I've been testing this device in the spring as of late. Early mornings with temps around 35-45 degrees. It's getting warmer now but I would set right up with the rifle staying locked in my winterized travel trailer overnight. I kept it in a cold environmment in a scabbard in the back of the truck while driving out of town. One morning I shoot at a 600 yd. Target, 4ft. By 4ft. Cardboard painted flor orange with a black circle 8" wide. Next morning I would return, device on and inside the barrell heating it (its really crude looking right now, but functionality is what matters right now.) Straight up one shot at the same target and compare. The previous day cold shot, lets just say its a good thing the target is as big as it is. The "heated shot" is much better, actually inside the blackened area most times. I have compared this scenario on 6 different cold mornings and the shot aided by the device is always better.
Granted, this is not a $5000.00 custom rifle
, but an off the shelf browning A bolt with some trigger and bedding modifications and a personal load that has taken alot of research. That being that, I find this device to substantially increase the accuracy of that moment in the cold fall when a game animal isn't going to give you a few warm up shots. Lol.
The trick is to 1, heat the barrel evenly from the inside and all along the bore. 2, heat a slightly fouled barrel, not a spit shined clean one, and 3, the "device" cannot be made of metal itself as metal expantsionn would prevent easy removal at the moment of truth. So yes, the device must be removed prior to shooting, but at ranges that far, a little setup, ranging etc. Has to be done anyhow so one more step in your setup is not that big a deal.
But so far, this thing appears to make a difference!