One of the things that isn't often considered when we travel to a range to shoot is the effect of temperature and the sun on our gear, especially ammunition. The facts are that extremes of heat and sunlight boiling down on the weapons and the ammo left on a shooting table can raise the pressure levels significantly. Also the reverse is true. Go to an outdoor range in winter in fairly cold weather and your ammo is suddely lower pressure than you expected and may even be a bit more unreliable. Your zero for your sights will change. Now this won't effect you much at the short ranges you use a Rohrbaugh at, but in heat it could be catastrophic regardless of the firearm.
I used to use a chronograph periodically and found that in the high summer heat, velocities would be higher than normal. I also had a major problem experience once which I believe was induced by my own lack knowledge at the time. Back in the early '80's when I was both building custom 1911's and also a designated foreign correspondant for a French Shooting magazine, I was contacted by the people at Devel. They had one of their chopped 9mm S&W Devel pistols that they were going to give away to a Devel dealer at the SHOT show. They teamed up with Glaser to promote both their pistols and a new high powered +P type Glaser safety slug for this drawing. Devel wanted me to test the weapon for the magazine and shoot it with these new Glaser Safety slugs which had a black tip instead of a blue. I had a photographer with me and we went to an outdoor range used by my department. We put the gun and test ammo out on the table in the sun and took, copious amounts of pics etc for about an hour. It was about 95 degrees out and we had no shade.
Then I went to shoot the pistol. First shot it blew in my hand. The pistol contained everything and only the grips fragmented but the hood expanded up into the port and the magazine was bulged out. Needless to say my hand hurt a lot and there were some plastic fragments imbedded in it. Devel blamed Glaser and Glaser blamed Devel. I wasn't smart enough to know what happened. As I gained a bit more experience I believe that the increase in pressure that was caused by having the weapon and ammunition in the sun may have been the culprit. Since then when I am outdoors I use a cooler to store my ammo at the range, unless the firing points are covered and in shade. When I attended the NRA Long Range Rifle Instructors course at Raton, NM, I had a cooler I carried with me on the line to store my ammo since the firing points on the 1000 yard range are not covered. I had a larger cooler with cool packs in it in my topper on my truck for my bulk ammo that was being used for the week, and I kept my back up sniper rifle in a aluminum sealed case. Something to think about.
