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08GTCS
10-10-2012, 7:27 AM
I've got a DPMS Oracle in .308 that I'm looking to modify into a long range rifle and I keep hearing different opinions on what the perfect barrel length would be for it. Most everything I've heard is either 18" or 20". I've never even shot a purpose-built long range AR before so I'm coming to you guys for some help.

My build plan so far:
Rainier Arms SS Ultra Match Barrel (Length?)
Low profile gas block
Rainier Arms 12" Quad Rail
Harris Bipod Mount and Bipod
Magpul PRS Stock

Also, what trigger would you guys recommend? For a basic AR10, I like the Oracle's trigger but I'd like to get something better for long range.

FMJBT
10-10-2012, 7:49 AM
Depends largely on how far you expect to regularly shoot, and what type of ammunition you are going to use. I'd say that within 800 yards, a 16" barrel is capable with any bullet that has a decent ballistic coefficient. Past 800 yards I'd start looking into something around 20". I think a good all around configuration in both 5.56 and 308 AR's is the 18" barrel with rifle length gas system. It's a good compromise that allows for long range while still being reatively lightweight. Another thing to consider is different calibers in the large frame AR platform that might be better suited for long range. 260 Remington and 7mm08 are both based on the 308 case, and have a large selection of high BC bullets available. Going with a different caliber based on the 308 is as simple as installing the barrel for that caliber, without any of the other parts changes normally associated with swapping calibers on an AR-15 (Bolt & magazine, etc.)

For triggers, I'm pretty impressed with how well the rock River Arms 2 stage triggers have worked in several of my builds. It's not the best trigger out there, but at it's price point it's a huge step up from the stock AR trigger.

gau17
10-10-2012, 8:16 AM
look into 6.5 Creedmoor.

http://www.accurateshooter.com/tactical/6-5-creedmoor-for-tactical-competition/

CK_32
10-10-2012, 9:11 AM
20" for the 700+ shots.. 18 can do it but barrel length helps at longer distances being it usually gives better muzzle velocity helping with FPS in the long end.

HK Dave
10-10-2012, 9:19 AM
For my Larue OBR, the difference in muzzle velocity from 18" to 20" using FGMM was something like 20fps. Given that, I went with the 18. I don't feel 20fps justifies a 2" longer barrel.

Now if I had gone with a 24" barrel that would have made a difference...

SoCalXD
10-11-2012, 10:16 AM
Since you've read my "New LR308 Build" post, and asked my opinion on a few issues via a PM, I'll post here.

Your "use model" for the rifle, and most importantly, the likely common minimum and maximum distance for shooting is a critical consideration for your intended build: barrel length, barrel precision, optics, trigger and stock all depend, more or less, on your intended use model for the rig.

A critical mistake commonly made is the desire for a "rig", without a well thought out use model for it. That can cost you a LOT of money in "rework" (reconfiguration after your initial build/investment).

Longer range rigs cost much more money and weight: Better quality barrel, better optics, better trigger, better stock. Skimp on one of these and overall, you lose repeatable accuracy that becomes very important past 600 or so, all other things being equal.

Longer range rigs are heavier. They suck to carry in the field. Considering that fact that your scope and mount will weigh AT LEAST 1.5lbs, on top of a LR308 rifle that is already 2lbs heavier that an 556 Rig, EVERY ounce counts if your use model includes hunting, remote field shooting, personal defense inside of 200 yards, etc. Every component you are considering should be analyzed for weight and usability in your decision process.

In your PM, you indicate that you are not going to be shooting long range (unlike here, where do do mention long range. See post below re NRA def of ranges and pick one, pick two... just define your primary distance needs ), just "a range toy and occasional hunting". That's what I configured my rig for...an "enhanced battle rifle", a "designated marksman rifle"... whatever you want to call a 600 yard semi auto that will be carried in the field, used at a shortish distance range, used for self defense, etc:

- 18", Medium profile barrel (the perfect length for my use model). If I wanted to shoot 600+, I'd go to a 20-22" barrel.
- Light, full length handguard with good configurability
- Good muzzle brake/comp for faster followup shots when not in prone/bipod.
- Good trigger
- Optic with solid CQB capability, yet distance capable to 600 (1-4x, 1-6x)
- A decent stock that is NOT heavy (PRS & UBR are great, but 1.5lb pigs!)

