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1337 with steel breech/lpa mim still shoots high.

Started by KBR97, March 14, 2013, 07:37:10 PM

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Crosshairs

You can order a AS2250XT front sight there a bit higher it might work.
                       Mike
http://www.crosman.com/pdf/manuals/AS2250XT%20EVP%20&%20PL.pdf
Treat people the way you want to be treated, Life will be so much better !!!

WyoMan

Quote from: Crosshairs on March 15, 2013, 09:02:57 PM
You can order a AS2250XT front sight there a bit higher it might work.
                       Mike
http://www.crosman.com/pdf/manuals/AS2250XT%20EVP%20&%20PL.pdf

+1  :-*
By my dead reckoning, 2" high in 30' would mean 1/16" increase in front sight for a 12" sight radius....
Wyo
Welcome to your life :)
Member of the Western Heretic Alliance

BDS

Wyoman is about right and... all you need to do is file a "flat" across the stock plastic sight (remove about 3/32" or the "shark fin") make a small groove in the flat (in line with barrel) and glue on a short piece of light-pipe or fiber optic tube (BTW green is brighter than the oranges and reds) Done.

Now, just raise the LPA MIM sight about 1/2 way and you will be within 1 inch of the bullseye.
Brian

Brent

#18
Quote from: WyoMan on March 15, 2013, 09:09:36 PM
+1
By my dead reckoning, 2" high in 30' would mean 1/16" increase in front sight for a 12" sight radius....

How about you figured that out for him Wyo  :)
Very Cool!  :-*

Good stuff too Brian!

quickster47 †

This might help and hope it doesn't confuse the issue.  If so, have additional notes.

Sight Radius and Perceived Blade and Notch/Aperture Widths

Definition - Sight Radius

The distance between the visible part of the front sight and the visible part of the back sight:
•   for pistol, this will be the distance between the highest part of the front sight and the rear of the back sight
•   for rifle, this will be the distance between the rear of the front sight insert and the rear surface of the back sight aperture
•   sight radius is not really applicable to Running Target or Shotgun

Definition - Perceived Blade and Notch/Aperture Widths

Effect of Sight Radius on the perceived Blade and Notch Widths for Pistol

Perceived ratio between blade width and rear sight gap.  There are three factors to consider:
1.   Distance from front sight blade to eye.
2.   Distance from rear sight to eye.
3.   Physical width dimensions of the front blade and the rear sight gap.

It should be noted that the distance from the shooter's eye to the sight combination (dependant on the shooter's stature and stance) is an important consideration:
•   For a shooter who holds the pistol closer to the eye (smaller stature and/or bent arm), the rear sight gap will appear wider in relation to the front sight blade.
•   For a shooter who holds the pistol closer to the eye, the front sight will appear wider in relation to the target.

Due to the effects of perspective, the rear sight gap will APPEAR wider in relation to the front blade – e.g. for a front sight blade width and rear sight gap both of 3mm, the APPARENT sight ratio for most shooters:
•   with a sight radius of 200mm will be around 1.25:1
•   with a sight radius of 150mm will be around 1.1:1

Effect of short sight radius
•   decreases the apparent effect of pistol misalignment as seen at the sight picture
•   decreases the apparent sight ratio

Effect of long sight radius
•   increases the apparent effect of pistol misalignment as seen at the sight picture
•   increases the apparent sight ratio

Effect of Sight Radius for Rifle

Given that there is little difference between shooters for the eye/rear sight distance, the main perceived difference from sight radius is in the relationship between the front sight and the target.

Additionally, 4" at 100 yards distance is approximately 4 minutes of angle.  You need to move the front sight of your rifle 4 minutes of angle.  Think of your rifle's sight radius as the radius of a circle.  I'll assume for this example that the radius is 25".  2 x the radius gives us a: 25"x 2 = 50" diameter.  Diameter x pi gives us the circumference: 50" x 3.14 = 157"  We'll call this our sight circumference.

Known: there are 360 degrees in a circle.  There are 60 minutes of angle in one degree.
Therefore 360 x 60 = 21,600.  There are 21,600 minutes of angle in 360 degrees.

Next, we take our sight circumference and divide by the number of minutes in a circle: 157" / 21,600 = .0073".  This dimension is the arc length for ONE minute of angle at this circumference.  Our last step is to multiply by four to get our correction.

.0073" x 4 = .0291".  Since you are drifting the front sight, you would move it in the opposite direction you want your point of impact to move.

Carl

I've never wanted something so useless in my life.
In Omnia Paratus
1947-05-19 - 2016-07-14 †

JEBert

You can drill a small hole in the top of the your front sight and stick a piece of toothpick in it.  Mark it where it goes into the hole and pull it back out.  Cut it off about 1/8'" longer than your mark.  Dip it is some black ink or color it with a sharpie, use a drop of glue on the end and tap it back into the hole in the front sight.  Shoot it and see if it is too tall, if so, cut/grind/sand/file it off until it is the correct height for your rear sight.  The hardest part will be drilling a small hole dead center of your front sight.  If you end up not using it, the little hole won't hurt anything.  If it all works, you may want to end up JB Welding it into place and sanding that smooth.
Cheers,
Jerry
NRA Life Member
USAF Veteran 1973-1977 (43151E) Sgt (E-4)


Brent

#21
Quote from: quickster47 on March 16, 2013, 01:52:27 AM
This might help and hope it doesn't confuse the issue.  If so, have additional notes.

