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14.5" 308 ar

T

Tarheelpwr

Sergeant
Full Member
Minuteman
Feb 22, 2013
320
18
SW PA
So,

I'm on the fence between an 18" or a 14.5" w/ pinned hider. After running the numbers, I'd expect about 2600 fps with 168 Amax @ 18" and 2475ish with 14.5". Assuming those are right, the ballistics really don't change much. Both still stable to around 1k and have enough energy/velocity to take a deer to 500ish.

What am I missing? This won't be a comp gun, just fun. I totally get the FPS matters in comps where slight mis judgements get amplified with drift/drop, but just for fun, I don't see much difference.

Assuming I go 14.5", what length gas system should I run? I'm new to 308's. Will I have any cycling issues?

Main reason for exploring the 14.5" is to aid in OAL with a suppressor, then when I did the research, the FPS DROP seemed insignificant.

What are your alls thoughts?
 
I'm kind of in the same boat as you. I currently run a 16" but it's a 1-12ish twist and doesn't care for the heavies so I'm hunt for a 1-10 and I'm considering a 14.5". When I crunched the numbers I kind came to the same conclusion, I'm only looking to go 6-800m max. I've only seen carbine length systems so far for 14.5", with a adjustable gas block in place I don't see any problems running a can.
 
You will need to be spot on with your range estimation and DOPE with a 14.5". We went from 20" barrels down to 14.5" and that was the biggest difference I noticed. 175 SMKs will help you to get out to 1k.
 
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Assuming you aren't hunting deer in PA.
I'd wonder about the life of your suppressor.
That's 300WM muzzle PSI.
 
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MLC said:
Assuming you aren't hunting deer in PA.
I'd wonder about the life of your suppressor.
That's 300WM muzzle PSI.
Click to expand...

Can't hunt with a semi in PA. Can is rated for 300 RUM. I will need to double check as thats a good point on warranty.
 
Coming from a dpms that's was 14.5 to my 16" LMT MWS I don't find its any less handy which is really the argument here considering ballistics are not going to to make a huge impact sub 800-1000. I'm glad I didn't hack this rifle as well, buddy just got a trick new can, no problem I can break off my birdcage and throw an adaptor on in the garage. You think you own the can your going to stick with, you think you have found the best muzzle device for you. Don't get stuck being married to it. Yea it can be taken off, but 5 minutes in the garage beats who knows how long at the Smith, for an inch and a half?
 
The insatiable quest for short barreled problems continues... A 14.5" barrel is just to short for a 308. That gun is going to beat itself to death. John Noveske poured his heart and soul into the short barreled large frame platform. He found a way to make them run but couldn't solve the how to make them last conundrum.

I have no doubt someone is going to charge into this thread sword drawn trumpeting their 308 SBR that has a quarter million rounds on it without a problem. 308's with barrels less than 16 inches, which is barely enough, are novelties. I'm OK with pursuing the project but its going to be expensive and it comes with a high failure rate. I have to believe that 300 Blackout would be a better choice.
 
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Ballista One said:
The insatiable quest for short barreled problems continues... A 14.5" barrel is just to short for a 308. That gun is going to beat itself to death. John Noveske poured his heart and soul into the short barreled large frame platform. He found a way to make them run but couldn't solve the how to make them last conundrum.

I have no doubt someone is going to charge into this thread sword drawn trumpeting their 308 SBR that has a quarter million rounds on it without a problem. 308's with barrels less than 16 inches, which is barely enough, are novelties. I'm OK with pursuing the project but its going to be expensive and it comes with a high failure rate. I have to believe that 300 Blackout would be a better choice.
Click to expand...

Agree to a point. A full sized 308 (full size carrier) will beat itself pretty bad. It needs a lot of gas to move the carrier and bolt. The DPMS GII and my Nextgen or a full size 308 with a lightened carrier would work better. Personally I don't think a 14.5 is much handier than a 16". Either will work with a mid gas system, I would never use a carbine length on a 308.

