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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Wed Sep 11, 2013 9:06 pm 
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Awesome, and THANK YOU Brobee!

A couple of suggestions: Try an 11% solution, moving your calibration gun away from the block a few feet to drop velocity to the acceptable range, and try two calibration shots in opposite corners for confirmation. Those few things will likely make adjusting penetration numbers to fit the calibration BB unnecessary, and give you a pass/fail criteria for each block (which is how the FBI does it, I believe).

I make these suggestions because one of the small, niggling items that we often have to remind folks of on the original photos and tests you did is the idea the images showing penetration are not accurate as-is without complex equations (which are truthfully beyond my expertise) to correct for calibration.



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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Wed Sep 11, 2013 10:27 pm 
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Thanks so much for the suggestion FMD, and it is a very good one.

Back when I did my initial testing 10 years ago, one of the things I learned at the end was the 11% solution which worked exactly as you describe. Fast forward to a couple weeks ago, and I had unfortunately forgotten about this when I made my first batch of gelatin.

Herein lies my current problem....I made 20 (yes twenty!) 8.5x8.5x18 inch blocks at 10% before I got out for my first shooting session. As I walked up to record the calibration data it all washed back to me, remembering that 11% would calibrate better to the 590fps bb standard. I've now got more than a dozen different loads tested and filmed with this gelatin, and to change to the 11% solution for the purpose of bringing all my tests into the FBI pass/fail criteria would mean I have to re-do the ones I've already done; representing about 12 hours worth of shooting time, 20 hours of gelatin preparation time, and $1200 worth of gelatin.

So what I've been seriously considering is to continue just as I've been doing with 10%. While it does not meet the standard, this mixture calibrates quite consistently with my slightly-faster-bb gun (in the range of 610 to 620 fps) and it is possible for those-so-inclined to use DMcP's method to correct. This would give me a complete library of tests all calibrated to my own standard, and it would give my audience the ability to compare one load vs another all shot in a consistent media. But no it would not quite be to the FBI standard.

I agree that DmcP's math to effect the corrections is a bit intimidating, and while it is not beyond my abilities I worry that going there would almost certainly result in a series of iterative explaining to get people to accept it as accurate and there could be great risk of the dreaded "war between experts" which is why I now, when referencing any of my old work, only publish the calibration data (absent the corrections), putting the onus on those criticizing to come up with their own math.

Rather, I had a different idea about approaching the problem. After I finish everything with 10% gelatin calibrated with a 610 to 620fps BB (and striving for homogeny across my test media), I would do a special video episode to address the calibration issue. I would make 4 blocks: 2 at 10% and calibrated with my 610fps bb, and 2 at 11% and calibrated with a 590fps bb. I'd then shoot them all with the same 12 gauge load to illustrate the correction visually via empirical testing. In the same episode, I could use the test as a spot-check against DMcP's equations (that's the cool thing about science!). What folks will see is there is a slight correction required, but the relative penetration in the original tests would still be applicable.

If there was enough interest in that video, I might do a second one with a different sized shot.

Thoughts?

And thanks again for your feedback!

Cheers,

Brobee


edited to add: one other thing I'm hoping to demonstrate is the effect of velocity on penetration. I'm shooting all my general series videos at a range of 5 yards, but when I'm done I'm going to take a load of bb, a load of #4 buck, and a load of 00 buck and test their penetration in gelatin at 25 yards, each into their own block. This should be super-interesting...:)


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Thu Sep 12, 2013 6:51 am 
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Brother, you've already done so much work, it would be ridiculous to ask that you go back and run another set of blocks. Would backing up a few feet to get the calibration BB to the standard velocity be feasible for future tests? It might help us make a linear rather than logarithmic scale that could be utilized for the slight number corrections.

Also, were you ever able to get a hold of "A Simplified Penetration Depth Correction for Data Taken in Non-standard Gelatin” directly from MacPherson? I know you were looking for one shortly after these original tests were done and I'd love to get a hold of a copy myself. While I have a copy of Figure 5-2 from "Bullet Penetration: Modeling...", it seems that the later simplified equation would be better to approximate valid number than my admittedly horrible uSWAGs based off of the chart.

I hesitate to ask you to do more, as you’ve done so much already, but:

If you published your own corrections to approximate the FBI protocol, I predict there would be little in the way of explanations required, and no real "war between experts". If you go back through this thread, you'll find plenty of folks who understand the basic science and those who see a tape measure and call it done. The first group (I among them) understands that this is an amateur endeavor (again, thank you!) and that you published uncorrected numbers. Unfortunately the latter often take the tale of the tape and report it as undeniable proof - primarily because the uncorrected penetration numbers seem to validate their pet choice in marginal ballistic performers.

