How much does a half grain really matter?

personally, yes.

I looking back at some of my test data there is difference of .250-.500 @ 100 yards with .3 grain differences in some of the groups.

Your sweet spot may be just a small window if your rifle is finicky.
 
I have found that some rifles are more sensitive than others. The m305 Norinco being one of them where .5 grains actually does mean the difference between group sizes.

In my rifle, 43.5grain of RL15 meant 1.5 inches, whereas 43 and 44 were 2.5, this wasn't one time research either. I spent a lot of time switching up the brass and shooting at different humidities and I found that 43.5 was the accurate load. This was with 7.62x51 nato brass.
 
As far as I'm concerned, for practical purposes, no difference.
The world class bench rest shooters, shooting in the US National Match, didn't weigh each load. They just used a powder measure to put the powder in with.
In a book written by a shooter, who among many other accomplishments, won the US National Match nine times, the word, "Sweetspot," is not mentioned. Nor have I ever read about it, except on CGN. What is told in the book is how to bed the rifle and how to load the cartridges. The loading is simple, full up. And that means heavier than shown in most reloading books.
With regards to the 308 Wincheater, it is stated in the book that there is only one way to load the 308, full. Usually, they also seat the bullet to touch the lands.
 
I found that for my Custom LRB M14S with M25 Receiver, the absolute best groups I get are with 41.5 Grains of IMR 4895, using almost any Brass (that I fully polish, form and trim) I use Bench-Rest Primers propelling a Sierra 168 Grain HPBT. Even half a grain either way increases my Groups by 1/4".


LRBM14S.jpg
 
Kelly Timoffee said:
personally, yes.

I looking back at some of my test data there is difference of .250-.500 @ 100 yards with .3 grain differences in some of the groups.

Your sweet spot may be just a small window if your rifle is finicky.
Click to expand...


I would think that would be attributed to user error/human nuances rather then the load, no one alive can consistently hit the same hole round after round, not at 100 yards.
 
In my custom bolt action with a heavy high quality bbl 1/2 a grain can open groups up from well under half an inch for five shots to about an inch for five shots in the upper end of loads. Down in the lower loadings being half a grain out of the "sweet spot" will make the groups any where from being a little bigger to being double the size. That is at 100 yards.


So being half a grain out may make a little difference or it may make a big one. Only your gun can tell you what the answer is.
 
Average group sizes, I have everything on a table so that I can follow my group sizes along with charge amounts.You won't hit the same hole but you sure will see grouping changes.

For example:

load 1 - 5 shot group - 1.125"
load 2 - 5 shot group - .800"
load 3 - 5 shot group - .500"
load 4 - 5 shot group - .750"
load 5 - 5 shot group - 1.005"
ans so on( not actual numbers , but my tables are similar)

Sniper### said:
I would think that would be attributed to user error/human nuances rather then the load, no one alive can consistently hit the same hole round after round, not at 100 yards.
Click to expand...
 
unlisted.handle said:
I found that for my Custom LRB M14S with M25 Receiver, the absolute best groups I get are with 41.5 Grains of IMR 4895, using almost any Brass (that I fully polish, form and trim) I use Bench-Rest Primers propelling a Sierra 168 Grain HPBT. Even half a grain either way increases my Groups by 1/4".
Click to expand...

Have you ever tried that load hunting? I'm curious how the hollow point held together on game. I tried the 41.5g IMR 4895 in my m305 and got 2.3 inches, but that was with NATO brass.
 
It only matters if 3/4inch at 500 yards matters to you...
I punched some numbers so here goes,

155gr A-Max over Varget

44.0 gr = 2759 fps
47.0 gr = 2909 fps
4 gr difference = 150 fps, 150/4 = 37.5 fps, 1/2 gr brings it to 18.75 fps

so, 155gr A-Max at 2909fps drops 53.33inch at 500 yards,
2909fps-18.75=2890fps (rounded down)
2890fps drops 54.1inch at 500 yards

54.1-53.33=.77inch

disclaimer, It's Friday night and I'm 5 drinks in so if this doesn't add up, too bad...;)
 
9x19p said:
4 gr difference = 150 fps, 150/4 = 37.5 fps, 1/2 gr brings it to 18.75 fps

so, 155gr A-Max at 2909fps drops 53.33inch at 500 yards,
2909fps-18.75=2890fps (rounded down)
2890fps drops 54.1inch at 500 yards

54.1-53.33=.77inch

disclaimer, It's Friday night and I'm 5 drinks in so if this doesn't add up, too bad...;)
Click to expand...

Even if it is friday night, powdercharge:velocity is not a linear equation :stirthepot2:
 
My most accurate rifles have "nodes", where they are most accurate and consistent.
Those nodes are typically 1/2 grain wide, so 1/4 grain either side of nominal will often start to open groups.
Some guns will double the dispersion at that amount of charge variation IMO.

For hunting or plinking, no big deal.
At 600 yards though, the variables start to stack against you.
 
Personally, I have not found that it does, but I am only now slowly starting to get into longer range shooting. Most of my load development and shooting has been with hunting rifles, where I have a simple pass/fail system for accuracy, and I tend to simply lay on the powder until I either see pressure signs (most common), or start to lose accuracy (much less common, but can happen). I have never farted around with a consistent 1" load to try and make it a .75" load, that's for sure.
 
Rocket Surgery said:
Have you ever tried that load hunting? I'm curious how the hollow point held together on game. I tried the 41.5g IMR 4895 in my m305 and got 2.3 inches, but that was with NATO brass.
Click to expand...


Due to Arthritis, I can no longer hunt. The load I mentioned was for accurate Target Shooting. You can not use a Full Metal Jacket for Hunting, and I have not tried Sierras Game Kings, just Match Kings. I think the Match Kings would just go straight through.


I also have a M305, and with the same load, I get about 1-1/2" to 2" Groups. The quality of the rifle plays an important part in accuracy. My M305 can not compete with my LRB M14S. Working up your own loads by doing your own reloading is the only way to find what your Rifle shoots it's best at.
 
Have a look at the groups below, and at the powder charges listed on the targets. I search out loads where the accuracy is reasonably constant over a few grain spread, and I usually find them.

223tikkagroups.jpg
 
Have a look at the groups below, and at the powder charges listed on the targets. I search out loads where the accuracy is reasonably constant over a two or three grain spread, and I usually find them.

223tikkagroups.jpg
 
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