Powder load and accuracy.

[nagantino]

I have recently taken up target competition shooting. 25 yards then 15 then 10. We call it Timed and Precision and I’m not sure if it’s a thing in the States. I bought a 6 inch S&W Target Champion which is pretty sweet. In trying out different loads I was using 3.6 of Vectan BA 9.5 which is equivalent to Red Dot or 700X. Today I lowered the load to .2.8 to try for “feel” and accuracy. To be honest I couldn’t fell much difference in recoil, but the accuracy was disappointing. I use a fairly good crimp and I’m reading that this is a factor too in accuracy.
My question is…..Is there a connection between powder load and accuracy?

[Toolguy]

There is. With the slow barrel twist rate of the S&W revolvers, they don't shoot light target loads accurately very far. The twist rate is 1 in 18-3/4" or 1 in 47.6 cm. At slow velocities, the bullets are barely spinning fast enough to stabilize. The further downrange they get, the slower they are spinning, and gradually destabilize. Heavier bullets keep their energy longer than lighter bullets. The faster a bullet goes out the barrel, the faster it's spinning.

 

All this means there are 3 ways to make the loads more accurate. Faster velocity, heavier bullet weight, or tighter barrel twist. That's why all the PPC guns have custom barrels with 1 in 10 to 1 in 14 twist rate.  You can combine solutions, like faster and heavier bullets, or just do one or the other. Usually, the groups will get tighter as the bullet goes faster, and will be pretty good when you get in the 900 to 1100 fps range.

 

These are general guidelines. You will need to work out the details to fit your particular situation.

Edited June 15, 2022 by Toolguy

[testosterone]

1 hour ago, Toolguy said:

These are general guidelines. You will need to work out the details to fit your particular situation.

part of the game...developing loads.

you can I think also overspin though.   I struggled to get my 929's to shoot 160g bullets into smaller than a 5" group at 20 yards, absolutely pathetic, when I slowed them down -50fps(for icore, 120pf...) they would at least stay inside a 4" x ring, though nothing to right home about.

[Toolguy]

I don't think you will overspin in a revolver. I shot 180 gr. bullets in a 686 at 1250 fps in a 1 in 10 twist barrel. I was getting consistent + or - 2" groups at 100 yards with a crosshair scope on a solid bench rest. There is probably something else wrong with the 929 for it to shoot that bad.

[pskys2]

3 hours ago, testosterone said:

part of the game...developing loads.

you can I think also overspin though.   I struggled to get my 929's to shoot 160g bullets into smaller than a 5" group at 20 yards, absolutely pathetic, when I slowed them down -50fps(for icore, 120pf...) they would at least stay inside a 4" x ring, though nothing to right home about.

Were you using .356" bullets?  My buddies 929 shoots much better with .358" bullets.

BBI 160 Coated RN .356" gave 3 3/4" groups at 25 yds.

BBI 160 Coated RN .358" gave 2 2/8" groups at 25 yds.

[pskys2]

To the original post, certain powders usually work best and the mix of all of the various factors will contribute.

Isn't the Target Champion a 9mm Semi-Auto?  

So in 9mm trya 124 jhp with titegroup for 1000 f/s.  You will need to keep the PF around 130 to function reliably and a fast powder should be best.  

Jacketed usually will do best in 9mm semi autos.

[Squirrel45]

6 minutes ago, pskys2 said:

Were you using .356" bullets?  My buddies 929 shoots much better with .358" bullets.

BBI 160 Coated RN .356" gave 3 3/4" groups at 25 yds.

BBI 160 Coated RN .358" gave 2 2/8" groups at 25 yds.

Iv had the same experience as well. 357/358 are much better then a 356. Currently I am running Bear Creek 170's and Blue 160's at 780' with decent results. I may try some 147's in the future just for kicks. 

[nagantino]

The bullets are PC 158 sized to .3565 cast from the Lee 358-158-RF mold.  I was always told that .38 sp need “ just enough to make them go” and that accuracy was inherent to the gun and you. I reduced the powder to the lowest data I could find, 2.8, but I suppose I could have been having an off day. I will raise the powder charge by one increment on the Lee powder disc and proceed from there.
Does anyone else use the “just enough to make them go” theory?

[tomjerry1]

I use 147s, 38/357 BB, very accurate through mu 929.

[Toolguy]

Just enough to make them go is dependent on the rifling twist being fast enough to stabilize them at that velocity. The 38 Special wadcutter is one of those loads. The guns they are accurate in have a 1 in 10 or 1 in 14 twist rate. For some reason, no one makes a 1 in 12 twist.

[testosterone]

18 hours ago, Toolguy said:

I don't think you will overspin in a revolver. I shot 180 gr. bullets in a 686 at 1250 fps in a 1 in 10 twist barrel. I was getting consistent + or - 2" groups at 100 yards with a crosshair scope on a solid bench rest. There is probably something else wrong with the 929 for it to shoot that bad.

358's even though they are giant pita to load on an automated machine...

I do understand what your point is, when i was on that odyssey, i came across a website for a bullseye gun builder that had boatloads of 9mm data with there notes, and one of the particular notes was in 9mm weights above 135 in 1/10 barrels flew straighter with less velocity and it def worked in my case and i was still +5 pf so win win..

 

I guess it may be possible that accuracy may follow a curve up and down?  as it climbs there is some weirdness until you get upto some new nominal velocity and things straighten back out?

 

180 at 1250 fps   thats seriously salty.

[Toolguy]

There are so many variables that can enter into this (thousands of possible combinations), that you have to work out the details with your particular set of conditions. SOME of the variables are: primer, powder, powder charge, case, bullet material, bullet shape, bullet weight, bullet velocity, barrel twist rate, seating depth, crimp, etc., etc..

 

The final judge of everything is group size on the target. I've seen guns or loads that should (theoretically) be awesome that didn't work, and guns with pitted barrel or other problems, or bullet shapes that shouldn't work, but they printed tight groups anyway. Everyone knows that a bumblebee can't fly, according to aerodynamic principles, but they didn't get the memo, so they do it anyway. So, there are basic proven guidelines, but many exceptions.

[Sinister4]

52 minutes ago, Toolguy said:

 

 

 Everyone knows that a bumblebee can't fly, according to aerodynamic principles, but they didn't get the memo, so they do it anyway. So, there are basic proven guidelines, but many exceptions.

 Yup totally correct     if you look at it  no way a 147gr wadcutter over 2.75gr bullseye should shoot near one hole groups but it will  lol

[pskys2]

7 hours ago, testosterone said:

358's even though they are giant pita to load on an automated machine...

I do understand what your point is, when i was on that odyssey, i came across a website for a bullseye gun builder that had boatloads of 9mm data with there notes, and one of the particular notes was in 9mm weights above 135 in 1/10 barrels flew straighter with less velocity and it def worked in my case and i was still +5 pf so win win..

 

I guess it may be possible that accuracy may follow a curve up and down?  as it climbs there is some weirdness until you get upto some new nominal velocity and things straighten back out?

 

180 at 1250 fps   thats seriously salty.

On the automated reloading press are you having trouble with .358" bullets not staying seated in the case?  If so go to https://uniquetek.com/product/T1736 and order the .358" funnel tube.  It solved my frustrations with my S1050.

[testosterone]

14 hours ago, pskys2 said:

On the automated reloading press are you having trouble with .358" bullets not staying seated in the case?  If so go to https://uniquetek.com/product/T1736 and order the .358" funnel tube.  It solved my frustrations with my S1050.

nice!  buying one.

I was able to make it way way better by putting a Hornady case mouth expander at the swager location, but not perfect by any measure.