Edit-always adjust the gas to the weight of carrier and buffer , length of barrel used where it just locks back.
 
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Ballista One said:
The insatiable quest for short barreled problems continues... A 14.5" barrel is just to short for a 308. That gun is going to beat itself to death. John Noveske poured his heart and soul into the short barreled large frame platform. He found a way to make them run but couldn't solve the how to make them last conundrum.

I have no doubt someone is going to charge into this thread sword drawn trumpeting their 308 SBR that has a quarter million rounds on it without a problem. 308's with barrels less than 16 inches, which is barely enough, are novelties. I'm OK with pursuing the project but its going to be expensive and it comes with a high failure rate. I have to believe that 300 Blackout would be a better choice.
Click to expand...

I agree. This is the sort of input I was looking for. I'm starting with a 10" 300 blk. The .308 is ring built from the ground up, so barrel length is easy with either choice.

Not sure I want to mess with the expense and trouble. Might just go with 18" like my original plan. The 14.5 was just a fleeting thought
 
I have a 12" with mid length gas (POF), and run an AAC MK13-SD on it. I get fantastic accuracy from the 155 SMK and 155 GMX at 2375fps. I've only had it for a little over a year but have put a lot of time into making it run as smooth and accurately as possible. I do like it for what I use a compact 308 set up for. Drumming up your own loads to manage pressures and accuracy might be the difference in accomplishing that. I've taken it to 650 yds, rarely do I shoot it over 500. Beyond 600 - where I hit 130 inches of drop - it gets pretty difficult to put on 6x6 steel (for me it does). To put it in perspective, I have to adjust for a total of 130 inches all the way through 600 yds at which point the projo is still at 1450fps. The next 200 (600-800 yds) I get 152" of additional drop and lose an additional 225-230fps . That is just a huge degree of variation to adjust for every 25 yards not to mention how hard it is to manage wind at that range with a 155gr bullet at those speeds. Your ranging has to be perfect and your optic has to be best of breed. It's difficult enough that I just use a rifle designed for longer ranges rather than one that's set up for 500 and in for LR shooting.

At the end of the day, the specifics of your application should determine your needs. Is a 12" 308 a horrible choice? It could be. It's great for some and horrible for others. Depends. I love mine. It's accuracy is great at the distances I shoot with it, it's only 7 1/2 pounds, and the OAL with my can is what a 20" rig would be. FOR ME, those were important factors being weighed in the context of what I wanted to do with it as I made my decision.
 
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And FWIW, a 155gr GMX is still supersonic out past 1000, albeit not for long past that mark, even out of a 12".
 
jasonfaz said:
I have a 12" with mid length gas (POF), and run an AAC MK13-SD on it.
Click to expand...

Confused... Piston or traditional gas gun?

Are you at all concerned with the battering your suppressor is taking running it on a barrel that short? There is a lot of propellant being burned externally using a barrel that short.
 
Ballista One said:
The insatiable quest for short barreled problems continues... A 14.5" barrel is just to short for a 308. That gun is going to beat itself to death. John Noveske poured his heart and soul into the short barreled large frame platform. He found a way to make them run but couldn't solve the how to make them last conundrum.

I have no doubt someone is going to charge into this thread sword drawn trumpeting their 308 SBR that has a quarter million rounds on it without a problem. 308's with barrels less than 16 inches, which is barely enough, are novelties. I'm OK with pursuing the project but its going to be expensive and it comes with a high failure rate. I have to believe that 300 Blackout would be a better choice.
Click to expand...

I guess Larue is going to have a lot of warranty work with thier predatobr then :/
 
Sterling Shooter said:
What supports getting a the best hit? The longer barrel will, for a multitude of reasons.
Click to expand...

I agree 100%. I guess my thinking was I'm not worried about this being a tack driver. I have a 7RUM when I want ballistics that are flat for LR.

Either way, I think the 18" makes more sense. After messing with my 28" Grendel, handling isn't much different that 26" rigs. I'd rather not have the added noise.
 
Ballista One said:
Confused... Piston or traditional gas gun?

