Shooters Forum banner
1 - 10 of 10 Posts

·
Banned
Joined
·
738 Posts
Discussion Starter · #1 ·
OK, I had my now functional Rossi Puma .45 Colt to the range yesterday. Tried to sight it in. Couldn't. To much front sight, or too little rear sight. I can get it to hit point of aim with the rear sight all the way up. I need a bit more.

Here's some info.
Gunsmith drilled the reciever a bit too low for correct position of rear sight. Ain't gonna ship it cross country again, and don't have the equipment to redo the holes.

Barrel band front sight was replaced with a dovetail sight.
Current one is too tall, I have one other but it is too short.

I want to sight this in at 25 yards (the only range I have) to hit 2.5" high. And I want the rear sight in the center of the available adjustment range.

What info do I need to have to find out what hight front sight to use?
The current one is .580" tall. Bottom to top, not from center of barrel.
Brownells lists Ashley front posts in .450" and .500". I need to find out which one will be the closest to what I want. I'd rather buy a new sight than altering the too tall one I have.
Might use it for something else down the road.

Can anybody help me on this?
 

·
Registered
Joined
·
1,168 Posts
So your saying the "front sight is to tall"? Is it a straight blade or bead? If it's a straight blade you could file it down-alittle at a time! :confused:
 

·
Registered
Joined
·
1,984 Posts
There is a formula for figuring this.

IM=D*K*SM divided by SR

IM= Impact Movement
D= Distance you are shooting
K= Constant, 12 for feet, 36 for yards
SM=sight movement
SR=Sight radius-this measurement must be carefully taken from the back of the rear sight to the back face of the front sight.

To figure how much change in front sight height, the formual rearranges to:

SM=IM*SR divided by D*K

If you do the figuring correctly and take exact measurements, it will work out every time. Put your rear sight where you want it, in the center, and with your front sight as is, shoot a group at a carefully measured 25 yards. How far off from where you want to me will be your IM. Take your measurements on SR and plug it in. That will tell you how much taller or shorter front sight you need from what you have now. Good luck.
 

·
Banned
Joined
·
738 Posts
Discussion Starter · #4 ·
Gunnut45/454,

I suppose I could file it down. That would be cheeper, but I want to try to figure it out first.
I like to keep tall front sights the way they are. Never know when they might come in handy.


Big Bore,

Wow! Thats some forumla. Kind of a bit harder than 2+2=?
What was that in the "new math", oh who cares.
I'll have to have help on it, I was never any good at formulas.
Wifie is the math genious here. I can shoot groups and file things till they fit, but math.................ouch.

Thanks I will give it a try.

J
 

·
Registered
Joined
·
518 Posts
All that effort and you end up having to do the work yourself, that is a shame, but I guess that just happens. I hope the formula works out for you, ought to have this permanently posted somewhere, I am sure there are always those that can use it.

Good luck, oh! One of the pieces of information I wanted to know about the Puma was about pre-drilled holes for reciever sight or scope mounting. I guess not?
 

·
Registered
Joined
·
1,168 Posts
J Miller
You also didn't say what was the load your shooting ? Light or heavy? I found out when I shoot 240 gr out of my 454 -even with the rear site all the way back it still shoots about 9" high at 50 yds? Shoot a 300 gr at the same settings and its about 2" low so when I shoot the 300gr I have the back site set at the Mid setting and it's 2" high at 50 yrds. :rolleyes: Iron sights are so fun:D
 

·
Banned
Joined
·
738 Posts
Discussion Starter · #7 ·
Ooppss, I sure didn't say what ammo I'm using. Plane old .45 Colt factory ammo. Win 255 lead. (Not the cowboy squib loads, the real stuff.)

I use factory, or an equivilent load as my basis in all my .45's. Then I can adjust the sights up or down for what ever I'm using at the moment.

I did this when I put the rear sight on my Win 94 Trapper .45 and it worked perfectly with the factory front sight. With this Rossi the original front sight hight would have been fine, except it was on the barrel band, and that was not stable.

With Big Bores formula I believe I know how high of a sight I will need. I will get this thing dialed in. It's just being a pain in the butt.

I have calculated that if I sight this rifle in to hit 2.6" high at 25 yards, that will put me either on, or very close at 100 yards. So that is my goal.

nfmMike, it sure is. I would love to have a gunsmith who can hear, listen, discuss, suggest, and then make it work. I don't know any. Especially in this area.
So yes I will do it over myself. Isn't the first time. :(
 

·
Registered
Joined
·
1,168 Posts
J Miller
It sounds like you have way to much front sight!!! try it with the shortest front sight you can get I bet it will be very close with that-if that don't work then you'll have to get a taller blade insert for the rear to compensate for the front. Now you might be beeter going with a peep setup instead. Good luck!
 

·
Banned
Joined
·
738 Posts
Discussion Starter · #9 ·
Gunnut45/454,

I just re-read my original post. Sometimes I type a sentence that somehow isn't complete. Like this one:
Gunsmith drilled the reciever a bit too low for correct position of rear sight.
I should have completed it and said that the holes were for the Williams Fool Proof peep sight I had installed.
My bad.

Anyway, yep your right, too much front sight.
Big Bore's formula is a good one and as soon as I get to the range to shoot it again with the rear sight centered, I'll be able to tell just how much too tall it is.
I have an extra front sight but it is too short. So as soon as I know, how much too tall the existing one is, I'll decide if I wan't to buy a different front sight, or custom file this one to where I wan't it.

J
 

·
Registered
Joined
·
49 Posts
J Miller said:
Gunnut45/454,

I just re-read my original post. Sometimes I type a sentence that somehow isn't complete. Like this one:
I should have completed it and said that the holes were for the Williams Fool Proof peep sight I had installed.
My bad.

Anyway, yep your right, too much front sight.
Big Bore's formula is a good one and as soon as I get to the range to shoot it again with the rear sight centered, I'll be able to tell just how much too tall it is.
I have an extra front sight but it is too short. So as soon as I know, how much too tall the existing one is, I'll decide if I wan't to buy a different front sight, or custom file this one to where I wan't it.

J
I'll bet the gunsmith put the high front sight on there so the gun owner could file it in to the load the gun liked. First you go for groups(the illusive clover leaf) to see what the gun likes. The best load. Don't worry about point of impact. Just aim at the same spot and get the load with the best group then file the front sight to hit point of aim.(coupla inches high at 25 yards like you want) You probably had a good gunsmith and don't know it. Unless you did the work to find the best load for the rifle and sent the gunsmith the loads to use to sight the rifle in the only way to get it done is to leave some adjustment for the shooter. The tall front sight is the adjustment. Find the best load and file it in by filing the front sight If you put the rear sight in the middle and can't get the groups down to the point of aim(front sight not tall enough) then lower the rear sight some. The rear sight doesn't have to be perfectly centered up and down. Actually having 1/3rd amount adjustment left under the rear peep and 2/3rds over it would be better. You'll use more "up" than down anywhooo. You need plenty of "up" to get out there a good ways with a pistol cartridge in a rifle.That's why if it were me I'd leave as less as possible "down" to the peep and give it all the "up" I could. That way I'd be able to shoot "way out" further. hee hee hee I mean what if some day you want to shoot prarie dogs or ground hogs and need to get that pistol cartridge to shoot way out there? What if you want to shoot a 300+ grain bullet out a good ways for deer? You'd need the "up" adjustment of the rear peep. Anywhooo, it's no biggie filing the front sight unless the front sight is a "bead". That's where that formula comes in handy. Front beads.
 
1 - 10 of 10 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top