rise in poi question.

mole trapper

Well-Known Member
#1
Hiya folks, and seasons greetings.
Decided to get the tika t3 lite in .308 out today and put a few rounds into the targets, everything going nicely but then I thought I hate this t8 moddy, makes it so ungainly. So I popped it off and fired a couple more rounds, well after my ears stopped bleeding I noticed that my poi was nearly 2" higher than before!
The barrel had been given time to cool, it shoots lower as it gets hot anyway on this one, so I wonder whether it's the gun jumping without the barrel weight or that not having a mod on effects the poi?
Thoughts please.
Regards,
Jamie.
 

woodmaster

Well-Known Member
#2
Very simple really. The gun will rise with no weight on the end. The barrel harmonics will be altered which can cause change in impact left or right. Simple test, screw it back on and see if poi returns to original.
 

big ears

Well-Known Member
#4
To change poi 2 inches at 100 yards the angle of aim changes by 0.285degress. This small angle will be caused by the weight if the moderator on the barrel unless it's not free floating. Harmonics will alter grouping rather than poi.
BE
 

bewsher500

Well-Known Member
#5
sorry but that is not right

free floated or not your barrel is a wobbly tube, you just can't see it wobble under load (firing)

mod on my 60gr .222 loads are 1" high
mod off they are 4" right 1" high

same group different POI (NB if your group changes when mod is removed you have other issues)

same gun shoots 52gr AMax 2" lower than the 60gr SP's with or without Mod

this pattern is replicated with my 300WM 208gr load, mod on 1" high, mod off 2" high and 3" right
With a right hand twist a push up and to the right is common
all depends where on the wobble/whip cycle your barrel is when the bullet leaves it.

muzzle flip can be affected and influence POI but by far the most relevant aspect of change in POI between mod removal/refit is harmonics
 

ejg

Well-Known Member
#6
I still believe the relevant movement for POI is that of the barrel until the bullet leaves the muzzle. The muzzle will follow a line dictated by the effect of accelerating an object (rifle) if the centre of gravity (vertically) of the rifle is below the line of force (Bore) then the rifle rotates in direction of "muzzle up". More weight at the muzzle will mean less rotation upwards and lower POI. Torque will of course also influence POI.
edi
 

Southern

Well-Known Member
#7
A good illustration of how little it takes to make a difference in POI is to remove the muzzle brake or closed tuning weight from a Browning or Winchesters with the BOSS on it.

Just turning that brake or weight a few notches on the threads will dial the group size in or out.
 

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