AR-10 in 6.5 Creedmore ... barrel length?

[Denny Gibson]

I’m working on building a 6.5 Creedmoor version of an AR-10 ... I’m faced with barrel length choices from 16” to 24”. These are heavy barrels so the longer the barrel the heavier and more nose heavy it gets. My question is: What’s the minimum barrel length needed to make use of this cartridge?

 

[Varminterror]

Minimum barrel length to make use of the cartridge is highly subjective.

Do you want a hunting rifle, a 1,000yrd G3 benchrest rifle, or a tactical/gas gun class precision competition rifle?

For hunting, I prefer 20-22” AR-10’s. For precision rifle competition, I would want a 24-26”. For Match Rifle or 600-1000yrd benchrest, I’d want a 29” Rifle.

So what are you wanting to do with your rifle?

 

[jmr40]

If you're shooting high BC bullets you can give up a lot of muzzle velocity and still be supersonic way past 1000 yards. If you want to shoot that far then 24" might not hurt. But people are shooting 6.5 CM at a mile with 22" barrels. You could probably go to 16" and have more performance than most people will use. But for balance and aesthetics I like 18-20" as a minimum.

A good read

https://rifleshooter.com/2016/02/6-...el-length-on-velocity-cutting-up-a-creedmoor/

 

[Denny Gibson]

I no longer compete except at club matches but the idea of the gun being able to shoot out to 1000 yards is attractive. These days (getting old) I find myself at a bench shooting 300 yards max. Opportunities to shoot further require a road trip so I don’t do it often. Obviously, since I’m not competing, there’s no need for extreme measures but it would be nice to be able to hit a 10” or 12” target at a 1000 yards. Does that help?

 

[Denny Gibson]

jmr40 ... thanks! I’ll check out the article. It’s hard to state a clear goal for the rifle other than I want sub-MOA at 100 yards that doesn’t entirely fall apart at 300 yards. At some point I’d like to try shooting 1000 yards but opportunities are slim here.

 

[Arizona_Mike]

22" inch seems to be a popular number. I would not go below 18". I think I went 18" on my 6.5x55 Savage build but only because I'm hanging a 9" 22.4oz can on the end of it

Mike

 

[Denny Gibson]

Mike ... thanks! Given the lack of a range with more than 300 yards in my area I think I’m going with 18”. If I get an opportunity to test it a longer distance and I’m not happy with it I can always put a longer barrel on then.

 

[adcoch1]

There are a lot of quality barrels for good prices in 18", I personally would go 20" or more, but I probably wouldn't hunt with an ar10 either. I spot and stalk, and a heavy rifle just sucks for that.

 

[Denny Gibson]

Adcoch1 ... I agree ... while I haven’t weighed my Rem 700 in 308 it feels noticably lighter than the AR-10. I’ll be shooting from a bench mostly, so weight isn’t an issue.

 

[adcoch1]

Adcoch1 ... I agree ... while I haven’t weighed my Rem 700 in 308 it feels noticably lighter than the AR-10. I’ll be shooting from a bench mostly, so weight isn’t an issue.

Cool cool, as a bench gun, or even as a blind hunting gun an ar10 is very cool. As a side note, the 6.5 seems way more useful than the 308 in a ar10 for me. If I build one it will be a 6.5 with a 20-22" barrel.

 

[lovethosesooners]

Every time I get the itch to add a 6.5 in semi-auto, I think about how I use my .308 versions and it becomes easy for me to talk my self back out of it.

I seriously doubt I’ll ever have the opportunity while hunting to shoot 300 yards, and for that, I prefer the .308 over the 6.5 due to:
-less loss of velocity using 16” barrel
-higher energy in the range I use them (hog hunting)
-greatly prefer the shorter barrel for hunting
-already have 3 308 semi autos I’m very happy with (scar which is 1 of my absolute favorite rifles...the other favorite is the scar 16), m&p 10 in 308, and an RFB which is awesome for hog hunting)

I too am big fan of the 6.5 as I have 2 long range bolt guns in 6.5, but for my use, there’s no benefit and there are disadvantages for how I use them.

 

[Denny Gibson]

100% of the shooting I do consists of putting holes in paper I got interested in the 6.5 Creed for that purpose ... though I must say I know a lot of hunters that shoot 6.5 Creedmoor or 6.5x55 for fairly large game.

 

[kimberkid]

I had this same discussion with long rang shooters and the people at Benchmark and JP Enterprise ... I finally settled on 22" as I'm going to be shooting paper at 500 to 700 yards which is the longest range I have available to me ... someday I hope to go shooting Prairie Dogs with it and my 223 varmint which has a 24" barrel on it. The 223 (above) is about 15 years old but recently replaced the receiver with Spikes "Jack" after settling on their matched upper/lower set when building the 6.5 Creedmoor.

