18" vs 22" vs 24" 6.5CM gas gun

[SamBlankenship]

I am curious as to the difference in velocities i would be looking at losing if i went with a 18" barrel vs say a 22" or 24" in a AR10 platform pro vs con if you have any it will mainly be used for hunting out to 400-500 yards max realistically around the 300yd range. I guess my question mainly is am i going to lose much more with the 18" should i go with a 308 instead of 6.5 ?

 

[flyer]

The reason for a 6.5 Creedmoor is long range so if you aren't shooting long range, the extra bullet weight, diameter and barrel life make .308 attractive.

 

[knuckleballz]

If you are considering a carbon wrapped barrel in 6.5 creedmore it is about 1 ounce per inch from 20 inches to 24 inches. Are you going to run supressed? I studied this extensively and came to the conclusion that with 130 grain bullets Going 2865-2900fps out of a 22inch 8 twist, I didn't want want to go any slower velocity wise. Especially if you want to run heavier bullets. If you are hunting in a potentially windy environment, slow velocities out of a short barrel and the higher wind drift values are more of a concern to me than the handiness of a shorter barrel. 22 is the optimum compromise for me running suppressed all the time and hunting out west in the mountains. I have total confidence in dropping deer out to 800 yards. 600 yards is the longest shot on a deer I have attempted and it was a 1 shot double lung kill that dropped him on the spot.

 

[NB4Z]

Basing it on many years of shooting the cartridge since 2008 and knowing the developers of the cartridge and shooting for Hornady and knowing the cartridge was developed around a 28" barrel. When asking what barrel length to use of the developer we were told 28". If they lost velocity after 24" then why would they have used and recommended 28"? Also even the tiny .223 gains velocity up into 26" lengths from shorter so why would a larger cartridge shooting slower powder start slowing at 24"? It doesn't. That "test" has done more to spread bad info on barrel length for this cartridge than anything. Every time barrel length comes up that is posted and this happens.

The original boxes of Hornady 140s were listed with 28" data and it listed velocity at 2820fps. When they changed a couple years later to listing the 24" velocity as more factory rifles came with 24" barrels the velocity of the same load was listed as 2710fps. If you were to believe that test then it should have went up. It didn't.

And so you do not think I am being to hard on the author I do not think he actually did it to spread bad info and if you look at he comments he doesn't even know why it happened. That test is not the norm or what thoughts on barrel length should be based on.

 

[SamBlankenship]

So what your saying is a 18" Barrel will do just fine for hunting out to 500yards?

Basing it on many years of shooting the cartridge since 2008 and knowing the developers of the cartridge and shooting for Hornady and knowing the cartridge was developed around a 28" barrel. When asking what barrel length to use of the developer we were told 28". If they lost velocity after 24" then why would they have used and recommended 28"? Also even the tiny .223 gains velocity up into 26" lengths from shorter so why would a larger cartridge shooting slower powder start slowing at 24"? It doesn't. That "test" has done more to spread bad info on barrel length for this cartridge than anything. Every time barrel length comes up that is posted and this happens.

The original boxes of Hornady 140s were listed with 28" data and it listed velocity at 2820fps. When they changed a couple years later to listing the 24" velocity as more factory rifles came with 24" barrels the velocity of the same load was listed as 2710fps. If you were to believe that test then it should have went up. It didn't.

And so you do not think I am being to hard on the author I do not think he actually did it to spread bad info and if you look at he comments he doesn't even know why it happened. That test is not the norm or what thoughts on barrel length should be based on.

 

[bfoosh006]

This will help some.. YMMV
https://rifleshooter.com/2016/02/6-...el-length-on-velocity-cutting-up-a-creedmoor/

And 2019 version..
https://rifleshooter.com/2019/03/6-5-creedmoor-effects-of-barrel-length-on-velocity-2019/

 

[SamBlankenship]

This will help some.. YMMV
https://rifleshooter.com/2016/02/6-...el-length-on-velocity-cutting-up-a-creedmoor/

And 2019 version..
https://rifleshooter.com/2019/03/6-5-creedmoor-effects-of-barrel-length-on-velocity-2019/

Both very interesting reads indeed. Seems only a loss of 200 FPS from 28" to 18" alot less than i was expecting for sure.