Don't add a half a pound of handguard (for rails, barrel nut strength, or just a poor weight design), unless you really need it... sure, it looks tacticool, but if you don't need all that rail space of a quadrail, it's a mistake for a rifleman to go that route due to weight. Ditto for a stock.

The PRS is a very heavy stock. The new version might be a decent solution for a long range rifle, but not for a medium range one. I like adjustable stocks for personal fitting and occasional vest use, so a collapsing stock is my preference. The E-MOD stock has a great buttpad, which is why I went with it. If you are ok with a narrower buttpad, I'd also consider the Magpul ACS-L: half the weight and one third the price of the UBR stock, and 80% of the value. While not tacticool, an A2 Stock works pretty darn well, if it fits you and you don't every wear a vest.

I spent the extra money on the "Ultimate Match" barrel from Rainier, rather than going with the Std. Match barrel. With my optic's low mag, I don't think I'm maximizing my accuracy potential of that barrel, so I probably could have downgraded one notch and got about the same practical accuracy (out to 600).

I like my PWS muzzle break on both my 308 Rig and my primary 556 Rig. That said, I have a secondary 556 Rig with a Troy Claymore that I like as well (it sends the sound downrange, vs. along the line, but doesn't comp upward recoil as well). If I had to save money, the Troy would have been my next choice. If you already have a 5/8" flash muzzle device, and are going bullet button, you can just use that now and upgrade later too.

I'm sold on the Geiselle triggers. I've tried a lot of the lower cost 2-stage options available from Brownells and MidwayUSA on my 556 rigs, and IMO, they all kind of sucked in one way or the other. The Geiselle is my "gold standard" and is well worth it to me. Shoot one and you'll understand why it's worth the money (assuming you can afford it). I think the SSA-E is very close to my old M21 trigger, which I loved, as it shot .4 MOA for me daily. I have SSA in my 556 rig, and it's perfect for a carbine, yet worked great on my LR308 as well, with no less.

Good Hunting!

donw
10-11-2012, 12:11 PM
Depends largely on how far you expect to regularly shoot, and what type of ammunition you are going to use. I'd say that within 800 yards, a 16" barrel is capable with any bullet that has a decent ballistic coefficient. Past 800 yards I'd start looking into something around 20". I think a good all around configuration in both 5.56 and 308 AR's is the 18" barrel with rifle length gas system. It's a good compromise that allows for long range while still being reatively lightweight. Another thing to consider is different calibers in the large frame AR platform that might be better suited for long range. 260 Remington and 7mm08 are both based on the 308 case, and have a large selection of high BC bullets available. Going with a different caliber based on the 308 is as simple as installing the barrel for that caliber, without any of the other parts changes normally associated with swapping calibers on an AR-15 (Bolt & magazine, etc.)

For triggers, I'm pretty impressed with how well the rock River Arms 2 stage triggers have worked in several of my builds. It's not the best trigger out there, but at it's price point it's a huge step up from the stock AR trigger.

^^^+1

ar15barrels
10-11-2012, 12:42 PM
For longrange shooting, you want the barrel as long as possible.
Longer barrels give more velocity which helps with the wind drift.

jvrotter
10-11-2012, 1:02 PM
I built a 260 upper for my Armalite lower and I'm running a 24" Kreiger on it. Getting 2800 fps plus with 139gr Lapuas. Go long

calishine
10-11-2012, 3:01 PM
High Quality 18 or 20 barrel - get your bolt headspaced
Stock - Magpul ACL or STR with enhanced rubber buttpad 0.70 - good ergonomics with cushion for recoil, and not as heavy as prs or ubr
Trigger - Geissele SSA-E, their is nothing better.
Brake - Surefire or Battlecomp - I prefer Surefire but the bc would be good too.

