What the crap?

[Solus]

So I went to the range with my buddy the other day. I took 50 CCI 155 grn aluminum case, 100 Independance 155 grn brass case, and 50 180 grn Remington brass case. I was just casually shooting through. Then shot the CCI and Independance side by side to see which I like more. The Independance. Then I tested the grain of the 155 to the 180.....what the crap, I shot EASIER with the 180 grn! The recoil was better and my shot was better. Not to mention it just overall felt better as I was doing quick taps. Why is it that the 180 grn was easier for me? I thought it was supposed to be harder because it was a heavier wieght but.......damn....that was wierd.

Little Help.

[LexDiamonds]

I have chronoed the Independance 180grn load in my 5" XD and they are pretty powder puff. They averaged only 900fps which may account for the lighter feel. Also, heavier bullets tend to reduce initial felt recoil.

[Solus]

Originally Posted by LexDiamonds

Also, heavier bullets tend to reduce initial felt recoil.

Why is that? I would think that the heavier the bullet the more there is to push out creating a heavier recoil. Why is it then that my buddies Glock 19 shooting 115 grn WWB has less recoil than the 180 grn Remingtons I shot? (The Independence are 155 grn, CCI 155 grn and Remington 180 grn)

[mcb]

Hmmm... Recoil discussions always have the potential for ugliness.

First up recoil is the change in momentum often called impulse. Impulse is a change in momentum and since initially the bullet has zero momentum since it has zero velocity the total momentum change or impulse is equal to the momentum of the bullet (and propellant gases if we are getting really picky) at the time they exit the barrel.

A common way to quantify recoil is what USPSA calls power factor. With power factor they do mass (grains) time velocity (fps) and then divide by 1000 just to scale the results to a convenient scale. Do not confuse PF/momentum this with kinetic energy that is 1/2 mass times velocity squared and is not very useful in recoil discussions but has its place in other discussion.

So you can have a light bullet going fast that has the same recoil as a heavy bullet going slow. Just for ****s and giggle let’s look at two extreme weights of 40 caliber loads.

180 grain load to make major (ie PF=165) would have a muzzle velocity of 916.7fps

135 grain load to make major (again PF=165) would have a muzzle velocity of 1222.2fps.

Both of these loads have the same total recoil impulse but they are going to feel drastically different in the hand.

I ran a real quick simulation in some internal ballistic software and the 135 grain load takes just over 0.5msec to exit a 5 inch barrel. The 180 load takes about 0.7msec to exit the same 5 inch barrel. Since they both bullets have to achieve the same momentum change during the time traveled down the barrel the average forces have to be higher for the light bullet to achieve the same momentum change in the 0.5msec as compared to the heavier bullet 0.7msec in the barrel.

This difference in the time and force curve results in the perception that the lighter bullet feels snappier/sharper. Most people find the sharp snappy recoil of light bullet less pleasant even though from and engineering point of view the total recoil impulse was the same as the heavy bullet that have recoil that is often described as a push rather than a snap.

If you watch what the serious USPSA shooters are using many of them shoot the heaviest bullet possible for their caliber to reduce the snappiness of the recoil. They have to make power factor so they cannot reduce recoil but they can make it easier to manage by taking the snap out of it. Many of the guys shooting 40 S&W in wide body 1911 style guns that are loading 40 S&W to 45 ACP length will load 200 grain bullets (most commonly used in 10mm Auto) in their 40's because the have the extra room to keep the from blowing up their guns.

Oh... too much rambling
mcb

Edit: to correct some bad writing/typos, don’t worry I’m sure I missed some.

[Solus]

Originally Posted by mcb

Oh... too much rambling
mcb

Dude that was an awsome expaination! So for me to kind of dumb that down....in other words sinse it takes longer...even in miliseconds to push out the heavier bullet it extends the recoil time making it less of a "snap" and more of a heavy push making it feel better in your hand and allowing for better follow up shots.

So what's the benifits of a smaller load?

[mcb]

Smaller in what way?

Lighter bullets for the same recoil impulse as a heavier bullet are going to obviously have a higher velocity and this results in a flatter trajectory although that rarely is a factor with most used of a pistol.

There is also other factors to be taken into account. Some guys shooting open guns will load fast light bullets to make major power factor. Since they are using and open gun they can have ported and or compensated barrels. By shooting lighters bullets pushed heavier charges of powder you make your porting/compensators more effecient in reduceing muzzle flip and recoil. Since a compesator work my redirecting propellent gasses you want as much of those gases as possible.

mcb

[mingomike]

mcb

Fisrt, great explanation on recoil! What I want to know is, where were you about 3 years ago when I started shooting 40 cal. in IDPA.!!! I had to find out all that info and more all by myself! Actually, I enjoyed the research. I started out with 155 gr bullets and for the past year I have been using 180 gr with 3.8 gr of Titegroup. Just recently I switched to 200 gr bullets with 3.3 gr of Titegroup.

Good shooting to all of you![/b]

[mcb]

Mingomike,

What is the PF minimum for IDPA. I was using Titegroup until here recently and had to use 4.5 grains with 180 grain Berry's bullets to get a PF of about 170. Those 3.3 grains of Titegroup and 200 grain bullet must be some smooth loads.

mcb

[backstay]

From IDPA rule book
http://www.idpa.com/Documents/IDPARuleBook2005.pdf

1. Power Floor.
The goal is to compete with “service type” ammunition, not light
target ammunition. Therefore, the following minimum power
floors will be in effect:
SSP - 125,000
ESP - 125,000
CDP - 165,000
ESR - 165,000
SSR - 125,000
Calculate power floor by multiplying the bullet weight by the
muzzle velocity. You will need a chronograph to verify muzzle
velocity.

[mcb]

I have never shot IDPA but I like the idea of the entire division has the same power factor. In USPSA with the major minor power factor/scoring in a division seems mostly pointless. At least the way USPSA scores things if you don't make major your not competitive. Shooting minor is a major handy cap in all but production.