Confused POA/POI Differences

[Silphidae 33]

Loaded up some 200gr LSWC for my 5" X-Tac for an indoor pistol league I'm doing, found a very accurate load with 4.7gr Bullseye coming out at 840fps (see target at 25 yards).  Problem is the poi is about 4" high at 25 yards, when I load up 230gr LRN (4.1gr Bullseye @ 72fps) the poi comes down significantly.  

 

This seems to go against the internet information I've read which typically states a heavier and slower bullet stays in the barrel longer than a light fast bullet, therefore the heavier bullet typically shoots higher poi because it experienced more vertical lift due to recoil while in the barrel.

 

Any insight why this discrepancy is so large, it remains relatively consistent from 10 - 25yds out?  I know I can get a new front sight or adjust my sight picture, I'm looking for reasons why the poi different from what I expected.  Only using LSWC for this one application and will only shoot 500 rounds, all other shooting done with the 230gr loads.  

 

 

[Sixtytwo327 14]

Good video by Jerry Miculek; it's about porting, but watch for the high-speed video showing recoil. And because it's JM.

 

http://youtu.be/Q6dWDFcoFFs?list=PLFWh-_7kw52pt0SC7ih7XhRAgK_Kzc8LQ

 

Takeaway is, the bullet clears the barrel before the slide begins to cycle. Recoil has no effect on POI.

 

In regards to velocity, I've read that in some applications, longer barrels and slower loads (for example, a .38 special out of a 6" barrel at target velocities of 700fps) provide more of a chance for the user to create error, flinching or heeling or in some way moving the gun.

 

It's also possible, at 25 yards, you're unconsciously looking up off the front sight and looking at the target the instant before the shot breaks, which will raise your POI.

 

From loading lots of different lead loads, I've found that different lead bullets shoot to different POI and that's just the way it is. If that target is 25 yards, that's a nice group. I'd adjust the rear sight (if they're adjustable) and write down your adjustment, and call it a day.

[T Bill 649]

Is power factor a consideration here?  If yes, try adjusting your taper crimp or bullet seating depth a bit. If not and this is for accuracy drop the power charge to where the slide just functions reliably.  There are too many variables with reloads and bullet types to accurately say why the POI is higher than you expected.