Results troubleshooting

jlcrss · March 12, 2013, 01:23 PM

I am loading 308 with arcomp 40 grains, Wlr primers, hornady match brass, and 150 btsp Speer. Here are the results at 100 yards
My ammo

Factory hornady 168 grain match amax

Where do i start in tightening my ammo group up?

Brian Pfleuger · March 12, 2013, 01:28 PM

For starters, you're at a minimum load.

You start by working your load up in 0.7-1.0% increments, which in this case would be 0.3-0.4gr, in groups of 3 at each charge, until you reach max load.

After that, compare the group sizes and retest at smaller increments in between the groups that are CENTERED in the same place. Not necessarily the smallest groups but two consecutive groups whose centers are in the same place. Then you can tweak OAL to make for smaller groups.

Here, do what Dan says.

http://optimalchargeweight.embarqspace.com/

Oh, and I'd guess that your gun likes those 168gr bullet too, so you might start there.

jlcrss · March 12, 2013, 06:51 PM

I wonder how much twist rates on the barrel play into this. This barrel has a 1:12 twist and it might be too light ofa bullet.

Brian Pfleuger · March 12, 2013, 07:18 PM

Too light is almost never a problem. Slow twist rates are bad for heavy bullets. Light bullets will stabilize in most any barrel, the only caveat being that spinning them TOO fast can also cause stability issues. 1:12 shouldn't though.

It's more likely that the 168s are closer to the rifling and they like it.

oryx · March 12, 2013, 08:01 PM

I would also venture to say that the Speer and Amax bullets are not equals.
What type of brass prep did you do and what type of resizing/seating die are you using? What is the delta between bullet jumps of the two bullets in your chamber? How are you measuring the powder? how many times has the brass been reloaded? Tons of other questions.

Powder alone (in my experience) is not going to make all of the difference, but the right charge can make a difference. There is a lot to pay attention to for precision reloading and careful attention to details can also make a huge difference. Make small changes and retest to see the affects so you can understand what you did that made the difference. You might also find that certain guns/chambers are more sensitive to different things.

Best of luck on your quest.... It's all part of the joy.

March 12, 2013, 01:23 PM	#1
jlcrss Member Join Date: March 7, 2013 Location: Lansing, MI Posts: 20	Results troubleshooting I am loading 308 with arcomp 40 grains, Wlr primers, hornady match brass, and 150 btsp Speer. Here are the results at 100 yards My ammo Factory hornady 168 grain match amax Where do i start in tightening my ammo group up?

March 12, 2013, 01:28 PM	#2
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	For starters, you're at a minimum load. You start by working your load up in 0.7-1.0% increments, which in this case would be 0.3-0.4gr, in groups of 3 at each charge, until you reach max load. After that, compare the group sizes and retest at smaller increments in between the groups that are CENTERED in the same place. Not necessarily the smallest groups but two consecutive groups whose centers are in the same place. Then you can tweak OAL to make for smaller groups. Here, do what Dan says. http://optimalchargeweight.embarqspace.com/ Oh, and I'd guess that your gun likes those 168gr bullet too, so you might start there. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

March 12, 2013, 06:51 PM	#3
jlcrss Member Join Date: March 7, 2013 Location: Lansing, MI Posts: 20	Results troubleshooting I wonder how much twist rates on the barrel play into this. This barrel has a 1:12 twist and it might be too light ofa bullet.

March 12, 2013, 07:18 PM	#4
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	Too light is almost never a problem. Slow twist rates are bad for heavy bullets. Light bullets will stabilize in most any barrel, the only caveat being that spinning them TOO fast can also cause stability issues. 1:12 shouldn't though. It's more likely that the 168s are closer to the rifling and they like it. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

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March 12, 2013, 08:01 PM	#5
oryx Senior Member Join Date: December 26, 2008 Posts: 142	I would also venture to say that the Speer and Amax bullets are not equals. What type of brass prep did you do and what type of resizing/seating die are you using? What is the delta between bullet jumps of the two bullets in your chamber? How are you measuring the powder? how many times has the brass been reloaded? Tons of other questions. Powder alone (in my experience) is not going to make all of the difference, but the right charge can make a difference. There is a lot to pay attention to for precision reloading and careful attention to details can also make a huge difference. Make small changes and retest to see the affects so you can understand what you did that made the difference. You might also find that certain guns/chambers are more sensitive to different things. Best of luck on your quest.... It's all part of the joy.