Mosing zeroing

[daniel craig]

In the military we zero at 25 meters because at 25 meters the trajectory of the bullet matches what the trajectory would be at 300 meters (or something like that, I'm a grunt so science is confusing ). Does anyone know enough about the ballistics of a 7.62x54R round out of a 91/30 to know what what distance would correspond to the trajectory at 300 meters? I ask because none of my local gun clubs have ranges over 75 meters.

Caveat: I usually use Priv-Partisan 182 grain full metal jacket boat tail ammo.

 

[carbine85]

Not exactly sure how to answer your question but every Mosin I shoot has to be zeroed for my range. At 100 yards they normally shoot 8-12" high and usually left. The front sights always require modification and drifted.

 

[herrwalther]

Hard to determine the zero range without knowing what ammo you plan to use.

 

[denton]

Zeroing at 25 yards might be a quick and dirty approximation, but it's not a very good way to do it.

Depending on sight height above the bore, the bullet might cross the sight line the first time at 25, 50, or even 75 yards.

Even a small error at the first crossover can translate to a big error at longer range, even if both are known.

You'll do better by shooting a single shot at 25 yards, and adjusting the sights so they are right on. Then move to 75 yards and shoot 3 shots and adjust the sights again. Then shoot 5 shots to confirm sight adjustment, and make any needed final tweaks. How much elevation you should have at 75 is something you'll have to determine with an external ballistics program... plenty of those around. It still won't be perfect, but it will be about the best you can do in the space you have available, and it will be better than you can do at 25.

Edited to add: A .308 boat tail at 2700 FPS should be about 1.6" high at 75 in order to be right on at 200 and about 28 yards. That's probably about where you want it.

 

[Palehorseman]

Not exactly sure how to answer your question but every Mosin I shoot has to be zeroed for my range. At 100 yards they normally shoot 8-12" high and usually left. The front sights always require modification and drifted.

Really? This is how my like new M91/30 refurb shot at 100 yards when brought home from Big 5, cosmo cleaned off and went to the range.

 

[Palehorseman]

Zeroing at 25 yards might be a quick and dirty approximation, but it's not a very good way to do it.

Depending on sight height above the bore, the bullet might cross the sight line the first time at 25, 50, or even 75 yards.

Even a small error at the first crossover can translate to a big error at longer range, even if both are known.

You'll do better by shooting a single shot at 25 yards, and adjusting the sights so they are right on. Then move to 75 yards and shoot 3 shots and adjust the sights again. Then shoot 5 shots to confirm sight adjustment, and make any needed final tweaks. How much elevation you should have at 75 is something you'll have to determine with an external ballistics program... plenty of those around. It still won't be perfect, but it will be about the best you can do in the space you have available, and it will be better than you can do at 25.

Edited to add: A .308 boat tail at 2700 FPS should be about 1.6" high at 75 in order to be right on at 200 and about 28 yards. That's probably about where you want it.

When I went into the army back in 1956, during basic with the M1 Garand we did a quicky pre-zero on 1,000" range, which equals out to 27.78 yards. If done correctly most rifles proved damn near dead on at 100 yards.

 

[bainter1212]

Really? This is how my like new M91/30 refurb shot at 100 yards when brought home from Big 5, cosmo cleaned off and went to the range.

Your rifle is an exception to the rule. I have 4 91/30s and they all shoot a foot high at 100 yds and that is the overwhelmingly common experience. The Russkies never zeroed for 100 yds.
You got lucky with a taller sight blade or a short rear sight.

 

[ColtPythonElite]

I only have 1 Mosin. It shoots pretty much dead on at 100. It's beer can zeroed dead on at 50.

 

[turbohugh]

My M38 was dead on at 100yards.
I read they were zero'ed at 100meters with the bayonet . The manual says using the rear sight at 300 should put u on target for 100-300 yards. If you're shooting high try adjusting your elevation ramp to 200 or 300 mark. - [at 100 yards]

 

[BCRider]

You'll need to find out or guess at a few numbers to fill in the details but to get some idea of how the sight height and bullet trajectory work to get the two cross over points look at the External Ballistics calculator at the Hornady web site.

http://www.hornady.com/ballistics-resource/ballistics-calculator

The lower the sight line to the bore axis the shorter the distance between the two cross over points will be. And the faster the bullet the longer the distance between the points. And finally the last of the generalizations is that the closer in the first cross over is set the further out the second will be.

 

[Loosenock]

What I've gathered the majority of 91/30s shoot high at 100 yards. This is because the Russian infantry was taught that their point of aim on the enemy was the belt buckle. This sight would compensate for any misjudgment on the range of the target for several hundred meters

A few that were sighted in for 100 meters for point of aim. They had a taller front sight. A point of aim mark was stamped into the barrel shank. The mark is a "K" in a circle.

I have one with the circle "K" mark, its front sight is taller. It is also an ex sniper.

Just what I've garnered, could be wrong so take it with a grain of salt.

Daniel craig you might want to check the inside of your receiver plugged screw holes and numbers over struck on the left side of the barrel shank. You might have an ex sniper.

'loose

 

[GBExpat]

Zeroing at 25 yards might be a quick and dirty approximation, but it's not a very good way to do it.

I disagree ... I think that it is an excellent approach.

I bench (iron-)sight all of my rifles at ~25yds initially. It allows me to quickly & easily solve any azimuth issues, leaving only the elevation adjustment.

I use a ballistics calculator to estimate where I need it to impact at 25yds in order for it to be very close to correct at my chosen zero range.

An added benefit to pre-sighting it at short range is that it makes it more of a sight adjustment exercise than eyetest.

 

[Dr T]

Start here.

http://www.hornady.com/

Look up the closest thing to the Privi bullet at http://www.hornady.com/bullets/rifle

Note the ballistic coefficient and use the muzzle velocity of the Privi load.

Then go to http://www.hornady.com/ballistics-resource/ballistics-calculator

Enter your data, and generate tables to your heart's content.

I have spent more time than I care to admit doing this for various loads.

I just sight things in 3 inches high at 100 yards. Work with the tables enough and you will see why .

Enjoy.