 

[The DFC]

The reason for a 6.5 Creedmoor is long range so if you aren't shooting long range, the extra bullet weight, diameter and barrel life make .308 attractive.

Exactly. Even the approach to ammo is completely different with 6.5cm then 308-basically buy and shoot match stuff. What's the point of shooting range ammo?

 

[Niles Coyote]

IIRC, the difference between my 22" JP barrel and 18" X-Caliber was around 100 to 120fps with 140 Eld's... I'll have to search my records. One issue with that comparison though, the 22" has a gas system 2" longer and the 18 shooting the same load trashes brass with 140's in just a couple firings. I resorted to using 130 and 123's in the 18" barrel.

 

[VegasHKShooter]

I can answer for the 18”, 22” and 26”.
My 18” is pushing a 140 gr Hornady ELD-M at 2609. My 22” is shooting the same bullet at 2717. My 26” is throwing the same bullet at 2760. These are all three factory loads. It should be noted that my 18” and 22” are gassers, and my 26” is an A.I. with a Bartlein barrel.
These numbers are going to vary gun to gun and lot to lot, but it is interesting to have 3 barrels that are 4” apart.

According to Applied Ballistics, my 18”
is at 1300 at 1000 yd, and has 1000 ft lbs at 570yds.
Based on that info, you’ll be great at about anything out to 500yds easy.

So yes, a 6.5CM will do better in an 18” than a .308. It’s really a great round.

 

[awpk03s]

I have 6.5CM AR10s in 22” and 18”.
For Hornady 140gr, I get 2640 out of the 22” and 2500 out of the 18”.
For Prime 130gr, I get 2815 out of 22” and 2640 out of 18”.

18” is plenty good enough if you seek shorter/lighter/handier.

 

[parumLuceat]

I can answer for the 18”, 22” and 26”.
My 18” is pushing a 140 gr Hornady ELD-M at 2609. My 22” is shooting the same bullet at 2717. My 26” is throwing the same bullet at 2760. These are all three factory loads. It should be noted that my 18” and 22” are gassers, and my 26” is an A.I. with a Bartlein barrel.
These numbers are going to vary gun to gun and lot to lot, but it is interesting to have 3 barrels that are 4” apart.

According to Applied Ballistics, my 18”
is at 1300 at 1000 yd, and has 1000 ft lbs at 570yds.
Based on that info, you’ll be great at about anything out to 500yds easy.

So yes, a 6.5CM will do better in an 18” than a .308. It’s really a great round.

Are you using a rifle length gas system for the 18" 6.5 Creedmoor? I want to go in this direction too but I have read a lot of conflicting things online about gas problems.

 

[VegasHKShooter]

I have the Intermediate on my Aero, and the rifle length on my GAP-10. That is a 22” Bartlein barrel, and it is a HAMMER. I get very regular .5-.7 moa groups out of it. My Aero is .8-1.0 moa. The Aero won’t hang with the GAP, but I absolutely wouldn’t expect it to. In fact, I’d be pissed if it did. ?
As far as reliability, they are both great. I have not had a single issue with the Aero. It shoots surprisingly well for a $1400 rifle.

 

[parumLuceat]

I have the Intermediate on my Aero, and the rifle length on my GAP-10. That is a 22” Bartlein barrel, and it is a HAMMER. I get very regular .5-.7 moa groups out of it. My Aero is .8-1.0 moa. The Aero won’t hang with the GAP, but I absolutely wouldn’t expect it to. In fact, I’d be pissed if it did. ?
As far as reliability, they are both great. I have not had a single issue with the Aero. It shoots surprisingly well for a $1400 rifle.

That's awesome! I am building one with Aero receiver sets. I would be happy to get .8-1.0 moa and thrilled if I can get better. Eventually I would love to get a GAP as well.