Move the POI by adjusting the powder load

[khpe]

Hello,

Revolver: S&W M10

I have an average "Point Of Impact" (POI) about 3-4 inches at "12 o'clock".
The POI is a relatively close group; ~3 inches on ca 25 yards.

Ammunition: Berry's Plated 158 grain RN (no cannelure/groove),
Speer LSWC 158 grain

Power: Vihtavuori N340 4.9 grain
Vihtavuoti N330 4.6 grain


As long as this is a Fixed Sight Gun. I had to put the "Aiming Point"
down on the target. -- But I like to do my shooting practice by
aiming at the target center.

So my question is:
Is there a way to lower the POI by means of adjusting the powder load?


Best Regards,
khpe


(pardon my non-native English)

 

[Tell Sackett]

English is better than mine!

khpe,
Dwell time is one thing to consider when talking about this.

How long is the bullet in the barrel is a part of this equation. Sometimes a bullet that is moving faster hits lower than one that is moving slower because of this phenomenon. Sometimes. That is just a part of handloading that you get to experiment with.

For sure in a handgun, a lighter bullet will drop POI. The dwell time can be the same but recoil, how far the gun moves upward, is much different.

I don't have any more definitive answer than that for you. Slower powder versus faster powder, don't know. It would be an interesting test though, go for it!

Try dropping to a 125gr bullet and seeing what happens. I can almost guarantee what will take place. Try to keep the velocity the same.

Have fun.

 

[zercool]

Tell is definitely on the right track with trying different bullet weights. You may find that a 125gr drops significantly, and want to try something in between - 135, 145, etc.

Just as an example, I have a 1911A1 "GI" style - low dark fixed sights. It was designed for (and the sights are zeroed for) 230gr ball ammo (at ~830fps). It does fine with cast lead at roughly the same velocity and weight. I tried a box of 165gr HydraShoks that are listed at 1100fps or so, and those were striking nearly 18" low from 25 yards. In other words, nowhere near enough dwell time. (I traded off the rest of the Hydras.)

It'll take some tweaking and tuning, but that's part of the fun of handloading!

 

[khpe]

khpe,
Dwell time is one thing to consider when talking about this.
....
Try dropping to a 125gr bullet and seeing what happens. I can almost guarantee what will take place. Try to keep the velocity the same.

Have fun.

Tell Sackett,

Thanks for you reply. -- Yes; my Barry's 125 gr plated HP bullets hits in the target center.

Regards,
khpe

 

[jibjab]

I to find lighter bullets from a revolver have a lower POI, also the way the gun is held (firm vs limp wrist) makes a difference.

 

[GyMac]

I just did this with my Model 10 - yesterday. Ny 5 inch was hitting slightly high with a 158 grain SWC so I went to a 150 grain RNL and it hit dead center. I also tried some 125 grain RNL and they hit about 3 inches lower.
Here's the good part, though. I had along another Model 10 HB that seldom gets shot because it hits 1-1 1/2 inches to the left @ 15 yards. On a lark, I fired some 148 grain DEWC's I had on hand and they hit dead center. I went back today and confirmed this. This Model 10 shoots wadcutters @ about 850 FPS to the POA but everything else (that I've tried) to the left. I "knew" it's possible to change windage by changing bullet/load but hadn't really tried it. Now, all my Model 10's hit POA.

 

[johngalt]

I've noticed that my groups move to the right as I increase the powder charge and using the same bullets. I've noticed more left/right movement than up/down when changing the powder charge, I never understood why that happened.

 

[Tell Sackett]

I have had bullet shape play a part in POI too. 158gr LRN out of my M586 w/3.5gr Bullseye hit about 2" high and 2" right over the same gun with 158gr LSWC. Nothing else changed, just bullet shape.

I wonder if the reason John's bullets have different impact as he goes up in charge weight is because of stance or hold. With lighter loads we may be able to force the barrel down, like Jerry Mickulek or Ed McGivern. Jerry has some videos on the Smith firearm site that show his grip for different revolvers. Maybe you could try that and see if the bullets moved like before.