M Rosslee
Well-Known Member
.308 Winchester
Remington Model 700 VLS
26" heavy varmint profile
1:12" twist ratio
Nodal velocity with 155gr Lapua Scenar is 2730fps, offering a 0.2MOA outcome at 220 yards. That is on 42gr S335. I am 2gr under the prescribed Somchem maximum... As I near 44gr S335 propellant on the same seating depth, the group spreads and opens up to around 1 / 1.2MOA at 220 yards... with slight pressure signs (sticky bolt).
The problem is with a 155gr bullet in 30 cal at 2750fps, the Ballistic coefficient is 0.46, and external factors influence the bullet quite sternly out at 800 yards which is my typical end shooting distance for a specific target shooting discipline.
The science dictates the higher the velocity, the less flight time, the less time the bullet is exposed to external manipulative forces between muzzle exit and target impact.
An observed outcome is also that higher ballistic coefficient bullets with heavier weights for calibre perform better and are affected less by wind at longer distances (although their velocity might be the same or slower than lighter bullets with lower ballistic coefficients launched at higher muzzle velocities).
Now- my question:
Should I shift to a heavier match bullet, 168gr VLD Target bullets to be more precise, does the fact that the 155gr Lapua Scenars don't like high velocity in my rifle have any influence on the predicted outcome of the velocity node for the heavier bullets I intend to shoot?
The bullet is stable in terms of its gyroscopic stability (1.8 SG) if I punch in a target velocity of 2750fps for the 168gr... Which a 26" barrel should easily attain..
I understand that 2750fps is where most rifles perform ideally with a 26" barrel with 1:12" twist ratio- but this is faster than the nodal velocity of the lighter 155gr bullet in my rifle...
So what are the chances that my rifle will shoot the 168gr at a higher or similar velocity and nodalise there?
I test loading the ogive 0.3mm from the lands uniformly over all test loads... Then I incrementally increase the charge from minimum to maximum observing the grouping outcomes over 5 shot groups and recording their velocity (test distance is 200m).
Look forward to some answers.gun)gun)gun)gun)
Remington Model 700 VLS
26" heavy varmint profile
1:12" twist ratio
Nodal velocity with 155gr Lapua Scenar is 2730fps, offering a 0.2MOA outcome at 220 yards. That is on 42gr S335. I am 2gr under the prescribed Somchem maximum... As I near 44gr S335 propellant on the same seating depth, the group spreads and opens up to around 1 / 1.2MOA at 220 yards... with slight pressure signs (sticky bolt).
The problem is with a 155gr bullet in 30 cal at 2750fps, the Ballistic coefficient is 0.46, and external factors influence the bullet quite sternly out at 800 yards which is my typical end shooting distance for a specific target shooting discipline.
The science dictates the higher the velocity, the less flight time, the less time the bullet is exposed to external manipulative forces between muzzle exit and target impact.
An observed outcome is also that higher ballistic coefficient bullets with heavier weights for calibre perform better and are affected less by wind at longer distances (although their velocity might be the same or slower than lighter bullets with lower ballistic coefficients launched at higher muzzle velocities).
Now- my question:
Should I shift to a heavier match bullet, 168gr VLD Target bullets to be more precise, does the fact that the 155gr Lapua Scenars don't like high velocity in my rifle have any influence on the predicted outcome of the velocity node for the heavier bullets I intend to shoot?
The bullet is stable in terms of its gyroscopic stability (1.8 SG) if I punch in a target velocity of 2750fps for the 168gr... Which a 26" barrel should easily attain..
I understand that 2750fps is where most rifles perform ideally with a 26" barrel with 1:12" twist ratio- but this is faster than the nodal velocity of the lighter 155gr bullet in my rifle...
So what are the chances that my rifle will shoot the 168gr at a higher or similar velocity and nodalise there?
I test loading the ogive 0.3mm from the lands uniformly over all test loads... Then I incrementally increase the charge from minimum to maximum observing the grouping outcomes over 5 shot groups and recording their velocity (test distance is 200m).
Look forward to some answers.gun)gun)gun)gun)