Since it's our purpose in the forum - this thread specifically - to provide as much science-based truth on the effectiveness of various loads to penetrate gel to a depth that meets the FBI criteria, it’s a suboptimal outcome. Some folks just won’t be convinced or will come to the incorrect conclusions without a short note/corrections from the author – namely you. :)

A follow up video with one or two blocks of properly calibrated gel to compare the early results to would be an excellent way to validate any mathematical corrections, and I love the idea of testing at range!


ETA: Looking at your first video, @ 1:14 in, there seems to be a misprint. The number should be 12.9 Cm rather than Mm, right? If so, and corrected for initial velocity per DMcP's chart, that looks like a calibration depth of 12.4cm, leaving us with something close to a total penetration on the order of 40% greater than an optimally calibrated block. If my dumbed down calculations are right, this produces a resulting corrected average penetration of ~10.35" for the BB load tested. Does that number look correct? It would seem to align with the average penetration of other, similar loads I've seen tested (most BB-T loads at ~1300 FPS MV exhibit average penetration on the order of 8-10").

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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Thu Sep 12, 2013 10:59 am 
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Outstanding contribution and work Brobee. Thank you.

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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Thu Sep 12, 2013 11:39 am 
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To be perfectly crystal clear: I agree wholeheartedly with my friend Shooter.

At the same time, we get enough "See, Birdshot is great for HD!" folks utilizing the photo results in the initial posts that it might warrant a bit of a disclaimer. By no means are my suggestions a critique of the time, effort, and expense of the work Brobee is putting in on our collective behalf.

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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Thu Sep 12, 2013 11:16 pm 
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FMD:

I was lucky enough to pick up a second printing of Mr MacPherson's book:

Image

The table you reference (figure 5-2) (Velocity Variation Correction to Measured BB Penetration Depth) is also present in the second printing, however it assumes that the gelatin meets the proper viscosity standard so it would be a mistake to use it in an attempt to infer correction parameters for my data.

Also, the General Penetration Depth Correction simplified method he describes in chapter 10 approaches the correction problem from the other perspective, that is it corrects for variable gelatin viscosity while assuming that the calibration bb velocity is 590fps.

Unfortunately, a fair bit of math that I believe is somewhat beyond the average reader would be required to walk our audience through the correction process dealing with both variables. On the surface, your suggestion to back up the BB gun to drop it's velocity is a good one, however this approach is still wrought with a bit of peril in that it's velocity spreads can be as much as 10 to 15 fps. This may not seem like much, but the model is sufficiently sensitive to this particular variable that shortcuts will definitely fall short of the right answer.

There are two very informative figures in Mr MacPherson's book though that would be of great interest to most readers here. They are Figures 10-8 (lead spheres) and Figures 10-9 (steel spheres), consisting of a series of curves that illustrate Penetration Depth as a function of Impact Velocity for spheres of each material of varying diameter. Based on his model, the curve predicts that a lead BB (0.170 inch dia) striking at 1300 fps will penetrate approximately 10 inches, and the same dia steel BB at the same velocity will penetrate approximately 7 inches.

I would post photographs of them, however this would put me offside of the author's well deserved copyright.

However, using his equations these two figures could be re-drawn with an increased number of curves on each, one for every shot size, and an everyday reader would be able to look at it and determine the predicted penetration from the model. It would not be useful for slugs, however it would cover just about every other shotgun projectile out there.

My math skills are only marginally capable of transcribing his method towards this purpose....but I have some ideas about how (or better yet who) might be able to help. This may take a while, but I'll start putting my feelers out and see if I can't re-create them in this context.

Anyway, the idea of making one block that absolutely meets the calibration standard and then using it to compare against one of my regular blocks seems like the best way forward now. I'll chew on it a bit more before proceeding though....more to follow as I get there!

Cheers,

Brobee

Edited to add: D'OH! I did make a typo in the calibration bb units in the video. It should read 12.9cm, NOT 12.9mm.

I will get it fixed an upload a new one. Thank you for catching that!


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Sun Sep 15, 2013 4:43 pm 
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Just finished editing up Episode 1.1 on Winchester's BlindSide Elite Steel Hex BB:

http://youtu.be/CZzbHavPA8k

I've got alot left to edit: 4 more BB rounds (various steel, lead, and plated lead), a couple BBB & T rounds, 4 varieties of plated and unplated #4 buckshot, some #2 buckshot, and 4 different loads of 00 buck.

