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I'm using a 91/30 PU sniper repro. Shooting PPU 182gr FMJ, if I zero dead on at 300 yards, how low will the impact be at 600 yards? Alternately, how high would my bullet impact need to be at 300 yards to be close at 600 with no further adjustment? The scope is currently zeroed at 100 yard. Thanks!
Terry
Dead-reckoning correction for an M91/30 sniper.
The following pragmatic method should enable you to be instantly in the black at 600 meters/yards. After that, it's up to you.
The method works for BPCRs with a trajectory that is very much more curved than for any rifle using smokeless powder, so you should have no problems. Since I rarely have a chance to practice at 300 meters, I have used this method at 50 + 100 meters to make corrections for upcoming 300 yard competitions. Tripling the range from 100 to 300 with a BPCR is much trickier than doubling the range from 300 to 600 with a smokeless cartridge, and if your first shot is not on the target at all, you are lost!
1) If you have already got the rifle zeroed for 300 meters/yards – do not alter the setting.
2) Shoot a target at 100 meters/yards.
3) Measure the height of the POI above the center of the black. Call this difference D300.
4) If the POI is so high that it is not on the target, tack an aiming point onto the target, below the normal black, and use that.
This height - which you already know is the correction for raising the range from 100 to 300 – can be used to calculate the correction required to go from 300 to 600. The drop at 600 will be about 5x the drop at 300, i.e. 5 x D300. Of course, you should ideally know the drop at 100, but this would be something in the range 2-4”, in other words of a similar magnitude to the height of the scope sight line above the barrel center line - which is why it is possible that the POI actually goes higher when you change from say 50 to 100 yards. So the method is KISS - simply forget the 100 yards drop and you should still be in the black.
Since the rifle is already set for the 300 yards drop D300, you only need to raise the POI by (5 x D300 – 1 x D300) = 4 x D300, while using the 100 yard target. This will usually take the POI above the target frame, so the solution is to tack a second black on the target frame 4 x D300 below the normal target black (or the aiming point you used in 4), aim at this, and correct the scope until the shots land in the same position as for 3) above.
The whole operation actually takes less time than I needed to write this contribution!
:wave:
Patrick
I may be missing something here but if your rifle is zeroed at 100 yards, you loosen and adjust your scope elevation ring at 100 yards and lock it down. Then all you have to do is crank it to either 300 yards or 600 yards and it should be dead on without having to guess anything. The scope should have settings from 100-800 yards.
I believe original period ammunition would be 149 gr bullets. The 182gr in the first post is going to have a different trajectory.Quote:
Originally Posted by Aragorn243
Tua sela Tonanti
Ordnancebob
ordnancebob is correct. The Russian scopes were set to for the use of light ball ammo only. You very well may have a problem trying to sight it in at distance with the heavy ball.
Quote:
Originally Posted by Aragorn243
I think you are. The scope correction will only beif you are using the same ammunition as that used for the original scope calibration. Or at least ammo with the same trajectory. It does not have to be the same bullet weight, just (more or less) the same trajectory.Quote:
Originally Posted by Aragorn243
But you are insamuch correct in thatand that should put the shots well in the black. But not automatically dead center.Quote:
Originally Posted by Aragorn243
:wave:
Patrick
Not only is the trajectory different between 182 gr and 149 gr bullets.
The scope is also calibrated in meters. If you are shooting in yards scope adjustments will tend to make you shoot high.
Every 100 meters on the scope will be 109 yards. Hence plus 54 yds if shooting at 600yds with a 600 meters setting on the scope.
Sua Tela Tonanti
Ordnancebob
I had my Russki snipers out this last sunday. 91/30 PE scope in long slide rail, 91/30 PU Scope and a 1940 dated SVT 40 PU Scope
Yards, meters, arshin, whatever... does it group?
I appreciate the help guys! I was trying to get ready for the vintage sniper match at the Eastern CMP Games held last weekend. Unfortunately I didn't make it because my shooting partner's grandma died 2 days before the match. I did find a range out of town that went out to 500 yards and got it on at 300. I then calculated how high at 500 the poi should be for 600 zero and got it close that way. Was planning to final adjust during the sighter period at the match. Got plenty of time to work on it now until next years match! Now I'll also have time to work up an accuracy load for it too. My biggest disappointment is that I missed my chance to shoot alongside R. Lee Ermey!
Terry