I was at the range today. Temp was around 68 degrees. I fired around 40 rounds and noticed that the last 3 groups were horrible. The barrel was very hot. When you guys shoot, how long do you wait in between shots. Also do you do anything to cool the barrel down?
After the first couple couple shots, I wait about 2-4 minutes between shots depending on barrel contour, cartridge, temperature and wind... what ever it takes to keep the bbl temp the same, which is just "barely" warm to "cool" to the touch. [img]images/icons/smile.gif[/img]
Throat errosion is the worst enemy with heating them up excessively. Groups may change as tolerances change and length of time the cartridge dwells is the chamber before firing, a "good" chronograph will indicate how bbl temp is affecting velocity and thus trajectory, also harmonics will change if this occurs. Alot can go on if things aren't kept consistant.
When I shoot steel at long range, I'll always shoot groups like I would hunting to see how the rifle performs in that situation. If I am making a drop chart, I keep all things consistant, as I do on load development.
Noting the cold shot impact is very important, as well as point of impact shifts.
I only start making a chart, load development, or head out hunting with at least 3 rounds through the barrel to foul it first, some guns take 5... no oil in the bore after that, just tape on the muzzle when hunting.
Some loads toward maximum load are more sensitive to bbl heating than others, a good chrono will tell you what's happening in the chamber though. [img]images/icons/smile.gif[/img]
I've noticed on my 300 Ultra, that after about 25-30 rounds... groups start to open up. I know to clean it after about twenty to 25 rounds now if I'm serious about getting meaningfull results, yours may foul up bad enough it needs cleaned under thirty rounds too.
samson, I think you shoot a 300 winnie, right. You might want start cleaning around 20rds as Brent stated, If you haven't started to do so already. If you want to know where your first shot is going, as for a hunting situation, you might want to shoot 1 round every 10min. that will give your barrel time to cool off quite a bit, if you just want to shoot the damn thing, take 3 shots and let er' cool down for 10-15min. Or you can do what the varmint guys do and bring out a portable air compressor and blow air down the barrel to cool er' off. [img]images/icons/wink.gif[/img] Jay.
Samson, I only let me barrels get warm to the touch, never hot. I wrap them with wet cold towels to help cool faster. I bring a small pop can cooler with water and an ice pack during the summer.
As to cleaning, I am different. I only clean when the rifle shows degrading accuracy. Maybe it is because I use moly but I rarely find the need to clean at 20rds. Usually, 50rds or more go before I think about it. A couple haven't been cleaned and they are approaching 70rds.
Some rifles shoot best when fouled, some heavily fouled. Over cleaning is just as bad as not cleaning enough. If you are shooting on paper, keep shooting until you see your groups open up dramatically (like double in size). Then only clean as much as you need to restore accuracy.
You will read that most will need a few fouling shots to get their barrels to settle down before shooting their best. Well, after those fouling shots, the barrel is pretty dirty.
I agree, I only clean if my gun won't group consistantly anymore. After groups fall apart when only 20-30 rounds been down the bore, it's definataly "over fouled". I've never shot beyond 20 more rounds after that point to see if it would settle down again, too easy to clean then go another 20-30 that I know for sure will be right on.
I've read that some guys accuracy don't fall apart until 100-150 round when using moly.... wouldn't that be the cats ass!! Haven't heard if the same's true with tungsten disulfide coatings or not.
I have a couple rifles that don't degrade noticably for over 50 rounds, but I rarely shoot one rifle over that many in one day at the range so they all get cleaned at that point if they need it or not. Just can't stand the thought of getting started the next time out and groups going to hell after the first few round down range basically. One of these rifles has the roughest bore you could imagine too. [img]images/icons/rolleyes.gif[/img]