Are you at all concerned with the battering your suppressor is taking running it on a barrel that short? There is a lot of propellant being burned externally using a barrel that short.
Click to expand...

It's a POF, so yes, gas piston with gas port at the traditional middy length location.

I was apprehensive initially, but after talking with the guys out at AAC and describing loads, rate of fire (slow, no mag dumps) and some additional machining I had done to the POF receiver I was pretty comfortable with the set up. BUT, and it's a big but, I'm not running factory ammo. I'm hand loading specifically for this rifle to get max performance at lowest possible pressures and minimize excess powder hitting the blast baffle. It really limits my choices of loads, but it's a 308. It's going to sport a softball trajectory either way. Again, getting 9-10 ring hits at 400-500 yds is not very difficult with a 12" barrel - especially if you're running a top notch optic and can effectively range and correctly adjust for wind and drop. I'm running a Leuy MK 6 with H58. It's really a walk in the park unless conditions are really bad. If I want pinpoint accuracy at 750-1200 yds I'll take my 6.5CM. If I'll be shooting 1250+ yds I'll take my Lapua.

When I go hunting - black bear or mulie's for example - I'm usually humping along some tough terrain with a week's worth of gear. I haven't taken anything past 375 on those hunts. Taking those things into account, this 308 fit the bill for what I wanted in the context of my specific application.

Comparing a 12" 308 to an 18" (or hell, a 14.5", 16", 22" or whatever length you'd like to throw up there) with evaluation criteria limited solely to the best possible chance for a hit wouldn't really make sense. A 12" isn't meant to outperform everything at distance. It's value rests in an entirely different set of characteristics which would only be valuable to someone with use cases that matched those.

Anyway, that's just my 2¢ based on my experience...
 
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I had a 14.5" 308 for awhile. with the permanently attached muzzle break, it was the most obnoxious rifle to shoot I have ever owned. At the range, people for 2 or 3 benches on either side would stop shooting and get up....heck, it was obnoxious even standing directly behind someone shooting it at the bench. So, my point is this, if you do go this short, do not get a muzzle break. get a flash hider or something like a Flaming pig that will not reflect the noise back. Most of my Semi-auto 308s are 20" or longer. I am currently finishing one 16" build with a rifle length gas system and a "Krinkovish" style break on it.....very smooth shooting rifle. If I do another, think it will be a 18" lightweight with rifle length gas system.
 
The Triple Port muzzle brake that came on my 14.5" P308 works great. Gun is extremely soft shooting for a .308 and no issues with range members on either side of me. Mines a joy to shoot and is a laser.

Haven't had it out past 200yds yet but will find out how it does at distance as I will be running it in a BHTC Precision Rifle class in October. They will have us engaging targets out to 1050yds with the majority of shooting from 750yds and in. I'll be running Southwest Ammo 175gr SMK.
 
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desertfox01 said:
I had a 14.5" 308 for awhile. with the permanently attached muzzle break, it was the most obnoxious rifle to shoot I have ever owned. At the range, people for 2 or 3 benches on either side would stop shooting and get up....heck, it was obnoxious even standing directly behind someone shooting it at the bench. So, my point is this, if you do go this short, do not get a muzzle break. get a flash hider or something like a Flaming pig that will not reflect the noise back. Most of my Semi-auto 308s are 20" or longer. I am currently finishing one 16" build with a rifle length gas system and a "Krinkovish" style break on it.....very smooth shooting rifle. If I do another, think it will be a 18" lightweight with rifle length gas system.
Click to expand...

What muzzle brake were you using on your 14.5" .308?
 
Lol, nothing like bumping a thread that died 5 years ago. It is interesting to see how far short 308's have come .

Short 308's are fun. what is your budget?

if you are interested in a shorter, i would recommend picking up an upper from one of the companies that have a good track recordin reliability, while its not hard to assemble a shorter upper, that lack of a mil standard increases the possibility that everything may not sync up/

Here is a supressed 13.5 MWS next to a 16 inch SR25 ACC . Kac and LMT have both had short 308's down range for some time now.

