.260-Long Barrel or Short?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by huckjare, Oct 18, 2011.

  1. huckjare

    huckjare Well-Known Member

    Messages:
    464
    Joined:
    Feb 1, 2011
    I have a CZ 550 tactical in .308. I am planning on rebarreling it in a .260. I have heard that with the .308 and the .260 barrel length (from 20'' to 26'') doesn't make a difference because all the powder is burned before it reaches 20'' mark. My question is, Is this true? If I can get away with a 20'' barrel and save the weight from a 26'' I would love it, but I don't know if this would hold up. There are a lot of 20'' .308s out there, but do they lose velocity. I am more interested in what a .260 would do. If anyone has experience with this please let me know. Thanks.
     
  2. LouBoyd

    LouBoyd Well-Known Member

    Messages:
    770
    Joined:
    Oct 15, 2007
    A bullet does not stop accelerating in the barrel the at the instant the propellant is 100% burned. It only stops accelerating when the force on the bullet from the hot propellant gas drops below the forces on the bullet from bore friction and air pressure in front of the bullet. The only place that happens is when shooting small capacity cartridges from long barrels,, usually subsonics. . Larger cases with smaller bores do need longer barrel lengths to efficiently reach their practical velocity capabilities, but sometimes it's desirable to give up some performance for a more compact firearm. That "wasted" energy can still be used with a muzzle brake to reduce felt recoil in a lightweight rifle.

    Here's an comparison of 260 Rem barrel length using a Quickload simulation. Shooting the 123 Scenar (l low drag bullet) from a 26" or a 20" barrel using 42.8 grains of H4350 which is a 100% case fill and about a 90% SAAMI max load, a 26" barrel gives 2959 fps and a 20" barrel gives 2781 fps. Muzzle pressures are 8940 and 12072 psi respectively.

    At sea level the range to where the 123 Scenar will reach 1300 fps with the 26" barrel is 1220 yards. Using a 20" barrel gives the same performance if shot from 100 yards less. (the 2959 fps bullet drops to 2781 fps in the first 100 yards.

    I won't comment on the suitable hunting range of either barrel length. There are too many variables including the animal, the wind conditions, and the shooter's skill.

    In the above example according to Quickload the powder is 97.44% burned in the 20" barrel, 98.99% burned in the 26" barrel.
     
    Last edited: Oct 19, 2011

  3. trebark

    trebark Well-Known Member

    Messages:
    3,475
    Joined:
    Jan 16, 2008
    My 260 has a 28" barrel. I shoot the 130grain JLK bullets at mag length with 45grains of H4350 (the go-to powder for the 260). I easily get to 3000fps without any pressure signs.

    I have longrange hunted with this rifle and shot several tactical matches. The extra couple of inches of barrel has never been a hinderance.

    http://www.longrangehunting.com/forums/f53/my-260-mcr-59628/
     
  4. huckjare

    huckjare Well-Known Member

    Messages:
    464
    Joined:
    Feb 1, 2011
    So at 1000 yards what would be the difference in where the 26'' barrel and and 20" barrel hit? For me, it would be more useful to know the drop at more like 500 yards. I might just end up with a barrel in the middle like a 24'' or 22'' barrel. I need to be able to pack it with me on short hikes but I want it to perform.
     
  5. trebark

    trebark Well-Known Member

    Messages:
    3,475
    Joined:
    Jan 16, 2008
    Go to JBM Ballistics...

    JBM - Calculations

    Drop in your expected information. For instance, the G1 BC of the 130grain JLK is .593. Then drop in your expected velocity. For instance, with my 28" barrel I get 3005fps. In a 20" barrel I would expect 2845fps. Drop in that velocity and you can do a comparison of drop and wind drift.
     
  6. Mikecr

    Mikecr Well-Known Member

    Messages:
    4,248
    Joined:
    Aug 10, 2003
    IMO, an important factor w/regard to accuracy(with boat tails) is the muzzle pressure Lou mentioned.
    This affects clean bullet release much like a poor crown, and greatly amplifies any crown issues.
    If you look at very accurate load & barrel lengths with cartridges of various capacities, I'm confident you'll see muzzle pressures 6Kpsi & below.

    But then shorter barrels(all else equal) are stiffer, so a rational balance is probably best.
    If releasing flat base bullets from a pristine crown, you can benefit fully from 20" barrels.
    Not so much with a 260 pushing VLDs as 12kpsi would bitch slap them bullets.
     
