Tuning Pellet vs slug point of impact differences?

[ddnzf]

Fx maverick .25 600mm 104bar PW 4
JSB king heavy 33.95 5 shots 870 fps
NSA 29 gr 5 shots 910fps.

I aimed for the red shown on the picture for 5 shots each at 86 yards.

Can anyone help me understand how the groups can end up like that basically 2.5 inches to the left/right of each other. Are the slugs spiraling?

 

[Solo1]

i would say its either harmonics or possibly barrel index or a combination of the 2

 

[starlingassn]

every projectile is going to have a different point of impact.

just goes with the territory.

 

[JimD]

I think your expectation is not appropriate. I would not expect the POI to be the same at 86 yards with any two projectiles out of any gun. I just resighted my P35-22 today for a different head size of the same H&N Barracuda Match pellet it likes. .551s and .552s are both very accurate in this gun but don't hit at the same point of impact at 25 yards. The .551s impact about 1/4 right and 1/4 above the .552s. To be fair, my P35 in 177 does shoot to the same point of impact with both Barracuda Power (copper plated) and Barracuda Match pellets. So sometimes you get lucky but I expect POI to change when I change projectiles.

 

[TDK]

i would say its either harmonics or possibly barrel index or a combination of the 2

Yep. Definitely start by indexing your barrel if you haven't. Might help, might not, but you never know.

 

[jdh2550]

I’ve only had experience with slugs in 3 different guns. In each case slugs (one particular slug manufacturer) always hits to the right of where my pellets do. It’s about a 4 inch difference at 100 yards for me. I just adjust the scope to my correct windage, mark the scope tape, and off I go.

 

[Scotchmo]

Any wind at all while shooting? Even a light breeze can move your groups and require windage adjustment, more so for “pellets”.

 

[Seeker]

Fx maverick .25 600mm 104bar PW 4
JSB king heavy 33.95 5 shots 870 fps
NSA 29 gr 5 shots 910fps.

I aimed for the red shown on the picture for 5 shots each at 86 yards.

Can anyone help me understand how the groups can end up like that basically 2.5 inches to the left/right of each other. Are the slugs spiraling?

View attachment 273722

Which is which?

 

[Revoman]

"Which is which?"
I would think that the low (left) are pellets as they do not leave clean holes. The ones on the right are slugs, they do leave clean holes.
mike

 

[ddnzf]

Below the point of aim are the 5 pellet shots. To the right of point of aim are the 5 slug shots. Very slight wind if any. I shot the 5 slugs first then right away shot 5 pellets using a single shot loader.

I have continued to test today at different speeds and such. Slugs seem to be at least a few inches to the right of pellet. There is of course vertical separation as well, I’m just focusing on horizontal separation.

 

[JungleShooter]

You discovered an inconvenient truth there — but it's true: The different POI with different projectiles is to be expected, also with different power settings, even with/or/without silencer.

For every projectile, power settings, and configuration I plan to use in a given rifle—scope combo I simply enter a new "rifle" into Strelok Pro ballistic calculator on my cell.
When I want to make a switch, I simply switch the rifle in Strelok and it tells me how much I need to dial or hold off.
The switch takes all of 6 (six) seconds.... (I timed it. ).


Of you need more info how to do it, PM me.

Matthias

 

[killahog]

The slugs are not leaving the barrel at the same time the pellets are, the muzzle is in a different orientation with respect to the harmonic node. Try increasing the velocity and you might be able to bring the groups together . Think ladder test as it relates to fine tuning a powder burner.

 

[bigHUN]

I read it a while back from the BR guys, I think Centercut was who explained it the best. Lets hope if he could chime in.
In meantime just a rough idea is that the air motion (and direction from which coming) effects the two - the slug or the pellet - differently.
For this same reason I gave up endless re-tunning and chose one projectile for a given gun and dedicate it for specific distance.

 

[Vetmx]

If your pellets and slugs have the same POI, then that’s worth starting a topic about. What you’re experiencing is completely normal.