629-6 Sight height question.

[AR15-SBR]

Gentleman,


I posted the question over on one of the S&W forums as well, but since it is load using my cast bullet, I thought I might get an answer here as well.

This weekend I was shooting my 629-6 4" with some of my reloads. My load was 8.8grains of Power Pistol under a cast 429421with WLP.

I was shooting at 25yards and the shots were hitting 6-8 inches high.

What I would like to know is if anyone else has had this problem? If so, did you replace the front sight or a combination of both front and rear sights to be able to zero the load. And what size sight did you use?

Any and all help would be greatly appreciated.

Thanks

AR15-SBR

[MtGun44]

Depends entirely on the gun, load and how you grip the gun. Understand that the boolit
is still in the barrel when the gun is moving in recoil. Heavier boolits hit higher because the
gun rolls up more. Tighter, more rigid grip holds the POI down, looser grip/wrist lets the
POI move up more.

You didn't state it, but I presume that the problem is that your rear sight is all the way down.

Two options, a lower rear blade or a higher front sight. I believe you front is pinned in, so easy
to change it, must replace the windage screw and nut plus rear blade, typically a lot more $.

Give me the measured distance between the tip of your front sight and the blade of the
rear and I'll tell you how much you'll have to add. Easy calculation.

If you want to calc the adjustment yourself, multiply the sight radius (dist from the rear
to the front sights - make sure you are measuring the parts you are looking at, not the
bases or something) times the error (say 7" here) and then divide by the range in
inches (25 yds times 36 inches = 900 inches).

So, assuming 5.5 inch sight radius ( guess) you have 5.5 * 7 / 900 = 0.043"

I would make the front sight a bit too tall so that you need to move the rear sight up a
touch so if you get a higher printing round (like with a 300 gr boolit which WILL print
higher on the target) you can go down some. I'd go with at least a 0.060" taller
front sight, which should require you to move the rear sight up about 0.017" to bring the
POI up to the POA. Then that 0.017 will be available in the future as about 40% of 7" or
a bit under 3" of adjustment down. If you think you want more range of adjustment
before you hit bottom, just make the new sight even a bit higher. With that sight radius (a guess,
remember) you'll get about 1.65 inches for every 0.010" change you make in the sights.

Bill

[AR15-SBR]

Thanks Bill,

I forgot to say that yes my rear sight was all the way down.

I have allready run the numbers and looks like I need to add .033 to the front. My current front sight is .280" so I need to get the .296" and put it on. That should get me in the ball park and if more adjustment is needed I can add a lower rear later.

AR15-SBR

[Shuz]

Bill is right on.
I have several 4" Smiths and I've not encountered the problem you have experienced with any of mine. I did have that problem with my 5-1/2"Ruger SBH, and a taller front sight corrected the problem.
Before you invest in a different front sight, I suggest you try changing your grip to a tighter one, or changing powder to a slower powder.

[AR15-SBR]

Shuz,

Good tips. Sometimes to find the solution to a problem you have to return to the basics and sometimes I need a reminder.;-)

My grip is already pretty tight. The technique I have used for 30+ years is squeeze until I start shaking, then relax my grip just to the point the shakes stop.(That Old Dog new trick thing) I do tend to grip handguns pretty high as well. I am one of "those guys" that get a case of "Hammer Bite" from a Glock:grin:

As to the tip on slower powder, wouldn't that increase the "dwell" time of the bullet in the barrel, allowing the barrel to rise more prior to the bullet exiting the bore? The later bullet exit would cause the bullet to impact higher on the target.

Thanks for the ideas.

AR15-SBR

[Thin Man]

The process I use to make adjustments on the S&W revolvers is to replace the rear sight blade. The process is quick, maybe 15 minutes, in the hands of an experienced S&W tech. The factory offers either solid black or black with the white outline in heights of .126" and .146" (probably what you have now) and .160". To lower your point of impact, move to a shorter (lower) rear blade. You can buy either the blade by itself, or the blade kit that also contains the windage adjustment screw and lock nut. The kit is the better buy because your original windage adjustment screw must be broken to remove the original blade. You can call Brownell's and ask to speak with a gun tech to get their part numbers and cost, they have both the individual blades and blade kits in stock. Good luck.

Thin Man