Author Topic: Alloy of pellets  (Read 213 times)

d_boom

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Alloy of pellets
« on: October 03, 2018, 05:28:32 AM »
I have been told Crosman pellets are of a harder lead alloy than other pellets.  Does anyone know the lead alloy is used in Crosman's pellets?  What lead alloy is used for JSB pellets, or is unalloyed lead used?  Are JSB pellets softer than Crosman?
Not inquiring about lead free pellets, as of yet I have not tried shooting them.   


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Alan

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Re: Alloy of pellets
« Reply #1 on: October 03, 2018, 05:37:37 AM »
Lead is lead! Although the addition of alloying metals makes lead harder, more easily cast, whatever, the fact is their effect on weight is a reduction, not an addition.

Let me add this. Bob Sterne, who is an authority in this matter, uses a lead alloy of ≈1% tin. Commercial pellets hover around 2% tin, and a few have trace amounts of antimony or arsenic. What alloy is used, depends on how the pellet/bullet is formed. Cast bullets are formed from molten lead alloys, and specific alloying is used to make sure the lead fills the mold without leaving a hollow inside the cast bullet. Pellets on the other hand, are typically swaged. Alloys used for swaging are different from those used for casting.

And I'll add... Hardness is a relative thing. You can make lead really hard, but compared to iron, it is still rather soft. In an airgun, the bullets/pellets have to obturate within the barrel (https://en.wikipedia.org/wiki/Obturation). If the alloy is too hard, that can't happen unless the propelling force is very high! Further, if the lead is too hard, it will not expand on impact. While the actual design (shape) of the bullet/pellet is important for multiple reasons, the ultimate we want (in most cases, except for punching paper at close ranges) is tissue damage, or terminal ballistic performance. You might want to read my thoughts on this here:

http://airgunguild.com/alan's-corner/my-thoughts-on-terminal-ballistics-of-pellets-on-small-game/
« Last Edit: October 03, 2018, 06:06:34 AM by Alan »
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Alan

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d_boom

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Re: Alloy of pellets
« Reply #2 on: October 04, 2018, 05:25:36 AM »
Having shot black power guns for years, bullets will obturate to fill the bore upon firing if the alloy
is not excessively hard.  Checking pellet diameters using a pellet gauge I found the skirts are always
larger than their head diameter.  My thoughts are; air guns lack enough pressure to obturate soft lead
pellet skirts.  Pellet manufacturing solved this issue by making the pellet skirts larger than the head
diameter sealing the air gun's bore. 
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rsterne

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Re: Alloy of pellets
« Reply #3 on: October 04, 2018, 08:48:14 AM »
Pellets do obturate in most guns, in some the skirts distort a LOT.... This would be typical (2 pellet on left fired, those on right pushed through the bore)….



Airgun pressures are NOT enough to obturate bullets, however.... a hollow skirt is required for the air pressure to be enough to do that....

I have used pure lead, or up to 2.5% tin (40:1 alloy)…. This would be from BHN 6 to 8....

Bob
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d_boom

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Re: Alloy of pellets
« Reply #4 on: October 04, 2018, 07:31:25 PM »
Thanks, you have made your point, air guns can obturate pellet skirts.  A friend target shooting with a springer sorted out the pellets with damaged skirts and set them aside, shooting pellets with round undamaged skirts.  He shot well, but just before stopping for the morning he shot the pellets with out-of-round damaged skirts.  His best target was with these skirt damaged pellets.  Knowing air guns can obterate pellet skirts explains why pellets with damaged skirts can still shoot well.
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Alan

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Re: Alloy of pellets
« Reply #5 on: October 05, 2018, 05:30:56 AM »
There are other issues as well. One is how far into the chamber the pellet is loaded. Too shallow, and the inrush of air through the transfer port can damage and even destroy a pellet's skirt. There are designs with ensure the correct depth, yet allow the bolt probe to retract away. Bob has one design, and a similar one is used on Wicked Air Rifles models.

I suspect the actual chamber design (shape) is important too, but you don't see a lot of ink about that specific issue, except in firearm design. Perhaps Bob has some insight on that issue?
  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.