I'm back into gelatin production mode too, and in my next batch of shooting I'll start knocking off the slugs....:)

Cheers, and thanks for watching!

Brobee

Edited to add: Typo in the video has been corrected. :)


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Mon Sep 16, 2013 8:58 am 
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Brobee wrote:
FMD:

I was lucky enough to pick up a second printing of Mr MacPherson's book:

The table you reference (figure 5-2) (Velocity Variation Correction to Measured BB Penetration Depth) is also present in the second printing, however it assumes that the gelatin meets the proper viscosity standard so it would be a mistake to use it in an attempt to infer correction parameters for my data.


That figures. :oops:

Quote:
...My math skills are only marginally capable of transcribing his method towards this purpose....but I have some ideas about how (or better yet who) might be able to help. This may take a while, but I'll start putting my feelers out and see if I can't re-create them in this context.


Obviously my math skills aren't even marginal. :mrgreen: I'm also impressed that you were able to nail my SWAG method of correction with nothing more than the post above.

Quote:
...Anyway, the idea of making one block that absolutely meets the calibration standard and then using it to compare against one of my regular blocks seems like the best way forward now. I'll chew on it a bit more before proceeding though....more to follow as I get there!


I'll keep quiet on the calibration corrections until you're all done with the tests. :s

Thanks for continuing on. The Winchester load you just tested looks like it would be ideal for my bird hunting.

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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Sat Sep 21, 2013 11:17 am 
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Just finished editing another...

Hornady's Heavy Magnum Nickel Plated Lead BB:

http://youtu.be/oOySzex190o

Have a couple more BB episodes left to edit, then I'll move on to some #4 buck and 00 buck!

Cheers,

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Sun Sep 22, 2013 1:57 am 
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Thanks again for doing this and keeping it going. Great work and contribution.

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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Wed Sep 25, 2013 8:35 am 
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And another

Remington Hypersonic Steel BB:

http://youtu.be/xs1SzUzhN2Q

Was thinking about changing the format for tightly patterning buckshot episodes: gelatin tests at 5 yards, 20 yards, and 40 yards, but only with a cylinder bored gun. Thoughts?

Cheers,

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Tue Oct 01, 2013 7:38 am 
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Got another one edited and uploaded last night:

As requested by a viewer, here's Remington's Express Long Range Lead BB:

http://youtu.be/KnyJ9t8yO_Y

Will be leaving the bb world for now, next up is Federal's Premium 00 buckshot into gelatin at 5 yards, 20 yards, and 40 yards.

Cheers!

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Tue Oct 01, 2013 9:18 pm 
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Typo fixed and new file uploaded...sorry about that!

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Wed Oct 02, 2013 3:03 pm 
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I would say whatever the military and police use is probably going to be the most effective(OO Buck). That being said for HD I wouldn't load anything else. If you need something smaller or tighter shot they are known as Rifles and Handguns. :)


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Sun Oct 06, 2013 12:00 pm 
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Hi there folks!

As suggested by some viewers, here's my first edit of the series 2 format: Long Range Gelatin Testing!!

Episode 2.0: Federal Premium Copper Plated Lead 00 Buckshot with FliteControl Wad:

http://youtu.be/S546W_L0tFo

Thoughts about the test format?

Cheers,

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Sat Oct 12, 2013 9:17 pm 
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Surprised there's no feedback on the format! Here's another one I just finished editing:

Hornady's Varmint Express LEad #4 Buckshot:

http://youtu.be/3VTk_7884r8

I got out this past weekend and filmed a bunch of different slug reviews...will get to editing them pronto!

Cheers, and thanks for watching.

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Sun Oct 27, 2013 8:21 am 
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Location: Calgary, Alberta Canada
And another long range test; Hornady's Heavy Magnum Coyote Nickel Plated Lead BB:

http://youtu.be/smJRQHss26w

Cheers,

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Mon Dec 30, 2013 8:41 am 
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New Format Test Run!!

A real-life performance test of Federal's Vital Shok Copper Plated 00 Buckshot:

http://youtu.be/41wBr7-QQlI

Cheers,

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Sun Jan 05, 2014 7:29 pm 
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And here's my first slug review:



Cheers,

Brobee


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 Post subject: Re: 12 gauge Wound Profiles (56k beware) Examples on page 3
PostPosted: Mon Jan 06, 2014 4:07 am 
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GREAT information, brobee!




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