Extreme Spread/SD

[zeeman]

What is the best way to reduce your extreme spread when you have your accuracy load maximized? I get great accuracy with hunting rifles and great accuracy with my target rifles, but I cannot appear to reduce that extreme spread in velocity.

 

[Seabeeken]

2 things that helped me. Adjust neck tension and using neolube 2 inside my necks. The secret is consistent bullet release, assuming annealing, powder charge are consistent. I also tested several primers which made a difference

 

[Tiny Tim]

Consistency is key.

Having an accurate scale that is sensitive enough to basically weigh to the kernel helps. Also being at a powder charge that is forgiving (a broad charge weight "node").

Also, as @Seabeeken pointed out, consistent neck tension is also important. Annealing helps. Dry lube can help. Also playing around with your bullets interference fit can help. With some bullets, a crimp can help. Alot of guys shooting Hammer bullets will use a Lee Factory Crimp die to assist in this aspect.

Primers can also have a large effect, both by brand and type (standard vs magnum). When the primer crunch hit, many found that standard primers gave better results in cases that most would recommend a magnum primer.

When all is said and done, Consistency is typically king in reducing ES and SD.

 

[Turpentine21]

Using the chronograph during OCW workup and being in the middle of the node helps. Sometimes I'll get a really good group outside of the node (even better than the ones inside) at 100 yards but the numbers won't be there to support it.

Consistency in process. Every piece of brass, charge weight, seating depth, etc. needs to be identical or as close as possible. Primer can play a big role.

In one of my rifles, Lapua brass made all the difference. From double digits with some brass to spitting out frequent duplicates and single digits with Lapua. All with the same load.

 

[ShtrRdy]

That's very good that you have a load that gives good accuracy even though the velocity is varying. If this is for distances within 400 yards I wouldn't be too concerned.

Are you using good components? Is the brass you're using from the same lot? Bullets, powder, primers from the same lot? Brass having same number of times reloaded?

As for case neck prep, I've been using a nylon brush in-and- out of the neck two times. Basically, I'm using the fired carbon residue as the lube between the bullet and the case. Case length can have some affect in that the amount of neck brass gripping the bullet will change when the bullet starts to move.

Powder charge weight variation can have an affect.

What type of scale are you using? What type of chronograph are you using?

 

[zeeman]

Thank you guys for the great observations. I am running a six BR and a 300 WSM out to 1260 at a high-quality range. Both rifles are custom and quality components my spreads are between 10 and 17 ft./s.

 

[imyourhuckleberry]

I used to weigh each bullet as there will be minute deviations in weight and also the brass. Measure for concentricity as well as that will help with bullet release consistency. If all else fails the way you stick your tongue out may help. Use same manufacturer brass, no range brass unless it is for plinking. Develop a code or mark your brass as to how many times you have shot it. Even the same brass may not have the same capacity as the inner diameters could be smaller or larger allowing for the SD variances.

 

[jseandsje]

Outside necks turned to consisten neck wall thickness.

Bump shoulders .002 with any kind of die you like. Inexpensive full length is fine.

Trim every case every firing to the same length

Then, prior to priming, finish resize with the Lee collet neck sizing die. Size once, rotate 180 degrees, then size a final time.

Read about the Lee collet die. Tried it on 3 rifles. ES and SD incredible. So use them for every rifle now, even if Lee has to make it custom.

Another note - when you get a really good group but high ES with several rifles, shoot them at distance at least 500. Several groups. If your groups match your 100 yard groups moa, it is likely chronograph error is giving you false high ES.