Bullet Weight and POI

[John Ralston]

All things being equal, hotter ammo prints lower - it gets out of the barrel sooner.

Many years ago Ross Seyfried wrote an article about big bore revolvers, and showed a target comparing the impact points of different weight bullets. The heavier bullets impacted higher due to the initial recoil impulse being higher with the heavier bullets. I would assume it is the same with a pistol.

[TGS]

I've always noticed lighter ammo to print higher. This was especially evident yesterday when I tried shooting 3x5's at 7 yards and forgot I was using 115gr instead of my usual 147gr flat points, which I usually use for such accuracy drills to mimic my carry load. All of my shots ended up high.

It's going faster, and is lighter.......it will drop less than slower and/or heavier ammo. That's how I thought it worked.....

[JV_]

I briefly experimented with the 95g 9mm loads, from Federal IIRC. It had a low POI.

[GJM]

I've always noticed lighter ammo to print higher. This was especially evident yesterday when I tried shooting 3x5's at 7 yards and forgot I was using 115gr instead of my usual 147gr flat points, which I usually use for such accuracy drills to mimic my carry load. All of my shots ended up high.

It's going faster, and is lighter.......it will drop less than slower and/or heavier ammo. That's how I thought it worked.....

With my multiple M&P 9's, the 147 grain ammo hits higher than 115 grain ammo.

[TGS]

With my multiple M&P 9's, the 147 grain ammo hits higher than 115 grain ammo.

How does the 147gr ammo play into the early unlocking issue on the M&P?

ETA: I'm going to hit the range tomorrow and test the ammo. This isn't matching up with my experience, so my brain is going into overload right now.

I'm reading other forums about how the bullet leaves the barrel as it's already recoiling upward, but that sounds pretty hokey to me. If a bullet were leaving the barrel as it's recoiling, I would think the shot dispersion would also suffer.....we're not machine rests, the gun will always move a little left or little right during recoil. In human hands, it's impossible for the gun to recoil completely vertically with no yaw or roll like a machine rest.

[JBP55]

With the same type ammunition in the same pistol the heavier round will impact higher than the lighter round.

[willypete]

I've noticed heavier ammo to impact higher at short ranges (25 yards and under) with revolvers. 158 gr vs. 125 gr in .357 magnum and 180 gr vs. 240 gr vs. 300 grain in .44 magnum. I always figured this to be due to slower acceleration and lower ultimate speed. Heavier bullet takes longer to exit barrel, thus has a longer time to affect muzzle rise.

I need to try this at longer ranges and see how it pans out...

Conversely, faster loads of the same weight will impact higher than slower loads. I suppose that shoots my theory down. Ah well, there's my anecdotal evidence for the day!

[Al T.]

John, there's an X-ray floating around the net showing a 1911 with the bullet exiting the bore before the 1911 starts the unlocking process, so we know that the recoil impulse has already started. That would effect where the bore axis is pointing when the bullet exits the muzzle.

Another factor is velocity. Two bullets same weight (.38 Special 125 gr. vrs. .357 Mag 125 gr.) should have the .357 hitting lower as the bullet exits the muzzle sooner.

Two bullets, different weights (.45 ACP 185 gr. and 230 gr. Match loads, both at ~800 FPS) but same velocity, should have the heavier bullet hitting higher due to increased recoil.

:D And then you have sheer random crap that happens with firearms, like my 1911 that hates any bullet over 215 grains (10 + inch groups at 15 yards, sub 2 inch on demand at 25y with 200 gr. target loads) or my .30-06 that shoots most any weight bullet (150 to 180 manufacturer irrelevant) into a four inch composite group at 100y.

Kind of like dating, sometimes the weird ones are more fun. :p

[John Ralston]

Two bullets, different weights (.45 ACP 185 gr. and 230 gr. Match loads, both at ~800 FPS) but same velocity, should have the heavier bullet hitting higher due to increased recoil.

I do believe that sums up the basis for Seyfried's conclusions.