20 gauge sabot barrel length

Discussion in 'General Shotgun Discussion' started by p35bhp55, Nov 18, 2012.

  1. p35bhp55

    p35bhp55 New Member

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    First, I don't use the splatter method of forum posting but I will be posting this anywhere there might be an answer.

    Does anyone have any information on how long a 20 gauge sabot barrel has to be to burn the powder and stabilize the sabot? I'm old enough to remember when slug barrels were shorter but back then the slugs were Fosters not sabots. The Mossberg brand I use is now standard at 24" and my friends and I have had nothing but trouble with group size. For whatever reason the 12 gauge seems to work fine. To be clear we have been through about 6 of the 20s. I have the last one now and will probably buy it if there is a chance I can mod it to work. The reason to fixate on barrel length is a history of using H.D. barrels or "riot guns" for deer hunting pre sabot. It seems that the closer the barrel ends to the mount for the magazine tube the more rigid the barrel stays and the better the group. My thoughts so far are either 20" or all the way down to 18 1/2" Any information about velocity or groups from someone who has a shorter barrel would help.
     
  2. hiwall

    hiwall Well-Known Member

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    Most or all shotgun ammo uses fast burning powder. I doubt you would get much or any velocity loss if you shortened your barrel to 18 inches.
     

  3. Old_Crow

    Old_Crow New Member

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    You might want to try another type of sabot. The sabots that are really a rifle bullet do very well in my 500 12 ga. You are not the first to complain about the 500 20ga sabot barrel. I have seen a 20 ga cantilever come out of the box unusable. Mossberg cuts every corner on the 20 ga 500. I own one I shoot sporting clay with. It does well for that purpose.
     
  4. hiwall

    hiwall Well-Known Member

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    If you decide to cut the barrel a wise move would be to cut a couple inches and test for accuracy then cut and re-test. Maybe there is a "sweet spot" at 22" or 21" or 19" or whatever.
     
  5. Virginian

    Virginian Active Member

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    Just remember if you go hacking on a rifled barrel you better get the crown right or you will get lousy accuracy. Think rifle.
     
  6. p35bhp55

    p35bhp55 New Member

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    I have access to a lathe, but if I can decide on a length it will probably just get sent to a shop.
     
  7. locutus

    locutus Well-Known Member Supporter

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    The powder will burn completely in 16-18 inches.
     
  8. Virginian

    Virginian Active Member

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    Tests have shown you still get velocity increases out past 32". The rate of increase certainly slows down, but it is still happening. Down in the lower 20" ranges the velocity changes may equal 25 to 50 feet per second per inch. What makes you think Mossberg didn't do a little homework before settling on 24".
     
  9. hiwall

    hiwall Well-Known Member

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    " Barrel length

    Shotguns generally have longer barrels than modern rifles. Unlike rifles, however, the long shotgun barrel is not for ballistic purposes; shotgun shells use small powder charges in large diameter bores, and this leads to very low muzzle pressures and very little velocity change with increasing barrel length. According to Remington, modern powder in a shotgun burns completely in 25 to 36 cm (10" to 14") barrels.
     
  10. Virginian

    Virginian Active Member

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    The powder may have burned, but the gasses still have sufficient pressure that the velocity will continue to increase out past 30". I have chronographed enough heavy loads to confirm this. With mouse fart loads I can't say, but it's interesting that the mouse fart shooters seem to be the longest barrel proponents. I can state with absolute conviction that a 10 gauge will definitely kill a skyscreen with one shot. Long barrels were demanded by black powder to burn all the charge.
     
  11. hiwall

    hiwall Well-Known Member

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    Virginian, its cool I'm not arguing as I never chroned any shotgun loads. I've chronographed many rifle, pistol, and airguns. Oddly never a single shotgun(I'm not a shotgun guy). I couldn't find any actual numbers on the internet. Though in one spot they did agree with you about longer=faster but I was hoping for actual data. 22 rifles reach their peak at about 16". "Deer" rifles vary alot but longer barrels for sure equal faster bullets out to reasonable length barrels.
     
  12. John_Deer

    John_Deer New Member

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    Another reason shotguns have longer barrels is the sight plane. One would think 2" doesn't make much difference but my skeet score drops when I use a gun with a 26" barrel. 28" or 30" barrel I shoot the same scores. My score does pick up with a 26" barrel but it takes a few rounds (50 shots) to start rising. For the life of me I can't figure out why.
     
  13. Virginian

    Virginian Active Member

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    Anyone who has ever shot a Magnum rifle at dusk knows the powder is still burning at normal barrel lengths. When the world thru your scope turns orange the first time it's an attention getter.
     
  14. p35bhp55

    p35bhp55 New Member

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    What makes me think Mossberg didn't do homework....About 4 Iron sight barrels that the factory sights could not be set on, no matter who shot or which brand sabot was used. For years about every Mossy I saw had a 24" barrel I think they settled cause it was easy and reduced inventory.
     
  15. p35bhp55

    p35bhp55 New Member

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    I feel your pain I have the opposite problem, need the 26" and for 500 fans that ain't easy. But this won't matter here, cantilever scope barrel.
     
  16. Virginian

    Virginian Active Member

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    Well I surely can't argue because I haven't owned a Mossberg for many years, but what makes you think shortening the barrel is going to help accuracy? Or are you just looking to try something to help the situation?
     
  17. locutus

    locutus Well-Known Member Supporter

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    The fast burning powders used in shotshells burn in 16-18 inches.

    The old myths that longer barrels will increase velocity just aren't true.

    Read any shotshell reloading manual, and the powders used are Unique, Herco, HS-6, etc. all fast burning pistol powders.
     
  18. locutus

    locutus Well-Known Member Supporter

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    The key words here are MAGNUM RIFLE. Rifles use slow burning powder.

    Pistols and shotguns use FAST burning powder.

    Check your reloading manuals for powder burning rate.
     
  19. Virginian

    Virginian Active Member

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    I don't have to read reloading manuals, I have chronographed hundreds of shotgun loads. And the velocity does continue to increase out past 30", but only slightly. As I said earlier, the powder has burned, but the gasses and the pressure are still bottled up behind the shot and wad. If you didn't still have pressure behind the charge when it exited the barrel it would not go bang nearly so loud.
     
  20. p35bhp55

    p35bhp55 New Member

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    Ok, the reason I'm thinking a shorter barrel might help is cause we found out mostly by accident that what us old farts call riot guns made good improvised sluggers, the reasons I could come up with were the imp cyl. choke and the fact the barrel ended shortly after that big ring that wrapped around the mag tube keeping the barrel still. I'm wondering also if maybe the 20 guage barrel is too thin adding to the movement.