Lot Variation WTF?

[TannerGun]

I'd put around 300 rounds of 178gr HPBTs through my 308 over RL-15, the stuff that came in the yellow labeled bottles, and it shot LIGHTS OUT. I didn't shoot many groups that went over .5", and it pounded steel out to 1k.

I grabbed a bottle of the new shit with the black label/red letters and of course it's a new lot, but I didn't think anything of it. Loaded up a bunch of the exact same load, headed out, and they kind of shot like hell. Some would double group, and some would just have one bad flyer, and I felt pretty confident it wasn't me. Headed home, scrubbed the tube and checked all the hardware, and tried again, to see the same results.

Am I just seeing a big lot variation? I've heard the suggestion to start increasing charge weight until I see the same # on the chrony, and then hopefully the accuracy will return?

 

[30SMK]

Re: Lot Variation WTF?

What is your average difference in velocity from the last lot to this one?

I have seen velocities go up or down by 50-60 fps easy between lots of powder.

You will most likely just need to tune your load to this lot of powder but their are other variables that could cause an increase of decrease in velocity besides the powder.

 

[Jeffvn]

Re: Lot Variation WTF?

lot to lot variation seems to be the norm, not the exception (there are several threads about Varget, H1000 and Retumbo on this topic). When you switch powder jugs you need to run the new lot over the chronograph and tweak it to match the velocity from the earlier lot. PIA, but its the only thing that guarantees the performance of the old load every time.

Jeffvn

 

[insight3b]

Re: Lot Variation WTF?

The older stuff was a lot hotter...this is the closest I've found to the old stuff:

http://www.gibrass.com/gunpowder.html

 

[High Binder]

Re: Lot Variation WTF?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jeffvn</div><div class="ubbcode-body">lot to lot variation seems to be the norm, not the exception (there are several threads about Varget, H1000 and Retumbo on this topic). When you switch powder jugs you need to run the new lot over the chronograph and tweak it to match the velocity from the earlier lot. PIA, but its the only thing that guarantees the performance of the old load every time.

Jeffvn </div></div>

The same threads also dispell these variations as myths.