I want to get an effective barrel length .308 with pretty damn good accuracy. Any suggestions on how to attain this? Any information would be great.

Barrel length is a factor in muzzle velocity, not accuracy.

Be well!

[email protected]

How nats ass do you want to get about this?

Dominant thought is that you need a length of  18" (min) to get full powder burn. As for a max length - dominant thought is that there is no advantage beyond 26".

If you are actually serious about accuracy YOU should do YOUR OWN homework on:

Min and max barrel lengths
Hammer forged rifling, button rifiling (both push and pull), and cut rifiling
Stainless vs any other kind of barrel
Number and type of grooves in the rifiling

Since we aren't discussing how and where the chamber is cut let alone a myriad of other strictly barrel topics ....... this should be thought of as merely the jump off point into the vast odessy that is the quest for accuracy......

If you are really intersted in rifle accuracy - start taking the mag: Precision Shooting.

The short cut response - a high quality stainless, 5 groove (I prefer cut but there are some great buttons out there), that is 18" - 22"  - expect to spend $250 to $400 for the barrel.

Good luck

If you are actually serious about accuracy YOU should do YOUR OWN homework on:

Min and max barrel lengths
Hammer forged rifling, button rifiling (both push and pull), and cut rifiling
Stainless vs any other kind of barrel
Number and type of grooves in the rifiling

this is merely the jump off point into the vast odessy that is the quest for accuracy......

I will do MY OWN research on the issue but I am using you people to know what I need to be proficient. I didn't even know that the style of rifling would affect accuracy that much. You offered a good start and I thank you for it. A super condensed version of the info from experts such as yourselves saves hours in the books as well.

Sorry - when I said do your own homework - what I was inferring - 1/2 of what you read on the web - esp on this site - is "my super tac buddy that is 15 and still plays D&D told me that the best set up is ......"

Confirm what you read - it will save you alot of money and time.

Good luck

I've got a chart on my server with data from a test done at Thunder Ranch but I can't access it from work. They took a .338 bolt action gun, chopped the bbl 2", recrowned the bbl and shot for groups at 100, 200 and 300 yds. I posted this info in another thread a little while ago but the Search function is FUBAR right now. I will re-post the chart tonight when I get home.

Cool thanks alot. I'm interested in seeing that chart.

Quoted: Barrel length is a factor in muzzle velocity, not accuracy.

This is more or less true at "close" target distance.  

If you lose too much velocity, it will affect the max distance at which you can realistically make hits in the presence of wind, ranging error, etc.   Besides those two factors, if you don't have enough muzzle velocity to keep the bullet supersonic at the target distance, forget trying to hit it accurately.  A 168gr @ 2600 will be subsonic @ 1000 yards.

The following is sort of my rule-of-thumb:

* If you want 308 to reach out to 700 yard solidly, get a 24-26" barrel.
* If you don't care about much past 500-600, 20" might be OK.

The less wind drift the load has at a distance, the more wind estimation error can occur and not cause a miss.  For example, if you're shooting a 10" square plate at 700 yards, the best 24"/308 loads will have about 3.5" of drift per 1mph of crosswind.    With a center hold, the wind call can be off by only 1.4mph to still make a hit.       A 20" load might have a factor of 5.1" per 1mph, which means you need to call the wind within less than 1mph (0.98mph).

Same deal for ranging error.  If the load is dropping at 0.5" per yard @ 600 yards, then on a 10" target you can accept up to a 10 yard ranging error and still have a hope of hitting it, in the absence of other changes in ballistic parameters (eg, temp, station pressure).  At 600 yards, an average 20" load might have 0.48" drop per yard, while the best 24" loads might have only 0.36" drop per yard.

Here's some data to think about.   Used a density altitude of 1000', wind is for a 10mph value.

_Bullet_           _BC_ _MV_         0     100     200     300     400     500     600     700     800 | YARDS
20 168SMK         0.46* 2575 >    0.00    0.78    3.24    7.59   14.14   23.20   35.06   50.15   68.77 | wind (inches)
20 175SMK         0.51* 2525 >    0.00    0.72    2.99    6.96   12.83   20.79   31.11   44.03   59.77 | wind (inches)
20 155LAP         0.508 2720 >    0.00    0.63    2.61    6.07   11.16   18.06   26.95   38.05   51.56 | wind (inches)
24 175SMK         0.51* 2700 >    0.00    0.65    2.71    6.30   11.59   18.78   28.06   39.70   53.92 | wind (inches)
24 155LAP         0.508 2830 >    0.00    0.60    2.47    5.73   10.52   17.01   25.37   35.81   48.53 | wind (inches)

20 168SMK         0.46* 2575 >    0.05   -0.01   -0.07   -0.15   -0.24   -0.35   -0.48   -0.64   -0.83 | drop per yard (inches)
20 175SMK         0.51* 2525 >    0.05   -0.01   -0.08   -0.15   -0.24   -0.35   -0.47   -0.61   -0.78 | drop per yard (inches)
20 155LAP         0.508 2720 >    0.04   -0.01   -0.06   -0.13   -0.20   -0.29   -0.39   -0.51   -0.64 | drop per yard (inches)
24 175SMK         0.51* 2700 >    0.04   -0.01   -0.06   -0.13   -0.21   -0.30   -0.40   -0.52   -0.67 | drop per yard (inches)
24 155LAP         0.508 2830 >    0.04   -0.00   -0.06   -0.12   -0.18   -0.26   -0.36   -0.46   -0.58 | drop per yard (inches)

