Polygonal rifled barrels and monometal bullets????

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by NorthernSniper, Jan 12, 2004.

  1. NorthernSniper

    NorthernSniper Well-Known Member

    Messages:
    150
    Joined:
    Jul 31, 2003
    [​IMG] Well I have been fighting with my Sako TRG-S 308 WarBird over Barnes monometal bullets. I read a post by Dave King which might explain my problem, Dave says Polygonal rifled barrels do not like monometal bullets like the Barnes TSX AND! can create over pressure situations even at minimum loads!!! This is the problem I have been having!! Does anybody know if the Sako TRG-S has Polygonal rifling???? If this is the case this explains my problem. Thanks Dave and thanks in advance for any info.
     
  2. Dave King

    Dave King Well-Known Member

    Messages:
    2,362
    Joined:
    May 3, 2001
    NS

    I did a quick search and didn't find anything relating to Sako and polygonal rifling... I believe the problem with polygonal rifling is not the style (polygonal) but the practice of making the bore a "little tight" so the polygonal system "works" as designed. There are other tight bore barrels around, Palma types I believe are tight .3078 and smaller vice the nominal .308. The bore on the rifles I tried apparently was quite tight too, regardless of rifling type, and this is where I feel the problem begins.

    Might try asking some of the Palma type about monometal bullets and observed results. I'd didn't go much further with the quest but if you come across anything please post it.

    TIA

    [ 01-13-2004: Message edited by: Dave King ]
     

  3. Nighthawk

    Nighthawk Well-Known Member

    Messages:
    429
    Joined:
    Mar 2, 2002
    So if monometal bullets don't work with poly rifling, what do and do you suppose there is a material that is a solid that would work with poly? I remember Warren saying the J40's don't like poly either.
     
  4. Varmint Hunter

    Varmint Hunter Well-Known Member

    Messages:
    2,519
    Joined:
    Dec 26, 2001
    Correct me if I'm wrong but I thought polygonal rifle barrels have no lands or grooves. They don't in my poly barreled handguns.
    It should be easy to identify a polygonal barrel just by looking into the bore.
    I would suspect that polygonal barrels would work best with bullets that are more compressable than the monometal bullets.
    Supposedly, poly barrels seal better for minimal gas leakage and are easier to keep clean. Is there an accuracy component to a polygonal rifle barrel? [​IMG]

    VH
     
  5. Dave King

    Dave King Well-Known Member

    Messages:
    2,362
    Joined:
    May 3, 2001
    VH

    There are a couple of types of polygonal rifling as I understand it, most notably "male" and "female". My polygonal rifled barrels look very similar to standard barrels with the exception that there are no sharp edges in the rifling... it looks like worn out standard rifling. The barrels are tighter to afford the better seal and a more compressible bullet would be a good idea. Thinks of a polar bear pulling a seal out of the water through a 4" breathing hole vice a 6" breathing hole... It kills the seal but the 4" "bottle cork" seal gets a little longer and skinnier, bear need to pull a little harder... The larger the projectile I fired through the polygonal barrel the more to the left the group would print, sometimes as much a 6 inches left at 100 yards. This group shifting was repeatable but the reuse of the brass was not as I often blew primer pockets... Polygonal barrels are tight, monometal bullets don't appreciate being reshaped any more than that 4" wide 6' long seal....
     
  6. littletoes

    littletoes Well-Known Member

    Messages:
    362
    Joined:
    Apr 12, 2002
    I read a study once that stated that poly barrels foul faster too.
     
  7. 4mesh063

    4mesh063 Well-Known Member

    Messages:
    374
    Joined:
    Dec 8, 2002
    According to a tech rep for one mfgr, poly rifling is inherantly less accurate. It's benifit is in longer barrel life and better performance under sustained rapid fire.

    This said, the one I chambered seemed to shoot pretty good. Fouling is significant though.
     
  8. 4mesh063

    4mesh063 Well-Known Member

    Messages:
    374
    Joined:
    Dec 8, 2002
    Also, it was way small too. In don't remember exactly how far but it sticks in my mind the minor ID of the rifling on the one I did was .2988 or something like that. I thought something was wrong at first.
     
  9. Nighthawk

    Nighthawk Well-Known Member

    Messages:
    429
    Joined:
    Mar 2, 2002
    If they were that inaccurate I don't think that HK would use it in the PSG1, SOCOM pistols and I don't think Tactical Ordinance would use it in there sniper rifles.
     
  10. Mikecr

    Mikecr Well-Known Member

    Messages:
    4,249
    Joined:
    Aug 10, 2003
    Are there any standards w/regard to polygonal rifling? Male, female, rounded lands, flats, octagonal, 6flats, tight, loose, hammered, puttoned, for handguns, for rifles?
    I have a Schneider poly(buttoned) that looks as described above, like std 6 lands, only with rounded edges. Gary told me that it would measure the same internal dimensions as any other barrel. I haven't used it yet(bought it for an experiment).
    Now, when I was looking around for one, an interesting observation was that ; any maker who offered one, claimed to be the only maker to ever offer them! Like they fail to recognize another makers rifling as polygonal, by their definition.
    All I know is that it doesn't look like the rifling in a glock. I can find no other pictures of polygonal.