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Discussion in 'Caliber Corner' started by JDK721, Jan 7, 2010.
"Free recoil energy" for "factory spec." FMJ ammo out of a "stock" Glock 17:
115 gr. @ 1155 fps = 5.0003 fpe of recoil energy
124 gr. @ 1120 fps = 5.3018 fpe of recoil energy
147 gr. @ 975 fps = 5.3782 fpe of recoil energy
As for the "most" or "least" accurate load; that depends upon more than just the bullet type and velocity. It is also effected by the individual weapon's quality, manufacturing tolerances, general quality of the ammunition, the shooter's skills and there is not "pat" answer for those reasons.
"Perceived" recoil is another matter entirely, although with standard pressure 9mm ammunition there is little real difference or significance since none of the three examples fluctuates more than ~3.75% from the median free recoil energy value.
I'd bet most folks would be hard pressed to recognize the bullet-to-bullet difference in the recoil if they fired a magazine full of mixed 115 gr., 124 gr. and 147 gr. FMJ ammunition.
It's not a big deal, really.
<S>No, not in typical factory loads. Just the opposite. Generally:
1) the more powder, the more recoil
2) the lighter bullet, the more powder
3) the more powder, the more velocity
Energy favors velocity. And, energy forward is energy back. Muzzle energy then gives a simple, rudimentary scale of comparison for recoil energy I think most can grasp since we all know: Energy = mass x velocity squared (e=mc2)
115 = 1145 = 150767875
124 = 1090 = 147324400
147 = 950 = 132667500
Note: All not +p loads
Gold Dot Data
115* = 1210 = 168371500
124 +p = 1220 = 184561600
147 = 985 = 142623075
* Not +p
The 147gr will have the least recoil energy. 481's velocity is watered down for the 115gr, and if I get the gist the math s/he used is relative to momentum. Generally, the velocity for typical factory 9mm is:
115 +p = +100 to +150fps over 124gr +p
124 +p = +200 to +250fps over 147gr
"Experienced" or "felt" recoil can be subjective. And, different gun designs handle recoil differently. Regardless, comparing a 147gr at 985fps vs. 124gr at 1220fps and you are talking a 33% difference in energy forward/back; I think almost anyone will notice that.
But, I don't need math to tell me a 165gr .40sw recoils noticably more than 180gr. Or, that a 124gr +p recoils noticably more than 147gr. Both are VERY easy to discern, very.
"Accuracy" will not relate to weight. Point of impact (POI) may (e.g. high/low).</S>
See my post #29 and on...
Load a 147gr bullet with a small dose of 231 and you will experience 9mm nirvana. Great accuracy with recoil that is as soft as butter.
+1 What he said...
Couldn't be farther from the truth.
Actually, your use of the equation, e = mc², is the relativistic expression for the conversion of an object's rest mass into energy (it works the other way, too) where the variable "c" is the speed of light, and as such, this equation has absolutely nothing whatsoever to do with calculating the kinetic energy of any imaginable handgun bullet in motion.
General Relativity aside, the correct equation for that exercise is: KE = ½mv²
Correctly calculating the KE of a 9mm 115 gr. bullet at 1155 fps using the proper equation yields:
½mv² = ~340.59 fpe
Using the improper equation, e = mc², (as suggested in your post #5, above) for the same task we get:
e = mc² = as applied to a 115 gr. bullet = 6.6975 x 10<SUP>14</SUP> Joules or 4.9398 x 10<SUP>14</SUP> fpe, which is equal to ~118 kT* (kilotons equivalent TNT).
*This represents a yield of approximately 7.8 times that of the Atomic bomb ("Little Boy") that was detonated over Hiroshima on 06 August 1945.
Obviously, as one can see from the figures, unless you have something that the U.S. Government might be interested in knowing about, the first equation (½mv²) is the correct equation for the application of calculating a bullet's KE.
The velocity quoted for the 115 gr. FMJ is indeed correct according to several commonly available factory data and is far from "watered down" in that Remington 115 FMJs run at 1135 fps, Hornady 115 FMJs run at 1155 fps and Federal 115 FMJs run at 1160 fps. My prior post had nothing to do with anything other than standard pressure loads and I never represented it as being otherwise.
While you might be able to "feel" a very slight difference between different standard pressure loads, the difference amongst these standard pressure 9mm loads' recoil is hardly what one might call "significant".
As for not needing math to tell you anything, I'd argue that you might want to seriously consider a course in something more than "general" mathematics as well as one in physics in order to bring your skills up to "par" before dismissing the entire field of study (mathematics) as being "unneeded".
There is less felt recoil in the heavier gr. ammunition of the same type and caliber.
147 has less felt recoil than 115.
180 has less felt recoil than 155.
230 has less felt recoil than 185.
I know this from shooting, not math.
While this is not incorrect, "felt" or "perceived" recoil is entirely a subjective matter. Individual "perception" is also influenced greatly by the amount and burning rate/characteristics (the "pressure curve" if you will) of the powder used to propel the bullet as well as the mass of the firearm employed.
Perception differs greatly from person to person and what might "feel" like heavier or lighter recoil to you may not be perceived in the same way for me. That is why I said above in post #4:
Still, the physics (as well as my math) above holds true and I prefer not to waste my time debating the "intangible" since our perceptions will differ anyway and certainly in an "unquantifiable" manner.
Generally the typical 115 fmj from Blazer or Winchester has pretty light recoil. If you buy Speer Lawman 115, the power level goes up along with recoil. Lawman usually clocks 80 -100 fps faster than WWB.
Winchester USA 147 is also pretty light, probably the lightest felt recoil in my experience, again, Speer Lawman is hotter, you can feel the difference.
