Advantages to having a .750 gas port vs . 625 on a mid-weight barrel

[TommyTwoTone]

Hi,

I'm trying to build my first AR15 with a mid-length 16" barrel as a range toy (unsuppressed). Anticipated firing position is 60% standing and 40% prone or from a bench. Favoring a lighter, but not quite pencil, weight I've narrowed it down to one of the following three contour barrels:

+Larue 16" Predatar (27 oz w/ 0.625" gas block)

+Midwest/Criterion MI-C16H223 (27 oz w/ 0.625" gas block)
https://www.midwestindustriesinc.com...mi-c16h223.htm

+ADM/Criterion AD-AR15Barrel-ADMContour-223 (24 oz w/ 0.750" gas block)
https://www.americandefensemanufactu...product/1225/?

I'm sure I'd be happy with any one of these but the ADM flavor shaves off 3 oz and roughly $40 from the other two. All of the mid-weight barrels I've taken into consideration call for a 0.625" gas block except the ADM, which seems odd. Is there any advantage to having a larger gas block?

Thanks in advance for the replies.

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[Clint]

The only possible advantage of a 750 gas block journal would be slightly better gas block availability.

For a light weight barrel, a 625 gas block journal is more appropriate.

[1168]

.750 vs .650 does not refer to the gas port, rather it is the diameter of the journal the gas block fits around. .750 is a common standard, and .650 is commonly found on lighter barrels. Either is fine, provided the gas block is attached appropriately.

[opngrnd]

Disregard.

[TommyTwoTone]

The only possible advantage of a 750 gas block journal would be slightly better gas block availability.

For a light weight barrel, a 625 gas block journal is more appropriate.

I think you're agreeing with me it's odd. Care to expand why it's more appropriate? Is it because the barrel has more weight where you don't want it? This could very well explain the slight discount.

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[Clint]

There's just no need to have abrupt changes in the profile.

They don't do any good and at best, add unnecessary weight.

Notice how smooth the profile is on our OPTIMUM LPR.

[Sry0fcr]

OP probably shouldn't be building a carbine with this little of a knowledge base. Maybe buying a complete gun or a upper/lower combo is a safer bet. You can build the next one...

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[TommyTwoTone]

OP probably shouldn't be building a carbine with this little of a knowledge base. Maybe buying a complete gun or a upper/lower combo is a safer bet. You can build the next one...

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I don't really agree asking why a lightweight contour barrel has a larger than typical diameter at the gas block disqualifies me from being capable of choosing components for or assembling a rifle. I've completely disassembled and reassembled (and I'm not talking field stripping) numerous pistols, a PCC (MPX), a shotgun, and built a bolt gun. Despite my experience with other platforms there are so many great suppliers, videos, and forums out there the population of folks that should buy, rather than build, their first AR15 is a very small one.

I started this journey thinking I'd get a Daniel Defense, which I agree would be safer but it's far more fun to roll my own and a heck of a lot cheaper.

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[1168]

I started this journey thinking I'd get a Daniel Defense, which I agree would be safer but it's far more fun to roll my own and a heck of a lot cheaper.

I wish you well on this undertaking, but its definitely not a heck of a lot cheaper if you use quality components.

[GH41]

I wish you well on this undertaking, but its definitely not a heck of a lot cheaper if you use quality components.

Plus the additional cost of the tools needed to do it right.