On a whim, I whipped up this form, for those of y’all that know the gas port of your barrels: https://goo.gl/forms/gxSiVMP0jITBxV2v1
It will auto-populate this spreadsheet: https://docs.google.com/spreadsheets/d/1tXunBDX5Gaz87BqxwNxDUlWNK9nEv-cZEQoLq2JXXrk/edit?usp=sharing
I will need to periodically clean up the formatting, but it should be usable even if I don’t.
Surprised to see the Centurion results. I always assumed they were conservatively sized. Guess not. 
You should add diameter of GB journal (0.750 vs 0.625).
Cool idea. Especially the automated Form. Easy for contributors, easy to maintain.
On the other hand, my cynical side says “great…another chart to fight over” 
The problem here is that identical barrels with the same gas port can be completely different shooters. While it’s a good place to start, based on the year the barrel was produced can lend complete different port sizes. It’s kind of a crap shoot without production dates and when those runs took place.
If I may make a recommendation. In the field that states “what is the gas port size in inches”, add something like “only enter a measurement from using pin gauges.” I worry that people are using drill bits, bbq skewers or other shenanigans.
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What’s wrong with drill bits? Robert Soong of MicroMOA has stated that he has used both pin gauges and numbered drill bits to figure out gas port sizes.
How dare you speak ill of The Chart.
Numbered drill bits ok enough, but I’m worried about regular drill bits, one not fitting, the other loose, and the “measurer” splitting the difference. This is the internet we are talking about.
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interesting to see the CA midlength so large… I thought it was mentioned in the past to be .076.
Per the OP… fantastic idea. I see this question numerous times, and it seems to be one that some manuf’s don’t like to publish
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Based on my experience I can tell you that generally speaking, the good names will probably all be within a .002+/- . Colt has been pretty consistent across the board for several years as are BCM.
I spy a sionics 14.5 mid in that data…either sionics is holding back or someone has a unicorn haha.
I agree with the Colt statement but I do have some early BCM mid barrels that pin out at .072 and later examples show .076. Apparently DD is making some changes to the MK18 ports but have seen some, and have had some variance with them. My Centurion barrels seem consistent. Some changes in KAC port sizes in Older vs new production examples. Not saying that they are drastic, but some defently worth noting.
It’s always been 0.080"/0.081" AFAIK. I suspect that the reason for this is that originally they were offering 14.5" mid barrels that were just their 16" barrels cut down, so they just ordered one size gas port for both. Speculation on my part, but I beleive that it is a hold over from when they were doing this.
The (3)14.5 mid examples I own are .076 but are in fact cut down barrels.
No, it was added because someone assumed that there is a 14.5" or will be a 14.5".
Interesting because I have several BCM uppers, have built hundreds of the uppers and I have never seen one that small.
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Great, now even Google knows how overgassed most barrels are!
:big_boss:
My very early run BCM 14.5" middy had a .073" GP. By very early run, I mean I think it may have been a first batch barrel. It was an ultra smooth shooter.
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