Sight Radius and Perceived Blade and Notch/Aperture Widths

Definition - Sight Radius

The distance between the visible part of the front sight and the visible part of the back sight:
•   for pistol, this will be the distance between the highest part of the front sight and the rear of the back sight
•   for rifle, this will be the distance between the rear of the front sight insert and the rear surface of the back sight aperture
•   sight radius is not really applicable to Running Target or Shotgun

Definition - Perceived Blade and Notch/Aperture Widths

Effect of Sight Radius on the perceived Blade and Notch Widths for Pistol

Perceived ratio between blade width and rear sight gap.  There are three factors to consider:
1.   Distance from front sight blade to eye.
2.   Distance from rear sight to eye.
3.   Physical width dimensions of the front blade and the rear sight gap.

It should be noted that the distance from the shooter's eye to the sight combination (dependant on the shooter's stature and stance) is an important consideration:
•   For a shooter who holds the pistol closer to the eye (smaller stature and/or bent arm), the rear sight gap will appear wider in relation to the front sight blade.
•   For a shooter who holds the pistol closer to the eye, the front sight will appear wider in relation to the target.

Due to the effects of perspective, the rear sight gap will APPEAR wider in relation to the front blade – e.g. for a front sight blade width and rear sight gap both of 3mm, the APPARENT sight ratio for most shooters:
•   with a sight radius of 200mm will be around 1.25:1
•   with a sight radius of 150mm will be around 1.1:1

Effect of short sight radius
•   decreases the apparent effect of pistol misalignment as seen at the sight picture
•   decreases the apparent sight ratio

Effect of long sight radius
•   increases the apparent effect of pistol misalignment as seen at the sight picture
•   increases the apparent sight ratio

Effect of Sight Radius for Rifle

Given that there is little difference between shooters for the eye/rear sight distance, the main perceived difference from sight radius is in the relationship between the front sight and the target.

Additionally, 4" at 100 yards distance is approximately 4 minutes of angle.  You need to move the front sight of your rifle 4 minutes of angle.  Think of your rifle's sight radius as the radius of a circle.  I'll assume for this example that the radius is 25".  2 x the radius gives us a: 25"x 2 = 50" diameter.  Diameter x pi gives us the circumference: 50" x 3.14 = 157"  We'll call this our sight circumference.

Known: there are 360 degrees in a circle.  There are 60 minutes of angle in one degree.
Therefore 360 x 60 = 21,600.  There are 21,600 minutes of angle in 360 degrees.

Next, we take our sight circumference and divide by the number of minutes in a circle: 157" / 21,600 = .0073".  This dimension is the arc length for ONE minute of angle at this circumference.  Our last step is to multiply by four to get our correction.

.0073" x 4 = .0291".  Since you are drifting the front sight, you would move it in the opposite direction you want your point of impact to move.

Carl

"Don't want to confuse" the issue ??  :o
I am still waiting for my brain to come back  ;) ;D

Actually it is Good stuff. Had to read it more than once... but good stuff  ;) :-*

Yours too Jerry! I got that first read lol  ;)

KBR97

#22
These are all great ideas, and great advice. As of now I'm going to hold onto the parts and see if I can get something going with the front sight and adding a piece of fiber optic to it. I noticed that they come in all different thickness, does anyone have a measurement on the thickness of the front site?


Does anyone have experience with these barrel band/sights...http://www.network54.com/Forum/79574/message/1357015849/13xx+Barrel+Bands+-+Same+Day+Shipping
I'm wondering if the front sight is in fact taller than stock. I would like to eventually upgrade to one of those but not if I'll continue with the high shooting issue.
1377C
Baikal IZH 53m

breakfastchef

Quote from: KBR97 on March 16, 2013, 04:29:55 PM
Does anyone have experience with these barrel band/sights...http://www.network54.com/Forum/79574/message/1357015849/13xx+Barrel+Bands+-+Same+Day+Shipping

First rate quality! Plus, it makes taking the gun apart so much easier and faster.
Larry

7624452

I find the Chavka sighted band works well with the lpa mim and a 10" barrel.  The fiber optic was a little small for my old eyes, so I bored it out a bit, notched the blade to allow more illumination, and installed a bigger light tube.  The Blue Fork designs bands are equally good and now come with notched blade
Stranded in California.

quickster47 †

That's a great mod and one I need to do on my wife's 1377.

Carl

I've never wanted something so useless in my life.
In Omnia Paratus
1947-05-19 - 2016-07-14 †

tnpaw

I am using Mike C., front site, barrel band with a 12" barrel and it works great! Took only about 3-4 shots at 10meters and I was busting bullseye and spinning small spinners in my Basement and busting soup cans out to thirty yds! I think you will like it! .....John

chongman

Quote from: 7624452 on March 16, 2013, 09:45:10 PM
I find the Chavka sighted band works well with the lpa mim and a 10" barrel.  The fiber optic was a little small for my old eyes, so I bored it out a bit, notched the blade to allow more illumination, and installed a bigger light tube.  The Blue Fork designs bands are equally good and now come with notched blade

Dude, where can I get some of that light tube?
Long days and pleasant nights to you...

7624452

Quote from: chongman on March 17, 2013, 07:41:46 PM
Dude, where can I get some of that light tube?
The ones I used were from a box of old sights I have.  I like fiber optics, so I bought every sight that was on sale that I could find.  I believe the cheapest way to get them would be to buy some 760 front sights (760-201) I can not remember the exact price, but I believe they were less than two bucks each.
Stranded in California.

Brent

Quote from: chongman on March 17, 2013, 07:41:46 PM
Dude, where can I get some of that light tube?

I was wondering that too. Am thinking I would like to put one in my stock 1377 front sight. It needs it... especially with the stock peep sight.