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  #31  
Old 09-09-2019, 03:41 PM
majspud majspud is offline
 
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Carbine functions properly now. Used a new box of Remington ammo. There were two misfeeds due to a bent magazine...switched to another and no problems. Unfortunately the rear sight moves when shot. It also needed to be set at 200 to hit at 100 yards, but otherwise fine.

t
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  #32  
Old 09-09-2019, 11:16 PM
DougS DougS is offline
 
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Quote:
Originally Posted by majspud View Post
Carbine functions properly now. Used a new box of Remington ammo. There were two misfeeds due to a bent magazine...switched to another and no problems. Unfortunately the rear sight moves when shot. It also needed to be set at 200 to hit at 100 yards, but otherwise fine.

t
Either the front sight blade is too tall, or the sights were set for point of aim, not for a typical target, where you hold at 6 o'clock to hit a bullseye 4 or more inches above the point of aim.

Last edited by DougS; 09-09-2019 at 11:18 PM.
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  #33  
Old 09-10-2019, 09:37 AM
majspud majspud is offline
 
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The front sight of the Underwood is taller than the one in my Winchester, which is a tack driver. So I need to find the right front sight. The Underwood sight is unmarked, the Winchester is "EU". How do I determine what to get?

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Last edited by majspud; 09-10-2019 at 09:41 AM.
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  #34  
Old 09-10-2019, 10:54 AM
DougS DougS is offline
 
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Quote:
Originally Posted by majspud View Post
The front sight of the Underwood is taller than the one in my Winchester, which is a tack driver. So I need to find the right front sight. The Underwood sight is unmarked, the Winchester is "EU". How do I determine what to get?

t
The M1 Carbine front sight was designed to be filed for targeting. So then, you could file the current one, or just get a new one and not mess with possibly ruining the original.
There are folks on the Forum that can tell you the formula for determining how much needs to come off the sight for the point of impact change at a given distance. Its based on the front to rear sight radius - geometry of a triangle etc.
I have a Inland where I've switched out the sight, but I don't have it filed down to the right point just yet. Of course, the filing amount is dependent on ammunition used, so you're locked in somewhat. I imagine the Remington ammo hit higher on the target than Aquila did.
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  #35  
Old 09-10-2019, 11:12 AM
majspud majspud is offline
 
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Never had a front sight I've had to mess with; this is my 7th carbine over the years.
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  #36  
Old 09-10-2019, 11:56 AM
DougS DougS is offline
 
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http://forums.thecmp.org/showthread....+carbine+sight
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  #37  
Old 09-10-2019, 07:11 PM
.Steve. .Steve. is offline
 
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From the sticky above:

The Why plus the short version in Bold.

Front Sight Reduction To Zero The Rear Sight Slider

The question frequently arises along the lines of: "My carbine shoots too low on its sight settings. I want to cut a gnat's whisker off my carbine front sight to make it shoot to zero at 200 yards set on the 200 mark instead of the 300. How do I do it?"

There are very accurate ways to calculate and measure the front sight height reduction/cuttage needed. Setting up the calculator is simple. All you have to do is construct the formula and solve it. It amounts too little more than turning around the “How much do I have to raise my rear sight” equation.


The bullet movement on the target paper desired in inches
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Goes over the range in inches


(That would be 7200 inches at 200 yards and 3600 inches at 100 yards.)

After making those two entries, they equal =


The unknown front sight cuttage needed
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over the sight radius (being 21.5" with a carbine set on 200)


Solve the equation and you have the exact amount to cut off.


Easier yet is knowing that for each 0.01" or each 1/100"

the change is:

At 200 yards, 0.01" = 3.35" of impact change on the target.

At 100 yards, 0.01" = 1.67" of impact change on the target.


If you divide those inches of change into the amount of change needed, you know how many 0.01” or 1/100” to reduce the front sight height by. (Oh, well, I guess I also told you the easy way to do it.)


How to measure and shorten the front sight is fairly simple. Take a solid square end flat sliver of really hard wood. Stand it up against the vertical face of the front sight. Press it against the sight and tip the top to the muzzle. That should leave a distinct impression in the wood showing the top of the face of the front sight. Repeat that wood impression in 8 or 10 slivers. Trust me, you will need them as you check repeatedly. (Packages of frozen popsicle sticks are perfect.)

File the front sight down keeping it level and tapered to the front. This is best done by taking a 3x5" index card, cutting to the center, cutting out a barrel size circle, putting the cutout on the barrel by the band, and then looking at the front sight from the muzzle end against the white card. Most fellows would unload the carbine first, lock the action open, and perhaps put a chamber flag into the chamber before looking down the muzzle line. Positioning in a cleaning vise so the carbine holds still helps. Use Magic Marker frequently to show where you are cutting. Focus on the top of the post for levelness. Lightly touch the sides of the sight and the vertical face to eliminate burrs before looking.

Reuse (make a second impression) a wood sliver and note the change in the impression line made. You will quickly see two lines. You cannot reuse a sliver a second time to check because the lines blur and the slot made becomes rounded rather than two crisp lines.

Set your micrometer jaws on the change desired and compare the impression lines to the gap between the micrometer jaws. When the gap on the stick matches the micrometer gap, that is your desired change.

Two things.

(1) Do this with/for ammo you will have a lot of. Putting back the metal on the front sight is a lot of work if you decide to change ammo or your case of LCX456 runs out and you start using Pusan489.

(2) Shoot a bunch of 10 shot groups before you decide the changes needed. Only when the group centers are in the same place with your shooting should you even consider changing the front sight.

As a quick screening device about where a carbine will shoot in relation to its slider settings at that slider set distance, look at the front sight, but from the side, left to right or right to left. Note that there are holes in the two front sight wings. Using the situation where a shooter wants a point of aim/point of impact sight adjustment style, the following would apply and is very often quite correct is assessing the sights.

If in looking, you line up the top of the holes/circles straight across with each other and then see that the top of the front sight post is materially above the top of the holes, most likely it is a new front sight that has never been cut down to zero that carbine. As such it is too tall and will cause the carbine to shoot low. It can be shortened.

If in looking, you see the top of the front sight post is about even with the top of the holes, then it has been cut down some. That location means it will probably shoot close to the distances set on the slider. Nothing to do but shoot it and see how it goes.

If in looking, you see the top of the front sight post is well under the top of the holes, again it has been cut down, but probably too much. Too short of a front sight will make it shoot high at the distance set on the slider.

That is a lot harder problem to solve. The US Army and the Italians welded up the top of too low front sights during rebuilds and then machined them off to look as an original new sight would have looked. It is sort of hard to do unless you intend to refinish the metal. Welding and grinding is messy and obvious unless done before a refinish. The resulting sights often had what appears to be metal missing from the shooter side of the front sight post. Rather than be perfectly square, there would be little holes. I had never heard of this until recently.

In the event a shooter is looking for a lollipop point of aim/point of impact is higher style of adjustment, then the front sight in each example would be ever so slightly lower.

If you have a carbine with a front sight cut too low so that USGI spec ammo shoots too high no matter what you do, don't give up completely or start hammering on the front sight in frustration. Some of the commercial ammo are 100fps+ slower than USGI and shoot lower. Find some commercial stuff that is slow or slower and it may well drop into the zero you want. Be sure of your impact points with good 10 round groups before you do anything. (3 shot groups are a joke and exist only because magazine gun writers can't keep more than three shots close together with most rifles, 5 shot groups need a bunch of groups for statistical analysis, and 10 shot groups provide good data very quickly.)

Last edited by .Steve.; 09-10-2019 at 07:13 PM.
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