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When loading, what is an acceptable +/- in grains?

Mr Wick

I think you all know me by now.

Shooting .308 Lapua Brass with a 39 grain load of Accurate 2495.

Every load can't be specifically 39 grains. 98% are. But there is that 2% that aren't.

What is an acceptable plus or minus in grains. Is shooting 39.2 grain or 38.8 grain round going to be a significant difference in accuracy?

Thanks.
 
Test and see.

Or take your average velocity at 38 and 40 gr (assuming 40 is a safe load)? Now divide the difference of those velocities by ten and you have the average effect of .2 gr variance. Plug that velocity variance into your ballistics program, what vertical is that?

Whether that’s acceptable depends on your application. Whatever that is because it’s not been provided.
 
If I'm up against the brink of maximum loads, I'm gonna weigh every charge to the best capabilities of my scale.

That being said, I almost NEVER load to max. If I'm seeing high pressure signs, I'll find a different combination of components that keep me in my "comfort zone".

For my "comfort zone" loading, +/- .2 grains is pretty acceptable. That also happens to be about the accuracy level of my charges thrown with my Uniflow powder measure.

This is just me though, -- I'm not a competition shooter. I'm not a 1000 yd shooter. I'm not trying to put max horsepower into my elk killing rifle.

One way I decrease the powder variable is to use powders that throw more accurately with my measure, and those powders are out there. Maybe I'm just a mediocre, or luke warm kind of guy, but I'm pretty happy with my results, and I know that of all the variables, a tenth or two of grain weight in my powder charge isn't even close to being THE most important one. jd
 
I assume you are asking this question because you are charging your cases directly via some mechanical device such as a powder measure without weighing each charge.

If you're weighing each charge, then the variation is fixed by the accuracy and repeatability of your scale otherwise the question is academic.

Some factors affecting direct charging of cases in my experience: extruded power is more tolerant of powder charge variations than ball powder; the larger the case capacity, the more variation can be tolerated; extruded powders do not meter as well as ball powders out of a powder measure.

As far as what is an acceptable variation, I imagine depends on the shooting discipline. I don't believe there is an a precisely absolute answer to this question because of all the variables involved with reloading. The only way I know is to test fire the loads you are dispensing and analyze the groups to determine if it meets your needs.

I'm not asserting that you have measure each charge to obtain a serviceable reload, what I'm saying is that you can eliminate the question and variable by just weighing each charge.
 
K22 said:
I assume you are asking this question because you are charging your cases directly via some mechanical device such as a powder measure without weighing each charge.



If you're weighing each charge, then the variation is fixed by the accuracy and repeatability of your scale otherwise the question is academic.



Some factors affecting direct charging of cases in my experience: extruded power is more tolerant of powder charge variations than ball powder; the larger the case capacity, the more variation can be tolerated; extruded powders do not meter as well as ball powders out of a powder measure.



As far as what is an acceptable variation, I imagine depends on the shooting discipline. I don't believe there is an a precisely absolute answer to this question because of all the variables involved with reloading. The only way I know is to test fire the loads you are dispensing and analyze the groups to determine if it meets your needs.



I'm not asserting that you have measure each charge to obtain a serviceable reload, what I'm saying is that you can eliminate the question and variable by just weighing each charge.
Click to expand...
 
I do measure each charge. But if I'm a grain over or under, it gets to be a pain in the rear to dump it back and recharge when doing 200 loads in a single sitting. I'm also case trimming and case prepping all at the same time.
 
Mr Wick said:
I do measure each charge. But if I'm a grain over or under, it gets to be a pain in the rear to dump it back and recharge when doing 200 loads in a single sitting. I'm also case trimming and case prepping all at the same time.
Click to expand...
I set my power measure to dispenser at about .3 grain short of my target charge. I dispense in balance pan then trickle in the reminder into the balance pan until it reads zero. I've never timed myself, but I can load 20 - 40 rounds quickly and smoothly which is my standard loading routine for one sitting. My final charge is only limited to the precision of my balance.

However, since you are loading 200 rounds at one sitting this is not practical for you. So, if I was going to dispense powder directly into a case, I would run some tests to see how much variation I get using this method with my powder of choice then test it on the range for accuracy.

As I said before, ball powder will dispense very uniformly. Small kernel extruded powder dispenses fairly uniformly. In addition, small variations in extruded powder are forgiving especially on larger case capacities like the 308 and above.
 
As mentioned earlier, you have to test your gun and find it’s accuracy node. If your node has a .4 grain spread, load in the middle of the spread.
Also, stick powders are notoriously hard to throw accurately. Ball powders flow better. I can throw charges, using ball powders, within .1 grains of my target weight. To me, that’s OK for my plinking loads that are always a grain or two below max.
For my “accurate loads”, I make them dead nuts on no matter how long it takes.
 
What is “acceptable” is really a function of the accuracy you are seeking and the distance at which you are shooting. I can tell you that at 1,000 yards 1/10th grain is 2.5”-3” on the target with my LR bench guns. The vertical dispersion is obviously going to be less noticeable at closer range but it is still there.

If you “tune” the rifle and find a “node” you can then theoretically get away with some powder variation without elevation changes, but everyone I know, still tries to measure as precisely as possible for competition shooting.

It all depends on the accuracy you are trying to obtain.

And yes I read Adams’s paper but the target at 1K when shooting a powder ladder is fact, not theory.

Dave.
 
what scale ?
most common are plus or minus 0.1...so your loads should be plus or minus 0.1
what are you doing with the ammo..plinking..then who cares
hunting..it probably does not matter
target shooting...look into a scale better than 0.1 and with magnetic dampening to speed things up
do the best with the equipment, rifle and shooter...else SPEND MORE MONEY.
THIS AINT A CHEAP SPORT
 
I avoid other actions(case prep, sizing, priming) when measuring/dispensing powder. Charging cases needs 100% attention. Often I throw into the pan and check on scale, if scale error +,- of charge weight is met,dump in case. If short I can trickle up. Over back in the hopper. 100 an hour, helps if the bench is clear and uncluttered. If I was loading for paper/score (load development or my 17 rems) I throw light and trickle to target weight. Find a .4-.6 gr minimal vertical dispersion load and throw in the middle for speed(prairie dog ammo).
 
As others have mentioned, it really depends on what kind of shooting you are doing, and what your accuracy standards are. Other factors are the resolving power of your shooting equipment, and your abilities. What kind of rifle are you shooting, and what is your realistic accuracy expectation. For me, there are many powders that do not lend themselves to being thrown accurately, and for those I throw light enough that there are no overcharges, and trickle up. Over the years I have earned a postgraduate degree in operating my RCBS trickler and by paying close attention to the scale, I know when I can go fast and at what point I need to slow way down. In the past, when working up varminting loads I would work with a ball powder because then lend themselves to being thrown with reasonable accuracy. I would work up my load in the same temperature range that I would be shooting in, so I never had any temperature sensitivity issues. It also helped that I kept load pressures below maximum. When trickling up, I usually am able to keep things within +- .05 grains, but for a lot of applications, and for large cases, twice that works fine.
 
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