Sight adjustment??

[P12]

Ok, here's the deal.

Para P12-45. I've shot several IDPA matches with it. It seemed to be a little off. Well, my son and I went to shoot our qualifier for Texas CHL today. This is the first time I've shot paper for the purpose of shot placement vs. sights.

The P12 seemed to be shooting consistantly left. Level but left. (My son was shooting the P12) So the instructor after the shoot was completed shot a couple of times and it was left. So I tried a couple of shots and it was left about 5-6 inches at 15 yards.

So, about the question. It's and older model with a crimped or pressed front sight and a dove-tail rear sight. Is this within the parameters to move the rear sight to the right to bring it in alignment? Or, is something wrong with the gun?

There seems to be quit a bit of play in the barrel-bushing-slide fit, when compared to my Springfield (PX9505L) although the Springfield has a bushingless barrel. And when looking at the muzzle of the gun the play seems to be held left when at rest. Meaning I can push it to the right but not to the left. I haven't measured it but is seems to be about .004"

Any advise will be welcome. If more info is needed then ask away.

 

[Archie]

Adjust the sight.

If the group you are firing is more or less round, the gun is basically okay. Don't worry about the bushing, as long as the group is more or less round.

If the group if oblong on a diagonal, up right to low left, you are moving your wrist and 'throwing' the rounds.

Yes, move the rear sight to the right to move impact of rounds to the right.

 

[P12]

Yes, move the rear sight to the right to move impact of rounds to the right.

Yes. But is there enough room to move the sight that far? Will this put the sight far enough to expose the male part of the dove-tail outside of the female slot?

I went ahead and measured the play, just because I wanted to know. It's .003".

My other gun(s) always pattern round, but the sight alignment was atleast within the circle. This one the pattern will be just touching the sight alignment on the right edge of the pattern.

My Spingfield shoots a good pattern with the point of aim being in the middle upper area of the pattern.

Also a note: the rear sight appears to be dead center of the slide. May be just slightly left.

So another question. If I move the sight say .001" right, how far will this move point of aim vs point of impact at 15 yards? If I can get it shooting maybe two inches left instead of 4-6" left I think I would be happy.

Also I'm a bit on the anal side. It would bug the crap out of me if the rear sight was obviously off center on the slide.

 

[wally]

Use the Trig, Luke.

Remember your similar triangles: E/D = d/R
where: E == POI error in say inches, but any consistent units work
D == target distance
d == sight displacement for correction
R == distance between front and rear sight

from your numbers:
5/(15x3x12) = d/R or move the sight d = 5*R/540 where R is you P12's sight radius.

You are in for major hassle and expense if you want to correct the error without having a slightly off center sight -- you'd need to change the barrel slide lockup to compensate. You might get lucky and get by with only fitting a new bushing, but I'd not bet the farm on it. Guessing the P12 sight radius, you probably only have to drift the sight ~0.050" Cosmetics lose out to cash everytime for me

HTH,
--wally.

 

[Bobo]

Hope this helps...

Here's the formula for sight corrections:

M=(D/R) * S

Where:

M=movement in inches needed to zero sight
D=impact deviation in inches
R=Range in inches
S=Sight Radius

Example: Firearm is hitting 6" low at 50 yards

D=6"
R=50 yd x 36" = 1800"
S=20"

6"÷1800" = .00333"
.00333 x 20" = .0666"

M = .0666" or about 1/16"

The example is for a rifle since the sight radius is so long but you get the idea. In the example you'd have to file off a 1/16" to raise the impact 6" at 50 yards.

 

[P12]

Thanks for the info.

I think I'll drift the rear sight to the right and then punch some holes.

If this makes it a good shooter I may send it to Para for a repair estimate.

Thanks again.