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Wads and how they work?

Discussion in 'Shooting Related Threads' started by maclellan1911, May 20, 2009.

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  1. maclellan1911

    maclellan1911 TS Member

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    As I sat and waited for my computer to be repaired/replaced, I got to thinking

    Just how does a plastic wad work? How does it seal? Do back bored barrels have an effect on the wads?

    Does any one have a simulation of how a wad works as it is leaving the hull into the chamber?

    just curious.
     
  2. mixer

    mixer Well-Known Member

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    Pardon the pun but I'll take a shot at it but I hope I'm not over simplifing it too much. When the powder is ignighted it becomes an expanding gas that pushes the over powder cup forward untill it collapses against the shot cup thereby moving everything forward.

    The wad petals then expand to the bore diameter cushioning the shot. I believe the over powder cup expands to the bore diameter to prevent any gases from escaping ahead of the wad so you get all the forward thrust of the gases. That's my story and I'm sticking to it.

    Eric
     
  3. hoggy

    hoggy TS Member

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    If you look closely at the wads you'll see they don't completely seal off where the base of the wad is. There are small reliefs. So some gas must get by the powder as it burns. I'm not sure why that is but all the wads I have looked at have them. Usually in three places around the sides of the base. Of course I have not seen every wad made. You have to look closely.
     
  4. samiam03

    samiam03 Member

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    This shell company has a video of a shot leaving a barrel and the wad expanding.

    Anyone have an opinion on their price and quality? I like the "Free Shipping"
     
  5. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    I believe the reliefs on the powder cup are for loading. It lets gas by the wad when pushing it down to the powder. Without the reliefs there's trouble seating the wad all the way down. At least that's what I've heard. I'll take the info because you can't get wads without the reliefs to see for yourself.
     
  6. phirel

    phirel TS Member

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    joe is correct. The reliefs around the over powder section of the wad are to let air go out as the wad is pushed in the hull. When the powder is ignited, the +- 10,000 PSI is enough to produce a seal between the wad and the hull/barrel. The chamber size is larger than the barrel and should produce a relatively smooth surface as the wad passes from the chamber through the forcing cone of the barrel.

    How wads work: The over powder cup seals the pressure behind the wad. The petals help protect the shot. The center section makes the wad the correct length to get a good crimp.

    Pat Ireland
     
  7. maclellan1911

    maclellan1911 TS Member

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    samiam, good link, I was thinking more about whats going one from shell to chamber to cone.
     
  8. timb99

    timb99 Well-Known Member

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    If your gun has a 2-3/4" chamber, the forcing cone starts to taper right at the end of the opened hull. That is, the open (fired) hull is about 2-3/4" in length, and then immediately the forcing cone starts. For 3" chambers, there is a 1/4" gap between the end of the 2-3/4" hull and the start of the forcing cone where the ID of the chamber is approximately 0.797".

    The heat from the powder burning softens the wad, and the presssure, as Pat noted above, flares or "obturates" the over-powder cup part of the wad so that it seals against the sides of the barrel.

    The jump from the end of the hull, even with a 3" or 3-1/2" chamber, through the forcing cone, to the part of the barrel that is down to the nominal barrel diameter of 0.729", happens so fast there is not enough time to completely "lose" the seal. Besides that, there is still a secondary (albeit less efficient) seal made by the back end of the shot cup, so really, there are two "seals" for a modern wad.

    So for the jump from the end of the hull to the forcing cone, you have momentum, high temperature, high pressure, and two seals working in your favor.

    A backbored barrel usually is not so large that the wad can't make a seal and be in complete circumfrencial contact with the barrel. For backbored barrels, we're only talking about 8 or 10 thousandths of an inch diameter bigger than a nominal bore.

    Even if there wasn't a complete circumfrencial seal, it would still work.

    Indeed, proof of this is those Briley Sidekicks and Seminole Chambermates, where there is a huge difference between the 20 gauge or 28 gauge wad diameter and the 12 gauge barrel inside diameter, and they still work fine. I suspect what is happening here is the pressure and momentum of the expanding gases behind the wad is enough to propel it out the barrel, even if there is not a complete seal.
     
  9. timb99

    timb99 Well-Known Member

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    Oh, and that little B&P video gives visual proof that swinging your gun will NOT give you the "spray hose effect" of making your pattern "curve" as water does as it is sprayed from a hose while swinging the hose.
     
  10. willing

    willing Member

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    I like the part about the struts(?) collapsing, tell me about the 2 part wad in the Walmart federals. I don't quite understand how that wad works.

    Bill
     
  11. maclellan1911

    maclellan1911 TS Member

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    timb99, you raise a good point and part of the reason why I got to thinking about this. I use the chamber mate in my XT for club 20gauge shoots, ???
     
  12. JerryP

    JerryP Active Member

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    Not all wads have the "reliefs" on the bottom. Windjammer 2 wads, for example do not, and they work fine.
     
  13. timb99

    timb99 Well-Known Member

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    Downrange XL-1's also do not have the reliefs.
     
  14. mixer

    mixer Well-Known Member

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    There you have it. The Rev's explaination makes sense and works for me.


    Eric
     
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