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Does Shortening a Barrel Affect its Accuracy ?

Discussion in 'Rifle Discussion' started by DuneHopper, Jan 16, 2016.

  1. DuneHopper

    DuneHopper Douglas County. Well-Known Member

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    My Two Questions?,
    One does Shortening a Barrel Affect its Accuracy ?
    I have a Chinese SKS and I am considering taking the barrel from 20" - 16.5
    dropping it 3.5 inches in length. I will be doing all the typical crowning etc.

    But my question is, does shortening the length really affect the accuracy and in my case being 3.5"
    is it significant enough ? Ive cut barrels before but as I am getting older and hopefully smarter
    I now don't want to affect the accuracy too much. And many ask what are ya going to use it for,
    well nothing over 100yrds and keeping iron sites.

    Secondly the barrel is 20 inches does taking it down 3" affect how the gas system works again something I never thought about when cutting before but wondering how that might affect things.

    Thanks
     
  2. BillM

    BillM Amity OR Bronze Supporter Bronze Supporter

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    Shouldn't affect the accuracy to any noticeable degree. Might be a pain getting
    a good crown on the chrome lined barrel, and not sure how it will affect the
    operation of the gas system. I do have a 16.5" SKS, if you have problems
    with the gas system PM me and I'll measure the gas port.

    One thing I do know-----7.62 x 39 ammo seems to be loaded with a barrel
    longer than 16" in mind. About 10% of the time you will get an IMPRESSIVE
    fireball of unburned powder with the short barrel.:)
     
  3. IronMonster

    IronMonster Washington Opinionated Member Diamond Supporter

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    I am not an expert, but here is what I think I know :D

    Velocity is effected, accuracy is not (provided the barrel is cut and crowned correctly)

    I have even read that contrary to what most think shorter barrels tend to be more accurate because they do not have as severe of harmonics as their longer brothers (why heavy matters when it comes to accuracy)

    As far as the gas system is concerned it does effect the time the system is pressurized and able to act on the bolt but I suspect a SKS is overgassed to an extent there is no way it would be an issue.
     
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  4. DuneHopper

    DuneHopper Douglas County. Well-Known Member

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    I think the Paratrooper barrel is 16.5 but I pretty sure the all use the same size gas port I think.
    The barrel shouldn't be a problem getting that done, but my mind started that thought process if it aint broke dont fix it . I am going thru the rifle, doing some other modifications this was only one that I started wondering the physics involved one thing led to another and then then I said ok maybe I should ask see if others have had issues.
     
  5. erudne

    erudne The Pie Matrix PPL Say Sleeping W/Your Rifle Is A bad Thing? Bronze Supporter

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    the shorter the barrel the stiffer the barrel which decreases the degree of the harmonic vibrations but in an SKS this may not have a noticeable effect A rubber dampener will do the same
     
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  6. ZA_Survivalist

    ZA_Survivalist Oregon AK's all day.

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    As proven with the M1A and PSL cutting the barrel down to 18" or even 16" doesnt diminish accuracy (just velocity) so long as other variables are accounted for.
     
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  7. jbett98

    jbett98 NW Oregon Bronze Supporter Bronze Supporter

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    Does the rifling twist rate for the longer barrel come into the equation when the barrel is shortened?
     
  8. The Heretic

    The Heretic Oregon Well-Known Member

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    In general, all else being equal, a short barrel is as *precise* as a longer barrel.

    I use the word "precise" because "accuracy" entails the whole firearm system, including the sighting system and the shooter.

    Precision, in this context, describes the ability of the barrel (and the rest of the firearm actually) to send a projectile to the same point of impact, with a certain tolerance. No sighting system or shooter is required; place the firearm in a fixture, have a large enough target that the projectiles will impact somewhere on the target, and fire repeatedly without changing the aim, such that you have enough impacts on target to measure the precision - generally somewhere between 5 and ten shots (although often the military measures a lot more than that in their tests).

    Accuracy describes the ability of the firearm and the shooter, to hit what the shooter intends to hit, with a certain tolerance.

    So, if the sighting system is iron sights then, depending on where the sights are located, the length of the barrel may affect the "accuracy" because the sighting system has a shorter length and the shooter has a more difficult time precisely aligning the sights from shot to shot. With an optic sight, then the barrel length generally doesn't impact the sighting system.

    There are some other factors.

    It can be argued in some cases, that a shorter barrel is more stiff (less likely to vibrate during a shot) and will therefore have a tendency to be more precise - since it is less likely to vibrate in such a manner where the projectile leaves the barrel at a different point in the harmonics of the barrel. This depends a lot on the design of the barrel too.

    I used to own and shoot an AWC G2A - my photo (despite somebody else stealing it and putting their name on it - that sight has the bad habit of doing that):

    wtf20070625ace.jpg

    That rifle has an 18" barrel and will shoot 0.5" three shot groups in my hands (or would about 10+ years ago). The barrel is a 1" diameter SS Kreiger, and it is tensioned; the scope is located atop a "bridge" which is affixed at one end to the action, and at the other end tensions the barrel with a "nut" about two inches long which is torqued with a special wrench.

    The torque value depends on the ammo you want to shoot - this rifle was tuned for 168 gr. BTHP Federal Gold Match ammo (I did try other match ammo with the same weight projectile, but they never did as well as the Federal).

    The tension stiffens the barrel, making it straighter and more resistant to vibration. You've probably heard of other systems that try to accomplish the same end - such as the Browning BOSS system.

