Gas Port Erosion of AR-15 Barrels

[Molon]

The bore-scope view pictured below shows the gas port of a 20" AR-15 barrel with a rifle length gas system that has not yet been fired.




https://app.box.com/shared/static/yyq9nsaduxparwgxtblu687orp9e98vy.jpg




The next bore-scope view shows a 20" barrel with a rifle length gas system after only 1000 rounds have been fired through it. This view illustrates one of the reasons that certain high-end barrel manufacturers make the extra effort to ensure that the gas port is drilled in the center of a groove.




https://app.box.com/shared/static/osnc7f1v8sr150d08vbw6rplpd41x1c7.jpg




The shorter the gas system, the more rapid the erosion. The bore-scope view below shows the gas port of a 14.5" barrel with a carbine length gas system after only 500 rounds have been fired from it.




https://app.box.com/shared/static/uhnhx8jmh6gycls9tjg06zd98p6wrjxb.jpg




.....

[Mecha_Arms]

Very interesting info.

How much does the metal involved, SS vs 416R for example, affect that erosion? Are those barrels chrome lined? It'd be interesting to see how a melonited barrel would hold up as well.

[alamo5000]

That is interesting. I would imagine that a lot of things will have an effect. Cleaning procedures and products, type of metal in the barrel, and possibly even the type of ammo.

Just knowing that this is a 'thing' though is definitely food for though.

[Soisauss]

Holy smokes....that's kinda wicked and interesting.

[Cold bore miracle]

What type of barrels? CL, stainless?

[UWone77]

This isn't surprising. All those hot gasses and heat start eroding that gas port starting with the first round. Mag dumps don't help either. Most guys won't notice their ports are opening up because they don't shoot enough lead.

Great pictures Molon.

[schambers]

very interesting

[MoxyDave]

Luckygunner.com did an article on brass vs. steel-cased ammo a while back. There is some interesting info about barrel & port erosion here:

Brass vs. Steel Cased Ammo – An Epic Torture Test (http://www.luckygunner.com/labs/brass-vs-steel-cased-ammo/)

I agree that most folks will never shoot enough for this to become an issue ... myself included [:)]

[UWone77]

Luckygunner.com did an article on brass vs. steel-cased ammo a while back. There is some interesting info about barrel & port erosion here:

Brass vs. Steel Cased Ammo – An Epic Torture Test (http://www.luckygunner.com/labs/brass-vs-steel-cased-ammo/)

I agree that most folks will never shoot enough for this to become an issue ... myself included [:)]

Dave we all know you just have lots of guns to rotate through before erosion becomes an issue. [:D]

[alamo5000]

Luckygunner.com did an article on brass vs. steel-cased ammo a while back. There is some interesting info about barrel & port erosion here:

Brass vs. Steel Cased Ammo – An Epic Torture Test (http://www.luckygunner.com/labs/brass-vs-steel-cased-ammo/)

I agree that most folks will never shoot enough for this to become an issue ... myself included [:)]


That is an extremely interesting test they conducted there. Thanks for posting that up.

Once again WEVO delivers and I learn something [:D]

[SINNER]

Is the damage in the direction of travel? IE muzzle up in the photos. Just wondering how much could be attributed to physical damage to the tailing end of the port from the bullet passing it.

[UWone77]

I'm curious to know if LMT's 45 degree gas port drilling on the MRP's reduces the gas port erosion rate.

[MoxyDave]

Dave we all know you just have lots of guns to rotate through before erosion becomes an issue. [:D]

Hah well yeah, but I have some favorites ... Sadly I just can't afford enough ammo to wear them out ...

[Molon]

What type of barrels? CL, stainless?


The first and second pics are stainless-steel. The third pic is chrome-lined.

[Molon]

Is the damage in the direction of travel? IE muzzle up in the photos.



Yes.

[GOST]

MicroMOA has started doing angled ports on some of their barrels. This is from their Facebook page:

Angled gas ports have been beneficial in regards to port erosion..but we have found significant reduction in port sizes while maintaining reliability. We are doing these for our 12.5 mids and some 16 rifle gas available now. Thanks!

https://fbcdn-photos-f-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-0/11231083_1620235348260977_6210124510980519910_n.jp g?efg=eyJpIjoidCJ9&oh=036eaf5ea26dba99bb6e65cf9dd21a54&oe=562F9C3A&__gda__=1445685866_65690163cb73fa52898c4c9b2810eb4 9