Farmboy Ring Groove Question

I had a caller a few weeks ago who stated the plans said to make a piston ring groove .105" wide by .110" deep for a .094" section by 1" diameter Buna-N "O" ring.  Sure enough, I checked the plans (Sheet #5), and this is what it shows.  The callers question was how could this seal the cylinder?

Does anyone have an answer for this, or is there an error in the plans?

Please advise.

Thanks...

Allen

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Yep, the sizes are correct. I thought they were incorrect also. But after making the groove to size everything works just fine. I have noticed that the "o" ring swells when in contact with acetone or alcohol.
I wouldn't change a thing on the plans as there correct.
Jim G

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Jim - I wondered if the perhaps the "O" ring would swell up to make the seal.  Now I (and future builders) will know!

Thanks...

Allen