These are the recommend parts for YOUR intended use. Trust me.

ar15barrels
10-11-2012, 4:32 PM
High Quality 18 or 20 barrel - get your bolt headspaced
These are the recommend parts for YOUR intended use. Trust me.

Perhaps YOUR definition of long range differs from the standard NRA definitons that everyone else uses...

As for the OP, he said:
a long range rifle

Let's make sure we are on the right track...

The NRA definitions of short, medium and long range:
Short Range: Up to 200yds.
Medium Range: 200 to 600yds.
Long Range: Beyond 600yds, out to 1200yds.

Though not specifically defined, Extended Long Range is generally considered to be 1000yds and beyond.

So, with that in mind, he specifically asked about shooting 600yds and beyond.
I'll stand by my recommendation for the longest barrel you can get.

calishine
10-11-2012, 4:38 PM
You're right Randal. I assumed wrong about the length.

Op, I do however, stand by the recommended parts.

Hoop
10-11-2012, 5:08 PM
Get a decent 16-20" barrel, some quad rail free-float handguards, either an A2 stock or magpul if you want it collapsible and a good trigger like a geisselle. Doubt it'll be a long range monster but it'll be better than what you have now.

The other option would be to buy a whole new rifle. Considering that you'll have to spend a grand to do the above that isn't out of the question either. I have seen heavy barrel bolt action savages in 260rem/creedmoor and 24" barreled 308 Rems grow on trees.

I am not a big fan of more than 20" of barrel on an AR. It's silly for both 223 and 308. If you want more barrel a bolt rifle will handle better. Why turn an AR into a 18lb, 4ft long artillery piece?

FMJBT
10-11-2012, 9:00 PM
I am not a big fan of more than 20" of barrel on an AR. It's silly for both 223 and 308. If you want more barrel a bolt rifle will handle better. Why turn an AR into a 18lb, 4ft long artillery piece?

Couldn't agree more.

Due to the extra weight of a semi auto vs a bolt action, I think it's a good practice to build as light as possible to end up with a finished weight near that of a bolt action rifle. My AR-10 with 26" heavy barrel weighs in at over 16 pounds. Shooting it feels a lot like shooting a crew served weapon. I hardly ever shoot it due to the bulk and weight of the rifle. My 16" AR-308 gets a lot more use, and surprisingly doesn't give up much in terms of performance against the 26" AR-10. Both rifles are consistent hitters at 1000 yards. The biggest difference is that the 26" barreled rifle will do it with a wider variety of ammunition. The 16" rifle requires very heavy bullets with a high BC to get out that far. 178 AMax's and 190 SMK's are good choices when running long range with a short barrel and reduced muzzle velocities.

hermosabeach
10-11-2012, 9:47 PM
If you use factory ammo, velocity tends to max out with a 20" barrell

If you reload, then the 24" can give you another 100-200 feet per second

The AR 10 is a heavy platform

For long range I would go with the 24"

For a hunting gun 18-20" is faster to get on target and easier to steady off hand

ar15barrels
10-11-2012, 10:04 PM
If you use factory ammo, velocity tends to max out with a 20" barrell

If you are gonna make outlandish statements like this, be prepared to prove it.
There are lots of published reports that say otherwise...

DannyInSoCal
10-11-2012, 10:09 PM
If you're going further than 18" is capable -

You should be switching to a bolt action and/or moving up in caliber...

lazyH
10-12-2012, 8:43 AM
On my Ar10 I Rainier arms 20" select barrel, with a Jp freefloat handguard and a geisselle ssa-e trigger love the setup, touching @ 100 yds with cheap remington and winchester ammo. I recomend both Rainier barrels and geisselle triggers. If you are only going to use this for long range bench / prone shooting than go with whatever length you would like, otherwise I would say a 20" is a nice compromise.

