16" Barrel...Best Twist?

[Shivesy]

I am having some barrels made and I have spec'd them out with a 1 and 7.5 twist. Just curious what you guys think. They will be 16" bull barrel profile, carbide length gas system with recess target crown. Plan on shooting factory Hornady 123gr Amax ammo. Thanks

[Drifter]

From someone who owns a 16" with 7.5" twist and carbine gas, I suggest midlength gas if you have that option. 8" twist would likely also be sufficient.

[hill.brandonj]

Beware of that carbine system. If I remember correctly that's what was wrong with my gun that wouldn't function at all. And I sent it to AA (which by the way was not the place of origin). And mr a ended up having to put a new barrel on it since the gas couldn't be dealt with kn the short system

[Shivesy]

Hmmmm?? Doesn't AA s market a 16" with carbine gas system? I have the option and can change my order to fit my needs. I just really wanted a shorter Grendel and was building this rifle just like my 223.
I have anticipated on customizing the gas port. I am purposely having the gas port drilled smaller by the barrel maker so that I can drill it out to funtion with the rifle as a whole. I think alot of problems arise when we customize our Grendels and most people are scared to tackle the process of drilling out the gas port in order to make these projects functon correctly. So when I read about someone stating that they couldn't get their rifle to cycle, I wonder have they even tried to modify their gas port. Of course the gas port should be the last thing to consider and only modified after all the other things have been ruled out. The question then remains is it the carbine length rifle or is it the person building it. I don't want you guys to take this post the wrong way because I do value input from this board. I'm just thinking out load here and could be wrong in my thinking. Am I?

[Drifter]

My 16" with carbine gas functions fine. Had to drill out the gas port to get reliable function, and I also use an adjustable gas block to fine tune based on ammo. But it's still a different animal, and midlength gas would be better.

In other words, carbine gas will work with a 16" barrel; it's just not ideal. But don't take my word for it. Consider the advice of the man that's surely built more Grendel rifles than anyone else on the planet:

16" barrels do not balance well with carbine gas systems. The mid works best with a port of 0.078". Will work down to 0.073" but becomes very fussy in a production gun. Carbine systems are very difficult until barrels are down to 14.5"

Link to source of quote above: http://www.65grendel.com/forum/showthrea...#post47479


Regarding twist, another quote from Bill Alexander:

It is our conclusion that the 9 twist offers the best solution for the Grendel for barrels of 20" and longer while the 18" and shorter barrels thrive on 7.5 twist.

Link to source of quote above, where Mr. Alexander elaborates on the topic:

http://www.65grendel.com/forum/showthrea...#post20344

[Shivesy]

Thanks for the info Drifter. I am building this rifle with a mid length handguard over a carbine gas system and was planning on hiding the gas block under the handguard. I like the clean lines that this system offers. Don't get me wrong I can still change the barrel to a mid gas system which will expose the block and I will still be sastisfied. I also want to keep the barrel at 16" though. What's the thoughts on a 16" barrel with a mid gas system? Is that feasible?

[LRRPF52]

I have an AA 16" barrel with MLGS. The carbine length gas works great on 14.5" guns, but not the 16". My 16" eats everything from 90gr TNT, to 123gr AMAX, 123gr Scenar, and 129gr SST's without issue.

The carbine-length gas system was originally made for the Colt Model 607 carbine in the CAR-15 Family of Weapons concept put forth by Colt in the 1960's. This gas system was later used on the XM177 10" Commando, which was found to have dwell time issues, resulting in the adoption of the various moderators with baffles to build back pressure so the guns would cycle. The Army asked for a fix for this problem that would better deal with the dwell time, and the XM177E2 was born.

Colt Model 607


Colt Model 609/XM177E1


Colt Model 629/XM177E2


Colt Model 653/"M16A1 Carbine"


The carbine gas system proved quite reliable in the XM177E2 and Model 653. The 16" civvy guns with CLGS are an aberration in AR15 family of weapon design, totally driven by BS NFA arbitrary barrel length compliance, not functionality. These issues of excessive dwell time are exacerbated by the Grendel's increased case capacity and significantly heavier projectiles.

You can tame the system with an adjustable gas block and heavier buffers, but the MLGS is much more smooth and reliable. To cover the MLGS under the handguard like I do, go with a rifle-length handguard. It's an ideal configuration, and very popular among competitive shooters, as well as the new SOPMOD Block II M4A1 RAS set-up.

This is discussed in the new 6.5 Grendel Reloading Handbook, Vol I, available at:

www.AR15BuildBox.com

[LRRPF52]

Here is how I have my 16" Grendel configured, and it is a relatively lightweight package:

[hill.brandonj]

I don't know about what they have for sale. All I know is the tool a POS that I bought from another company and alexander fixed it by putting a new barrel 16" and a mid length on it. I put a 13" troy battle rail on it. With my wci brake it looks super badass and all I know is.... No more boom boom ..... Nothing ! I can crack away like it was supposed to be!

[VASCAR2]

I have a 16" Shaw barrel from J&T which uses the carbine gas system with 1:9 twist. There may be better uppers out there but I have not had any issues with functioning or accuracy. I've shot factory 123 grain A-Max and B/H 123 SMK Les Baer ammo, Wolf MPT & SP ammo. I have shot reloads from 85 grains to 123 grains with no functioning issues. I have a 6 position stock with carbine buffer and spring. I just recently started using an H-2 buffer after reading on this site. My upper uses a fixed A-2 gas block front site. Most of my shooting has been on hot days with temps in the 90's down to the upper 30's with no functioning issues. Largest group so far off the bench at 100 yards was around 2 3/4 inch with Wolf 123 SP. I personally believe the 6.5 Grendel is a vary forgiving accurate intermediate cartridge.

[Shivesy]

LRRPF52, do you know what size your gas port is?

[LRRPF52]

I believe it is the .078", since AA did it. I measured it before installing the gas block, and I know it was .07_" something.

[Lead Chucker]

I put together a 16" with a Stoner barrel form midway, mid length gas system. Not shot it much so far, but did work up a load that shot .5" group at 100yrds. It shoots very smooth, cycles great, very happy with it.