Is SD a factor of your reloading, or the rifle? or both?

[CShooter92]

I got thinking about this last night after a couple pops and I figured I'd ask the more knowledgeable here. We always chase a small SD for our loads, that part makes sense. We want the most consistent load to avoid vertical dispersion at distance. However I started to wonder what truly affects, and creates a small SD. Is it the precision of loading or is it the rifle itself?

If I load 43.0 grains of H4350 in my 6.5 Creed and shoot a group of 5, with an SD of 5 that's good. However, is that because every single case is filled with exactly 43.000 gr of powder or because the rifle likes that load? What if my loads varied between 42.95 and 43.05 gr? Obviously, not as precise in the charge weight, so this could affect the velocity spread. I guess what I'm asking is, should we really be trying to find a load based on a low SD when doing an OCW test, or should we find a load based on another method, and then fine tune the SD with more precise reloading practices? Also, with this theory, it would be possible to make any load have a low SD if the precision of our loading was exact.

 

[Howland]

I don't place much faith in SD calculated from 5 shot groups so I ignore SD and focus instead on ES, group size and location.

In a perfect world all three would point to the same load but trade-offs are necessary.

 

[Fig]

Not trying to be a smartass, or clobber your question..., but....

The difficulty of actually answering that question is that it's a moving target. Every shot down the barrel is changing everything slightly. The stuff we can control we do, to try and create as much consistency as possible, but I think that most of us are constantly recalibrating and changing our hand loading technique slightly as the round count climbs on that barrel. The distance to the rifling is getting longer with every shot. The rifling itself is wearing down with each shot and changing the speed. Every small thing comes into play the further out you go, and the accumulation of all that means that precision starts wandering off, and we have to do things to correct. Then by the time we re-barrel you have to start over (with a good idea of what neighborhood to start in).

So it definitely both, but it isn't a static thing if you shoot matches or at least shoot so much you roach a barrel or more a year.

 

[Steel head]

It’s certainly something I watch for
Most of my shooting is at 1100 and further so vertical is important.

I recently started another 260 barrel and after 100 rounds of mild loads I tried the load my previous barrel(same maker) was rocking.

Ten shots with an SD of 4 and about the same as previous barrels, last barrel with this load did really well at distance, I’ll find out this weekend how the new barrel does at a mile.

Before I started running reliable chronys I absolutely did not trust SD/ES, just down range results.

 

[Cjwise5]

I'm definitely not a "professional" reloader, but it my experiments, SD has been a factor of neck tension and seating depth. Open to corrections on that. When I get neck tension consistent from case to case and seating depth dialed in, I usually see single digit SD and usually ES too. Obviously you need accurate powder charges too. Quality components don't hurt either.

 

[Milo 2.5]

I have said this many times, if you have a load that holds vertical and groups at distance, numbers become irrelevant. On the same hand though, if indeed your load does do what I just said, more than likely your numbers are also good. Or good enough.
I guess you'd have to prove to yourself that going from an SD of 8 to an SD of 4 really improves things.
One other thing, does every time you chrono your load, are the numbers the same? I do not get into lengthy chrono sessions, if my load is shooting, how much data is needed. I can take a sampling one day, numbers damn tight, month later load still hammering, but the numbers have opened some, does that mean a pattern is set?

 

[Steel head]

I have said this many times, if you have a load that holds vertical and groups at distance, numbers become irrelevant. On the same hand though, if indeed your load does do what I just said, more than likely your numbers are also good. Or good enough.
I guess you'd have to prove to yourself that going from an SD of 8 to an SD of 4 really improves things.
One other thing, does every time you chrono your load, are the numbers the same? I do not get into lengthy chrono sessions, if my load is shooting, how much data is needed. I can take a sampling one day, numbers damn tight, month later load still hammering, but the numbers have opened some, does that mean a pattern is set?

in the the end down range results trump all.

 

[Milo 2.5]

I'm definitely not a "professional" reloader, but it my experiments, SD has been a factor of neck tension and seating depth. Open to corrections on that. When I get neck tension consistent from case to case and seating depth dialed in, I usually see single digit SD and usually ES too. Obviously you need accurate powder charges too. Quality components don't hurt either.

Not trying to argue, but dialing in neck tension and seat depth result in better grouping, IMO, the numbers then become a byproduct, and a good one though. Or on the positive side of things.

 

[Cjwise5]

dude, feel free to argue. like I said, I'm open to correction. Definitely don't consider myself a reloading expert.

All I really know is that when I have quality components, measure and dispense my powder accurately, pay attention to neck tension, and then tune my seating depth, I usually get single digit SD and single to low double digit ES.
LOL that's it. What portion of that is actually the component that results in the single digits, I'm not entirely certain. Ha.

 

[Milo 2.5]

dude, feel free to argue. like I said, I'm open to correction. Definitely don't consider myself a reloading expert.

All I really know is that when I have quality components, measure and dispense my powder accurately, pay attention to neck tension, and then tune my seating depth, I usually get single digit SD and single to low double digit ES.
LOL that's it. What portion of that is actually the component that results in the single digits, I'm not entirely certain. Ha.

I guess you could answer it for yourself, regardless of experience, did or does group size shrink or is that something you ssre not concerned with?

 

[Cjwise5]

I don't usually have trouble with group size. Whatever I'm doing in my reloading process typically gets me 3/8" groups at 100y.
I have noticed that group size can be adjusted with neck tension and seating depth.

 

[2aBaC̶a̶]

I feel like each rifle has a predetermined capability. You load to reach it.