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MaximumSmoke
PostPosted: Tue May 29, 2018 8:35 am  Reply with quote
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Recently some more "square load" talk on this site tripped me over into trying to replace the B.S. of the square load with some realities. First of all, "square load" advice is in a good direction if reduction shot damage on ignition/launch (or vibration excitation in the case of very hard shot), is the objective. However, the "square load" amounts typically listed for the gauges are usually incorrect, and the extension of the square load concept falls apart quickly in bores smaller than 16. Square loads -- i.e. loads with height equal to the bore diameter -- are in proportion to the cube of the bore. Square loads in ounces of typical lead shot in the gauges/bores are listed below. These are fairly accurate for shot sizes up to 6 and maybe as large as 5. I use and have measured a "packing factor" of about 0.55. "Packing Factor" is the ratio of the weight of lead shot in a given container to the weight which would be there if it was fill solid with a lead alloy of the same density -- i.e. it is a volume filling factor. As mentioned, 0.55 seems to work well up to and including #6 shot in bores from 10 to 28 at least, but the packing factor gets less the larger the shot and the smaller the bore. i.e. More space is lost as the size of the container gets closer to the size of the pellets. Here are the square loads:

10 = 1.29
12 = 1.07
16 = 0.80
20 = 0.64
28 = 0.46
.410 = 0.19

The square load is not a good way to compare shot damage on set-back. For such damage comparison, it is best to use shot charges of the same height. Pellet damage on setback is due to the inertia of the column, and the acceleration driving it. The pellets at the back of the column experience the greatest crush forces because they have the most mass in front of them. If columns have the same height, the same damage to the same proportion of the pellets is the same across all bore sizes. If, since typical muzzle velocities of all the gauges are similar, and we can assume the time history of acceleration (and hence the peak acceleration) provided by combustion to be about the same, then it's the number of pellets in front of any given pellet that governs the compression force it experiences -- i.e. it's the height of the shot column that determines set-back damage. Yes, though not a stretch, it is not an ideal assumption that peak accelerations are the same across all bores for loads producing the same velocities. However, any physicist out there who can provide a more relevant assumption is welcome to give it a try -- PM me. The upshot of all this is that for the same set-back damage, charges would be proportioned gauge-to-gauge, by the area of the bore, i.e. by the square of the bore. In the "square load" concept (column height = bore diameter), charge weight is proportional to the cube of the bore. Here are the loads by gauge/bore for shot columns of the same height, if all were compared to the height of a 1 1/8 ounce 12 gauge load.

10 = 1.27
12 = 1.125
16 = 0.93
20 = 0.80
28 = 0.64
.410 = 0.36

This makes more sense and basically agrees with the amounts often cited as traditional square load advice, but they are not square loads. Some old advice says 1 ounce in the 12 is a better "square load", and in fact it is closer to square than a 1 1/8 ounce load. Loads of this height would be:

10 = 1.13
12 = 1.00
16 = 0.82
20 = 0.71
28 = 0.57
.410 = 0.32

So anyway, there's some food for thought if you're concerned about shot column behavior disruption, and hence pattern disruption, due to combustion forces -- either set-back damage for soft shot, or from vibration excitation on very hard shot like steel, tungsten, etc. This also shows what an odd-ball the .410 is, and why it often is prone to pattern inconsistencies. We are loading it with up to twice the shot column height of the larger bores. Pretty hard not to expect some relatively heavy set-back damage compared to the larger bores, not to mention the greater proportion of bore-scrub damage a small bore produces (even if the shot column height was the same!). Looking at relative shot column heights also blows away the so-called "magic" of the 28 gauge and the "square load". Let's face it: we like the 28 and the 16 because they are great packages to carry for upland hunting, and in a properly sized gun, nice looking, too. The 20 is just as magical, but being almost entirely restricted to yellow shells is a huge aesthetic drawback Wink

Cheers!
Tony
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Dogchaser37
PostPosted: Tue May 29, 2018 9:20 am  Reply with quote
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Uhhhhhhhh..... Tony you must be bored. Laughing Laughing Cool

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AmericanMeet
PostPosted: Tue May 29, 2018 2:21 pm  Reply with quote



Joined: 26 Apr 2010
Posts: 3172
Location: NCWa

Or, the shortcut version: spherical lead shot averages about .288 cu in per ounce.. Bores are: 12ga .73, 16 .66, 20 .615, 28 .55; This results in areas: 12ga .42; 16 .34; 20 .30; 28 .24.
Pick your gauge, divide .288 by your area and you'll see the height of the shot column. As noted, the heights are usually taller than expected.
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Dogchaser37
PostPosted: Tue May 29, 2018 2:55 pm  Reply with quote
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........and what exactly is the square load gonna do that other loads don’t or can’t?

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Hootch
PostPosted: Tue May 29, 2018 2:59 pm  Reply with quote



Joined: 28 Mar 2008
Posts: 1460
Location: Eagle, Nebraska

Not sure if mine are square or not, I pattern and shoot them to see if I like them, pretty much have settled in on my loads for sometime now.

For birds I am using 1 1/16 oz of lead. Works pretty well for me.
Clays I usually just use 1oz or buy Federal 1oz loads. If I can't break them, not pay load but this shooter
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MaximumSmoke
PostPosted: Tue May 29, 2018 4:32 pm  Reply with quote
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Go through the units and instructions of your post, AmericanMeet. Your instructions are just a bit shy of complete. You said, "Pick your gauge, divide .288 by your area and you'll see the height of the shot column." No, you won't. If you divide .288 in.^3/oz. by area, which has the units in.^2 you will get something of units in./oz. not the height of the shot column. If you multiply that by the ounces in your charge, then you'll get the height of the shot column.

