Tuning .177 m-rod, nsa 12.5g slugs, l-r poi shifts (?)

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jdanvers

jdanvers

Member
Jul 7, 2019
951
372
South Central Upstate NY, United States
I'm playing with shooting slugs out of my little .177 m-rod ( LW barrel ). I've got a huma in it with the reg throttled up to 140 - I've no idea what the shot count might wind up being . . . lol

I'm using the 12.5 NSA's and have it shooting them at 932 which at a 25 yd zero is punching damn near hole on hole for 3 to 5 shot groups. ( perfect - take it out a little further to 35 ) Vertical is good - but all shots 'pulling' to the right. (?) I dial the windage turret and get the shots back on target and again - tight and consistent. Out of curiosity I come back to 25 - yeah - now they're all off to the left. Grrrr . . . . 

It is cold and windy - shooting into more or less of a headwind though. Besides me pulling it when I trip the trigger ( which is entirely possible ) - can you guys think of what might be causing this? Again - vertical is fine - I'm just getting these weird left / right shifts ( at other distances too - not just 35 - I took it out to 40 & 45 yards too before I bagged it - couldn't feel my fingers - to damn cold )
 
An angled headwind will cause lateral shifts that land high or low:



The other common possibility is cant error, either in how the scope was mounted or by how the gun is being held. However the difference between 25 and 35 yards would probably be too slight to discern confidently in windy conditions so you’d need to try again on a calm day to determine if that is another source of error. 
 
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Guys -- thanks. Actually I googled it because it struck me as being quite strange. Readers digest -- potential misaligned scope. First hit off of this google search. So . . . I pulled the scope and mounts and was just going to flip them / move them / etc .... when I remembered that I (actually) had a nicer set just kicking around not being used. I mounted those, leveled the scope and went back outside for a real quick test and lo & behold - much better. Still frickin' freezing and crappy out there!!! Grrrrrrrr . . . lol!


 
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@vetmx -- indeed. I took your advice on moving to closer target and dialing up/down on speed until groups started tightening up and tighten up they did BUT - way down at just over 700fps. {sigh} 10.3 pellets going at 885 out of this gun dead accurate and actually carrying more energy so . . . whats the point with these slugs? ( lol ) I pulled out the reg, jacked it up knowing I'll likely give up shot count but - again - just curious to see if I can. ( reporter: "why do you climb the mountain?" climber: "because its there" ) :) I've now got the speed and it is indeed grouping well. Hopefully the damn weather will cooperate . . .
 
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CANT-00.1615925043.jpg

 
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I think that is the wind rose for pellets, and the one for slugs with a RH twist is diferrent. Lateral displacements with slugs are the same, but wind from 7:00 thru 11:00 causes LOWER impact, and from 5:00 to1:00 causes higher. 9:00 wind displaces down and right.
Click to expand...

Thanks, you are correct. I overlooked that the OP is shooting slugs.

For bullets:


For pellets:

 
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