didn't stop. One of the barrels just disintegrated so due to the danger, WE stopped the gun!

[skiprat]

At my 1st Unit we had an Air Defense Battery that used to run the Divisional All Arms Air Defense course, 2 weeks of firing at radio controlled aircraft.
Using the L37 version of the GPMG ( fixed gas regulator....So firing as fast as 1000 rpm) 24 guns for the whole Div. .... Inspection of the guns after the shoot I dropped the bore gauge 0.297 and it ran all the way through as it should...
Then I dropped the 0.306 ( to measure throat erosion) it should not enter the barrel more than 4 inches (including the chamber) the .306 ran the full length of the barrel freely.

We sectioned the barrel ( had nothing better to do for the week) there was no visible rifling in any of the bore, it looked more like the surface of the moon.
The throat had opened up wider than the neck of the round, and the erosion was not even along the length of the bore, more like a series of bulges.
The gun was still firing (all be a bit slower!) all the way till the last round down range

At the start of the shoot the barrel was well within spec, as they were inspected every 6 months..

[mrclark303]

At my 1st Unit we had an Air Defense Battery that used to run the Divisional All Arms Air Defense course, 2 weeks of firing at radio controlled aircraft.
Using the L37 version of the GPMG ( fixed gas regulator....So firing as fast as 1000 rpm) 24 guns for the whole Div. .... Inspection of the guns after the shoot I dropped the bore gauge 0.297 and it ran all the way through as it should...
Then I dropped the 0.306 ( to measure throat erosion) it should not enter the barrel more than 4 inches (including the chamber) the .306 ran the full length of the barrel freely.

We sectioned the barrel ( had nothing better to do for the week) there was no visible rifling in any of the bore, it looked more like the surface of the moon.
The throat had opened up wider than the neck of the round, and the erosion was not even along the length of the bore, more like a series of bulges.
The gun was still firing (all be a bit slower!) all the way till the last round down range

At the start of the shoot the barrel was well within spec, as they were inspected every 6 months..

Its a credit to the designers at Fn that the thing was still rocking and rolling, even though effectively smooth bored Andy! Was the sectioned barrel kept, sounds like a great training aid...

[browningautorifle]

The pics of the four M4 barrels are possibly combat failures, they had various...sand blockages, extreme heat failure, bolt locking lug failure...various that we might expect with educated guess. That's what they look like anyway, that was a while ago.

[CINDERS]

Found this table interesting.