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bullet ogive measuring for mile shooting

 
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  #1  
Old 11-30-2004, 06:16 PM
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bullet ogive measuring for mile shooting

I am currently trying to hit my steel 15" gong at 1 mile with my 6.5-.284, and I am shooting Berger 140 vld bullets at just a touch over 3100 fps. I noticed that even though the Bergers are great bullets, the ogive length varies on them about .002-.004 on bullets of the same lot, and when I've been shooting them, I have to segregate them into rows of same length or I get 5 to 10 feet of vertical displacement at 1760 yards! Has anyone else ever run into this???
It doesn't really seem to make all that much difference at 1000 yards, but you guys shooting a little farther with the .338 might be able to help me. I'm just curious.
thanks! -goodgrouper

[ 11-30-2004: Message edited by: goodgrouper ]
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Old 11-30-2004, 09:33 PM
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Re: bullet ogive measuring for mile shooting

G Grouper,

I haven't shot the mile but am setting up to do it soon with my 338 Edge. I have shot 1560 yards. I shoot the 300 gr SMK @ 2900+. The biggest biggest group problem I have seen is accountable to velocity spreads. 20 FPS from one shot to another should change your vertical impact bout 70 inches or so. The ogive could be accountable for a certain ammount of velocity spread. My 338 EDGE/300 SMK/H1000) load runs an extreame velocity spread of 8 or 10 fps if I do my part loading. I can consistantly hit 14-16" rock I shoot at, at 1560 yards in good conditions. I would take a hard look at my ES and try to get it trimmed down to single digits even if you have to drop a little velocity.

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Old 12-01-2004, 12:44 AM
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Re: bullet ogive measuring for mile shooting

goodgrouper,The measurement of base to ogive at the land dia position is not going to give you the same shaped bullets as a given..I spend a lot of time on qualifing bullets in many areas for 1000yd bench ,i do so because i believe it's worth it especially when u see the targets come back..JR..Jeff Rogers

[ 12-01-2004: Message edited by: Jeff Rogers ]
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Old 12-01-2004, 06:31 AM
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Re: bullet ogive measuring for mile shooting

I shot some sighters at 1 mile in Iowa with my 6.5/284 with 140g Amax bullets in my HG and had the same problem as you are describing but with bullets that had the same baring surface length. Shoot good at 1k 7.???" groop but were all over the place at 1 mile. Try putting a paper target at 1 mile and see if the bullets are starting to key hole. I had a bullet that would shoot 10 on paper at 1000 yards and all the bullets were key holed. [img]images/icons/mad.gif[/img]
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Old 12-01-2004, 07:49 AM
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Re: bullet ogive measuring for mile shooting

goodgrouper, Dan Lilja has a whole series of articles as well as computer programs that should help you with this. BTW it is all free.
http://www.riflebarrels.com/articles...ballistics.htm
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Old 12-01-2004, 07:53 AM
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Re: bullet ogive measuring for mile shooting

Not all but some bullet/twist/velocity combo's do some wild and sometimes entertaining things when they go sunsonic. This is probably happening to the guys with the 6.5-284 at about 1600 yards. I have seen in paticular 308's that shot like a million bucks at 800 and not worth a crap at 1000 (some not all), most go subsonic before 1000. I always thought the 260 was a better round for distance shooting for this reason over the 308. Have you guys ever tried shooting at 1400 or so to see what is happening with the groups. If it is a vertical problem I would still look at the extreame velocity spreads. If the group just opens up or you are getting keyholes look hard a velocity vs distances. I believe this to be one of the huge advantages of the big 338's. My 338 EDGE depending on conditions goes subsonic around 2000 to 2100 yards. Good luck. Lots of people talk about mile shooting, few ever try it.
Shawn
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  #7  
Old 12-01-2004, 08:57 AM
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Re: bullet ogive measuring for mile shooting

I would also agree that your probably having some stability problems as your bullet drops out of supersonic velocities.

This can be hell on accuracy for most bullets in fact.

If your loads are shooting well at 1000 yards but not at 1760, you are having something happen to the bullets stability somewhere in between.

IF you have access to ground where you can do this, I would recommend shooting at 1250 and 1500 to get an idea where your problem is happening at.

While the 6.5mm is a hell of a 1000 yard caliber, there is a reason the big dogs are used at the mile mark.

I have not tested my Kahn out at extreme range yet but the ballistic models say it will stay supersonic at my altitude out to 2250-2300 yards with the 300 gr Wildcat ULD.

I have shot the 50 BMG out to 2300 yards usingthe 750 gr A-Max loaded to 2750 fps and it has performed well. We have a rock that we are trying to turn into gravel and once dialed in and the wind is doped correctly, the big 50 will hammer this rock which is about 7 feet in diameter with suprizing regularity if a good pilot is onthe rifle.

My personal feelings are that shooting groups at 1000 yards is very difficult to do with the proper equipment, for evey 100 yards past that, I would say the difficulty of holding consistant, tight groups multiplies by 10!!

Many feel that since they are shooting good groups at 1000 yards, stretching it another 760 yards should not be that big of a deal. Us that have tried it know the opposite is the trueth.

There is nothing like dropping a piece of lead on target at a mile though. Nice thing about the 50 when that big 750 gr A-Max lands, the dust cloud is extremely easy to see, sometimes with the naked eye and the report drifting back over that mile and a quarter is the most beautiful sound. Hearing a solid smack at 2300 yards come back to you makes you realize the power of the 50.

The 338's are nearly identical in ballistic Performance withthe larger 338's and the ULD class bullets but nothing compared to the terminal performance of the BMG, well, nothing I have shoulder fired yet!!! [img]images/icons/grin.gif[/img]

If you want to play with the mile range, you may need a little more bullet and a little more horsepower for consistant results.

Shawns comments on velocity spreads are right on the money. I though my initial 50 BMG loads had a good E.S. with 25 fps. At +2000 yards, you would miss a house. After some extensive tinkering I was able to get spreads in the single digits and this greatly controled group spreads. Even a 10 fps spread will result in a dramatic difference in impact location. This is what makes extreme range shooting so difficult.

We are basically unable to produce ammo that is perfectly consistant enough for in velocity for really tight groups. I would say 80% of my group variation at 2300 yards is vertical unless I am having a bad day or its breezy. Get a little shaky if I don't eat breakfast before a day of shooting, not a pretty sight at 2300 yards.

IF we could get velocity spreads into the threoretical 0 range, this would greatly reduce group sizes. This is impossible though so we do the best we can.

Good Shooting!!

Kirby Allen(50)
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