Barrel length and twist rate for .308

[hotrodder636]

I am looking to build my first "precision" bolt gun that I would like to shoot anywhere from 100 to 1000 yards (after much learning from a fellow ex-Marine sniper). What I was wondering is how does one determine the correct barrel length and twist rate? Or does twist rate depend on barrel length? What determines the combo here? Thanks in advance for any replies!

And yes, I did try the orange search button for those who will inevitably ask.....

[jmart]

Bullet weight (and length) and bbl length guide twist selection. Heavier/longer bullets and/or shorter bbl's, if you're really wanting to extend range to 1,000 yds, require faster twists.

[MOA]

you generally want a faster twist rate the heavier the bullet. For long range 308 I would just say 1/12 twist rate just guessing that you would probably shoot 175 matchkings at the heaviest.
For length, thats a hot argument. Longer barrels will give a velocity boost. Shorter barrels of the same dia are stiffer.

[Wolf Spyder]

hotrodder636,

How much do you have to spend?

It is important to figure out what your budget limit is before you start this project. There are budget rifles, in .308, that start in the $300 to $600 range and everything goes up from there to as much as $6,000 or more. Some of us, myself included, are building "budget" rifles where the finished product; factory Remington 700, medium grade scope, and an after market stock will put us in the $2000 range. So figure out what your willing to spend, first. Then second would be to figure out what caliber.

What I was wondering is how does one determine the correct barrel length and twist rate?

Barrel length can be any length from 16" to as long as 32" and greatly depends on the rifle's main purpose. Urban Tactical Rifles are very popular right now and tend to have barrel lengths around 20". While Intermediate & Long Range Varmint Rifles have barrel lengths around 26", and Long Range Competition rifles have barrel lengths around 30". Obviously, the shorter the barrel the lighter and easier the rifle will be to carry around. The opposite side of that coin is that the longer the barrel the greater the velocity of any given cartridge.

As for twist rate, like jmart said above; it greatly depends on the length of the bullet that you intend to fire. The heavier, and therefor longer, bullets require a faster twist to stabilize them during flight. Factory Remington 700's come in one of three, that I know of, twist rates; 1:10, 1:11.25, & 1:12.

To give you an idea here is what I am trying to do;

Remington 700 SPS-Tactical in 308 with 20 inch heavy barrel .......$500
Weaver Tactical 4-20x50mm mil/mil FFP 30mm Scope .................$750
Manners MCS T4 stock for Remington 700 Short Action (Tan) .......$500
Badger Ordnance 20MOA base & Medium Height Rings ................$300
Badger Ordnance M5 Stealth DBM kit ........................................$300
Timney Trigger ......................................................................$100

This puts me in the $2,500 range

Now trade out the $700 Weaver Tactical Series scope for a top of the line Schmidt & Bender Police Marksman 5-25x56mm PM with Illuminated P4F Reticle at about $3,600 and the price of the rifle goes up to $5,500. Add a Krieger barrel with 5-R rifling and have the action "trued" and polished and you've tacked on another $500 or $700 to the price of the rifle.

So figure out what your budget is first, and go from there.



ETA; Of course you can go the other direction...

Remington 700 SPS-T ($500)
Wal-mart Special Scope ($100)
Wal-mart base and rings ($50)

Add some Krylon camo paint ($4 @ Wal-mart) in Khaki and Army Green and your good to go.

[hotrodder636]

hotrodder636,

How much do you have to spend?

It is important to figure out what your budget limit is before you start this project. There are budget rifles, in .308, that start in the $300 to $600 range and everything goes up from there to as much as $6,000 or more. Some of us, myself included, are building "budget" rifles where the finished product; factory Remington 700, medium grade scope, and an after market stock will put us in the $2000 range. So figure out what your willing to spend, first. Then second would be to figure out what caliber.




Barrel length can be any length from 16" to as long as 32" and greatly depends on the rifle's main purpose. Urban Tactical Rifles are very popular right now and tend to have barrel lengths around 20". While Intermediate & Long Range Varmint Rifles have barrel lengths around 26", and Long Range Competition rifles have barrel lengths around 30". Obviously, the shorter the barrel the lighter and easier the rifle will be to carry around. The opposite side of that coin is that the longer the barrel the greater the velocity of any given cartridge.