HK Dave
10-12-2012, 8:48 AM
If you use factory ammo, velocity tends to max out with a 20" barrell

If you reload, then the 24" can give you another 100-200 feet per second

The AR 10 is a heavy platform

For long range I would go with the 24"

For a hunting gun 18-20" is faster to get on target and easier to steady off hand

... velocity does not max out at 20". Not sure where you got your data, but even with factory ammo, it's got a ways to go before it maxes out.

I do however agree with another poster though... for me, a 24"-26" barrel on an AR is just silly. I'd rather put that on a bolt action rifle.

Bobby Hated
10-12-2012, 8:53 AM
velocity difference from 16 to 18 is big, but 18 to 20 is bigger.

if you want to have a prayer of consistent hits out to 1000yds you gotta have a 20".

theres a table somewhere that shows the data on this but i cant find it.

chicoredneck
10-12-2012, 8:54 AM
For longrange shooting, you want the barrel as long as possible.
Longer barrels give more velocity which helps with the wind drift.

This.

Velocity is very important in the long range game. Range is generally known and easily compensated for. Wind, however, is very unpredictable. The faster your bullet gets to the target the less time the wind has to play with it. Keep in mind though, that a longer barrel requires a more robust profile to maintain the same barrel rigidity as a short barrel. The 308 is really not an ideal cartridge for true long range shooting other than it is easy to load for. It has severe speed and BC handicaps compared to other cartridges that do fit the AR10 platfrom.

neal0124
10-12-2012, 10:21 AM
Personally, on an ar platform .308 18" would be my minimum and 20" would be my max. When I buy a barrel for the 6.5 creedmoor I plan on building I'll go with a longer barrel. I currently have a 22" barreled .308 and have no problem hitting a 1000 yard plate. I used to have a 19" barrel and was also able to hit the same target with ease. Elevation adjustments on the scope were negligible between the two barrel lengths.

Your ideal barrel length is totally dependent on what you want to do with the rifle. I plan on swapping out my 22" for a 20" eventually because I want a slightly more compact rifle.

FMJBT
10-12-2012, 10:42 AM
velocity difference from 16 to 18 is big, but 18 to 20 is bigger.

if you want to have a prayer of consistent hits out to 1000yds you gotta have a 20".

theres a table somewhere that shows the data on this but i cant find it.


Actually, the velocity gains from barrel length decrease with added length. The gain in velocity going from 16" to 18" will be more than the gain from going from an 18" barrel to 20". A 20" barrel will definitely help in the velocity deparment for getting rounds out to 1000 yards and beyond, but is not exactly required for consistent hits at that range with a 308. The key to getting long range performance out of shorter barrels is to use heavy, long bullets with high BC's. They start out with a slower muzzle velocity, but due to the high BC they don't lose as much velocity downrange as lighter, faster bullets do.

As an example, my 16" 308 is pushing a muzzle velocity of about 2590 FPS with a 190 grain Sierra Match King. At 1000 yards it's velocity has dropped off to about 1225 FPS, still about 100 FPS above supersonic. Not the ideal solution for shooting long range, but it definitely works consistently out to 1000 yards. I havent tested it yet, but I imagine this rifle will also work beyond 1000 yards, as the 190 SMK should transition pretty well into subsonic.

Hoop
10-12-2012, 12:05 PM
I'd like to hear what your barrel and load info thats getting 2600fps with a 190 in a 16.

FMJBT
10-12-2012, 1:45 PM
I'd like to hear what your barrel and load info thats getting 2600fps with a 190 in a 16.


Barrel is a Rainier Arms "Select" 16" with 1:11 twist.

FC 7.62 NATO brass (full length sized on small base die)
BR2 primer
Hodgedon CFE-223 (I'll have to double check my book when I get home, pretty sure it's 44 grains)Edit: 43 grains
190 grain Sierra SMK seated to OAL of 2.80"

The 2590 figure was estimated from reverse engineering the trajectory of 39 MOA elevation dialed from 100 yard zero.

ar15barrels
10-12-2012, 1:51 PM
I'd like to hear what your barrel and load info thats getting 2600fps with a 190 in a 16.

