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Old November 21, 2012, 11:35 AM   #1
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Join Date: September 9, 2008
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Windham Weaponry - "Compass Lake Chamber" info

A few days ago, I sent an e-mail to Windham Weaponry asking what the differences were between the "Compass Lake Chamber" and other types of .223/5.56 NATO chambers. Here's my inquiry, and the much appreciated response from Erik Winter at WW. The bold type and underlining is mine.


I have a question regarding the "Compass Lake chamber". All I ever see is that the chamber is "slightly smaller" than the Wylde chamber.
Is there an actual drawing, or a spec sheet with comparative values/dimensions for any of .223 SAAMI, Compass Lake, Wylde, AMU and NATO chambers?

Thanks very much for your time.


Hi C,

I don’t have drawings to share but basically the lead in our 5.56 NATO chamber is .0566” and the lead of the 5.56 Compass chamber is .0250”

The mil-spec NATO chamber has a longer lead but has an included taper per inch of .0427” so it results in a much longer but more gradual lead. Our NATO chamber has a shorter lead for achieving much better accuracy than can be achieved with the longer mil-spec lead.

All things being equal you would have about .093” less throat length on the Compass chamber compared to the NATO, and .119” less on the SAAMI
compared to the NATO.

I have tested our Compass lake chambered rifles with 5.56 NATO ammunition and there are no signs of overpressure.

I don’t have any info on Wylde or AMU chambers.

Keep in mind I’m not an engineer and the above information I put together... as it was explained to me by our engineer.

I hope this helps,
Erik Winter
Gunsmithing/Tech Support
Windham Weaponry

So there ya' go. I'd like to again thank Mr. Winter for taking the time to obtain and share this info.

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