If you divide the bore diameter by .288 in^3/oz. and multiply it by by bore area, you'll get the weight of the square load for that gauge.

If the height of the square load is what you were after, you needn't have gone through the exercise as you already know the height of the square load is the same as the bore diameter.
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Dave In AZ
PostPosted: Tue May 29, 2018 4:35 pm  Reply with quote



Joined: 13 Oct 2015
Posts: 348

Uhm... I'm pretty sure you guys are missing that this is mostly an ANTI-square-load post, kind of debunking the "magical square load" if you will. At least I read it that way.

Anything that is against the pseudo-science wishful thinking that is the "Square Load", I am for Wink Nice post Tony.

Your 410 comments are interesting; I just shot 410 at skeet first time the last couple weeks, and was totally amazed to get a 23, about what I normally get with all the other gauges with 3/4oz loads. Someone on another forum wanted a 1/2oz 20ga load, so this afternoon I loaded up some attempts at that, and I'm going to chrono/pattern them tomorrow. Just messing around bored (thx for an interesting thread!).

Now your thread here makes me think it would be worth shooting a couple 1/2oz WinAAHS 410 loads too, just for a 20ga vs. 410 1/2oz stackheight pattern comparison.
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Dogchaser37
PostPosted: Tue May 29, 2018 4:45 pm  Reply with quote
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Dave in AZ,

You just might be correct seeing how Tony left out the weight of the payload in his essay......... er um um post.....I mean his wonderful thought provoking post.

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MaximumSmoke
PostPosted: Tue May 29, 2018 4:47 pm  Reply with quote
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Dogchaser37 -- As you, myself and others here well know, the "square load" concept is not magic, and is not even very practical in all cases. Comparing loads across various gauges with shot columns of the same height propelled to the same velocities is more relevant to both internal and external ballistics, and gives a much better guide to comparing the performance capabilities and limitations of the various bores.

I think the square load is a hoot. Like a lot of old tales sacred to an interest group (e.g. old wives tails, etc), it brings out the most illogical but reverent, ardent, and rigid followers from time to time, even if they don't know the very definition of the square load. It gives me great pleasure to test the logic and thinking of such folks, with tongue firmly in cheek at all times.Wink

Cheers!
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MaximumSmoke
PostPosted: Tue May 29, 2018 5:03 pm  Reply with quote
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Good shooting with the .410, Dave In AZ. When you're on, you're on, and you'll know it fast with the .410 -- not so much room for error. It doesn't take much to break a skeet target, you've just got to get a pellet or two in the right place, but you do have to be "on".

So we're talking shots at clays 20 yards and less, right? -- OK maybe some folks ride some skeet targets out to 25 yards. However, try any load in the .410 at the various target types, sizes and presentations in sporting clays, and the true capability of the .410 starts to show. It's definitely an indication of how the .410 might perform on game. If you shoot game with a .410 you will want the birds to be handy, and you'll need to be pretty handy with the gun, too.

I'm sure someone will now mention his routine 60 yard dead kill .410 shots on geese -- no, these guys usually are pheasant shooters, aren't they.
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Dogchaser37
PostPosted: Tue May 29, 2018 5:10 pm  Reply with quote
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Stirring the pot Cowboy!!?? Razz

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MaximumSmoke
PostPosted: Tue May 29, 2018 5:17 pm  Reply with quote
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By the way, I'm "working up" that 3/16 ounce .410 "square load" in a 3" hull to baby that shot with plenty of wad cushion. (We can "work up" shotgun loads, right Mark M.?) Then I'll show you all how really miraculous the square load concept is. I'll make you all forget about Charles D. Wadmaker -- you know, the Olympian of Shooting, that guy. I'll be using Red Dot, too, maybe even Bullseye. I'll probably use nothing bigger than #12 shot. Watch out geese and pheasants; If you're close enough for me to see you, I'll put your eyes out with that stuff. That's what square loads can do. After those successes, I'll bump the velocity up to 2000 fps and hammer those coyotes that run all over the place. Watch this channel!

Cheers!
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16gaDavis
PostPosted: Tue May 29, 2018 5:45 pm  Reply with quote



Joined: 24 Jun 2013
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Max - BPI 's sporting 410 , 3/8 , and 10 grns herco . My 410 SQ load for stations 1.2.6.7.8 !!

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JNW
PostPosted: Tue May 29, 2018 5:55 pm  Reply with quote



Joined: 15 Jun 2010
Posts: 1358
Location: Twin Cities, MN

For those who haven’t realized it yet, Mr. Smoke is an engineer, hence his detailed number driven analysis. Thanks for that - I love logic and reason.
There are a number of “beliefs” in the gun world that bother me and I think they are hogwash. The square load theory is one of them. It has nothing to do with physics, just filling magazine pages. Another one is how the 28 gauge performs better than it should because of its special, magical qualities. More BS. If you see someone shooting a 28 gauge and doing well with it, it is most likely because that shooter is an excellent shot. Who buys 28s? Mostly guys who really like shotguns, shoot a lot and already own a bunch of guns in the larger gauges. They shoot everything that fits them well.
There are a bunch of other common misbeliefs that are hooey, but I’ll leave them be for now. Any load that patterns okay, and most of them do, will work if you do your part.
Regards,
Jeff
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Dave In AZ
PostPosted: Tue May 29, 2018 6:18 pm  Reply with quote



Joined: 13 Oct 2015
Posts: 348

I agree with all of the above stuff, so many old wive's tales out there... it can really make it hard to sift through to find the actual truisms, like the facts that 16ga shooters are inherently more witty, urbane, and better looking Wink

Heck, I just loaded up some 7/8oz 16ga DR loads to try tomorrow, and walking past the bathroom mirror I can absolutely verify I'm all sorts of more urbane than I was just hours ago.
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