20 168SMK         0.46* 2575 >  2.3135  2.1469  1.9870  1.8319  1.6786  1.5342  1.3989  1.2710  1.1582 | mach ratio
20 175SMK         0.51* 2525 >  2.2686  2.1198  1.9764  1.8387  1.7068  1.5807  1.4599  1.3474  1.2442 | mach ratio
20 155LAP         0.508 2720 >  2.4438  2.2921  2.1459  2.0049  1.8692  1.7391  1.6149  1.4973  1.3871 | mach ratio
24 175SMK         0.51* 2700 >  2.4258  2.2712  2.1223  1.9789  1.8410  1.7090  1.5829  1.4620  1.3493 | mach ratio
24 155LAP         0.508 2830 >  2.5426  2.3872  2.2376  2.0933  1.9543  1.8206  1.6926  1.5707  1.4559 | mach ratio

The muzzle velocities used for the 20" are what I chrono'd from my 20" AR10.    The 24" velocities are what I chronod from my 24" AWP.

Excellent KevinB. Thanks for posting that link. I am happy to learn about that search engine too.

BTW, here's a direct link to the article that details the test I mentioned:

www.findarticles.com/p/articles/mi_m0BQY/is_1_50/ai_110470564

Quoted: Dominant thought is that you need a length of  18" (min) to get full powder burn.

For a 155gr/VARGET load, 90% of the powder is burned by 10", 95% by 15, 97% by 20", and 98.6% by 24".  150FMJ/IMR4895 loads are within 1% point.  (data from QuickLoad).

As for a max length - dominant thought is that there is no advantage beyond 26".

Tell that to the Palma guys?!    It'll be 35-45 fps per 2" from 24 - 30".  But nobody likes to carry around a rifle with a 30" barrel.    

Zak your point is well made - and that point is - know what you intend to do with the rifle and build it accordingly.


Zak - how variation in the burn rate if a heavier / lighter bullet is used?


Good luck

I believe the norm is heavier bullet = faster powder and lighter bullet = slower powder, though that may only be for handguns.   The slower powders would benefit more from a longer barrel and show more velocity increase.

Quoted: Zak - how variation in the burn rate if a heavier / lighter bullet is used?

For example, if you stick with 308 and VARGET, but transition to the 175SMK from the 155's, more powder is burned sooner, so at any distance the percentage will be higher than the 155 data I posted.    With the same powder type but a heavier bullet, there is more initial resistance which evolves higher combustion pressures and rates faster.

hope this helps

More good links:
www.accuratereloading.com/223sb.html
www.riflebarrels.com/articles/longrange_shooting/ideal_barrel_308_tactical_rifle.htm

Quoted: I believe the norm is heavier bullet = faster powder and lighter bullet = slower powder, though that may only be for handguns.

This is basically backwards.  To get maximum velocity out of a heavier bullet (or a more overbore situation), you'll generally need to use a slower burn rate power.  

That same slow burn rate powder might be "too slow" for   light bullet.  By that I mean there won't be enough initial pressure to get it burning fully.    Imagine shooting #2400 or H110 out of a 45ACP-- it just isn't going to work.

Quoted: Zak your point is well made - and that point is - know what you intend to do with the rifle and build it accordingly. Zak - how variation in the burn rate if a heavier / lighter bullet is used? Good luck

Bingo.  I think that's the point Phil was trying to make in the article response in the linked thread, but it was better articulated here by Face N the crowd and Zak.  Sticking with this thread's question, it's clear from Matt B's linked article and Zak's chart that if you'll be shooting at relatively close range (300 yards and thereabouts), you don't need to be fretting about barrel length.  On the other hand, if you want to push it, Zak's chart (well done, by the way) as well as his (correct) comments on drift and drop show that you'll be better served by a barrel longer than 20".  So I guess it comes right back to what Face in the Crowd said- know what you intend to do with the rifle, and build it accordingly.

Sorry to go off topic, but this will be brief and I'm not opening a can of worms.

Zak:  What was the type and weight of the charge you used for the 175 SMK?  I ask because I've recently left the 168 SMK (my long time favorite) to give the 175 a shot.  I've just started workups with IMR4064.

Quoted: Quoted: Sorry to go off topic, but this will be brief and I'm not opening a can of worms. Zak:  What was the type and weight of the charge you used for the 175 SMK?  I ask because I've recently left the 168 SMK (my long time favorite) to give the 175 a shot.  I've just started workups with IMR4064. To step on toes - You need to figure that out yourself/your rifle. I have a 22" bolt gun that loves 175s w/748(2700fps), and an 24" AR10(2800fps) that loves Varget. Both loads are off any published charts, but I'm not having any pressure signs.

Well of course.  That's why I'm doing a workup, and will be doing several more.  But the more info I can acquire the better.

Sorry I took us off topic.  I didn't think anyone would get flamed by my question to Zak.

VARGET is a really good powder for 308.   I am partial to it because of its versatility and temperature insensitivity.  I use it for my factory match replica loads of the 155gr Lapua SCENAR, and my 175SMK loads (when I used them).

For the 175SMK's, a bunch of guys I know, shooting a variety of barrel types in the 24-26" range, tune their 175/VARGET load to get right around 2700fps.  The exact charge used of course depends on specific gun, barrel, leade, brass, primers, etc.   The hotness of the load will also affect brass life, most likely manifest in how many firings you get before the primer pockets get a little loose.   Regardless, if you start at 43gr and work up it should be OK.    That is NOT my load, but should be a safe starting point in all modern 308 rifles. duoble check with published data, etc....

Email me privately if you need more specifics.

-z

Call the Chandlers at Iron Brigade and talk to them.  They are usually happy to talk to people about barrels and rifling, and build great rifles.