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Old November 16, 2017, 02:07 PM   #1
rjinga
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Experimenting with BSZ at 25 yds

After reading conflicting posts and seeing conflicting graphs on the internet (25 yds = 200 yds; 25 m = 200 m; 25 yds = 200 m; 25 m = 200 yds; BSZ position = 200 m; BSZ position = 300 m) I decided to (try to) zero in the BSZ position at 25 yds and then see what happens as I shoot at different distances. The rifle is a Chinese Type 56 SKS; the ammunition is Golden Tiger. Unless noted, I was shooting off of a bench rest (big rubber notched block and airsoft BB tube sock) with the iron sights set on the BSZ position.

This is my “even a blind squirrel” photo. Believe it or not, that is two bullet holes at 25 yds:


This is a scaled “Dog” target at 25 yds. Eight rounds; 40 out of 40 possible points, with six rounds in the “V” circle and a seventh touching it:


Next I put a BC-27 target at 100 yds (max distance at the public range):

I can’t actually see the “X” at that distance, but I thought I was aiming in its general location. The first 10 rounds are shown in the photo on the left. After seeing how high and to the right the shots were, I fired another 10 rounds (photo on the right) while focusing on holding a little lower, and as centered as possible. I was able to tighten up the width from the first group to the second group by just over 1”; and, if you discount the one low shot as a flyer, then I cut 3” off of the height. I’m still shooting to the right; however, in a combat situation, those nine shots would all be in the heart/lung area.

I ended up by placing one target at approximately 29 yds and another at approximately 33 yds:

Then I stood and fired snap-shots offhand at both targets (raise rifle, fire at 1st target, transition and fire at 2nd target, pause, repeat):


Once I get back to the gun club, I'll see how the BSZ position does at 200, 300, and maybe even 400 yds.
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Old November 16, 2017, 03:24 PM   #2
Bartholomew Roberts
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Typically for AR15s, the near/far zeros are: 25/300 and 50/200. If you are shooting E silhouettes, a 25yd zero gives you maximum point blank range. If, however, you are shooting at smaller targets (holding center on a 12” tall target for example), you can miss them entirely at 100-150 due to the height of the arc on the 25/300 zero.

As for yards vs. meters, under 300m it rarely makes any practical difference in 5.56. 100m=109yds, so if you have a 300yd zero and are shooting at 300m (327 yards), you’ll only be an inch low with a short, squat 55gr out of a 16” barrel.

With 7.62x39, you have to pay more attention to those differences as the trajectory is less flat and less height over bore usually. I couldn’t speak to near/far zeros for the SKS but I imagine they are close to the above.
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Old November 17, 2017, 12:04 AM   #3
tangolima
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Looks like the near zero is 50 yards, and the far zero is 200 yards. It can point and shoot and hit 6" diameter circle around the poa from 0 to 250 yards. It is not for hitting a squirrel's head, but a man size target.

-TL

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Old November 18, 2017, 12:22 AM   #4
rjinga
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More Experimentation

After doing more reading on the internet, I headed back out to the public range this afternoon, shortly before it closed at sunset. A poster on another forum wrote that zeroing at a distance of 41 meters, with the rear sight on the 100 meter position, will put you back on zero at 100 meters. So, I decided that I'd give it a try.

I went out to the 50 yd marker and then walked back six strides to get pretty close to 41 meters. Here's my forth and final target as I shot and adjusted the elevation:


Next I went out to the 100 yd marker, and then paced off nine more strides to get close to 100 meters:


After seeing the shot placement at 100 meters (high and to the right again), I came home and ordered a sight adjustment tool, so that I can finally adjust the windage (and fine tune the elevation better than I can currently with my small needle-nose pliers). I also ordered another pack of green silhouette targets (pay for shipping or order something else you need and get the shipping for free). Next time, I think I'm going to attach a blank sheet of 11x8.5 copy paper to the chest area of the silhouette, to give myself something more defined to aim at, at 100 meters.
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Old November 25, 2017, 12:14 AM   #5
rjinga
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I got my sight adjustment tool on the Wednesday before Thanksgiving, so I took a quick trip to the public range that day to do some adjusting (no photos). In anticipation of getting the tool, I'd sprayed the front sight with PB Blaster three different times starting Monday night and then just let it soak in.

I bought the adjustment tool primarily for the windage adjustment; however, it was so much easier to adjust the elevation with the tool instead of my small needle-nose pliers. [Note to self: take bent pliers to Sears for replacement under the lifetime warranty.] I ended up adjusting the windage at least one full (180 degree) turn with the tool also.

I went back to the public range today (day after Thanksgiving) and set some 12" diameter targets at 100 meters. I shot off of a bench rest with the rear sight set on the 100m position. At that distance the target is just a little bit wider than the front post. I was using a 6:00 hold, so I tried to touch the bottom of the target with the top of the front post. I say "tried to" since I've got 57 yo eyes looking through progressive lenses at a black front post and a black target.

I fired five rounds each at the three targets:


Then I checked, patched, and fire five more at each target:


And then I checked again, patched, and fired 10 rounds each at each target:


Next up will be a trip to the gun club to see how these adjustment translate at 100, 200, 300 and 400 yds.
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Old November 25, 2017, 12:53 AM   #6
rjinga
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And, just in case you're were curious, here are the targets with the mean radius for each one. The mean radius is the method of measurement of the dispersion of shot-groups used by the US Military for accuracy testing of ammunition. It provides a more useful analysis of the consistency of ammunition and rifle accuracy. Mean radius as defined in Hatcher's Notebook “is the average distance of all the shots from the center of the group. It is usually about one third the group diameter (extreme spread).”





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Old November 27, 2017, 09:17 AM   #7
DMK
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Quote:
Once I get back to the gun club, I'll see how the BSZ position does at 200, 300, and maybe even 400 yds.
Looking forward to this to prove the point.

My problem with the 25yd zero on all rifles (and the 50y BSZ on AR15s) is the higher probability of error. Just being off 1/4" to 1/2" at 25 yards can lead to being several inches off at 100yds or 200yds and being feet off at 400+yds.

IMO, these close in zeros are only useful for getting on paper for verification at least at 100y with longer range being better.

I realize some folks may only have access to a pistol range and if that's all they have then so be it, but try it get to the longer range for verification if it's at all possible.
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