I haven't been reloading long,and this is my first expirament working up a load.Is it your all's experience that 1 or 2 grain variances in the amount of powder can make huge differences in group sizes? I ask becuase today while test firing 5 different loads(same bullet,case,primer,etc,just the differnce in charges),and in the middle of shooting,I come up with group pictured.the 2 groups before weren't anything this good.And I'll admit that I can't shoot worth a damn.But this interested me .the 2 other groups sucked too.All shots were from sandbags,100yrds,with me cleaning between each 5 shot string.I waited at least 1 minute between shots.It this the norm?

It has been my experience that 1 to 2 grains will make a huge difference. I usually start out with good cases, 1 kind of powder, 1 or 2 different bullet weights and 5 rounds of each bullet weight in 1/2 grain incremments. Thats 5 rounds with the same powder, 5 more with 1/2 grain more, etc. If you start with some thing in the middle of a the "normal" and work up by 1/2 not exceding max, you will usually find a load that will shoot well. If this fails I will change powders and try it agian. Once you find this load you can try changing, cases, OAL and primers to see if you can improve more.
JL

Unless you are loading the .50BMG, 1 or two grains will make one hell of a difference.

I usually increment my loads in 0.3 grain steps.

Doesn't seem that you are all that bad of a shot either. With the exception of one flyer, which I am betting was the 4th or 5th shot, you seem to be doing well.

If you have a variance of any more than .1gr, use them as fouler shots. That's the way I do it,...but then again, I'm anal about the whole thing

My experience is that sometimes it does make a difference and sometimes it doesn't. It just sorta depends on your gun and the loads. It's a weird unpredictable thing.

Since you won't really know until you try it... It's wise to aproach all reloading as if it DOES matter.

Make sense?

I prefer not to exceed 1% increase in charge weight as a general guideline, but as stated above it depends what you're shooting and what the starting point is. Simple math really, 1 grain is 2% of a 50 grain charge etc, etc, etc. 1 grain in a .22 Hornet is 8-10 % If you're are starting very low maybe a 1-2% increase is okay, but certainly not at the upper end. Your load manuals are guidelines not objectives insofar as max loads are concerned. You gun is an individual, and not the same one the manual writers used in their tests. Also, when you race full speed to max charge weights with large incremental jumps in charge weight you're likely to miss the load that makes your gun shoot well.

Rule of thumb: Increase your powder charge 2%, increase velocity 2%, AND increase pressure 4%.

Yup, that is why we work up loads incrementally. All of a sudden one charge weight will tighten up your groups dramatically. When I am developing loads I make groups of 10 rounds, each 1/2 grain apart in charge weight. I shoot 2 five shot groups with each. Then I make groups of 10 rounds 1/10 gr apart, 1/2 gr each side of the best load. The best shooter is then my load. Looks like you found a winner. Good work.

Everyone else pretty much covered your question. I have one question/comment though: You said that you clean after every five shots - Do you then shoot a couple of fouling shots before trying your 5 shot group? My guess is that the flyer was your first shot and if it was, then I would throw that one out of your group. I usually shoot a couple of fowling shots before shooting groups.

One or two grains can make a significant difference. I have seen half a grain make as much as 1" difference in group size!!