Velocity vs. SD vs. Accuracy

[Squaregrouper]

I was reworking my 6.5 Manbun load for a Peacemaker trip and came across a load that gave me less velocity, but <1/4" group at 100yds. The SD was single digits, excluding one round which was waayy off (chrono?)
This new load is 41.8gr of H4350, CCI LRM, both 139gr Scenars and 140gr ELD-M. @ 2.820" OAL. I'm getting a pretty standard 2745-2755fps out of a 24" Bergara BMP.
My question for the braintrust is "Am I better off with an uber consistent round that is slower than I hoped for, or should I chase another node?" The highest I have gone was 42.6gr with no pressure signs, a 3/4" group and no chrono data.

 

[steves1911]

Consistency wins everytime....a lower velocity simply means a few more clicks on the elevation turret.

 

[4g64loser]

Sequester the "wild" shot case and evaluate it very carefully.

To answer your question, take the consistent load every time. That is plenty of velocity.

 

[holesonpaper]

Personally I'm of the belief that SD comes first, then accuracy, then velocity.

 

[Squaregrouper]

Sequester the "wild" shot case and evaluate it very carefully.

To answer your question, take the consistent load every time. That is plenty of velocity.

The oddball was something like 2506fps. I trickle charged all of them and visually inspected the lot before seating bullets. Even with a seating difference of 0.02" I don't think that would have accounted for ~250fps less.
BTW, this is my chrono...
.

 

[Squaregrouper]

The targets on the left (ELD-M) and bottom (Scenar) were what had me load a bunch more and get chrono data yesterday. I was able to replicate the group size with multiple strings. (They were all 5 shot groups.)
The braintrust has spoken, 2750fps it shall be.

ETA- This is from 2 weeks ago when I was testing different charges.

 

[4g64loser]

The oddball was something like 2506fps. I trickle charged all of them and visually inspected the lot before seating bullets. Even with a seating difference of 0.02" I don't think that would have accounted for ~250fps less.
BTW, this is my chrono...
.

Something was wonky. Either a bad pickup by chrono or a wicked short charge. I'm going with chrono as you say the group was quarter minute. If you have a round that much slower it will almost always print high on target. Even 80-100fps shows up when you have a load that tight.

 

[Squaregrouper]

Something was wonky. Either a bad pickup by chrono or a wicked short charge. I'm going with chrono as you say the group was quarter minute. If you have a round that much slower it will almost always print high on target. Even 80-100fps shows up when you have a load that tight.

The chrono isn't exactly top of the line. I'm going with bad chrono reading.

 

[4g64loser]

The targets on the left (ELD-M) and bottom (Scenar) were what had me load a bunch more and get chrono data yesterday. I was able to replicate the group size with multiple strings. (They were all 5 shot groups.)
The braintrust has spoken, 2750fps it shall be.

Nice shooting. And that's plenty of speed. Anything over 2650 with 140s is going to do you fine for most purposes. If you can get that kind of consistency at or above 2800, it might be worth it but that's probably pushing it

 

[4g64loser]

The chrono isn't exactly top of the line. I'm going with bad chrono reading.

Well, if I'm there you are welcome to shoot a string past the Labradar.

 

[BradMacc82]

Consistency/stability is my priority, velocity is a bonus.

My 260 loads are 'hot' by some peoples opinion, but the primers and targets are telling me that I'm in a good spot.

 

[Biggfoot44]

Personally I'm of the belief that SD comes first, then accuracy, then velocity.

I can comprehend the logical reasoning behind that . But seen enough imperfect relation of SD & accuracy to put accuracy > SD> velocity .

* With the Caveat that SD isn't stupid high . and velocity is reasonably suited for intended purposes .

 

[holesonpaper]

I can comprehend the logical reasoning behind that . But seen enough imperfect relation of SD & accuracy to put accuracy > SD> velocity .

* With the Caveat that SD isn't stupid high . and velocity is reasonably suited for intended purposes .

