barrel length on new build?

[diderr]

I just heard from my smith that my 308 is about two weeks out. I originally decided on a 22" barrel from lug. Right now it is 25". He said he would cut it shorter if I didn't like it. The only problem is I'm going to get it cerakoted right away, so a cut and recrown really wouldn't be an option. Should I stick with the original plan of 22"? Will the 22 to 26" velocity increase justify the added length? Scope elevation is not going to be a problem as my scope should get a 308 out to 1,700 yards in the 22" configuration.
Thanks.

 

[ArmyJerry]

is that 22" or 32" for the 1700 yards?

 

[JB02]

You're going to need a really long barrel if you want to consistently get out to 1000 yds. I doubt a 22" is sufficient. If you are looking to regularly get out past 1000 yds, there are better options (magnum calibers are best suited). 168s tend to go transonic ~ 800 yds. 155s will get you there, especially if you have a 1/12 barrel, but then you'll need to fight the wind.

Don't make that rifle be something it's not designed to be. If you want it short and handy, accept the fact that it will only be really accurate for ~ 600 yds max.

 

[diderr]

is that 22" or 32" for the 1700 yards?

22". I have a 28 mrad scope.

 

[ArmyJerry]

Oh sorry you have a 25" barrel, yeah keep it 25", 1700 yards is asking a lot from a 308 in any length barrel.

 

[Graham]

Yes: A 22" barrel is ideal on a .308.

No: You won't get to 1700 supersonic with a .308, even with 4000 feet of altitude. Give up on that idea.

 

[diderr]

Yes: A 22" barrel is ideal on a .308.

No: You won't get to 1700 supersonic with a .308, even with 4000 feet of altitude. Give up on that idea.

Sorry, didn't mean I was going to be shooting 1,700 yards. It was merely added information that I could easily reach 1,000 yards with either barrel length and my scope.

 

[Graham]

22" is fine with a custom barrel. There is very, very little you will gain on a .308 by adding three inches of barrel.

 

[sobrbiker883]

I run barrels as long as practical. Not the current rage, I know but I don't deploy out of vehicles much.

 

[Graham]

I run barrels as long as practical. Not the current rage, I know but I don't deploy out of vehicles much.

I tell Moon what I want it to do, and he sends me a rifle.

If I ever ask for a specific barrel length I ask for it in terms of how much rifling I want. Because length can be measured different ways, resulting in different amounts of rifling ahead of the chamber.

The issue with .308, like .223, is that the cartridge capacity limits the advantage to barrel length, so practical length is often to be determined by other considerations like balance or sight radius or intended use.

 

[Pusher591]

You're going to need a really long barrel if you want to consistently get out to 1000 yds. I doubt a 22" is sufficient. If you are looking to regularly get out past 1000 yds, there are better options (magnum calibers are best suited). 168s tend to go transonic ~ 800 yds. 155s will get you there, especially if you have a 1/12 barrel, but then you'll need to fight the wind.

Don't make that rifle be something it's not designed to be. If you want it short and handy, accept the fact that it will only be really accurate for ~ 600 yds max.

This is a partially true statement. 1000 yards is not that hard to engage with a 308, however you are reaching it's effective limits. A 22" custom barreled gun is a great all around 308 gun. I had a 17.5" Brux barreled gun that consistently ran 178 bthp's at 2570-2580. I consistently drilled 2/3 Larue style torso targets at 730 yards, if you follow through on fundamentals it's not hard.
You should be able to push a 178 bthp from Hornady (which has a very high .308 BC of .530) around 2670-2700.
That should only be around a 2.3-2.5 mil hold at 1000.

 

[TXTransplant]

If yer shooting off the shelf stuff, 175 gr FGMM, you should be fine at 4,000 feet keeping those slower FGMMs from going transonic before 1,000 yards. If yer shooting at sea level you will prob notice a big change in cone of dispersion getting past 900 yards. That extra few inches of barrel means nothing until yer getting near 1,000 yards--then it starts to matter. But again, at 4K feet, you should be good with 22"

Handloading you can run stuff a bit hotter so it matters even less--sure 22" will do it.