44gr of bullseye.

The Virus
10-12-2012, 2:56 PM
18"

Hoop
10-12-2012, 3:30 PM
44gr of bullseye.

LMAO


The 2590 figure was estimated from reverse engineering the trajectory of 39 MOA elevation dialed from 100 yard zero.

I'm going to wager it's not going that fast but if it works for you I wouldn't worry about it.

FWIW I use almost the same load in my 16" only with 2000MR and a 190nosler and it's about 2400fps.

hermosabeach
10-12-2012, 4:31 PM
I read several articles about mil spec and match .308

After reading other data, i stand corrected in that a lot of commercial will be hotter from a longer 308 barrel

For reference- here is one of the articles where they chop down a barrel

http://www.tacticaloperations.com/SWATbarrel/
Exerpt-
During the development of the Tango 51, Tac Ops took a standard 26-inch barrel and cut it down to 18 inches in one-inch increments. Between 10 to 20 rounds were fired at each invrement. They found that a 20-inch barrel provides for a complete propellant burn and no velocity loss when using Federal Match 168-grain BTHP, a cartridge that has become something of a law enforcement standard. Going to an 18-inch barrel only resulted in a loss of 32 feet per second (fps).

FMJBT
10-12-2012, 4:35 PM
LMAO



I'm going to wager it's not going that fast but if it works for you I wouldn't worry about it.

FWIW I use almost the same load in my 16" only with 2000MR and a 190nosler and it's about 2400fps.

It wouldn't surprise me if that is a bit fast for the estimate, but it does fit with what I'm seeing on the range. I tried running the numbers through Android Sooter with 2450, and 2500 FPS and the elevation correction is quite a bit larger than what I'm actually dialing. The program could be off, or more likely my inputs into the program are off. Smart phone apps aside, the rifle/ammo combination is still a decent performer out to 1000 yards. It wouldn't be my first pick for long range shooting out of the rifles I have, but it'll do th job reasonably well. For a rifle that is destined to see regular use at 800+ yards, I'd opt for an 18 to 20 inch barrel with a slightly heavier contour.

FMJBT
10-12-2012, 4:38 PM
44gr of bullseye.

Sweet! I'll go load that up now. Let you know how it went when I get back from the E.R. :D

hermosabeach
10-12-2012, 4:44 PM
Another federal gold metal match test

The purpose of this test was to find out how the barrel length affects velocity. There are several other velocity tests available, I had the opportunity to perform the test. Firing 5-shot strings of 168 grain Federal Gold Medal match ammo collected the data. The test rifle was my M40A1. I wanted to go down to 16” because that is the minimum rifle length.
Test conducted 6/17/09 at 11:00 am Temperature 62 degrees
24”barrel average velocity 2696 FPS
22”barrel average velocity 2663 FPS
20”barrel average velocity 2621 FPS
18”barrel average velocity 2566 FPS
16”barrel average velocity 2524 FPS
The rule of thumb I’ve heard was that in a .308 you will lose 25 FPS per inch you cut off. As you see, that is not the case. Velocity from 24 inches to 20 inches lost was 75 FPS for an average of 18.75 FPS per inch.

bomb_on_bus
10-12-2012, 4:49 PM
Randal nailed it on the head.

The longer the barrel the higher the velocity in a nutshell. Ammo comes into play with this almost as much as the length of the barrel. Powder type and burn rate, bullet weight, etc can play into long range shooting as well.

ar15barrels
10-12-2012, 5:03 PM
http://www.tacticaloperations.com/SWATbarrel/

The most often quoted article on why you should run a short barrel... :rolleyes:

They forget to mention that they are using a TIGHT BORE barrel with a match chamber and that is the reason they get more velocity with a shorter barrel.

