Sight Zero

[WineMan]

This may be a silly question but at what distance would a Colt 1911 Series 70 in 38 Super (fixed sights) be sighted in at? The factory ammo ballistics show a 25 yard zero. At 50 feet I have to hold at the lower right corner of an 8.5x11 size target to get in the bull.

Thanks,

Wineman

[KCSO]

Then it isn't sighted in for yo at all. I would pick up a higher rear sight from GPC and try that. They have one that is styled after the military sight only higher.

But before yo do that, how are the groups? If you are not shooting round groups in the 3-4" range you may be flinching as that low is afwul low for a factory boo boo. Have someone else shoot the gun and see how and where they are printing. If that IS where it hits you are going to end up with a rear sight twice as tall as the front (assuming factory sights) and drifted was off to the left.

Now there is a secret to getting a factory 38 Super to shoot a group. Seat the bullet out so that when the round chambers the bullet is pressed tight to the rifling. Otherwise the half a$$ed chamber will let the round slip under the 1/2 rim o the case and groups will be awfull. Seated like that a good 124 gr. cast bullet will hold into 2-3" easy at 25 yards.

[10-x]

Sell it and get a .45 ACP:mrgreen:

[44man]

It depends on the load with fixed sights. Try all the other brands until you find one that hits closer to center.

[Morgan Astorbilt]

Raise the elevation by increasing the powder charge:mrgreen:
Morgan

[WineMan]

As always great input! We were shooting 130 gr LFP from the Bullshop over 4.5 gr of Bullseye. Two of us had the same experience and even from a rest there was a trend to shoot up and to the left over the course of 100 rounds. My friend shoots a Colt Series 80 Commander in 45 ACP and it/he is more accurate at the same distance.

This one was made between 1976 and 1980 and has the rim seating barrel so the tip on seating to the lands makes great sense. A new barrel that headspaces on the case mouth is on the wish list.

The rear sight is drifted slightly off center to the left and I assumed this was done at the factory (it was shot maybe 50 rounds before I got it as an heirloom). I am going to move it right and see if that helps the left issues.

Thanks for all the information.

Wineman

[scrapcan]

Make sure I have this right. Your Point of Impact (POI) is higher than the Point of Aim (POA)?

When adjusting windage (left or right) move the rear sight int he direction that you want POI to go.

Here is a little formula from Brownells for determining the sight height

Correcting Sight Height
If your rifle or pistol is shooting high or low, there is a formula you can use to determine what the correct height for your sight should be.

Terms
Amount of Error: Measure in inches the distance from the bullseye to your shot.
Sight Radius: Distance in inches from the front sight to the rear sight. *
Distance to Target: The distance in inches from your shooting position to the target.

Note: Be sure that your rear sight is at its mid-point before you shoot.

Formula

Amount of Error X Sight Radius = Sight Correction Needed
Distance to Target

If you are shooting low, you would replace your front sight with a lower sight, and conversely, if you were shooting high, then you would replace your front sight with a higher sight. Add or subtract the number of thousandths needed to the actual height of your sight and you will have the correct height of the replacement sight.

Example
At 100 yards, your shot is 6" low and the distance between your front and rear sight is 19.5".

6 X 19.5 = .0325
3600

Since you are shooting low, you would need to lower your front sight by .032".

You can find their calculator and the above a tthe following address

http://www.brownells.com/aspx/NS/GunTech/sight.aspx

Or as stated, you can use your loads to adjust POI relative to POA.

[Lloyd Smale]

what he said!
It depends on the load with fixed sights. Try all the other brands until you find one that hits closer to center.

[Morgan Astorbilt]

Lower the elevation by decreasing the powder charge:mrgreen:
Morgan

[NSP64]

That load should give you 1000fps. Shooting 4" high at 50 ft will place the zero around 150 yrds. Try some diferent loads(boolit weights/powders) to get something closer to what you want. I would set the rear site back close to center and try again.:drinks:

[WineMan]

Good Stuff!

I have some testing loads set up and I drifted the rear sight to the right (I remember FORS: front opposite, rear same) to center it.

I was reading Hatcher's Notebook and in his chapter on recoil, he has a cool chart that shows an increase in POI with increasing bullet weight. His explanation was that handguns were set up to account for the slight upward movement when fired and the POI was purposely low to account for this. A heavier bullet makes the gun "jump" more and the POI goes up.

Just about everything I have read said to get a new barrel that headspaces on the case mouth if you want better than "dark alley" accuracy with this round. Well I have always liked a challenge, and anything that goes "bang" is pretty fun.

Wineman

[leftiye]

Increasing boolit weight will cause a gun to shoot higher. Generally, lighter or faster rounds will shoot lower.

[Echo]

Dick Shockey chambered his .38 Super conversions so the case headspaced on the mouth - he cut the chamber short for that reason, and his guns did shoot.

On the other hand, do as KCSO says, and seat the boolit out so that it contacts the lands, and do as several have said, and try a lighter, faster boolit that will print lower. Maybe a Lee 105 gr swc sized down to .356?

[WineMan]

I am low now with the 130 grain RNFP so my next try will be with something heavier to see if I can raise the POI.

Thanks for all of the great interest!

Wineman

[WineMan]

Well here is the latest update:

158 gr SWC @ 0.358 seated to the lands (almost out of tolerance of the Magazine)

5.5 gr Unique

One type of brass (WW)

Drifted rear sight to right (more centered)

Tighter grip, concentrate on front sight more, and a better stance

10 yards

Out of 20 shots, eight in the bull and 11 at one o'clock just outside the bull (slight "healing"?)one at six o'clock, low; bad form

I have always had a FTE (empty stovepipes) only one in this round, but still unacceptable. The extractor had no tension on an empty case so a slight tweak gave it more grip.

More testing (= fun)

Wineman