 

[sjb269]

Depends on barrel contour, overall rifle balance would tell me what length to go with. If your shooting at 3700ish feet mostly, that'll help your ballistics...you should be fine at 20-22 inches. Push a 175 SMK at 2600-2650

 

[JB02]

You should be able to push a 178 bthp from Hornady (which has a very high .308 BC of .530) around 2670-2700.
That should only be around a 2.3-2.5 mil hold at 1000.

I think you're off on the hold. Although I shoot at sea level, I need to hold about 2.1 mils at 400 yds. I plugged in the values the OP has above into JBM (175 Berger VLDs and assumed atmospherics, but used a generous 2700 fps) and at 4000 ft we have a 2 mil hold at 400 yds and a 9.3 mil hold at 1000. He goes transonic around 1200 yds.

Does anyone have any empirical data for the amount of velocity you get per inch of barrel past a certain length? That might be the info the OP is looking for.

 

[Sniper Uncle]

I think you're off on the hold. Although I shoot at sea level, I need to hold about 2.1 mils at 400 yds. I plugged in the values the OP has above into JBM (175 Berger VLDs and assumed atmospherics, but used a generous 2700 fps) and at 4000 ft we have a 2 mil hold at 400 yds and a 9.3 mil hold at 1000. He goes transonic around 1200 yds.

Does anyone have any empirical data for the amount of velocity you get per inch of barrel past a certain length? That might be the info the OP is looking for.

I know that 30.06 and .308 are different in their capabilities and characteristics, but Lilja says that for a 30.06 I could figure on 25fps per inch of added barrel length.

 

[ArmyJerry]

From another forum I am on.

26 2826
24 2722 104
22 2713 9
20 2677 36
18 2654 23
16 2552 102

Average change = 55 fps or 27.5 fps/inch

As far as the cited article goes, a good experiment analyzes the data and then draws conclusions from it.

Beware of articles that have an obvious point of view they want to propound, especially ones that don't cite their data.
natman is offline

 

[Shoots 700's]

I would keep it at 25" if I didn't have to lug it around

 

[Shotplacement]

I would have it cut to 22". Its a good mid range barrel.

 

[diderr]

Thanks for all the input guys!

 

[diderr]

From another forum I am on.

26 2826
24 2722 104
22 2713 9
20 2677 36
18 2654 23
16 2552 102

Average change = 55 fps or 27.5 fps/inch

As far as the cited article goes, a good experiment analyzes the data and then draws conclusions from it.

Beware of articles that have an obvious point of view they want to propound, especially ones that don't cite their data.
natman is offline

Is that with 175s?

 

[Shoalwater]

Go 25", and just wait on the Cerakote until you decide on the length.

 

[ArmyJerry]

sent you a pm with teh link to the data I found.

Is that with 175s?

 

[diderr]

sent you a pm with teh link to the data I found.

got it. thanks.

 

[Pusher591]

I think you're off on the hold. Although I shoot at sea level, I need to hold about 2.1 mils at 400 yds. I plugged in the values the OP has above into JBM (175 Berger VLDs and assumed atmospherics, but used a generous 2700 fps) and at 4000 ft we have a 2 mil hold at 400 yds and a 9.3 mil hold at 1000. He goes transonic around 1200 yds.

Does anyone have any empirical data for the amount of velocity you get per inch of barrel past a certain length? That might be the info the OP is looking for.

I double checked and my data is showing 2.3-2.5 mils but I switched it to MOA and it's showing 9.1
Are you sure you are in mils? I'm also using a 10mph cross wind from 3-9/9-3

 

[wrhunter]

I double checked and my data is showing 2.3-2.5 mils but I switched it to MOA and it's showing 9.1
Are you sure you are in mils? I'm also using a 10mph cross wind from 3-9/9-3

Something is off Pusher. My 168 Amax load at 2625 fps needs 14 moa to get to 550 yards. There is no way a 175 is getting to 1000 with 9.1 moa. Jbm says about 36 moa. Not corrected for 4000 ft though. Switched it to mils and its close. I'm assuming a 100 yard zero?

