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how to reduce velocity extreme spread?

 
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  #8  
Old 06-11-2008, 01:26 PM
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Quote:
Originally Posted by boomtube View Post
Okay. Sounds like you are doing everything right.

An ES of 50 fps at that speed sounds quite good to me. It's hard to get below that and it really won't make any noticable difference in the field if you do. If the accuracy is good I'd smile and use it!
Whoa. I disagree. For long range shooting or hunting, an ES of 50 would not be acceptable to me. You would be asking for big time vertical dispersion at distance!

I like to get my SD down into the single digits and the ES around 20 fps or less. Not only will this be a better long range combination, these numbers will be a result of a load that is burning efficiently and will be much more dependable day in and day out.
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  #9  
Old 06-11-2008, 04:01 PM
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Roger what GG said!

I've had good luck with heavy for bore bullets using US-869. That is, 300 SMK in a 338 RUM @27xx FPS ES = 1 for 6 shots.

However, same load w/265 gr bullets wasn't that good. Thus the heavy for bore consideration.
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  #10  
Old 06-11-2008, 06:55 PM
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Thanks guys for the tips. I will try another 0.5 grains of this powder to see if accuracy is better and if the velocity spread is lower. If not maybe I will try H1000 or RL25. Brian.
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  #11  
Old 06-11-2008, 08:53 PM
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the suggestion for powder was RL22, not 25. if you can't get a 300WM to shoot with RL22 or 4831, it probably won't shoot with anything.

after 4 firings, it would probably help to anneal the necks.
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Last edited by davewilson; 06-11-2008 at 08:56 PM.
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  #12  
Old 06-11-2008, 09:31 PM
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I have had good results with RL22 in this barrel and the previous barrel but when using 180 grain bullets. I just figured I would use the slower burning powders for the heavier 200 grain bullet, thinking that I could possibly get a bit more velocity at a lower pressure. Is that not proper thinking? Is there something wrong with using RL25 with the 200 grain bullets?

By the way this rifle is my pack up the mountains big game rifle. As such it has a sporter style Rimrock synthetic stock and a Leupold VX3 3.5-10 scope with the Boone and Crocket reticle. It weighs 9.3#. It is not a heavy bench gun. I can quite consistently get sub 2" groups (3 shot groups) at 250 yards which is the distance at which I zero my main crosshair.

The load mentioned earlier of using Ramshot Magnum to get an average velocity of 2960 gave me a 1.58" and a 1.41" group at 250 yards. That is about all I can do with this gun. I have occasionally gotten smaller groups but this is pretty standard. Still I would be happy to reduce my extreme velocity spread. I very seriously doubt that I would take a shot beyond 600 yards but would feel more confident if the high and low velocities were closer to the average.

I have never annealed a case neck. Can someone recommend a product for me to use? I think I remember hearing that Hornady is making one that works pretty simply. Thanks, Brian.
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  #13  
Old 06-11-2008, 10:20 PM
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I use 72grs of RL22 in my 300 win mag with a 180gr Nosler accubond and it is grouping right at an inch at 200yds seated .010 off the rifling.
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  #14  
Old 06-12-2008, 07:39 AM
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goodgroup: "Whoa. I disagree. For long range shooting or hunting, an ES of 50 would not be acceptable to me. You would be asking for big time vertical dispersion at distance!"

No argument on the value of an ES of 2 or less but as a percentage of the speed, 50 isn't bad. That varation, taken alone, won't prevent many hits at any range, IMHO.

Consider a 7 Mag shooting a .534 Hornady SPBT at a specific speed ( ie, not an average) of 3,100 fps and zeroed at 500 yards. That's a pretty fair long range load. Hornady's #4 book of charts says it will drop 17.1" at 600 yards. Then, at 3,000 fps (100 fps slower) the same bullet expects to drop 18.4" at 600 yards, a full 1.3" difference.

An ES of half that velocity difference (50 fps) would only cut the drop to something like 7/8"? If even that estimation is off by a half inch, it's certainly not enough to cause a miss on a 600 yd. p' dog! And all that calculating assumes zero wind and mirage to make aiming harder and assumes each bullet is cutting one hole groups out to infinity, none of which is likely in my world!

I think an accurate, reliable load with an ES of 50, varying only 25 fps from the middle speed, is a pretty good load in the real world.

Not perfect, but pretty good.

Last edited by boomtube; 06-13-2008 at 02:04 PM.
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