Simply cutting a factory barrel down to 18" will NOT give you the same performance as an 18" long tight bore barrel with a short throated chamber...

08GTCS
10-12-2012, 6:53 PM
Thanks for the replies everyone. As I said, I'm new to long/medium range ARs so all of the info has been a big help. I don't plan on making shots beyond 600-700 yards so from what I've read, I'll probably be going with an 18".

XxManWitHaGuNxX
10-12-2012, 9:53 PM
Like you said, for your purposes 18 inches is more than enough, However if you go to 20-24 inches you will have the option to reach out a little further if you ever decided to try... But on that note, like someone said above, going wiht a bolt gun would serve much better for longer than 600 yards..
I did have a Armalite AR10-T with a 24 inch barrel (nice rifle) and got rid of it and picked up a R700 Acc-sd in 308, slapped on a HS precision stock, and with its 20inch barrel, and I find it Much Much better for even 200-400 yards... (as far as my range is) Just a thought, have fun and be safe...
MWaG

WHITE MAMBA
10-13-2012, 8:06 AM
Its a Ar platform, build 2 uppers, one short one long!

fcr
10-13-2012, 9:30 AM
I built my .308 with a 21" Noveske a few years back. It is way too heavy for my purposes. The parts at the time were scarce so I had to jump on the barrel when it was available.

SoCalXD
10-13-2012, 10:05 AM
As a side note, the Army has pretty much determined that their pig of an M110 rifle is way too heavy and too long. They will likely be converting most of them into lighter, short barreled, retracting stock rifles (36" collapsed, 9lbs slick), possibly DI vs. piston (for weight reduction), good out to a max of 600/800 meters. This will become their DMR/ Urban Sniper/Sniper Support Rifle(s), while going to a new 300WM/338LP bolt gun for long range sniper work. This was all based upon 10's of thousands of combat soldiers field experience over the last 10 years... not to be taken lightly! (I bet once they are fielded, we will see a bunch of 1-8x Leupold MK-8's on top of them too!)

If a 16 or 18" barrel is good enough for the Gen2 Army CSASS rifle, its good enough for most citizen's LR308 rifle configuration. The difference between a 600 yard effective range rifle and an 800 yard effective range rifle has much more to do with a shooter's range estimation and wind doping skills, than an extra 100-150fps in bullet velocity. If I wanted a 800 yard + rifle, it would be a bolt gun in 300WM or 6.5C, depending upon my terminal ballistics needs (unless I just HAD to have a semi-auto, then I'd look to Fulton Armory to build up a 6.5C Dreadnought for me!)

CSASS Bid
https://www.fbo.gov/index?s=opportunity&mode=form&tab=core&id=78aa32aa1cf1c788ebb1afd2bdae4680

Fulton's Dreadnought
http://www.fulton-armory.com/fariflecal556mmupruniversalprecisionrifle-3-4-2-1-1-2-1-2-2-1-4-4.aspx

p.s. There is some very good advise and well reasoned opinions posted on this thread by fellow calgunners. I really appreciate everyone chiming in!

BigBamBoo
10-13-2012, 10:25 AM
One thing I feel is worth mentioning here with all the talk of weight. Barrel profile plays a large part in how heavy a given rifle will be. So if you get a "varmint" or bull barrel profile, expect it to be heavy.

One of the things I like (and why I use) JP barrels is they use light or medium barrels and then add a heat sink.
This allows for very effective cooling while saving weight. Just some food for thought.

fcr
10-13-2012, 11:00 AM
One thing I feel is worth mentioning here with all the talk of weight. Barrel profile plays a large part in how heavy a given rifle will be. So if you get a "varmint" or bull barrel profile, expect it to be heavy.

One of the things I like (and why I use) JP barrels is they use light or medium barrels and then add a heat sink.
This allows for very effective cooling while saving weight. Just some food for thought.

You have way too many cool toys.

nothing4u
10-13-2012, 11:34 AM
44gr of bullseye.

Someone will be dumb enough to try that :facepalm:.