 

[D_TROS]

SWAT Article BARREL LENGTH

Good read. I would go 22" max. I think 20" is about perfect for the 308. My last GAP was a 22" 308 and it shot VERY well as far as I was capable of reading the wind. (the furtherst I shot in a match was 875 yards and had a 1st rnd hit...holding 8MOA!! ha)

Regards,
DT

 

[Sniper Uncle]

Good article, but one serious flaw. This so called "only lost 32fps" is predicated on factory ammo. In real world here, the OP is talking with reloading, correct? If so, then this article forgets the fact that with a reload one can use a powder that is still burning to then end of the barrel.
I have a 338LM with a 34" barrel, and by using RL-50, I can get a 98.5% burn which is actually gaining speed all the way out the barrel---no way the air pressure and barrel drag is up to 8000psi at the end of the barrel. I can achieve speeds of 2850 fps with this powder and a 300gr bullet, and hit an accuracy node, and keep the max pressure lower than with any other powder,(as in 54K versus 59.5K).
This is not achievable nearly as easily with a 20" barrel. The article is talking about urban environment also. How often does the shooter encounter 800yd shots in an urban environment? If he is shooting that far, then length of barrel and maneuverability would be less of an issue.
To each his own, but I don't see 25" being too long here, In MY ARROGANT Opinion!

 

[Graham]

I was wondering when that old tacops article would resurface......The premise is correct, but the argument is flawed when it comes to the larger case capacities. For example:

If so, then this article forgets the fact that with a reload one can use a powder that is still burning to then end of the barrel.

I'm not sure what you mean by powder not burning to the end of the barrel, but with the case capacity of a .308 the opposite of what you are saying is true: If one reloads one can use faster burning powders for shorter barrels.

I have a 338LM with a 34" barrel, and by using RL-50, I can get a 98.5% burn which is actually gaining speed all the way out the barrel---no way the air pressure and barrel drag is up to 8000psi at the end of the barrel. I can achieve speeds of 2850 fps with this powder and a 300gr bullet, and hit an accuracy node, and keep the max pressure lower than with any other powder,(as in 54K versus 59.5K). This is not achievable nearly as easily with a 20" barrel.

I'm not sure how you measured the 98.5%, but I can tell you it's not acheivable at all with a 20" barrel on a .338. Because what works in barrel length for a .338LM does not work for a .308. (or even a .338NM for that matter).

The article is talking about urban environment also. How often does the shooter encounter 800yd shots in an urban environment? If he is shooting that far, then length of barrel and maneuverability would be less of an issue.

And now you've stepped completely out of your element.

In MY ARROGANT Opinion!

There's nothing wrong with arrogance, as long as it is backed-up by competence.

 

[Sniper Uncle]

Points taken Graham, but you missed the point of my remark about powder burning to the end of the barrel. The article talks about factory ammo and that no loss of velocity with one size, and only 32fps with the other was found in their tests. This would indicate that the powder was fully or very nearly burned before the bullet reached the end of the barrel, as little to no velocity changes were noted between the longer and shorter barrels in the 20-26" range, and only 32fps when cut to 18". A change of powder could change this relationship dramatically.
Where my example does relate, though it be a different caliber, the principles are the same. If you hand load, you can use a slower powder to burn longer down the tube. A faster powder will be fully burned sooner, and in a longer barrel will give rise to the claim in the article that the bullet will succumb to resistance in the barrel and air pressure against it and lose velocity in the last stages of barrel travel. With hand loading you could put more powder in, but the flip side to this is the possibility of a higher max pressure, which may limit the safe amount of that powder usable in that cartridge. Doesn't matter what cartridge you are talking about, nor which powder, the principles are the same, just the actual numbers must be checked for each cartridge.
I would never try RL-50 in a .308.
Conversely, a slower burning powder will give possibilities of lower extreme pressure, and allow the powder to burn farther down the barrel.
The figures I cited were derived from QuickLoad, a very reputable internal ballistics software. I could run the numbers on a .308, but I don't need to right now, as I am talking principles here, not actual data for one rifle versus another.
The article is talking about SWAT teams in Urban environment, and the OP is talking of 800 or more yard shots, not typical for an Urban SWAT team. This generalization is not getting out of my element, respectfully, and anyway, how would you know what my element is?
Thank you for your point by point critique.

 

[Pusher591]

Something is off Pusher. My 168 Amax load at 2625 fps needs 14 moa to get to 550 yards. There is no way a 175 is getting to 1000 with 9.1 moa. Jbm says about 36 moa. Not corrected for 4000 ft though. Switched it to mils and its close. I'm assuming a 100 yard zero?

