Temperature Sensitivity or LabRadar vs Magnetospeed?

[Tim_WNC]

I loaded a couple hundred rounds in a single session a few weeks ago. Same lot of powder, same box of bullets, all loaded at the same time, etc.

I ran 5 rounds over my Magnetospeed at 59*F, DA last week. Average 2706fps.
Today, same range, I ran 3 rounds past a LabRadar for 2686 FPS average. Temp was 42*F

My load uses RL-17, which is supposedly temp sensitive.

So, how do I account for the 20FPS difference? Chrono differences or powder temp sensitivity? It’s only 20FPS so who the hell cares?

 

[918v]

It’s to be expected. Temp was cooler, velocity dropped. MS and LR are within 8fps of one another in my experience.

 

[Steel head]

Wait till you shoot it at 85-90 degrees!
You can account to it in many ballistics apps and devices

 

[wpgk58]

I tested RL 17 as a back up to H4350 and found it to be Temperature Sensitive to the point of not being able to shoot it above 85 F without high pressure signs. The initial testing was done 45 F, and further testing done as low as 29 F and highest 90 F. There was 10-12 fps increases per 10 F from 30-60 F, the 15-30 fps increases per 10 F from 60-90 F, with high pressure signs of very stiff bolt and primer sooting above 85 F.
The performance results were quite good at lower temperatures, yielding sub 10 fps SDs, but above 60 F the performance were less consistent, 15-20 fps SDs.
I determined it would be an acceptable alternative in sub 60 F circumstances.

 

[psychogecko]

I would agree that the temp had the most to deal with that, but if you want consistency use the same device, and what Steel Head said many ballistic calculators can help compensate for the changes from one event to the next.