Berger vs sierra bt

[remcraz]

i have a question. Today i was trying some loads for my remington 700 7mm mag. I was reloading 71.5 gr. Of retumbo and was loading both 168 gr. Berger vld and 160 gr sierra bt. When i shot 3 shot groups at 80 yds. The 168 berger was 51/2 in. Lower than the 160 gr. Sierra. Was the sierra arching more at that range or was the berger just shooting flater and also is the 160 gr. Sierra a good long range bullet. I dont want to use the berger if they are dropping that much more than sierra bt. I CRONO BOTH AND THE BERGERS WERE SHOTING 2926 AND THE SIERRA WAS SHOTING 2976 Thanks ted

 

[7mmRemMag]

I am far from being an expert. But I would think the reason the why the Berger shot a little lower is because of the weight of the bullet and the speed. Its seems correct to me that the heavier bullet will shoot a little lower when trying loads. At least that has been my experience.

I dont think you would go wrong with either. I just started my long range shooting and have so far tested the sierra MK out to 575yards has been my longest kill so far on a deer. Although I have never tested the VLD berger myself, my friend has and he dropped a good buck at 300yards with his berger and his 7mmRemMag. I have read really good things on both the VLD and the SMK.

 

[remcraz]

Thanks for the reply. I didnt know if the 8 grs. Would make it drop the 5 1/2 in. No furthur than that.
Thanks again

 

[moombaskier]

I'm no expert either, but i'm positive that at the velocities you stated that there is no arc to any of those bullets in 80yds. On the contrary, I have found that heavier bullets tend to shoot higher at close range out of the same gun. Were you using the same hold or rest for each bullet, while making sure the barrel itself was not resting on something? Something's fishy! 5 1/2" at 80yds. seems like a lot of change.

 

[remcraz]

I was using the same rest and the barrel sticks out past the rest so the barrel is not touching anything. I am not an expert, it just didnt sound right to me. I didnt even remove the gun from the rest when i shot the 2 bullets

 

[Topshot]

I have noticed a similar thing with a .458 Win Mag. In that case a 500 grain bullet shot higher than a 350 grain bullet which is the opposite to what I would have expected.

I put it down to barrel whip. I think it depends on where the end of the barrel is pointing on bullet exit as to where the bullets land. It may be a case of one bullet exiting at the top of the barrel flex and the other exiting at the bottom of the barrel flex.

Try a different powder and primer combination in the 160 grain load to the 168 grain load and see what happens.

 

[MontanaRifleman]

I...I put it down to barrel whip. I think it depends on where the end of the barrel is pointing on bullet exit as to where the bullets land. It may be a case of one bullet exiting at the top of the barrel flex and the other exiting at the bottom of the barrel flex.

That is exactley what I think it is. When working up loads in my rifle, I will often see a 2 - 3 inch difference in POI when using the same bullet and only a grin difference in load. The difference is usually vertical or almost verticle.

That small differnce in velocity would not account for the difference in "drop" and heavier bullets dont drop any quicker than light bullets. If you hold a 300 gr bullet side by side with a 100 gr bullet and drop them at the same time, both will hit the ground at the same time.

It's almost certinly barrel harmonics IMO

 

[remcraz]

I am using the remington 700 boone and crockett gun. The barrel is a magnum contour that they fluted making it more like a sporter barrel which would probably cause that. Thanks a lot that makes a lot of sense

 

[RBrowning]

I have seen that heavier bullets almost always hit higher, but I don't think it is a result of the barrel flexing as much as it the shooter flexing. I first observed it shooting a 44 mag pistol and the heavier bullets hit higher than the lighter by several inches at 100 yards. The heavier bullet is slower getting going and stays in the barrel longer and it leaves the barrel after you have been rocked back more by the recoil.

Try laying a sandbag over the barrel and see if it changes the POI. 5 1/2" is a lot more than I would have expected thou. Try it again at a longer distance and see if one of the bullets isn't flying wild. You may have something else going on, like under sized bullets. I know it is rare, but it has happened. By trying to make it repeat you may also find a scope loose or something.

Best of luck and let us know what you find.

 

[Tyler Kemp]

That much difference is certainly not one bullet shooting flatter than another.

Two factors would come in here, barrel whip and recoil. Your barrel moving will have a reasonably small effect at 80 yards, but more recoil and a very slightly slower bullet could have the gun recoiling just a bit more "up", shifting your groups that way.

 

[remcraz]

I will try the sand bag this weekend i am out of town now. I will try shooting at longer ranges also. When i had the crono out something funny happened. When i shot the sierra 160 bullet through it it went through without anything happening but when i shot the 168 berger it blew off all the back post and the white cover off. I saw that it had a lot more muzzle blast would that have anything to do with it?
Thanks ted

 

[barm]

I am guessing your barrel is not free floated. I have seen crazy points of impact changes on barrels with pressure points with different bullets. You will still get a point of impact change with a free floated barrel, but it will not be that extreme.

 

[davewilson]

maybe the bullet hit the back post holding the white cover and made it fly a bit off course?

 

[long450]

This seems extreme to me for 80 yards, but i would bet on barrel whip. It sounds like a light long barrel problem. I would not worry about it much. If either of them shoot in the same hole, use it and adjust the scope.

I have a Remington 700 ADL 308 that shoots 150 bullets dead on at 100yards while 165's were 2" high and 180's were 4" high and right about 1 2/3".