Need Help 1911 sight specs

[hindu.hendrickson]

Ok here goes-- My first Colt ever what a headache; this is how great guns at cheap prices are born !!
Colt 1991A1 Compact front sight falls off (Jul 2010) customer service has been no help can't give me sight hieghts or any specs; still to this day.
Order a front trijicon sight from a "popular" custom shop (won't drop names) it comes and is the wrong one (narrow tennon) send it back, recieve the wide tennon and run down to my local (40 miles away) gunsmith and get it staked in.
Here is where the fun begins; point of impact 4" low at 10 yds.
Figure no big deal; just order matching trijicon rear sight, right? Wrong !!
Call trijicon where they inform me my big name custom shops parts department sent me the wrong front sight, I now have a staked in Gov't front sight, oh well it is in now. But it gets better, their customer service department (not meaning to name drop here, have their sights on about 3 other guns) can't tell me which rear I need either as they don't know any of their sight hieghts.
So here is what i have
Rear is a factory Colt, I measure at 3/16 to the center of the dot and 1/4 overall height.
Front is a Trijicon CA-01F I measure it at 1/8 to the center of the dot and 3/16 overall.
Any body got a clue what i need for a rear sight to turn this paperweight back into a shooter? Thanks

 

[Jim Watson]

Ten yards is pretty close to be calculating sight corrections from but 4" low error at 10 yards calls for a rear sight about .067" taller. Or a front sight that much shorter, but that tends to reduce them to a nubbin hard to aim with.

 

[hindu.hendrickson]

Jim,
Thanks for the reply.
Wanted to keep the front sight since it is a brand new $40 investment, and just change the rear sight, what i have been told is mine came with a high profile rear sight. Any drop in suggestions to get me where i need to be. Last resort i will drop it off at the smith and get Novak's front and rear installed.

 

[Jim Watson]

A King's Hardball might be tall enough.
The King's website is still up but I don't know if they are really doing business, they were not at one time. Worth a call.
http://www.kingsgunworks.com/newcatalog/page02.html

 

[hindu.hendrickson]

Well might be taller, but if I have to replace might look for something a little different than a standard factory style. Anybody have any experience with a Novak adjustable?

 

[1911Tuner]

It's hard to predict which combination of heights are needed to zero the gun because of the design. The barrel tilts up at the rear when it's in battery, and therefore isn't parallel with the slide axis. The problem is that each gun is different, and will have a different degree of tilt...depending on several factors. The best we can do with fixed elevation sights is get close.

Sometimes we get lucky, and sometimes we don't. When we don't, about all we can do is cherry-pick or mix'n'match front and rear sights until we hit the right combination...or we find a front or rear sight that's a tick too tall, and file it to zero.

To do a rough estimate on how much difference is required...use the ratio of sight radius to distance for the required zero. This is simplified for demonstration and won't be exact.

Assuming a 6-inch sight radius...distance between front and rear sights...25 yards is 150 times the sight radius...a 150:1 ratio. Each .001 inch change in sight height changes the theoretical point of impact .150 inch...or a little more than 1/8th inch. In a direct proportion, .010 inch will change the POI 1.5 inches. Of course, bullet drop is also part of the equation, but 150:1 will get you very close. After that, it's a matter of removing a few thousandths with a file to fine-tune.

The POA/POI adjustment for an ordnance-spec pistol is 2 inches high at 25 yards with standard hardball. That theoretically zeroes the gun at 50 yards. Depending on how accurate the gun is, some shots will be lower and some will be higher...but the center of the group is what determines the zero.

Hope this helps.

 

[BBBBill]

Novak and Heinie both make replacement sights for shorter-than-gov't-model 1911s. The rear sights are .050" taller than the ones made for the gov't models to compensate for the angular difference in barrel lockup between the short guns and the gov't. Short guns lock up at a steeper angle. With your 4" at 10 yards error, that would get you back to about 1" low. A front sight about .015" shorter would take care of that last inch.

 

[1911Tuner]

Yes...and don't forget to factor in the shorter sight radius with short pistols. taking the example that I gave as 150:1 and assuming a 3-inch radius...the ratio would be a 300:1 at 25 yards...and for every .001 inch change in the sight height, you'd realize a .300 inch change in POI.

 

[hindu.hendrickson]

Thanks to JW, 1911Tuner, & BBBBill for the insight, think I have a grasp on the ratio changing your POI, now if we could get the manufacturers to list their heights instead of just there dovetail dimensions or someone who answers the phone with the same knowledge we would be in business. Guess I will go with an adjustable, problem solved.

 

[Jolly Rogers]

They should list all of the dimensions of the sights. I have gone to sight websites and they list heights and blade widths but no information on what dovetail they fit.
And there are only a couple of manufactureres that have front sights to fit Springfields dovetail which ain't a Novak cut.
Joe