The reason I say that, is because I've learned from more experienced reloaders, that some portion of accuracy can be picked up by adjusting seating depth - or specifically locating the amount of jump preferred by a bullet. When shooting at longer distances - honestly, both matter.

There's clearly other reloaders more experienced than I - but generally I've seen that SD and accuracy come along together. Saying the reverse, I've never had great accuracy with horrible SD.

 

[teratos]

Nice shooting. And that's plenty of speed. Anything over 2650 with 140s is going to do you fine for most purposes. If you can get that kind of consistency at or above 2800, it might be worth it but that's probably pushing it

What’s the difference in barrel life between the 2 velocities? Is it even worth considering that as a factor?

 

[holesonpaper]

What’s the difference in barrel life between the 2 velocities? Is it even worth considering that as a factor?

I'm sure the hotter load would reduce the barrel life over the lighter load - but what is that difference and is it worth considering... My opinion - shoot what works and don't introduce another constraint. It's a similiar conundrum to Reloder 16/17 with nitroglycerin. Folks see higher velocities but the nitro runs hotter and is notorious for reducing barrel life (versus other powders nearby in the burn chart).

 

[4g64loser]

What’s the difference in barrel life between the 2 velocities? Is it even worth considering that as a factor?

In the same case, sleazemoor in this instance, significant. Once you run the pressure up, even a "less blowtorching" powder is still abusive. This coming from someone who had measurable throat issues in a 308 Palma gun in 2500 rounds. More.than once. Running a load of RL17 that I would never admit to and using an 18" drop tube I still had to finish seat the bullets the day of.the match. Basically, I got 260 barrel life on a 308 barrel.

How hot you get it is still the biggest issue but PRS guys are PRS guys and F class guys are F class.guys and hunters are hunters.

Keep in mind that you are going to shoot a lot more money OUT of the barrel than you spend ON the barrel. Regardless.

 

[teratos]

In the same case, sleazemoor in this instance, significant. Once you run the pressure up, even a "less blowtorching" powder is still abusive. This coming from someone who had measurable throat issues in a 308 Palma gun in 2500 rounds. More.than once. Running a load of RL17 that I would never admit to and using an 18" drop tube I still had to finish seat the bullets the day of.the match. Basically, I got 260 barrel life on a 308 barrel.

How hot you get it is still the biggest issue but PRS guys are PRS guys and F class guys are F class.guys and hunters are hunters.

Keep in mind that you are going to shoot a lot more money OUT of the barrel than you spend ON the barrel. Regardless.

Thanks for the perspective.

 

[4g64loser]

Thanks for the perspective.

I still clench up when I have to buy a Krieger barrel blank for one of my .30 cal match rifles but if I total up the powder, primers, and bullets that went out of it, the 800-1000 dollar total price barrel suddenly doesn't look as bad. Then I realize that I am a degenerate shooter and I need some alcohol.

 

[Biggfoot44]

What’s the difference in barrel life between the 2 velocities? Is it even worth considering that as a factor?

With the same powder , more powder = more throat erosion to some degree or other .

If comparing different powders to achieve different velocities , that would be a deep dive into Chemical Engineering .

Meaningful difference ? Subjective . A 6.5 Magnum inherently has more bbl erosion than say a 6.5 Creedmore . The ratio isn't linear with the bore expansion ratio , but it's a decent rule of thumb .

 

[lazarus]

I can comprehend the logical reasoning behind that . But seen enough imperfect relation of SD & accuracy to put accuracy > SD> velocity .

* With the Caveat that SD isn't stupid high . and velocity is reasonably suited for intended purposes .

Ditto. Most of my loads if I switch to mag primers with CFE223 my SDs usually run to high single digit, low double digit (generally 8-14fps range) versus generally around 15-25fps with standard primers. But in almost all cases, every charge weight and bullet type I’ve tried in 223, 6.5 Grendel and .308 has been 20-30% tighter groups with standard primers, just as an example.

Interestingly in most cases my lowest SD node is not my most accurate for most loads as well (often it is my second lowest SD though).