Powder affecting accuracy?

[Quoheleth]

This may be a silly question, but how can powder make such a difference in accuracy? I was just looking at the post about VV powders and how benchrest shooters love it so much. I understand there are different types of powder (flake, ball, stick, etc.) and I could see how different types would burn differently. But what makes one powder a more accurate shooting powder than another? I can understand bullets making a big difference in accuracy, and of course, the bullet weight being matched to the gun's barrel and twist rate. But the powder???

I can handle Greek and Hebrew, but if this is a complicated physics and/or chemistry answer, just say so and I'll leave well enough alone. I'm no where near that point in my shooting (or my science and math). I look for inexpensive and relatively clean stuff. Other than that, for me at least, it's academic - and I've been out of school for 7 years

Quoheleth

 

[W.E.G.]

The issue is getting the velocity standard-deviation to a minimum.

The lower the SD, the less vertical dispersion you will get on longer shots.

Whatever powder gives the lowest SD, is arguably the "better" powder.

 

[jfh]

Without going into complicated explanations

that I really don't fully understand yet, I think that 'accuracy' and powder selection has a relationship with the characteristics of an individual firearm. That is, a particular powder's 'burn characteristics' mesh unusually well with the way a pistol (for example) goes through it's cycle.

Firearms, even (especially) the higher-end custom ones, are really individually-tweaked firearms, not merely ones made to better / tighter / whatever standards.

There may be some QC variables, but I doubt that--at least in the realm of safe operation.

Jim H.

 

[tkendrick]

My experience with most regular rifles (never shot Bench Rest), is that the powder may be important, but primers are critical.

Changing primer brands on many of favorite loads will often make as much as 1 to 2 inch differences in the groups. I don't know why it happens, but I know it does.

 

[Quoheleth]

So, the point is to find a powder that has Ivory soap characteristics - it's 99.44% the same, all the time. So that way I know if my recipie calls for X.XX grains, I know that each time, my X.XX measurement will have exactly the same power curve (for lack of a better understanding of a term to use) as the next round.

Yes?

If that's the case, I can understand how a powder can make a difference. It's like buying store-brand ibuprofin vs. Advil. They both have the same "power" of 200mg, but the Advil works more efficiently, lasts longer, etc. Well...something like that at least. Simple minds...simple analogy.

Q

 

[Bullet]

For short range powder has more to do with the barrel harmonics. About when the bullet leaves the barrel in relation to the barrel vibration or oscillation. For long range the bullet speeds being consistent (SD’s) are more important. Where the short range leaves off and the long range begins I don’t know.

 

[peterotte]

Quoheleth , I have a theory that a powder that produces a steady pressure rise over a longer time period will produce less 'shock' in the barrel system, which produces less barrel vibration. This seemed true in my mini-14 in which I was using a slower than recommended burning powder, to good effect. The spherical powder that was 'designed' for the 223 gave me poor results.

303Guy

 

[peterotte]

tkendrick, are you saying that one brand is better than another or that one brand may suite a particular rifle or load, better than another? The choice of primers in my local gunshop is overwhelming! Where does one start? (I currently use Federal - a price compromise).

303Guy

 

[Grumulkin]

The following are my experiences that are unsubstantiated scientifically as are all the other opinions thus far expressed on this thread:

1. A particular powder can make a LOT of difference in a particular cartridge. Many may be suitable but one or two are probably ideal. Some cartridges seem inherently accurate and shoot well with more powders than others. Why is this...I don't know. I think the reasons are very complicated and probably no one knows.

2. A particular type or brand of primer can significantly affect accuracy but usually not as much as the powder selected.

3. Some powders seem to shoot well in a larger variety of cartridges than do others.

4. The particular bullet selected can make a huge difference in accuracy and it's not just the expensive ones that shoot very well. I believe that slight variations in the weight of bullets is agonized over too much and that concentricity and shape are much more important.

5. As long as the same brand of brass is used and it's not absolute junk with eccentric flash holes, etc., I don't think the particular brand of brass used makes much difference in accuracy for those satisfied with 1 MOA groups. If you want to get smaller groups, you have to be more picky.

 

[sansone]

I am also on the NEVER-ENDING quest for perfect loads. I have no idea why certain powders or primers do better. I use to think it was all in burn rates and consistency of bullets and charges. now I just keep trying different products and record the results. my wife thinks(knows) I'm insane with all this reloading stuff.

 

[peterotte]

Grumulkin, I think you have answered Quoheleth very well indeed. Maybe scientifically unproven but pretty well anecdotally proven I think. My limited experiences pretty much fit your observations.

Regards
303Guy

 

[peterotte]

sanson1, depending on what you reload for, I have a technique you may be interested in experimenting with.

Regards
303Guy

 

[tkendrick]

peterotte- Primers are like any other component in reloading. Certain primers will work better for certain loads in certain rifles.

I have yet to find any rhyme or reason to it, but I know it does.

As the ignition source, I think it has to do with heat distribution into the case in conjunction with the burning characteristics of the powder. Your primary goal in working up super-accurate loads is consistency. Some primers will allow(cause?) more consistant burns than others.

I know that my experience shows that the few times I've worked on getting sub MOA groups, the primer has always ended up making the difference between "almost" and "got it". Generally I will work up a load that is as accurate as I can get it, then fine tune it with primer selection.

I can usually find a primer that will add that final "tweek" that changes a good load into a great load. But I also frequently find one that absolutely screws the good load. I have a .264 WinMAg load that opens up over two inches at 100 yards if I switch from Remington to Winchester primers.

I will tell you, however, that if you are working up regular hunting or plinking loads, the primer isn't going to be nearly as important as bullet choice. I generally aim for a three inch group at 100 yards in my sporting rifles, 5 inch groups in my milsurp stuff, and call anything any better as icing on the cake.

In these cases, I generally buy whatever's on sale.

 

[peterotte]

Thanks tkendrick. I appreciate your trouble. I feel a lot better about my hornet's accuracy. I got 1 1/2 MOA at 100m and 200m the last time I was at the range, using Speer 45gr SPS. With the 50gr Sierra Blitz I was getting 'centre of the small leaf' at 65 paces. Also, I hit whatever I aimed at with the cast bullets. Now to find the best bullet for my uses.

Regards
Peter