Standard Deviation & Extreme Spread - What does it take?

[couesaddict]

How many shots are you taking to determine es and sd numbers and are you allowing adequate cooling between those shots? Just wondering if barrel heat may be one of your contributing factors. You may consider recording the first shot velocity for each outing and use that for your figures if it is on dedicated hunting rifles. First shot or two count the most in my book.

 

[J E Custom]

How many shots are you taking to determine es and sd numbers and are you allowing adequate cooling between those shots? Just wondering if barrel heat may be one of your contributing factors. You may consider recording the first shot velocity for each outing and use that for your figures if it is on dedicated hunting rifles. First shot or two count the most in my book.

Normally I shoot each round about 5 min. apart and take another rifle to shoot or check the zero while I am waiting. (When working up loads you cant get in a hurry)

I also clean between different loads and shoot a fouling shot to assure that each test is as consistent as the others in bore condition. This can also tell me how many rounds can be shot before fouling starts affecting accuracy. some bullets will go 7 to 10 shots before accuracy is effected and other bullets have a hard time making 5 shots without accuracy loss.

SDs and ES can change if the barrel fouls early because velocity will change.

J E CUSTOM

 

[cycloneshooter]

I did a little 7mmRemMag measuring tonight. Nosler brass and get a .313 seated bullet outside neck diameter. 0.002 neck tension would suggest a .311 bushing. Measured a FL sized brass from a standard Redding FL die and outside neck diameter was already the .311. So I already have the .002 neck tension.

So a bushing die would really on gain me concentricity and less brass working correct? Not sure thats my SD/ES issue source...

Did get some better numbers with the 280AI sunday. Got 6/21 and 8/27, lots better that the 15/45ish I have been getting. Took some time brushing inside case necks and polished expander ball.

7mmRemMag was still 18/48, but I believe I am over pressure. 68.8gr H1000, 162gr ELDX, but still showing 3075fps w 26" barrel. Brass and bolt lift not showing pressure signs, but had one shot 130fps low and one shot 230fps high. I discarded those 2 shots, and the remaining 8 still showed 18/48. Hoping a back off in charge will help the SD/ES numbers...

 

[Kansaswoodguy]

I load five rounds each powder charge with .3gr differences in each charge weight tested in a 7mm mag you migh go to .5gr charge weight jumps and look for the load that shoots with the single digit SD if I don't find one I switch powders and try again. I prefer stick powders for accuracy and low SD's although I have had good luck with Superformance which is a ball powder. I do the same thing with seating depth of the bullets looking for best groups and low SD's. I have had bullets that a given gun just didn't like and powders that where not conducive to low SD's as well.

 

[Kansaswoodguy]

I did a little looking on Hodgdens reloading center and you might just be running to hot and need to back down the load until you hit a node. Speed is great but I'll take accuracy and low SD numbers any day over speed alone. I was shooting at a 1000yds Saturday and my buddy asked if I was getting bored hitting a 12"x20" target at that range with my 6.5 Creedmore because I hadn't missed in several shots. I said yep thats why I bring my AR-15 it's more of a challenge.

 

[jrock]

I've done about everything listed in this thread other than using bushing dies. I have one for a new gun but haven't used it yet. I did find regular intervals of annealing helped but in the .243 to 7mm RM range of cases, my ES are typically around 40. My 204 is very tight on the ES in comparison. I found no difference in ES when using my Charger master or beam scale. I stopped worrying about ES for now as my downrange groups are great even if the F-1 chrony says my ES is high. Paper tells all right??? I'll keep trying new techniques and see what happens. My latest test will be using dry lube on the inside of case necks.
I went shooting with a friend once and his loads had single digit ES values one day and 30+ on another day. ???
All my testing has been done on factory guns of various makes and models.

 

[Kansaswoodguy]

I do find some powders simply don't give me low SD's in some guns. I just did a full work up using CFE 223 in one of my 223's and never did get anything acceptable to me for anything other than spray and pray ammo in that gun. In a different 223 I've gotten very good results with the same powder so my point is guns are like women you have to figure out what makes them happy and give it to them. Now it could be you have tried many powder bullet combinations and the thing will not shoot that does happen more often with factory guns than customs but any of them could be flawed. I have at least 4 guns that I would place in that category of simply being lemons. I have used David Tubbs fire lapping bullets on one of the lemons and was able to get a weak lemon juice from it so to speak. It did help with group size to the point I may keep it although I often consider re barreling it to a 280 AI or 6.5-06