​

The "red" under the handguard is an aluminum heat-sink that wraps around the barrel ... I need a longer one for the 6.5 and just haven't gotten to it yet

 

[Gordon]

24" for 6.5CM LR uses gets about the most you will get out of it in an AR 10. I use 18" in .308 .


As usual the lighter bullets do well in shorter tubes

 

[Denny Gibson]

Thanks guys! I appreciate the comments!

 

[rbernie]

For my 257 Roberts AR10-pattern build, I settled on an X-Caliber 22" SPR barrel as the best compromise between ballistics and weight/size. Given the similar "case volume to bore area" ratio of the 6.5CM to 257Rob, I'd probably reach the same conclusion for that chambering.

The rifle is well balanced, and comes in just over 9lbs with optic - suitable for bench work or for carrying a little while.

 

[MachIVshooter]

Minimum barrel length to make use of the cartridge is highly subjective.

Do you want a hunting rifle, a 1,000yrd G3 benchrest rifle, or a tactical/gas gun class precision competition rifle?

For hunting, I prefer 20-22” AR-10’s. For precision rifle competition, I would want a 24-26”. For Match Rifle or 600-1000yrd benchrest, I’d want a 29” Rifle.

So what are you wanting to do with your rifle?

Pretty much sums up my thoughts. Depending on the intended use, I might cut back to 18" for suppressed use, but the 6.5 starts to lose it's merits in barrels under 20". Most of the bolt guns people have had me put together for them with 6.5 CM barrels are 20"-22" and intended to be suppressed.

 

[Denny Gibson]

Thanks for the info folks! I’m doing the first build with an 18” ... curious to see how it behaves out to 300 yards. I love shooting off-hand so the weight and balance is important. The 18” barrel should help reduce nose-heaviness and overall weight. We’ll see how it works for me. One nice thing about ARs is how easy it is to change a barrel so a 22” barrel might follow quickly. With no real opportunity to excercise the long distance capabilities of this round, you might ask: “why do I want a 6.5 Creedmoor AR-10?” ‘Cause I like the idea of a rifle able to reach out and touch something a long way out there and do it without punching a hole in my 70 year old shoulder. If I get an opportunity to shoot a longer distance I will gladly purchase a longer barrel!

 

[rbernie]

Just for the sake of proportion, this is a picture of a 22 inch barrel:

 

[Denny Gibson]

Rbernie ... nice rifle!

MachIVshooter (or anyone else) ... can you give me a brand name of the type of suppressor you’re talking about? What I find searching popular gun retailers (Midway, Brownells, etc.) I find what I would refer to as muzzle brakes or compensators with the exception of “inert training devices”.

 

[Skylerbone]

Not sure it matters in Illinois, unless laws have changed recently.

 

[Denny Gibson]

Ok ... so I assume suppressors are illegal (in Illinois, anyway)? Sorry, but I’m not familiar with these devices except as seen in pictures. Could someone fill me in? Couple questions:
1. Is a suppressor so acurately produced and installed that it serves as additional barrel length? Again, I’m not very familiar with these things but, given the tolerances required to mount a threaded can on a barrel thread (neither of which can be perfectly aligned to actual bore) accurately enough to avoid “opening up” the suppressore bore nominal diameter seems unlikely (unless both threads are ground ... which would help but still leaves some mis-match). The idea that adding a suppressor is the same as making the barrel longer does not seem likely to me.
2. What is the expected function of a suppressor? Recoil reduction? Noise reduction? Counterweight to make the gun nose heavy?

Please fill me in.

 

[Skylerbone]

Noise reduction is the purpose of a suppressor and recoil reduction is a nice side benefit. Typically a suppressor increases in size and weight as it increases in effectiveness. It is similar to a brake but vents into baffled chambers. Beyond that I know they aren’t cheap if you want a good one.

 

[Denny Gibson]

Skyerbone ... thanks for the info. I’m still waiting for someone to explain the belief that adding an 8” suppressor effectively adds 8” (ballistically) to the length of th barrel. I think it’s nonsense! Just like “make sure you fill up your 223 cases because empty space means they might blow up like a stick of dynamite” ... unless you’re shooting 50BMG or an artillery piece this is nonsense, too.

 

[Denny Gibson]

I guess what I’m suggesting is that adding a suppressore leaves you with the same length barrel you started with. If it’s too short without a suppressor it’s too short with one, too. That’s the facts as they appear to me (45 years as a mechanical engineer teaches one to think through statements like these rather take them at face value). If you disagree please explain why.