Gas Port Math

[MarkG]

Expressed as a percentage, a MK18 gas port (0.070) is how much larger than an LE6920 gas port (0.062)?

Hint: It's not 13%!

[Complication]

Assuming gas ports are perfectly circular and flat (as opposed to on a cylinder:
0.070" diameter = 0.003848451 in^2
0.062" diameter = 0.00301907054 in^2
(pi * r^2)

0.003848451 / 0.00301907054 = 1.27471384

27.47% more area in a 0.070" gas port than a 0.062" gas port.

13% more than 0.062 would be 0.00341154971 in^2 or 0.0659" diameter.

But that's both a) a flat circle and b) a circle.
So are gas ports perfectly circular (on a cylinder) and why do you ask?

[MarkG]

Bingo...

I just ran across an article by a well known instructor who claimed the difference was 13%. My math came up to 27.4%. I just wanted to make sure my calculator was working correctly.

I'm going to say a gas port is as close to circular as you can get if a reamer is used to finish them v. a drill.

[mechelaar]

Bingo...

I just ran across an article by a well known instructor who claimed the difference was 13%. My math came up to 27.4%. I just wanted to make sure my calculator was working correctly.

I'm going to say a gas port is as close to circular as you can get if a reamer is used to finish them v. a drill.

I'm guessing that the 13% figure is from the fact that that the number .070 is literally 13% larger than .062.

(070 - .062)/.062=0.129

What probably happened is whatever instructor you heard that figure from did not take into account that increasing a circle's diameter does not increase the area an equal percentage.

[Iraqgunz]

One thing for sure is that my head hurts now.

[MistWolf]

Wait till you try to figure out how much more the larger hole flows

[Bimmer]

Wait till you try to figure out how much more the larger hole flows

Now you're going way beyond 10th grade geometry... To do this right you'd need some kind of flow bench, or some pretty fancy computer modelling.

Bimmer

[jahwarrior1423]

Now you're going way beyond 10th grade geometry... To do this right you'd need some kind of flow bench, or some pretty fancy computer modelling.

Bimmer

Wrong...

[militarymoron]

Wrong...

what would be the 'right' way?

[Complication]

what would be the 'right' way?

I'm sure you can get a pretty close approximation with some accurate numbers about the cartridge being fired and some somewhat "basic" physics. It wouldn't be especially simple physics, though--college level stuff but no PhD stuff, I imagine. I don't think you'd need any fancy modeling to get pretty good numbers.

Either way, you're going to need some tools far beyond the technological capabilities of the word "Wrong."

Unless, of course, you just want to be a smart-ass.