  7. Capt Academy

    Capt Academy Well-Known Member

    Messages:
    1,665
    Joined:
    Dec 31, 2006
    huckjare, I was facing a similar issue, like you. I plan to shoot my 260 suppressed for tactical matches and did not want a long barrel that would unbalance the rifle, at least for me. Instead of the 28 or 26 inch barrel I opted for the middle of the road, a 24". I feel it will give me the best of both worlds.

    I just cut down my 308 barrel from 26" to 22" for my suppressor and lost about 60fps. The accuracy stayed the same and the rifle seems more balanced for me. I shoot this rifle out to 700 yards often. I am happy with the 22" on the 308, but want to keep the 24" barrel on the 260.

    Just my 2 cents
     
  8. huckjare

    huckjare Well-Known Member

    Messages:
    464
    Joined:
    Feb 1, 2011
    So from everything that you guys have said it looks like I need at least a 24'' barrel. I want to be able to shoot the VLDs for sure and with a really short barrel it sounds like that is not a possibility. What bullets shoot well out of a shorter barrel?
     
  9. LouBoyd

    LouBoyd Well-Known Member

    Messages:
    770
    Joined:
    Oct 15, 2007
    Besides having a length barrels also have a twist rate and a chamber. They also have to work with some magazine length. SAAMI says the cartidge OAL is 2.80" but that's not good for shooting heavy low drag bullets. In picking a barrel for a custom rifle you need to decide what bullet you want to shoot and what environment you'll be shooting in, then pick an appropriate barrel length, twist rate, and chamber including the throat depth.

    Most factory 260s are sold with a standard short action 2.85" magazine. Available bullet weights in 264 caliber range from 75 to 160 grains. You won't find one barrel which is optimum for all of them. Twist rate and throat depth determine that more than barrel length. Barrel length determines what portion of the propellant energy goes to pushing the bullet faster and what portion becomes muzzle blast. Muzzle blast can be useful with a brake and longer barrels have to be heavier, especially if they're to be be stiff. Excessive muzzle pressure can hurt accuracy.

    I built my most recent 260 Rem rifle using a Rem 700 long action receiver specifically so I can shoot the heavy VLD bullets. The action was from a 30-06. My handloaded cartridges are well over SAAMI OAL and they won't fit the magazine or the throat of my factory 260 Rem. That rifle has a 24" x 8" twist barrel. It won't be used for bullets under 139 grains.
     
    Last edited: Oct 20, 2011
  10. huckjare

    huckjare Well-Known Member

    Messages:
    464
    Joined:
    Feb 1, 2011
    So out of your 24" barrel what kinds of velocities are you getting with a 140 grain bullet? Something like the bergers?
     
  11. Pons

    Pons Well-Known Member

    Messages:
    124
    Joined:
    Mar 13, 2011
    I know you are looking at a .260,

    I have been looking at the .260 Rem, 6.5x47 Lapua, and the 6.5 Creedmoor.

    (I am leaning toward the Creedmoor right now)

    anyways, you were asking about velocities out of short barrels.

    Here is a review where the gun is 20 inch barrel, 6.5 Creedmoor,

    He is getting 2776 fps with 120 amax, and 2624 with 140 grain amax.

    Savage Model 11 6.5mm Creedmoor Lightweight Hunter Bolt-Action Rifle.

    -Pons
     
  12. Mikecr

    Mikecr Well-Known Member

    Messages:
    4,248
    Joined:
    Aug 10, 2003
    W/regard to LONG RANGE HUNTING;
    Although the linked Savage is a nice gun(practical), you should also recognize that it would fall woefully short of respectable long range performance.
    It also represents very odd choices from someone babbling so much about 26-vs-30cal BC and muzzle blast....
     
  13. Pons

    Pons Well-Known Member

    Messages:
    124
    Joined:
    Mar 13, 2011

    Only put the link for the fps data.
     
  14. J E Custom

    J E Custom Well-Known Member

    Messages:
    7,264
    Joined:
    Jul 29, 2004
    Any rifle with a 26" barrel will gain velocity over one with a 20" barrel ! It's just a matter of
    how much. With any cartrige there is an optimum barrel length where the percentage of
    velocity increase drops off, and the gain may not be worth the other issues.

    If you plan to carry the rifle to a shooting position and shoot long distances only, then I would
    recommend a 28"+. But if it is to be used as a Carry rifle and used in an enclosure (Blind) I would
    recomend 22 to 24" max. the loss in velocity will be minimal.

    The 308 based cartriges perform well with 20 to 22 " barrels but 24" will do a little more and still not be cumbersome.

    Just my opinion

    J E CUSTOM