hmm this isnt right?

S

savage440

Regular
Rating - 100%
2   0   0
Im trying to work up a load for my savage 10pc and something funney happened. The targets were at 100yards. First 5 shot group was just left of the bullseye at 42grains of varget)

IMG-20110517-00103.jpg


The last 5 shot group was at 44.8 grains of varget I was aiming for the top target but as you can see I was way low (the hole up top was from an extra round I had shot after I adjusted the scope.

IMG-20110517-00104.jpg


From 42grains and up the bullet started to drop isnt it suspost to go up:D
 
SouthPaw700 said:
Maybe the shooting caused the action to settle some after a while and then it started to shoot lower? I dunno.
Click to expand...

It is a new gun, including the 50 rounds shot that day it only has 100 rounds through it. It has a vortex pst 6-24ffp farrel rings, and farrel 1pc base all torqued I used locktite.
 
Hmm that is weird. Maybe your rounds were mislabeled? I'm not sure 2 grns of powder would change the velocity enough for them to drop that much even if they were mislabeled though. Just odd I says!
 
SouthPaw700 said:
Hmm that is weird. Maybe your rounds were mislabeled? I'm not sure 2 grns of powder would change the velocity enough for them to drop that much even if they were mislabeled though. Just odd I says!
Click to expand...

yup got me, I did label all the rounds on the case. Also they slowly dropped the more powder I used...:confused:
 
Measure how much volume your brass has. Your brass for the last load may have a smaller or larger volume. I notice when my brass weight is different, i can be a 1 MOA up or down.If your real OCD about things then weigh the brass and load up the rds that have the same brass weight. Sometimes when i load 42.5 grs and 44 gr there can be a difference up or down. The other thing may be that which i don't think it is because it would have happened on your first shot but your scope may have a tracking issue. The recoil of the rifle might bump your crosshairs up or down a smidge..Highly unlikely though but it can happen. I think it is the volume issue of the brass.
 
R700 said:
Measure how much volume your brass has. Your brass for the last load may have a smaller or larger volume. I notice when my brass weight is different, i can be a 1 MOA up or down.If your real OCD about things then weigh the brass and load up the rds that have the same brass weight. Sometimes when i load 42.5 grs and 44 gr there can be a difference up or down. The other thing may be that which i don't think it is because it would have happened on your first shot but your scope may have a tracking issue. The recoil of the rifle might bump your crosshairs up or down a smidge..Highly unlikely though but it can happen. I think it is the volume issue of the brass.
Click to expand...

The brass was once fired and full sized, I didnt weigh them I will do that. As for the tracking I was dialling in 100 to 500 yards and in between the day before POA was perfect, tracking was right on.
 
Thats good your scope is soild.For the first while, my Mark 4 bounced around a bit after the first shot and would be a bit off after some long range shooting when i returned it to its "0". I would tap the elevation turret with my knuckle a couple of times after every adjustment to simulate recoil. After about 50 rounds with the .308, the Mark 4 settled down and now she tracks spot on. I noticed the other day also that when i shot some 44 gr loads in some 8x fired brass it was lower than my 42.5 gr loads with the brass that was 2x fired. I threw the 8x on the scale and compared the 2x brass with each other and there was a substantial difference in weight.I guess the 8x stuff brass volume expanded allowing the powder to sit more loose inside. The 44 grain load was exactly 0.75 MOA lower than the 42.5 gr load.Hope that helps.
 
