When I got my texan 357 several years ago I got it just to do something different deer hunting. I tried many bullets, including for grins trying jacketed bullets(that's another thread) and settled on Hornady's 158gr semi wadcutter cowboy bullet balancing cost/accuracy/availability. It is a swaged lead bullet, knurled and lubricated, and works very well in my texan with a fire lapped barrel. Shooting off my front deck I settled on a 3100 psi fill and get two shots that are within 5 fps of each other. I use a Labradar and typical two shots are 906 and 903, if I am just a touch below 3100 it typically shoots 908 and 900, a touch over 3100 and it typically goes 903 and 902-904(valve lock starts happening around 3120 and is very sensitive to even 10 psi at that point. By 3150 psi or a smidge over, it is in the mid 600's fps. One thing I never thought about was the temperature in my house where I fill my texan when going hunting, and the temperature while I'm hunting. My very first day taking it hunting several years ago the temperature was 64F when I walked out of the house at 5am. Around 1 pm temperature was up to 87F and I was about to walk back to the house and have lunch when a coyote trotted down the draw below me. I never pass a shot on a coyote, even a bad shot, they are non native here and decimate the turkeys and do a number on the fawns. I don't care where I hit them, I will take any safe shot with whatever I have on me when I see one. So I take a shot at 40 yards on a trotting coyote in the brush and the texan goes BLOOP, almost zero recoil. WTF!!! was my reaction. I sat there stewing for several minutes and looked at the pressure guage, it was clearly at the point of valve lock close to having a slug stuck in the barrel. That actually made me feel better as I thought the rifle may have broken. There was filtered sunlight where I was sitting on the ridge top and that had warmed up the bottle even more than the ambient temperature. I walked to the house, got on the internet and found the math for pressure change in air vs temp. P2=(P1 * T2) /T1 where pressure is in pascals and temperature is in kelvin. Did the conversions and the math and had my answer. I have to fill the texan according to the temperature range I expect when hunting and protect the bottle from sunlight, and often that means only one good shot until the temperature climbs as I'm hunting and only 1 shot if temperature falls enough while hunting. One shot doesn't bother me, other than crop damage shooting I did in Va. back in the 80's I can count on 2 fingers the number of times in 40+ years of deer hunting the number of times I took more than one shot. Other than crop damage shooting, twice in over 40 years I have shot 2 deer back to back and I have never shot twice at the same deer.
I filled the texan that morning in the house to 3100 psi at 75 F, at ambient temp of 87F when I took the shot the pressure would have been up to 3170 which would be getting into serious valve lock on my tune probably less than 400 FPS from my testing, with the filtered sun on the black bottle assuming 100F the pressure would have been up to 3244 which would have left the slug in the bore so the filtered sun did not get the bottle temp up that high. With my firelapped barrel and sized slugs, getting a slug stuck in the barrel is no big deal, it pushes out easily. I don't recall ever reading about filling according to temperature range expected when hunting, and protecting a bottle from being in the sun while hunting. Live and learn.
I filled the texan that morning in the house to 3100 psi at 75 F, at ambient temp of 87F when I took the shot the pressure would have been up to 3170 which would be getting into serious valve lock on my tune probably less than 400 FPS from my testing, with the filtered sun on the black bottle assuming 100F the pressure would have been up to 3244 which would have left the slug in the bore so the filtered sun did not get the bottle temp up that high. With my firelapped barrel and sized slugs, getting a slug stuck in the barrel is no big deal, it pushes out easily. I don't recall ever reading about filling according to temperature range expected when hunting, and protecting a bottle from being in the sun while hunting. Live and learn.