As for twist rate, like jmart said above; it greatly depends on the length of the bullet that you intend to fire. The heavier, and therefor longer, bullets require a faster twist to stabilize them during flight. Factory Remington 700's come in one of three, that I know of, twist rates; 1:10, 1:11.25, & 1:12.

To give you an idea here is what I am trying to do;

Remington 700 SPS-Tactical in 308 with 20 inch heavy barrel .......$500
Weaver Tactical 4-20x50mm mil/mil FFP 30mm Scope .................$750
Manners MCS T4 stock for Remington 700 Short Action (Tan) .......$500
Badger Ordnance 20MOA base & Medium Height Rings ................$300
Badger Ordnance M5 Stealth DBM kit ........................................$300
Timney Trigger ......................................................................$100

This puts me in the $2,500 range

Now trade out the $700 Weaver Tactical Series scope for a top of the line Schmidt & Bender Police Marksman 5-25x56mm PM with Illuminated P4F Reticle at about $3,600 and the price of the rifle goes up to $5,500. Add a Krieger barrel with 5-R rifling and have the action "trued" and polished and you've tacked on another $500 or $700 to the price of the rifle.

So figure out what your budget is first, and go from there.



ETA; Of course you can go the other direction...

Remington 700 SPS-T ($500)
Wal-mart Special Scope ($100)
Wal-mart base and rings ($50)

Add some Krylon camo paint ($4 @ Wal-mart) in Khaki and Army Green and your good to go.

Thank you for the time and info you provided. I am going into this knowing that all said and done that this would be significantly more expensive than my AR project. I already have decided on a Nightforce scope, Bartlein or Krieger SS barrel, McMillan or Manners stock. Still deciding on an action and the length of barrel I want. I have been thinking either 22 or 24 inch.

[taliv]

i always do this the same way. first, i pick a bullet i want to shoot. second, i call the sierra ballistics hotline or berger etc and ask them the range of twists that will stabilize it, and what twist shoots my chosen bullet best. they usually ask what cartridge and what i'm going to do with it, but that's usually a 30-60 min conversation where i wind up getting educated on a wide range of tangents. next, i call the gunsmith that i plan to use to chamber the barrel, and ask him what everybody else is using and what he recommends. if he says same thing, i go with it. if he says something different, i usually get another 30-60 min of education.

yeah, i know what you're thinking... it's no wonder the good gunsmiths have a 6-12 month waiting list when they spend all day on the phone talking about bullet and barrel selection!

[Wolf Spyder]

hotrodder636,

Sounds like your all set. I am limited in the amount of money I can spend, but it sounds like you don't have quite the same limitations. When you get done building your "Race Horse" you'll have to post a range report and lot of photos.

[nineteenkilo]

ETA; Of course you can go the other direction...

Remington 700 SPS-T ($500)
Wal-mart Special Scope ($100)
Wal-mart base and rings ($50)

Add some Krylon camo paint ($4 @ Wal-mart) in Khaki and Army Green and your good to go.

Singularly one of the most useful pieces of information I've ever seen given to a long range rookie. It may have been intended as tongue-in-cheek, but it is what more people need to do. Spend enough money on ammo and range time to get the 'Wal-Mart' rig where you want it - then start looking at Nightforce, etc.

Some people don't want you to believe you can score thousand meter hits with 'junk'.

[SRT72]

As far as barrel length to me it would depend on what you want to do with it. A 20 inch barrel will get you to 1000yds with no problem. I'm sure an 18 inch would do the same. Having a short barrel is nice for maneuverability. If you are just going to be shooting prone at a range it doesn't really matter.

[AR15barrels]

Let's assume 175smk's and 178 hornady BTHP bullets as the standard 1000yd 308 fodder.
Then let's pick 26" as a good compromise between weight and length.
Go 1:11 twist and you are good to go.