R700 said:
Thats good your scope is soild.For the first while, my Mark 4 bounced around a bit after the first shot and would be a bit off after some long range shooting when i returned it to its "0". I would tap the elevation turret with my knuckle a couple of times after every adjustment to simulate recoil. After about 50 rounds with the .308, the Mark 4 settled down and now she tracks spot on. I noticed the other day also that when i shot some 44 gr loads in some 8x fired brass it was lower than my 42.5 gr loads with the brass that was 2x fired. I threw the 8x on the scale and compared the 2x brass with each other and there was a substantial difference in weight.I guess the 8x stuff brass volume expanded allowing the powder to sit more loose inside. The 44 grain load was exactly 0.75 MOA lower than the 42.5 gr load.Hope that helps.
Click to expand...

hmm I could see .75 MOA but what about 4 MOA that is a BIG difference
 
I recently purchased a 10FCP Mcmillan and when I went to strip it down to clean the storage oil off I noticed the action screws were just over finger tight, barely any torque at all, maybe 10-15 inch/pounds max. I was quite surprised at how little torque. maybe the same guy who built mine one day, worked on yours the next.
 
Changing the amount of powder changes more than just the muzzle velocity. In fact, by increasing the powder amount by such a small amount would not make such a difference in muzzle velocity to justify the change in POI (lower). Barrel harmonics are at play here. The bullet going lower (POI) with higher speed (more powder) means that when the bullet exited the barrel (less time that with smaller powder charge), the barrel was pointing lower. The barrel oscillates when the rifle is shot and the amplitude of the oscillation and frequency change. Long skinny barrels are more sensitive to short heavy ones. So, if you are certain that all screws and bolts are tight, barrel harmonics are at play, in other words normal!
 
Miltiades said:
Changing the amount of powder changes more than just the muzzle velocity. In fact, by increasing the powder amount by such a small amount would not make such a difference in muzzle velocity to justify the change in POI (lower). Barrel harmonics are at play here. The bullet going lower (POI) with higher speed (more powder) means that when the bullet exited the barrel (less time that with smaller powder charge), the barrel was pointing lower. The barrel oscillates when the rifle is shot and the amplitude of the oscillation and frequency change. Long skinny barrels are more sensitive to short heavy ones. So, if you are certain that all screws and bolts are tight, barrel harmonics are at play, in other words normal!
Click to expand...

ok, crazy to think the barrel moves like that. The barrel is 20" heavy contour the action bolts are torqued to 25 inch pounds.
 
BigMofoFrog said:
I recently purchased a 10FCP Mcmillan and when I went to strip it down to clean the storage oil off I noticed the action screws were just over finger tight, barely any torque at all, maybe 10-15 inch/pounds max. I was quite surprised at how little torque. maybe the same guy who built mine one day, worked on yours the next.
Click to expand...

haha what did you torque them to?
 
savage440 said:
ok, crazy to think the barrel moves like that. The barrel is 20" heavy contour the action bolts are torqued to 25 inch pounds.
Click to expand...
It's not really surprising when you think about it. Let's say that with the lower powder charge the bullet exits when the barrel is at the maximum amplitude up but at the higher charge when it's a maximum down. Since the barrel is free floating and bedded at the action, the muzzle is at the "free end" and oscillates the most. There are 100 yds x 36"/yd = 3600" from your muzzle to the target. If the difference in elevation when the bullet leaves the barrel is say 1 mil (0.001") between lower and higher charges, you get a 3.6" of POI variation! A 0.001" is not that much when you think of it.
 
savage440 said:
haha what did you torque them to?
Click to expand...

On the advice of a review on snipers hide and a few other posts around on the 10FCP Mcmillan (w/o pillars) I used 40 in/lb. I haven't shot it yet due to MVMA closed and too many people shooting themselves/each other at the public Homestead- one is too many...
 
Last edited:
Miltiades said:
It's not really surprising when you think about it. Let's say that with the lower powder charge the bullet exits when the barrel is at the maximum amplitude up but at the higher charge when it's a maximum down. Since the barrel is free floating and bedded at the action, the muzzle is at the "free end" and oscillates the most. There are 100 yds x 36"/yd = 3600" from your muzzle to the target. If the difference in elevation when the bullet leaves the barrel is say 1 mil (0.001") between lower and higher charges, you get a 3.6" of POI variation! A 0.001" is not that much when you think of it.
Click to expand...

ya, that makes perfect sense. Is what happened to this rife a common occurrence during load development then?
 
You must log in or register to reply here.
Back
Top Bottom