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Explanation of why POI is lower than POA when projectile is moving faster?


Quiet Burp

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This might help:
 

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All other factors equal, if you speed up a bullet it will have a lower POI than a slower one of equal weight. That’s because it’s in the barrel for a shorter period of time, hence less muzzle flip.

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And the forces and recoil reactions make a difference in how a revolver shoots, compared to a rifle. 

 

The first thing folks often think about is how bullet drop affects long range rifle shots.   There, more velocity results in higher impact AT DISTANCE because gravity works on the bullet for quite a while in rifle shooting.

 

In short range handgun shooting, gravity is not the major influence (force) on point of impact, the direction the barrel is pointed when the bullet leaves the barrel is the major influence. 

 

good luck, GJ

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7 minutes ago, Quiet Burp said:

So I should try to lower my powder charge to bring the POI up?

 

I'm printing really low using my vaqueros over just 7-10 yards (hand held aiming well).

 

Find a load that you really like, ideally one that also groups well, then file down your front sight while at the range.  Remove a tiny bit, test a few rounds, repeat until you get it where you want it.

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First, let a good pistol shooter test POI as well.  If he shoots well and on target at 10 yards, then it's you.

 

good luck, GJ

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19 minutes ago, Doc Shapiro said:

 

Find a load that you really like, ideally one that also groups well, then file down your front sight while at the range.  Remove a tiny bit, test a few rounds, repeat until you get it where you want it.

 

If I had a lifetime supply of one pistol powder that's what I'd do. Unfortunately pistol powder is rarer than rocking horse droppings here presently (and no one knows when it will improve) so I have a mixed lot of powders to hopefully get me through the powder drought, but not sure if changing powder it would be hard to get back POI?

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Not to be a pain, no one can sight in your pistol or rifle but you.  Doesn't matter how good they are in Re: how you shoot. We all are different in many ways.  Find a good load, work off a rest and also free standing.  When you get a good group low  several times, you can decide to play with loads and bullet weights or file.  I filed the sights on my first pair of Rugers. It worked well.  High is a different issue, and pretty much the only option is ammunition or a taller front sight, and there are slip over and glue or solder accessories available.

Here is an old thread.  

 

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20 minutes ago, Garrison Joe, SASS #60708 said:

First, let a good pistol shooter test POI as well.  If he shoots well and on target at 10 yards, then it's you.

 

good luck, GJ

 

Not boasting, I'm an 'A' grade ISSF (Olympic) pistol shooter at 25yds and 'B' Grade at 50yds

 

I'm squeezing off beautiful groups at very short distances and they are all low....really low.

 

 

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46 minutes ago, Quiet Burp said:

 

If I had a lifetime supply of one pistol powder that's what I'd do. Unfortunately pistol powder is rarer than rocking horse droppings here presently (and no one knows when it will improve) so I have a mixed lot of powders to hopefully get me through the powder drought, but not sure if changing powder it would be hard to get back POI?


I would expect that if velocity stayed the same, POI would stay the same. 

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16 minutes ago, Doc Shapiro said:


I would expect that if velocity stayed the same, POI would stay the same. 

 

Another question, what's a good FPS for a 125gn pill out of a a 5 1/2" barrel for SAS?

 

Using 3.5gn's of an Aussie powder AP50N I'm averaging around 1000fps out of my rifle (unfortunately the chrono gave up the ghost before I could put pistol rounds over it).

 

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9 minutes ago, Quiet Burp said:

 

Another question, what's a good FPS for a 125gn pill out of a a 5 1/2" barrel for SAS?

 

Using 3.5gn's of an Aussie powder AP50N I'm averaging around 1000fps out of my rifle (unfortunately the chrono gave up the ghost before I could put pistol rounds over it).

 

 

Badlands Bud and I did a crap ton of research on this topic quite some time ago -  825fps for us.  There are a lot of reasons for this, which have been previously posted.  Your mileage may vary, but it's a solid starting place.  My ability to search the Wire ain't so good.  I'm sure someone out there can link to what I previously posted. 

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15 minutes ago, Doc Shapiro said:

 

Badlands Bud and I did a crap ton of research on this topic quite some time ago -  825fps for us.  There are a lot of reasons for this, which have been previously posted.  Your mileage may vary, but it's a solid starting place.  My ability to search the Wire ain't so good.  I'm sure someone out there can link to what I previously posted. 

 

Appreciate your time.

 

Roughly (I mean real rough) until I get my hands on a working chrono what would one expect to lose in FPS from the difference between a rifle barrel and a pistol barrel?

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My Marlin 1895 shoots ALL ammo (factory and reloads) through it at or very near my POA EXCEPT Hornady Lever Evolution ammo which shoots consistently 12" low. :blink:

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I usually expect about 250 FPS difference between a revolver and a 20" rifle using same load and having same barrel groove diameter.

 

good luck, GJ

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