 
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My 14.5” 308 build is my go to 308. Weighs under 8lbs with a unloaded mag . I reload so I’m pushing 178 Amaxs to around 2700 using Tac powder and it’s an absolute tack driver to 300 yards, which is as far as I’ve taken this rifle . I prefer the shorter 14.5” barrel without a doubt and I have an 18” setup as well. Probably my favorite all around rifle for versatility.
15B0C8D2-3FDC-43B8-96F7-F282A88BF708.jpeg
 
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I have a 14.5 308 ..love it ..my favorite deer rifle ..was a just for fun build with Noreen upper and lower on sell with on sale parts be came my go to hunting rifle
 
I'm assembling a 14.5 barreled 308 to run with a can and a pistol brace so I can deer hunt with a "pistol" in a shotgun only zoned area of my state. I'll be using a custom ballistics curve in my range finder binoculars to deal with the drop. Range will be within 500 yards. I considered other calibers but with lower velocities of short barrels, I wanted a heavier bullet to improve energy delivered to take down a deer. I got a fluted Wilson barrel on sale for around 200$
 
Completely agree with @TonyTheTiger I would not want a carbine gas system on a 6.5. I have been thinking about doing a 14.5 6.5 myself. I would want a midlength gas system at least.
 
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Raffica762 said:
Carbine gas creedmoor that bad Tony? Sounds bad when you put it that way
Click to expand...
Compare a 14.5" 5.56 with a carbine, then mid, then intermediate gas and you'll never touch a carbine gas barrel this side of 11.5" again. Now look at the huge difference guys see in 20-24" 6.5CM's when they go from rifle to +2 gas and imagine all that in gas systems half the length.
 
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TonyTheTiger said:
Compare a 14.5" 5.56 with a carbine, then mid, then intermediate gas and you'll never touch a carbine gas barrel this side of 11.5" again. Now look at the huge difference guys see in 20-24" 6.5CM's when they go from rifle to +2 gas and imagine all that in gas systems half the length.
Click to expand...
Makes sense thank you sir
 
6.5CM 16inch Criterion rifle length, non adjustable block, Mil-Spec tube, shorty carbine buffer, carbine spring and Toolcraft 6.5 single ejector. Ran great with FGMM 130 and Hornady 140 ELDM. Ejection was 3-4 o’clock. Hand loads with H4350 the ejection was 4 o’clock but wasn’t burning all the powder and the muzzle was fouled pretty bad. I’ve done initial load work with Varget and it runs better and cleaner but it needs more testing for a better comparison. Threw a can on with all the ammo above and was slightly over gassed and ejection was 2 o’clock. Added a Superlative adjustable block and back to normal. I probably should’ve tried a heavy buffer first. Still might try it and not use the adjustable block. Looking at the Criterion 308 14.5 for the next build.
 
I cut my 16” LMT down to 14.5” and pinned the brake. It breaks transonic around 1125 yards depending on the weather with M118lr or AB39. Cutting it down doesn’t reduce the accuracy and barely affected the muzzle velocity. I did it to keep the overall length down with the suppressor. I realize the can I’m running isn’t rated for 308 with a 14.5” barrel. But I don’t care. It works great for what I intended and still has plenty of kill power. I dropped a 1000 lb. Nilgai at 270 yards with one well placed shot.
 

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JLo210 said:
I cut my 16” LMT down to 14.5” and pinned the brake. It breaks transonic around 1125 yards depending on the weather with M118lr or AB39. Cutting it down doesn’t reduce the accuracy and barely affected the muzzle velocity. I did it to keep the overall length down with the suppressor. I realize the can I’m running isn’t rated for 308 with a 14.5” barrel. But I don’t care. It works great for what I intended and still has plenty of kill power. I dropped a 1000 lb. Nilgai at 270 yards with one well placed shot.
Click to expand...
Impressive! I have been curious if going down to 13.5 or 14.5 had that much impact on real world performance for hunting.
 
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