    I had a number of people question whether this rifle could shoot "accurately" with such a short barrel. I would then demo it for them, once at over 1 km. It made believers out of them.

    IMO - the only thing you really give up with a shorter barrel are velocity, but you do gain noise and blast.

    wtf20070625ace.jpg
     
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  9. BillM

    BillM Amity OR Bronze Supporter Bronze Supporter

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    Actually went and did some measuring. Standard 20" and Sporter (16") SKS's, both
    Norinco.

    Standard gas port is about 7" from muzzle. Sporter gas port is a touch over 4"
    from muzzle.

    SO----barrel 3.5 or so shorter, but the gas block is also moved back a touch.
    Gas tube and piston are bit shorter on the Sporter. Pretty easy to spot if you look
    at the amount of gas tube in front of the handguard.
     
  10. Otter

    Otter Oregon - mid Willamette Valley Active Member

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    It could affect accuracy but not because of the length of the barrel, but because the tune of the load. You may have to develop another load, or if using factory ammo find something else.
     
  11. DuneHopper

    DuneHopper Douglas County. Well-Known Member

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    Well I did the barrel project today have not tested it I cut the barrel at 16 3/4 I wanted 3/4 added back in case I ever thread the barrel wanted some wiggle room. Thanks everyone for the feedback, I had already done allot to the rifle the barrel was the last, crowning and polish turned out nice. Getting the sight block pin removed was a PITA, had to setup a jig to remove it set the site back 1/2 inch from the end. I took a Yugo stock and put the Norinco Chinese in it to have some weight as the Yugo stock is heavier. Anyways I will try an post some pictures as soon as I finish the clean up.
     
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  12. Velzey

    Velzey Estacada, Oregon Gunsmith Gunsmith Bronze Vendor Bronze Supporter

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    Accuracy no, velocity yes! But this is a sks we are talk about. A few inches won't hurt.

    I have a custom 32" heavy PAC NOR bbl on a rem 700... Long tube equals more time for all that powder to burn and squeak all the velocity I can out of those 32inches!

    Short barrels are more rigid but like anything when it gets hot they move around!

    If you ever have a rifle with a favorite load worked up for it, chop 6" off the end of the barrel and see how that load works. Some bullet/powder/velocity combos will still be very accurate. Along with say a twist rate of 1 in 10
    For me I tried it and couldn't get the thing to make a decent group..had to switch to a lighter bullet and different powder charge.
     
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  13. Boboclown

    Boboclown North Carolina Well-Known Member

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    After a certain point the powder is already burned. If powder burn is the only goal, then a 32 inch barrel is more than necessary. Its pressure after that point.


    That being said, a shorter barrel would be more precise with less range. How much less range idk, but its probably still capable of going as far as you'd normally shoot anyways.
     
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  14. DuneHopper

    DuneHopper Douglas County. Well-Known Member

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    The purpose of the particular upgrades firearm was to make it more compact in the idea of a paratrooper model added an old AK-47 as a fore-grip, and kept the wood as it has writing in translation Bosnia or Croiation. I have other Sks's but they are bigger and more of a sniper setup yes I realize I could just have bought and Ak-47 ( which I have ). The purpose was to build it and have a functional, practical truck gun and yet keep allot on classic look and feel. I added a 2" stock pad to increase the reach slightly it looks good I should have pics next week I just have some fine tuning I am bluing the carrier and its still a tad lighter then I want.
     
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  15. ogre

    ogre Vancouver, WA Well-Known Member

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    It could most certainly effect accuracy, either way, depending on your craftsmanship and skill. You might muck it up (this I personally doubt) to the detriment of accuracy or you might replace a less than stellar crown and cause accuracy to improve.
     
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  16. Boboclown

    Boboclown North Carolina Well-Known Member

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    An SKS as a sniper? Blasphemy. ;)

    If its a truck gun it won't matter too much tbh, a 16" barrel is more than enough to hit what you're aiming at. Just do a proper crown and you'll be good.
     
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  17. DuneHopper

    DuneHopper Douglas County. Well-Known Member

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    If it helps I keep one its a 62 Yugo SKS in pristine safe queen all original condition, I only bubbafy sks's when all number don't match. On the crowning I did very slow and meticulous I have always thought for myself less is more on crowning. I am no expert by far but rifles I have with conservative crowns tend to shoot straighter longer then ones with what I would say deep angled I guess it looks nicer but I find conservative works for me.

    ( use the same method hedge trimming you can take it off but you cant put it back on ;))
     
    Last edited: Jan 17, 2016
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  18. nwwoodsman

    nwwoodsman Vernonia Bronze Supporter Bronze Supporter 2015 Volunteer

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    You may loose 150fps but it'll still be SKS accurate
     
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  19. H2O MAN

    H2O MAN Georgia - USA Well-Known Member

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    I ran a similar set up, but with a standard weight 16.25" barrel.
    Very accurate with surplus Portuguese NATO ammunition.
    It's tuned for M118 LR, but I never used it.
    100yards%20%281%29.jpg

    Here is the same rifle today in a Blackfeather "RS".

    BF-RS.SFU.12.06.JPG
     
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  20. oli700

    oli700 Rogue Valley Well-Known Member

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    that statement is cartridge and powder dependant. A 22lr dosent need that much but a 416 Rigby would benifit from it ,,,,along with a lot of other belted magnum loads