With Glocks it seems like anything with a reverse jacket like a hollowpoint or Winchester's Winclean BEB rounds are more accurate than fmj's. Winchester Winclean 115 BEB has ben a tack driver in all my 9mm's.
Win. USA 147 jhp has very soft recoil and excellent accuracy as well as being affordable enough to practice with.
The most accurate round I've ever tested in my G-17L is the SBR 90 grain frangible round SBR 90 at Midway
It has very light recoil due to the lead free (sintered copper) bullet. There not as cheap as discount fmj's, but they are cheaper than most hollowpoints and will drill the centers out of the targets at 50 yards.
Not necessarily. Applying the basic kinetic energy equation to the bullet weight and velocity is not the correct method for calculating recoil energy. It does not account for the weight of the powder charge, nor does it account for the portion of recoil due to the “push” of the expanding gases as they leave the muzzle. It also does not account for the weight of the firearm. The correct equations for calculating recoil energy can be found in Hatcher’s Notebook, chapter 12.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
As examples of correct calculations of recoil energy, the following three bullet weights in standard pressure loads fired from a SIG Sauer P229 are used below: 115 grain, 124 grain and 147 grain<o></o>
When fired from the SIG P229, Federal’s 115 grain JHP 9BP load, with an actual muzzle velocity of 1122 fps, has a recoil energy of 3.7 ft-lbs.<o></o>
When fired from the SIG P229, Federal’s 124 grain HST load, with an actual muzzle velocity of 1098 fps, has a recoil energy of 3.9 ft-lbs.<o></o>
When fired from the SIG P229, Federal’s 147 grain HST load, with an actual muzzle velocity of 962 fps, has a recoil energy of 4.1 ft-lbs.<o></o>
As long as the proper twist rate is used, the construction/quality of the bullet will be far more important to accuracy than the actual weight. I've had great results with 9mm bullets as light as 90 grains and of course many people report great results with 147 grain loads.
Generally speaking, a quality JHP will be more accurate than most other designs. The single most accurate 9mm bullet that I have tested so far, is the Hornady 125 grain HAP. The 10-shot group pictured below was fired from 25 yards using 125 grain HAP bullets.
I've come to expect no less from you and your last two posts do not disappoint.
As for your 10 shot 0.413" group at 25 yards...
I hate you.
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That 10 shot group is amazing.
<S>We remain in disagreement on this matter. Energy, which velocity greatly favors (because it's squared), keeps it very simple and reliably states the order of recoil energy w/in caliber by weight when comparing full-power loads.
I find the more folks want to show how smart they are, the more complicated explanations get unnecessarily. Sounding smart, and being right are not the same thing.
This all can get really complicated with all the math. However, the answer, comparing typical full-power factory loads w/in caliber, is really quite simple: more powder = more velocity = more recoil. Having shot 115gr +p+, 124gr +p and 147gr (which are the ideal defensive loads in each weight IMO) from the same gun, actual and "felt" recoil of these loads are very different.
While you consistently try to make your argument in this post (and those of yours I have read along these same topics) with lots and lots and lots and lots and lots and lots and lots and lots and lots and lots and lots of math, I base mine on more simple math and experience, and still get the correct answer. And, least recoil is the 147gr when comparing typical full power factory loads w/in caliber for the reasons I mentioned.
Same goes for in the .40sw for 155gr, 165gr and 180gr. Least recoil in typical full-power loads is 180gr.
The .357sig fires 9mm .355" bullets. The 10mm fires .40" bullets. Are we really going to debate which has greater recoil, "felt" or otherwise: 9mm or .357sig ... 10mm or .40sw? Since bullet size is identical, the differences in these loadings are clearly 1) powder and 2) velocity sequel to it. And, the real difference is powder since more of it generates more velocity all other things being equal (bullet, OAL, crimp, primer and gun). Hence, more powder = more velocity = more recoil. So, so simple.
Seasoned reloaders are very, very concerned about energy. Though it provides little opportunity to display math wizardy on your part, this Reload Calculator and this Hogdon data should help you wrap you head around it. Just plug these Hogdon numbers into the calculator:
Firearm = 1lb
Firearm = 1lb
Let us know what you get.
The above example may be reloading data, but the principles are the same with factory loads. Comparing typical factory full-power loads w/in caliber, it's a sliding scale: any speed a heavier bullet can be pushed to, a lighter bullet can safely be pushed faster. And, velocity is the critical element. Meaning, in simple terms sans math, the relative scale of comparison (w/in caliber) remains the same: More powder = more velocity = more recoil. Again, so, so simple, and complex math not required. </S>
<S> Your closing comment was insulting; as coy and sly as you may think you were being. Few are as smart, or clever as they think. Given your math love and excitement to showcase it, I suspect an advanced Sciences Degree, so suggest an additional course in etiquette and we'll call it good.</S>
See my Post #29 on...
The vast majority of what you have said above (in both of your posts) suggests an abyssmal (at best) understanding of basic physics.
The simple math involved in the expressions of these very basic physical concepts is nowhere near as complex as you portray it, this too confirming my suspicion that you haven't any real comprehension of the "information" that you "regurgitate", oftentimes incorrectly. This is exhibited, by way of one glaring example (there are many more), in your suggested use of the relativistic equation (E=mc²), where it most certainly does not apply, for the simple Newtonian calculation of kinetic energy.
For these reasons, I cannot take seriously anything that you have to offer in either of your two posts and it is my hope that you will endeavor to increase both your education as well as your knowledge level so that you will no longer risk leading others so far astray with such fictitious "material" and misinformation.