Prime subsonic HP - temperature sensitive

[DownhillFromHere]

A number of Hide denizens have posted about experiences with Prime 40-grain subsonic hollow point ammo bought during Prime's moving sale. The consistent finding is the ammo is inconsistent.

Now I'm finding it's temperature-sensitive as well.

At temperatures of 80-90 degrees F., it chrono'ed near its box-printed velocity of 1034fps out of a 16" CZ 455.

Today, with ambient temp of 54 F., I got a 20-round average of 985 fps - a 50fps drop for 30-degree temp drop.

In fairness, my other .22 ammo may be similarly temp-sensitive but I haven't checked it... if my Wolf and CCI ammo slows down at a similar rate, the cool-weather velocity will fall to about Prime's warm-weather velocity. I'm finding the Prime is so soft now that it doesn't cycle my semi-auto pistols reliably.

Anyone else seeing this?

 

[straightshooter1]

Well, I ran a little test just a little while back on the effects of temperature variance on CCI SV's, Federal Ultra Match and Lapua Center X and posted the results in the ER Shaw Ruger Precision thread. And based on my results . . . yes, you'll find some variance with that much difference in temperatures with 22 LR ammo. With these particular 3 makes, you can see the differences I got in the attached PDF file (blue colored font are the cold rounds). One of the things I found of surprising interest in this test was not just the difference in MV's (BTW, used Magnetospeed for my chrono), but also in the standard deviations where some did better and other's did worse and that tended to show up on the paper. So, it's not just MV that's gong to be affected.

I guess this is why some manufacturers have specialized loads for cold weather (e.g. Lapua's Biathlon Extreme)

 

[DownhillFromHere]

Good stuff, straightshooter... looks like the Prime still had significantly more substantial velocity falloff over a smaller temp spread.

As said before... as good as Prime centerfire ammo is, it's surprising and disappointing that Prime .22 ammo - at least the 40-grain subsonic HP - doesn't measure up to the same standard.

 

[Rover31]

As an fyi
Both of the Prime 22lr’s are made by RWS