Hey Rich. Cool idea trying to quantify this. It’s nice to have repeatable numbers for setting up multiple holster.
As far as ideal? I don’t know. The shake test is my usual. But it would be fun to try this with various holsters and see how close I am.
But the Prussik is not a knot or we couldn't use it for jumaring and anchoring (and such). At least it wasn't a knot when I was still climbing.Originally Posted by ViniVidivici
There's nothing civil about this war.
I'll grant you it's sort of a knot...I use Prussik knots when attaching lines for a poncho shelter, so I can easily loosen or tighten that line. Extremely useful for such applications!
Now back to your regularly scheduled thread...
Just working the OP's idea through in my head I believe attempting to quantify the draw weight would only be remotely valid for setting up one specific gun across multiple holsters.
The weight of the gun is going to be a huge part of the equation and render any one single DW number invalid for multiple platforms.
SWAG: a 5lb DW may feel right for a G19 but will be too light for a steel 2011 and too heavy for a J frame.
It couldn't possibly hurt anything to test this. I like the concept. Some additional variables to consider, though. For one, the holster off-body for testing vs. in the actual waistband with a tightened belt compressing it, there's probably going to be a difference in tension. Also, the weight of an empty gun versus with a loaded mag. Maybe the weight is a factor, maybe not.
Best case scenario, hey, maybe it gives us a few more data points of interest. More data can't hurt, as long as people don't get caught up in paralysis by analysis. I get the point about "overthinking", but I would also say the "don't overthink" side of things has an extreme spectrum of its own: bro science.
Administrator for PatRogers.org
Warning: Math Ahead.
Thanks for all the tips about "turn the gun over and shake it a bit". That's led me to reexamine this problem.
I realized I'd been thinking of this all wrong. In fact, the correct expression for the "draw weight" to remove a gun from a holster is not "weight", per se, but Force. Per Newton's second law of motion, the Force (vector) on an object is equal to the mass times the acceleration (vector) being applied.
Or:
F = m x a
Where
Force in SI units is Newtons, or kg.m/s2
m is kilograms, kg
a is acceleration in m/s2
Now looking at the problem from this point of view, it's clear that in this test, the gun is resting in the holster. If turned upside down, to shake it a bit, the force on the gun is now the sum of the (vector) Force of gravity, as well as the (vector) force of "shaking it a bit".
If you "shake it a bit" harder, or "shake it a bit" more over a longer distance, then you'll apply more force. You still have gravity pulling the gun down. But the sum of the two may make the gun pull out.
So, how to compute that?
If we assume that the friction of the gun in the holster is simple static, and not kinetic, friction, we can pose that the Force resisting the gun pulling out is at least greater than the sum (vector) of the forces needed to drop the gun out.
So, from simple Physics, the force due to gravity is easy:
F = m (of the gun) x g (the universal gravitational constant)
Assuming a Glock 19, with magazine, loaded, let's pose a number of 0.855 kg.
So the force of gravity on the gun is thus
F = 0.855 * 9.8 = 8.36 N
Now, how to compute the Force (vector) of "shaking it a bit"?
If we reapply Newton's second law, we can derive that the acceleration, a, of the gun and holster from rest to "being shaken" induces a stop at the end of the "shake". Let's say the shake is about the hand breadth of a NA male, say about 3". For the duration of the shake, let's say the shake takes place 4 times a second, so the duration will be 0.25s.
Now to approximate a without calculus, we can simply say that v = delta d / delta t, and a = delta v / delta t. Delta V in this case is V(final) - V(initial). Since V(initial) is zero, then the acceleration at the end of travel of the "shake" (where the gun drops out) is approximately:
3" = 76.2 mm = 0.08 m (SI unit)
So therefore
V(final) = 0.08 m / 0.25 s = 0.30 m/s
and a is thus
a = 0.30 m/s / 0.25 s = 1.22 m/s2
So now we can calculate what force that was, using our gun, as follows
F = m * a = 0.855 kg X 1.22 m/s2 = 1.04 N
So what to think? Interestingly (to me anyway) you can compare the gravitational pull on the gun vs. the force of a simulated "shake". Using the numbers here, the force of gravity on our mythical Glock 19 is about 8 times the force induced by a notional "shake".
Continuing, the equation obviously still holds when the gun is drawn. In this case, the gun is still being affected by gravity. You have to overcome that force, as well as the static friction of the holster retention.
One thing I've left out of the above is the anthropometric considerations of the draw. In terms of North American population, a 95% male will not require the same effort in drawing a gun as a 5% female, because of the disparity in musculature.
In closing, I used my original method and "calibrated" a new to me used DSG Hitchhiker AIWB holster for my G48 that arrived this week. It was originally set with the retention so tight, that I could just about yank it out of my MMT belt without jerking the holster out of the clip, but it was close. As say, aside from hit or miss, it was bugging me that the draw wasn't smooth at all. So even though my original post in the thread was in terms of "weight" and essentially incorrect, I used my Wheeler pull gauge today to set the draw weight of the DSG hitchhiker, to exactly the same as my JM CK. And so I did manage to save about the length of time it took you to read this entire post.
This year I’ve been using the GX Vice holster, with a quick-release lever. No more worrying about losing my gun during stage walkthroughs an rehearsals.
“There is no growth in the comfort zone.”--Jocko Willink
"You can never have too many knives." --Joe Ambercrombie
I see he has the G34 in that model. Very tempting. Also very much like the fact you can order a color combination for inside and outside colors. I would vastly prefer a lighter colored interior for a USPSA holster.
I have a sawed-off (literally) Blade Tech classic OWB I bought 4 years ago for my G19 that I'm currently making do with for the G34. I really need to get something better for this coming season.
For ccw I've been quite partial to orange lately.
FWIW, it's not friction we're dealing with in most kydex holsters, it's overcoming an interference. There are quite a few things to consider as well. Metal vs plastic frame, the shape of the indent in the trigger guard, etc. Belt tension also plays a huge role, as already mentioned, but the shake "test" is bullshit. There are plenty of good holsters that would fail when not worn, but are 100% passable as worn. You'll get a number measuring them, but it's of little value.
I'd really rather see it in a force/distance drawn graph. This will show the snappiness, or lack of.
Think for yourself. Question authority.
It may be unnecessary to look so closely at retention for most holsters in most situations but I like a scientific method and objective data over "feels", ambiguity and only subjective information. Thanks for presenting some thoughts and processes.
If it helps I went through Craig Douglas's ECQC class in 100+ degree heat index using only a hybrid holster (White hat) that was made for a Glock 19 and never had an issue with losing the gun in scenarios nor having any issue with draws for life fire or simunitions. I used a CZ P10C for live fire so it wasn't even a perfect fit. That along with over a dozen years of wearing a hybrid holster without issue has been enough for me to trust retention and ease of draw balance in some of these holsters. It may fail a inverted shake test but going through ECQC was enough proof for me.
Reply With Quote