Ok you are measuring drop, I'm measuring wind. 2.5-2.7 mils was a wind hold at 10 mph at 1000, not elevation hold.

 

[Graham]

Thank you for your point by point critique.

It's never a problem when I hear my name called. I thought that you were calling me out with your comment about arrogance, but that could simply be my arrogance. LOL!

how would you know what my element is?

Your profile; and the link to your homepage trucking company that you recently deleted from your profile.

 

[D_TROS]

... A change of powder could change this relationship dramatically.
Where my example does relate, though it be a different caliber, the principles are the same. If you hand load, you can use a slower powder to burn longer down the tube. A faster powder will be fully burned sooner...

Exactly. SOO if you reload, with a shorter barrel, you can optimize powder burn. The point you, and possibly the OP, are missing is the that a kettle is black. You can paint it, but its still a kettle. You can shoot a 308 at 800+ yards, you can also shoot a 22LR at 400+ yards, both of which I have done. You can shoot a 308 out of a 50" barrel with the slowest powder available, but its still a 308 and will be limitied by more than its case capacity. Its still not a porclein (sp?) bowl. The point is to optimize a cartridge for your use, and the 308 is not optimal for long range, but since you own a 338 LM, I feel you have grasped that concept.

If you want to discuss how you can engage a target at 1200+ lards with your 223/308 there are other forums more inclined towards sprayin/praying and non accurate rifles.

If you call a gun smith and ask for a custom build, he will ask what you want. If you ask a GREAT smith to build a custom rifle, he will ask what you want to use it for and build from there.

Again nothing wrong with a 308 as a rifle to learn the basics, but dont try to paint it porclein and call it a shitter...wait...what?!?!?! haha...

Regards,
DT

 

[l115a3]

It depend on what projectiles and purpose of this rifle.

If you plan for Competition, The longer would be appreciate due to gain more MV.

If you need for Tactical Look, The 20" will be nice and can reach those 1,000 yards target.


Bryan Litz had test .30 Berger 175 OTM and success 10 shots within 1 MOA from Larue AR 10 20" Barrel. The bullet go transonic before reach the target but the new design of OTM make them stabilize after Transonic.

 

[Sniper Uncle]

Exactly. SOO if you reload, with a shorter barrel, you can optimize powder burn. The point you, and possibly the OP, are missing is the that a kettle is black. You can paint it, but its still a kettle. You can shoot a 308 at 800+ yards, you can also shoot a 22LR at 400+ yards, both of which I have done. You can shoot a 308 out of a 50" barrel with the slowest powder available, but its still a 308 and will be limitied by more than its case capacity. Its still not a porclein (sp?) bowl. The point is to optimize a cartridge for your use, and the 308 is not optimal for long range, but since you own a 338 LM, I feel you have grasped that concept.

If you want to discuss how you can engage a target at 1200+ lards with your 223/308 there are other forums more inclined towards sprayin/praying and non accurate rifles.

If you call a gun smith and ask for a custom build, he will ask what you want. If you ask a GREAT smith to build a custom rifle, he will ask what you want to use it for and build from there.

Again nothing wrong with a 308 as a rifle to learn the basics, but dont try to paint it porclein and call it a shitter...wait...what?!?!?! haha...

Regards,
DT

Yes, Sir. I understand what you are saying. You can optimize a load and powder burn with a shorter barrel. BUT, you may (repeat MAY) run into problems getting the higher velocities with said shorter barrel, because of max pressure constraints. If you are trying to stretch the capabilities of a .308, one way to do so is to use heavier projectiles and a longer barrel, creating the possibility to regain velocity lost with the heavier bullet by the use of slower powders in the longer barrel.

I was saying to the OP that given he has a 25" barrel coming, and given that it is a .308, and given that he seems to want to get some range out of it, the longer barrel increases the chances of doing so, although, admittedly, the platform is not optimal for doing what he wants to do. Question still remains what twist he has, and can he do heavier bullets well with it.
And, agreed, porcelain bowls used to be very popular for shitters.....

 

[wrhunter]

Ok you are measuring drop, I'm measuring wind. 2.5-2.7 mils was a wind hold at 10 mph at 1000, not elevation hold.

