Author Topic: Temperature and accuracy (Read 378 times)

jack19512 · « **on:** September 24, 2005, 01:28:50 PM »

In the rimfire forum I posted that I was disappointed with my new 22Mag Ultra"s accuracy. When I was shooting the 22 Mag I also had my 223 Ultra also. Funny thing was my 223 wasn't grouping like it had been either. I chalked it up to a long hot day and it was just me tired.

My son-in-law also had his 223 Handi and his 17HMR also and he could not group well with either of those rifles either. His 223 Handi was new and was being shot for the first time but his Marlin 17HMR had always been very accurate at 100 yards before.

Now it was almost 90 degrees here in the shade so you can imagine how hot it was in the full sun. Now, is it possible that it can be so hot that every rifle that you have that was accurate before now won't group worth a crap? I know it sounds crazy but neither myself or my son-in-law could group well with any of the rifles we shot real good with before.

And no, there were no drugs or alcohol involved. But there was plenty of heat.

Mac11700 · « **Reply #1 on:** September 24, 2005, 01:45:24 PM »

Absolutly...high tempreatures can make all rifles group differently...it not only changes the pressure the cartridges produce,but cause shifts in the POI from the barrel reacting differently...and it can cause the shooter to change his shooting technique from being too hot and rushing to aiming wrong because of mirage...on the opposite exteme...being too cold can have simalar results...including the mirage from shooting over warming snow and ice..

Mac

jack19512 · « **Reply #2 on:** September 24, 2005, 02:46:00 PM »

The reason I asked about temperature was because I have been reading everything I can on reloading and I came upon this post about loading ammo in let's say February and saving the ammo and shooting it in August.

The author of the post talked about the difference in pressure the ammo would exhibit between the varying temperatures.

My last shooting at the range was very disappointing to say the least. My new 22Mag Ultra and even mine and my son-in-laws past accurate rifles weren't grouping at all like they had been and this has been on my mind a lot as to why they weren't.

I find it difficult to believe temperature was the problem but this is the first time this has happened to me and I am at a loss as to what went wrong. Now to be honest we don't have the best of scopes on these rifles and how much they may have played in this I don't know.

trotterlg · « **Reply #3 on:** September 24, 2005, 03:04:24 PM »

Just in general: Ball powders are more temperature sensitive than extruded powders, I don't know about flake powders, but I do know about the ball and extruded ones. Too bad, ball powder is so much easier to load with. Larry

jack19512 · « **Reply #4 on:** September 24, 2005, 03:09:55 PM »

Would someone care to explain to me what is the difference between ball powder and extruded powder? Thanks

trotterlg · « **Reply #5 on:** September 24, 2005, 04:01:59 PM »

Well.............................Ball powder looks like tiny round balls, extruded powder looks like small broken up pencil lead. Larry

Mac11700 · « **Reply #6 on:** September 24, 2005, 05:43:33 PM »

A simple solution to the problem with powders is to use Hogdons Extreme series of powders...they are way less sensitive to tempreature swings.

If you haven't had a-lot of experiance with shooting in extreme temps...you won't know why you got the differences...if your scopes,rings,mounts are at fault...then this could be a big problem,if your barrels are heating extremly fast and you have a bedding problem..it will do the same thing....I would check to see if something is off with them first...but I doubt if all of them are off at the same time...and would bet that your POI has shifted because of the heat.I also suggest shooting you ammo across a chrony with those temps and at the temps you sighted in for..you'll see right off what I mean.

Mac