Interesting read on ar-15 barrels

[budlight]

It's kind of why mine are mostly stainless 20 inch match grade. One place that I do have a comment on is the M855 and barrel length speed topping out at @ 20 inches and then a drop off. This is mil spec powder. I also have all rifle length gas/piston barrels, but that is only part of the story. The diameter of the gas hole has a big effect on barrel pressure bleed off.

I did a post years ago about the hole diameters and how you want to select or request the barrels with the smallest hole possible. Higher velocity and the ability to use the slowest powders that will increase velocity even on to like my 24 inch target AR. Smarter people even go to rifle plus 2 inches on the gas port hole.

The AR-15 Barrel Cheat Sheet: Everything You Need to Know

Choosing the right AR-15 barrel is a daunting task, so let me help break down everything you need to know to get started

www.everydaymarksman.co

 

[budlight]

I just got done watching a video from a barrel maker and he was on the big hole size side of the fence. All I can say is that if you are buying off the shelf relatively low pressure .223 rounds only, there is some validity to using bigger gas port diameter and or the use of adjustable gas blocks. I don't like adjustables because I've had them fail out in the field. Then you have to muck with them. I prefer simple is better. Light weight micro or smaller gas blocks using high temp red silicone around the gas tube before inserting and pining. Also tape and spray high temp header paint on the barrel the size of the length of the gas block. Drill or grind two small indentations where the gas block allen locking screws go. You don't want leaks or movement of the gas block in the future. I've had all kinds of things go wrong in the past before I took the time to follow the rule of the 7 P's. Military term!


Reasons for going with rifle length gas systems and save your BCG etc.

 

[ARlife4me]

There are reasons for h3 buffers and higher spring pressures also.................save bcg or do you want a blowback 5.56? no thanks!

I have rifle length on 20"ers, but couldn't get it on 18's (intermediate) and 1 16".
Gas port size is extremely important for sure regardless of cartridge and barrel length.
+2 on a 24" 5.56 is ridiculous, but doable if the have the proper bcg, buffer and spring!
Wanting that dwell time can cost you IF you don't have enough pressure due to which powder you use. Fastest powders will drop like a lead balloon.

 

[budlight]

Yes, I've got an assortment of removeable buffer weights, assemblies, and all kinds of springs. I've also seen the beat up front of the buffer weights from the high pressure hits from carbine and pistol gas tubes.

 

[ARlife4me]

1 thing about 308win in AR's is that production barrels will only give you rifle length gas on 20-20+" length barrels. Unless you get a custom barrel and hopefully be able to get a + 2 or 3, but most aren't necessary. Going longer than 26" then a + gas system might work? Dwell time to get pressure down on bcg I agree on whole heartedly! Delaying it with a heavier buffer and/or stiffer spring is a help and will make it softer shooting. I have a 22" m118 chamber 308win AR10/SR25/AR308 that shoots very soft and cycles 100% with a standard rifle gas system. 308's are easy.

 

[budlight]

All my bolts are the heavy M16 type, so I use lighter buffer weights and flat wound silent springs. It seems like only my piston builds were problematic when it came to setting up the adjustable gas blocks

 

[budlight]

I have all superlative pistons systems. My buddy went adams. They have actually gone down in cost from years ago when I did mine. One thing I never could figure out is: Why do they sell you the bolt without the BCG extractor and parts. You also need a roller extractor cam pin.

Adams Arms Gas Piston Conversion Kit AR-15 Pistol Length .750

The Adams Arms Gas Piston Conversion Kit with Picatinny Gas Block features a patented one-piece bolt carrier with a picatinny gas black designed for...

www.midwayusa.com

Adams Arms Gas Piston Conversion Kit P-Series AR-15 Mid Length .750

The Adams Arms Gas Piston Conversion Kit has a short stroke free floating piston system which is self cleaning and resistant to corrosion. Carbon and...

www.midwayusa.com

AR-15 Piston System / .750” Clamp On Gas Block / Right Hand,

suparms.com