How much does the amount of powder affect accuracy?

[KQguy]

I have never really taken the time to thouroughly test loads.I alway's just load a happy medium of powder,and as long as it grouped o.k.,I just stuck with it,I never got into testing loads 1/2 grain at a time like some people do.I was just curious how much of a difference it can make from 1 grain to another as far as grouping is concerned.
In the past I was just shooting 100-150 yds,so it was never really that big of a deal to me.When you guy's develope loads,do you shoot 3-4 rounds @ various charges to see wich one groups the best?If so,in what incraments?

 

[AJ Peacock]

You have no idea what you've just asked

There are so many ways to skin this cat and sometimes the discussion gets heated.

Yes, small changes in powder amount can have affects on accuracy. In general, an accurate gun will shoot most ammo well. However, there are often particular loads that shoot GREAT! I've seen rifles that liked really hot loads and others that shot the most accurate with mild loads.

There is a technique called a ladder test that some folks use and swear by. Others call it un-scientific and mathematically flawed.

An easy and typical approach would be to determine what velocity level you are looking for. Then using a chronograph, shoot a range of 3-5 shot groups at every 1/2 grain or so over that range. If a couple really shoot well, you can try that recipe again and see if it suits your needs. Or you can then hone into that range and test every .2gr or even .1gr if you feel like it.

If you need some reading, do a search on ladder test and you will get all the info your heart desires (and more). Or you can use the method above, find a nice load and be content.

Merry Christmas,
AJ

 

[James Jones]

Alot of it depends on the case size , for instance , a full grain differance in a 6mmPPC will have a big differance , it could cause to the gun to group well or bad , it may group .5" with one weight and you increase by one grain and it may group.5" with that but it may gorup .2" with one grain les or more , so the samller cases are going to be affected mor so , with cases of the 308 size and smaller I would up in .2 grain incriments. If you more one grain up or down in a 30-378Wby the differance will likely be very little.

BUT , once your pressure are high the small differances in powder can make huge differances so be mindfull of that.

Genberaly speeking guys that work up in .5grain steps will find a happy load for their gun

 

[Bart B]

First, I'd suggest testing ammo with nothing less than 15-shot groups. Anything less doesn't give good info on accuracy. Remember that if you average several few-shot groups, half of the groups will probably be larger than their average. And a composite of all fired groups will be larger than the biggest few-shot group.

Second, half-MOA groups through 600 yards can easily be had with a 0.75% grain spread in charge weight; that's 3/10ths of a grain for a 40-grain charge. But you've got to have several good things to do it; components, assembly techniques, rifle, sights and shooter. If any one of these things isn't up to snuff, accuracy won't be either.

Third, I'd use half-grain increments to test loads with. I don't think any smaller increments will show consistant differences. Especially if you shoot test groups of at least 15 shots. Note that if your test/measurement process doesn't produce the same results each time, it's not a good one.

 

[KQguy]

thanks for all the help,I will take your advise and hopefully come up with some good loads for my 110gr V-max for varmint hunting.

 

[jes10x1]

Testing loads

I have no argument for 15 rounds per try, but 7 will give you an ok idea as you are culling out the large numbers-and save wear and tear on the barrel. Cast out a flyer in each group, if necessary.

Just to make things interesting, that's not your only variable. I shoot an AR in competition and when working out my 600 yd load, I found that seating depth varied my group from 1 to a max of 2 moa. Off the lands wasn't the answer. My Krieger barrel liked them .035" off - go figure.

Experiment with the charge until it's good. Play with seating depth, perhaps primers and then look at seat depth.

Any comments?