Need Help with Inconsistent OAL

[707electrician]

I'm not using the 178gr Amax. I'm using the 178gr hpbt match and I actually have seen the ring around the ogive that you're speaking of. Thanks for the reply though.



I'm setting up for a ladder test that I wanna do soon so I'm loading up 42.0gr to 45.0gr of Varget in 0.5gr increments in brand new, full-length sized Lapua brass. I'm using CCI LR primers and trying to seat at a mag length of 2.80".

I usually hear powder compressing at around the 43.0gr to 43.5gr mark. Would compressing powder really change the OAL in that way?

Do you guys think I should increase my OAL? I was thinking about doing it 0.020" from the lands but in my rifle that's an OAL of about 2.94". If I load to this length then I won't be able to use my internal magazine. What do you guys think?

YES! If you can hear powder crunching that can definitely cause differences in OAL. The powder will keep the bullet from seating all the way.

I usually do my ladder testing with the bullet just touching the lands. Once I find the load the rifle likes, I fool around with the seating depth if needed

[Kappy]

I would say...
1. A compressed load.
2. Using a competition seater.
3. Ojive differences.

Try loading a few without powder, and see if you can eliminate #1.

[AeroEngi]

Thanks for all the advice guys! I'll try the suggestions in here and let you all know how it goes. Thanks again!

[gau17]

I don't know if anyone has mentioned this but neck tension can play a roll in this as well.

[RayB]

Is the die set to shell plate contact??

If so, the die might be trying to crimp as well as seat the bullet.

Unscrew the die 2 full turn & readjust the seater.

[Whiterabbit]

so many folks trying to be helpful! I have a dumb question, popping in here at post 21:

What are your groups sizes NOW? do you need to care about the "inconsistency"?

For example, you are setting up a ladder test. The reason you are doing so is so that you find a sweet spot so that "inconsistencies" in your powder charge do not yield large changes (if any at all) in your elevation on target.

In short, noone here really knows if your "inconsistencies" are really out of spec. Maybe your loads are so robust (and yes this is possible!) that you can remain sub MOA on a good shooting day with rather loosey goosey tolerances on your loading. Including the tolerance you are working hard to reduce.

My suggestion? sort them by OAL if it make syou happy. try shooting them in groups to see if one groups better. But at some point, let them be loosey goosey to +0.02 -0.0. You might be surprised. You might find the change yields no difference in downrange performance.

And make sure you test a couple times. We all have bad days at the range sometimes!

[gau17]

try using .001-.002 neck tension. You might be surprised with the results.

[AeroEngi]

try using .001-.002 neck tension. You might be surprised with the results.

So for .308, I'd size the inner diameter of the neck to .306-.307?

[Bill Steele]

I have found .3065" (.0015" neck tension) works best for my gun.

[gau17]

Take a loaded round and measure the neck. Subtract .001-.002. So lets say you were using Lapua Brass and your loaded round measured. .337. The correct bushing to get is .336 for .001 neck tension.

Bill - sounds about right. Mine fall between .001-0015.

[Sheldon]

Mixed brass will have different hardness and probable neck tension. If the cases are untrimmed and not of uniform length that will add to your issue as well.

[Whiterabbit]

Aero,

What are your group sizes at the range? Have you found your optimal charge weight on the reported group sizes? If so and the group size is big, what's the vertical spacing of the group size?

[AeroEngi]

Aero,

What are your group sizes at the range? Have you found your optimal charge weight on the reported group sizes? If so and the group size is big, what's the vertical spacing of the group size?

Group sizes are very respectable. I'd say anywhere from 0.5-0.75 MOA. I'm not exactly sure yet but the optimal charge weight is somewhere between 44 and 45 gr.

Sent from my DROID RAZR using Tapatalk 2

[Whiterabbit]

Thanks.

IMO, you are herding cats. I am confident the difficulty of measuring performance differences between consistent vs inconsistent OAL (testable by sorting your OAL now) will alone yield more noise than good data.

In short, I believe your loading now is robust to the point of being tolerant of .02" OAL variance.

That is only my opinion, for what it is worth.

Nice groups, BTW.

[echang72]

sorry fellas.. im sort of new to reloading.. what is OAL?