9mm 115g really have more kick than 124g ?

[FrankD]

I'm comparing two 9mm ammunition weights, 115g and 124g. When I shoot the 115g it seems to have more of a snap to it as compared to the 124g. After thinking about it, I'm wondering if it really does, or is it in my head and ears because of their sound. I group with both of them fine and just being analytical. Theres not much of a difference (40 ft/sec) between their velocities. I don't think that's much. The 115g moves at 1,160 ft/sec and the 124g at 1,120 ft/sec. Speed of sound at 75dgrees is 1,135 ft/sec. The 115g has a loud crack sound, I presume traveling faster than sound, and the 124g quiter traveling below speed of sound (sub-sonic). Do you think the 115g are really physically snappier, or it it all in my head and ears.?

 

[Gordon Fink]

It’s all about the muzzle energy. Take Winchester USA loadings, for example.

115 gr. = 362 ft-lbs.
124 gr. = 358 ft-lbs.
147 gr. = 320 ft-lbs.

In this case, the 115-gr. bullet will produce the strongest recoil impulse. Other loadings by other manufacturers can and do vary, of course.

~G. Fink

 

[R.H. Lee]

Funny you should ask. I was shooting both for comparison last weekend, didn't notice any difference in felt recoil. The 124 gr, however, impacted slightly higher on the target.

 

[P95Carry]

I tested these rounds thru my R9 amongst other ammo - and found recoil not to be different enough to notice a whole lot but - see the wetpack pics below - it does seem the 115's have a slight edge re effective expansion energy - and so a bit less penetration. The 124's penetrated a bit further but expansion that bit less.

From my own chrono figures tho I seem to recall the energy differential between the two was minimal - without checking I got around 285 calculated ME ft lbs from both, out of the 2.9" barrel.

 

[Dave R]

I have not shot much 124gr. 9mm, but I shot some 115gr. and 147gr back-to-back, and it seemed to me that the 147gr had noticeably more recoil.

 

[Gordon Fink]

Barrel length is another factor. I believe the manufacturers’ published ballistics data are usually based on four-inch or five-inch test barrels. A shorter barrel will allow less powder to burn before the bullet exits the muzzle.

~G. Fink

 

[armoredman]

The final peice of needed reloading equipment...the chronograph...then I could tell you what my speed is. I will say my reloaded 115s definately have much more oomph than my reloaded 124, but those are powder puff loads, 3.7gr AA#2. I am amazed it makes it all the way to the end of the range....
The factory 115 have lotsa boom.

 

[Ankeny]

IPSC shooters are constantly in search of the softest shooting loads. In IPSC, there is a thing called power factor which is really momentum. The muzzel velocity of the bullet multiplied by the weight yields the power factor.

As a general rule, when comparing two loads of equal power factor, the heavier bullet will be softer or exihibit more of a roll or push. The lighter bullet will have a sharper impulse or more of a snap. For a really soft 9mm load, try a heavy bullet like a 147, load it long if the shooting platform will allow, over a fast powder.