Makes perfect sense now...

 

[40xs]

you have to decide what the main purpose of you rifle is. 22" bbl's are fun and handy. However, if you are serious about long range, and particularly 1000 yd shooting ie: as in comps, etc. remember that your mv. must be at 2700fps with about 175gr. giving at least .500 bc. ,depending on elevation above sea level to keep you super sonic at 1k. which on the east coast is around 1125fps. A bullet does funny things when it goes transonic. Any F/class shooter can tell you about these things if you have doubts. the technology in F/class is changing so fast I can hardly keep up. I have a competitive rig that has a 29" custom bbl. in 308 that shoots Berger 185 very well, however the going thing now is 230 grain bullets with custom chambers and leads allowing these longer bullets to be fired in 308's which are winning the matches. I said all that to say this, what do you want your gun to do?? It's all about choices and being happy in what you do. All the above is just an attempt to keep you from being dissapointed. If you bbl is already 25" that pretty much knocks you out of being "competitive" at a 1k in comps. So build it like you want it!!!

 

[ArmyJerry]

Fount this on accurate shooter.

Barrel Length & Twist Rate
You’ll see a wide range of barrel lengths and twist rates on precision .308 Win rifles. At one end of the spectrum, a tactical shooter who needs a compact, quick-handling rifle, may select a 20″ barrel. The popular Rem 700 LTR (Light Tactical Rifle) features a 20″ fluted barrel. On the other hand, Palma shooters, who need to keep a 155-grain bullet supersonic at 1000 yards, normally opt for barrels 30-32″ in length. The extra length also provide a longer sight radius–a big benefit when using iron sights. A shorter barrel definitely delivers less velocity, all other factors being equal. With most powder/bullet combinations, you can figure an additional 25-30 fps per inch going from 20 to 25 inches. From 25 to 30 inches, add an extra 17-20 fps. From 30-33 inches you may pick up 15-17 fps or so, with appropriate powders. Here are some velocity estimates projected by QuickLOAD for 44.5gr Varget (ADI 2208) and IMR 4064 with a 168gr SMK set at 2.800″ cartridge OAL, bullet not touching the lands.
QuickLOAD Projected Velocities in FPS with Increasing Barrel Length
Powder 20″ 21″ 22″ 23″ 24″ 25″ 26″ 27″ 28″ 29″ 30″ 31″ 32″
44.5gr Varget (ADI 2208) 2592 2620 2646 2671 2694 2716 2736 2756 2775 2792 2809 2825 2841
44.5gr IMR 4064 2628 2656 2681 2705 2728 2749 2770 2789 2807 2824 2841 2857 2872

Note: This is a software prediction only. Different barrels will perform differently based on a variety of factors including groove diameter, land configuration. Primers, seating depths, and powder lot variations can affect the numbers significantly as well.


Towards the bottom of the article
http://www.accurateshooter.com/cartridge-guides/308win/

 

[thrusty]

I'm thinking my next .308 build will have a 23" Bartlein tube...22" measured from the lug. Should give a happy medium of ease of handling and decent 1000yrd shots if needed...Anyone else agree? Will be a tactical rifle, not benchrest or F-class....

 

[sobrbiker883]

I love a good pissing match, and especially love "other forum" and "research I found online" data from people giving advice
DOPE trumps interpolated and anectdotal advice every time.

If you want to sell 20" tacticool rigs to internet commandos you will provide all sorts of research on how the cool guys use 20" 308's and why, and there's nothing wrong with that if your intent is to have a really cool rifle you can post pictures of on forums and you will be hailed as a cool guy.
Me, function trumps form every time, and I try to pick the best tool for the job. If I need to do what folks do with short 308's (which I don't as a hobbyist shooter, not an operator) I'd probably be running a semi for the best compromises that a tactical environment would demand, rather than a boltgun anyway.

Can a 20" 308 make hits at 1K? yes
Will you see anyone that is really needing reliable accuracy at 1K bring a 20" 308 as their first choice in rifles? not so much

For me, 26" is 308 length for 175 class pills.

 

[sobrbiker883]

There's nothing wrong with arrogance, as long as it is backed-up by competence.

Now that is good stuff! Well put my friend-maybe see you in Albuquerque?