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Old 10-02-2020, 04:53 PM
Dosssch Dosssch is offline
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Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion  
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Default Question: drilled gas port and low/high power ammuntion

Greetings from Sweden

Like everyone else, I have had problems firing low power 7.62 ammunition in my M&P10 Sport.

I recently drilled up the gas port with a 2mm drill (0.078 ").
I have also changed my gas block to an Odin adjustable gas block.

My question is if I will destroy the barrel or gas block if I tune my gas block to shoot low power 7.62 ammunition and then fire high power 308 180 grain Sierra GameKing ammunition?


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Last edited by Dosssch; 10-02-2020 at 04:56 PM.
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Old 10-02-2020, 08:16 PM
WR Moore WR Moore is offline
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Please define "high power" and "low power". I vaguely recall some really low pressure/velocity/light bullet gallery ammunition used at one time by the Bundeswehr that I expect required manual operation of the bolt on the G1 and G3. If you're just referring to bullet weight, I'm not terribly familiar with the AR10/M&P10. A better way to take care of your functioning issue might have been a lighter/shorter recoil spring and/or a lighter buffer (if available). You'd have to change them to shoot the different types of ammunition but it'd been a much less of a potential problem.

Now, if you have your gas system set to function the rifle when using low pressure ammunition and then shoot high pressure ammunition without changing the gas adjustment you won't harm your barrel (except for possible excessive wear/cracks on the barrel extension locking lugs, but that may be available as a separate part). You will however, probably (rather depends upon the difference in chamber pressures) severely batter your bolt/bolt carrier/buffer due to higher than design specification bolt carrier velocity. The bolt will also be unlocking earlier at higher than than design spec chamber pressures and this will increase wear on the cam pin and bolt/bolt carrier. Expect cracked bolt body/locking lugs. We see those bolt problems on extensively used AR15 pattern rifles with standard ammunition in heavy use.

Hopefully, Odin included instructions on how to properly adjust the gas system. Writing down the adjustments (from fully closed) for both loads would be a good idea. Change adjustments as required.

Last edited by WR Moore; 10-02-2020 at 08:32 PM.
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Old 10-03-2020, 05:49 AM
Dosssch Dosssch is offline
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Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion  
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Thanks for the advice. It sounds healthy to set the gas block to two diffent settings. 7.62 or 308.

7.62x51 NATO are made for M1 Garand and use a lower pressure (50,000 psi). While the 308Win has a higher pressure (62,000 psi).
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Old 10-11-2020, 10:06 PM
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sgtsandman sgtsandman is offline
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Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion Question: drilled gas port and low/high power ammuntion  
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Mine has run both 7.62X51mm NATO and .308 Winchester just fine.


As far as your question, you may need to adjust the block for higher pressure ammunition when you go to shoot it. The easiest way to see if the gun is over gassed or not is to pay attention to the ejection pattern of the ejected brass.


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