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Discussion in 'The 10 Ring' started by orangeride, Dec 1, 2012.

1. ### ModGlock17

4,564
1,520
Dec 18, 2010
DisneyWorld
Agree.

I think penetration relies on simple momentum mass*velocity and the cross-section of projectile, but not so simple when it sheds part of its mass along the way. Given the same bullet design, the 165gr would have the same momentum as the 180gr@1,200 if it goes at 1,309fps.

If more than 1,309fps then the 165ge would have more "mo" and likely to penetrate deeper, if other variables held constant.

Then we get into the age-old discussion of whether it's momentum MV or it's energy 0.5*M*V*V ....

At a minimum, we should have proof here, that penetration is not simply a function of the bullet mass.

A more informative experiment would be using two bullet weights but same JFP, 165gr and 180gr. Design and Verify their speeds to have the same momentum, say 1,309fps and 1,200fps respectively. See what penetration tells us, about the momentum model or the energy model fits better.

Remember, the 135gr@1,600 would have the same Mo as the 180@1,200 , as far as the momentum model is concerned. So if the Mo model holds for penetration, these two would have the same penetration ???

Last edited: Dec 3, 2012
2. ### Andrew Wiggin

626
0
Dec 15, 2011
There are other factors involved. Speer may use a different lead alloy for the two bullets. Although both my gelatin and tnoutdoors9's Simtest are BB calibrated (he doesn't post BB velocities, though) my gelatin is not actually 250A bloom photographer's gelatin and his Simtest is not even gelatin. The fact that they are different substances but nearly the same density may contribute to the discrepancy. Or it could just be a statistical anomaly. Only one bullet was tested by each of us.

3. ### G29SFWTF

205
0
Aug 3, 2012
Andrew, thanks for those gel tests. It would be interesting to see if the 180gr deforms the same way it did for TNOD9 on multiple shots.

No car doors but drsjr1969's channel has some vids of shooting various rounds at what appears to be mild steel.

4. ### ModGlock17

4,564
1,520
Dec 18, 2010
DisneyWorld
That's why you'd use the same bullet make up, except for weight, to narrow down factors.

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5. ### Andrew Wiggin

626
0
Dec 15, 2011
Problem is, we don't know if Speer uses the same alloy for the 180 gr bullet as they do for their 165 gr bullet. I doubt if they'd be willing to say because that's going to be kind of a trade secret.

I'll definitely have to re test that load. Once I get through some more of these tests, I'll go back and retest the ones that were most interesting.

6. ### ModGlock17

4,564
1,520
Dec 18, 2010
DisneyWorld
Sounds like you've got to make the assumption that they are the same, for now. Possibly cross check with the two weight classes from another mfgr, like Hornady. This can be a team work thing. Those of us have Hornady in possession, should be able to mail you like 5 bullets each type. That way you'd have a variety. I can send what I've got. Decide what you need, then post it. Folks can participate this way.

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7. ### Andrew Wiggin

626
0
Dec 15, 2011
I've got 165 and 180 gr Gold Dots but I have no idea how to tell if the alloys used are the same.

8. ### orangeride

577
16
Oct 19, 2011
I know there's a way that they test lead for hardness. It might be pretty simple.

9. ### countrygun

17,069
18
Mar 9, 2012
Lee makes an inexpensive"kit" for hardness testing but it doesn't even need to be that complicated. The alloy itself has it's own characteristices. You aren't designing a Mars lander.

As far as testing factory bullets, fire them into media and recover them. Bullets are funny things. All the scratching on paper and crunching numbers often falls flat in predicting performance.

Last edited: Dec 4, 2012

601
0
Oct 25, 2009
Florida
I agree with maine1 , I myself would like to try casting my own. As far as bullet choice I really like the xtp 180 grainers.

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11. ### dm1906Retired SO

428
0
Sep 7, 2010
PRK (Kalifornia)
You don't need rocket science to find out all of the above. The lead core will be essentially irrelevant, as they are swaged, and almost always at or near pure lead. The jacket provides the structural hardness, and bonding, if applicable, is either by soldering (heating), adhesive, or both. The difference between "hard" or "soft" pure lead is so far below what is considered "hard" (such as hard cast), it just doesn't matter to a degree we (consumers) can measure. Hardened lead (alloyed) is not ideal for swaging, and would lead to inconsistent finished bullets, even in a laboratory type process. Most bullet mfg's (such as Hornady) claim to use pure lead for the core. Of course, there are exceptions, but these would be classified in an "exotic" category, and apply mostly to non-lead, non-toxic bullets (some Winchester non-lead have a pure tin core).

To determine the core (lead) weight, peel the jacket from the core and weigh it. Or, you can melt the lead out of the jacket and weigh the pour.

To examine the jacket, hold a bullet with long pliers, and use a propane torch to melt out the lead. Keep the temperature at just enough to melt the lead, without damaging (burning/melting) the jacket. Once the jacket is empty, it can be weighed, and mic'd for thickness. Measure the base, as it'll be the most likely common section of differing bullet weights (they may use the same cup/blank for different bullet weights). If you want to test the jacket for hardness, do it before heating, or molesting in any other way.