AR10T case rim strike - issue?

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12 years 6 months ago #37032 by OleCowboy
Replied by OleCowboy on topic AR10T case rim strike - issue?

MrMarty51 wrote: There also appears to be a little bit of a crease at about the one to two o-clock positions.
Not exactly opposite the smear mark.

I noticed same same. It light but clearly there and its visible on at least 3 of them.

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12 years 6 months ago #37034 by MrMarty51
Replied by MrMarty51 on topic AR10T case rim strike - issue?
The angle and the light on the third from left casing makes the mark almost invisible.
I did`nt see it on that one at first either. :busted: :rotfl:

Might be a thing as "Tired eyes" for Me. :whip: :rotfl:

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12 years 6 months ago #37054 by jtallen83
Replied by jtallen83 on topic AR10T case rim strike - issue?

MrMarty51 wrote: There also appears to be a little bit of a crease at about the one to two o-clock positions.
Not exactly opposite the smear mark.


That mark appears to be from the extractor cutout on the bolt face, I think......
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12 years 6 months ago #37077 by delta6
Replied by delta6 on topic AR10T case rim strike - issue?

jtallen83 wrote: I would be curios to see if these marks show up on another load. The primer strikes almost appear to show signs of high pressure which would explain the transfer of marks from the ejector and extractor.


Good suggestion. Definitely marks made by extractor and ejector. Over gassed or hot loads?
Have you mic'ed the cases to check OAL once fired?
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12 years 6 months ago #37087 by SOC
Replied by SOC on topic AR10T case rim strike - issue?
Basically your cases are still under pressure while the bolt starts to unlock. This gives the circular mark and scrape. Since the case hasn't contracted and let go of the chamber walls while the extractor is trying to pull the case out it is bending the rim.

This is commonly interpreted as overpressure issue when in fact it is not.

PPU ammo in general uses a relatively slow burning powder so the case stays pressurized longer. Not an issue in bolt guns.

Try ammo loaded with a faster burning powder and you will see this issue stop.
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12 years 6 months ago #37088 by MrMarty51
Replied by MrMarty51 on topic AR10T case rim strike - issue?
I had been concerned about some of My reloads, but, I have not seen any marks like this on the casings and they have all cycled well, I guess I am OK with My loads then.
I did get a chrony, so, next journey to the range will be setting the chrony and firing some rounds through it to see what is really going on.

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12 years 6 months ago #37090 by blazermark
Replied by blazermark on topic AR10T case rim strike - issue?
Thanks to all for your feedback.
Armalite tech responded with 'not of concern', and a phone # to contact an individual for more info.

I will get out again with some different ammo and post the case's ...
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12 years 6 months ago #37358 by blazermark
Replied by blazermark on topic AR10T case rim strike - issue?
got out again, and ran another 10 rounds thru (5 & 5) ..

used some Norma this time, better results on the brass.. still beating the rim up a bit, but I'm thinking I will continue with break-in and get to about 200 rounds and see where it is..


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12 years 6 months ago #37359 by jtallen83
Replied by jtallen83 on topic AR10T case rim strike - issue?
I loose about 30% of my cases to bent rims, they mess up the sizing process and length measurements. The slightly bent ones may flatten out in sizing but some are just ruined.
The price you pay for a semi-auto I guess. :usa:

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12 years 5 months ago #38065 by Siscowet
Replied by Siscowet on topic AR10T case rim strike - issue?
I went out today to break in the barrel on the new AR10T carbine. As construction was going on at the range, I couldn't sight in, but was able to shoot the break in process at one of the berms. The point I am making is that my brass had exactly the same kind of marks as Blazermark had on his, and the rim was beat up as well. As my full length gas system on my other AR10 doesn't cause this, I am wondering if it is due to the shorter carbine length gas system having a more violent ejection pattern. Function was flawless, recoil is definitely more than with the rifle version, but manageable. I was shooting M118LR and FGMM 175 SMK's as that will be what I will be initially feeding this one, so I decided to use them for break in.

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