Pressure signs for AR Rifles ?

[cya305]

What pressure signs can I look out for on a semi auto rifle like my LR-308? I can't really check for a tight bolt. Flat primers I can check for but I have been told that flat primers alone is not a good indicator, that it serves better in conjunction with other signs.

Thank you,
Eric

 

[Victor Co Heather]

Re: Pressure signs for AR Rifles ?

The main thing I'd be looking for is sticky brass or non-extraction. Mashed primers can be hard to tell sometimes. Also headspace cracks would be a no-go.

 

[19Scout77]

Re: Pressure signs for AR Rifles ?

Looked for a bloody charging handle imprint in your forehead

 

[MitchAlsup]

Re: Pressure signs for AR Rifles ?

Actually you can check for a tight bolt. Hold the gun upside down with the stock pointing towards the ceiling. Insert a case in the chamber and slide the bolt closed with your finger. The bolt will snap over the case flange and you can feel the bolt close into the chamber. Use the milled relief in the BCG to extract case and bolt.

At this stage of disassembly, its easy to remove the firing pin, So I suggest doing so. So you want the carrier, the cam, and the bolt assembled with typical amount of lube on the slides.

 

[Downzero]

Re: Pressure signs for AR Rifles ?

You will see ejector marks when you hit the limit for pressure. Factory M193 and M855 ammo does this on every round.

 

[Powder_Burns]

Re: Pressure signs for AR Rifles ?

Ejector marks; little circle on the case head.
Extractor swipes; small brass burrs or dents on the extractor rim.
Blown or leaky primers; either missing a primer altogether or black soot visible around the pocket, pierced primers will show black soot where the firing pin struck. Not necessarily indicative of high pressure though.

 

[cya305]

Re: Pressure signs for AR Rifles ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 19Scout77</div><div class="ubbcode-body">Looked for a bloody charging handle imprint in your forehead

</div></div>
LOL! Got any pictures of how that looks?

Thank you all for the input.
Eric

 

[MJC]

Re: Pressure signs for AR Rifles ?

Rim pulls caused by the extractor is another sign. This can be caused by an overgassed barrel or rough chamber but otherwise is an indicator of powder charge limitations. It's hard on the extractor too.