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Thread: Barrel length / moderator / velocity question

  1. #1

    Barrel length / moderator / velocity question

    So, at the moment i'm shopping for a .270

    Looking at the Sako 85 as an example, it can be bought with a 20" barrel factory screwcut for a moderator, or with a 22" unthreaded barrel.

    It's my understanding that a .270 performs better with a 22"+ barrel, eg less fireworks and higher velocity.

    Would I be better off getting the longer barrel version and then getting it screwcut locally or does it not matter too much? Am I being too picky here?

    I know the moderator will help to lessen the fireworks on the 20" barrel, but will it help in any way to keep the velocity up too?

    Velocity is more of a concern here than usual as there's a good chance i'll be using lead free which I understand needs to be driven as fast as possible to ensure adequate expansion. I'm not overly concerned about the total overall length of barrel and moderator combined.

    Any thoughts chaps?

  2. #2
    On paper your barrel length will make a difference.
    However out stalking there would be many other factors having more of an effect than just the velocity. I would suggest you just get the factory screwcut one.

    The new copper bullets will have a window of velocity that they operate in and you will find that for the first 80m the bullet will be travelling to fast to expand properly whatever the bullet make up, once it slows down a bit it will knock them flat well past most stalking ranges.

    The moderator is catching the gasses (the big bang) from the end of the barrel it will do nothing to maintain the velocity of the bullet

  3. #3
    Thanks for that .25-06

    Is there no truth in the idea then that copper bullets need to be driven fast to expand correctly? I'm only going by what i've heard vs what you may actually know. I'm new to this.

    Here's a quote copied from another forum which got me thinking about barrel length and moderators....

    "If you google the term "freebore boost ", this will explain how certain types of moderators will increase the velocity a bit, its thought that the moderator acts as an extension to the barrel allowing the pressure to keep pushing on the bullet as it travels through the can, thus boosting velocity."

    It would suggest that "some types" of moderators (although it doesn't say which?!) can help to increase velocity?

  4. #4
    .270 sako ammunition travels between 400-900 meter per second the bullets will perform within this. Most animals hit with this tend not to ask for a second one.

    On the rumour mill though -People shooting the new copper ammunition have reported a small increase in second shots to put an animal down. I believe this was reported as a quality control issue over the bullet construction but not linked as such to velocity on impact. Initial batches of the copper bullets shot well and expanded well, latterly the bullets shoot well but some lack expansion. Maybe the copper mix is a little harder.

    I doubt any moderator increases the bullet speed, by its very nature it is capturing and slowly releasing the gas that is propelling the bullet

  5. #5
    Thanks for the clarification.

    So you'd have no worries about a moderated .270 with a 20" barrel?

  6. #6
    I use a Remington 270 with a18 inch barrel and I use copper bullets with no problems so far it is going at 2857 ft per second so plenty fast enought for me this is factory ammo hornady 130 gmx super performance

  7. #7
    fireworks are a consequence of the powder column still burning when the bullet breaches the muzzle

    this is controllable regardless of barrel length with faster or slower powders

    your MV is unlikely to make any difference to expansion inside 150yds
    velocity drop in the first 150yds should be less than a third and still be shifting well over 2000fps

  8. #8
    Thanks for that patterdale.

    Brewsher: I'm limited by both ability and contract terms to factory ammunition only.

    Is big muzzle flash/unburnt powder likely to shorten a moderators lifespan or will it just need more regular cleaning?

  9. #9
    depends on your moderator material (aluminium? quite possibly, but then ordinary use can do that too)
    burning powder may not differ much in temperature compared to hot gas of fully ignited powder

    personally I don't use a mod on my .270
    very unbalanced, still noisy enough to induce tinitus and requires earplugs
    So I saved 200+ and just pop in some plugs before the shot (takes a second and I have never had to rush a shot to the point that I have never had time to put them in!)

  10. #10
    Quote Originally Posted by Wheesht! View Post
    Thanks for the clarification.

    So you'd have no worries about a moderated .270 with a 20" barrel?
    The 30-06 family of cartridges {30-06 .270 + 25-06} perform at their optimum in barrels of 24'' an over . . . .however given that the vast majority of shots taken at deer will be under 300 yards, loosing 4'' of barrel will matter not a jot . . .With the 25-06 I calculated that I would be dropping around 70fps from my 22'' pipe against the book speeds for the same load. . . none of the deer I shot complained.

    Velocity is overrated !!!
    Last edited by Cadex; 06-05-2013 at 12:37.

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