Bad things can happen if your barrel gets too hot. First, with some barrels, the point of impact (POI) will shift or “walk” as the barrel heats up excessively. Second, even if the POI doesn’t change, the groups can open up dramatically when the barrel gets too hot. Third, if the barrel is very hot, the chamber will transfer heat to your loaded cartridge, which can lead to pressure issues. Finally, hot barrels wear out faster. This is a very real concern, particularly for varmint shooters who may shoot hundreds of rounds in a day. For this reason, many varminters switch among various guns, never letting a particular barrel get too hot.
How do you monitor your barrel temperature other than guessing by “feel”? BAR-L Benchrest strips visually display heat readings from 86 to 140 degrees. Think of these strips as compact, unbreakable thermometers. With adhesive backing, they can also be used to monitor barrel heating. Put a strip on the side of the barrel and the barrel’s temp will be indicated by a stripe that changes from black to green. There is also a “general purpose” strip that reads to 196 degrees (bottom row). The Benchrest strip (86F to 140F) is in the middle.
Value-Priced Temp Strip 10-packs
If you have many rifles, McMaster.com (a large industrial supply house) offers the same reversible, 7 temperature, 86F to 140F strip (item 59535K13) for $11.86 per pack of ten (10) strips. That’s an excellent value. Thanks to reader Josh B. for this tip!
Another source for BAR-L Temp Strips is Neconos.com. This vendor offers Bar-L temp strips for $9.00, or $25.00 for a 3-pack.
Controlling Ammo Temperature is Important Too
Keeping your loaded cases at a controlled temperature is vital for maintaining good ES and case life. At a late summer varmint match we observed pressure signs with cases that had been sitting in direct sunlight for about 15 minutes. As we were running a “moderate” RL15 load, the pressure indications were surprising. Testing over a chronograph, cases that had been sitting in direct sunlight showed velocities up to 70 fps higher than those that had been kept in the shade. Using QuickLoad’s temperature function, we calculated from the rise in velocities that case pressures had increased by over 4,000 psi–just from 15-20 minutes in direct sunlight!
how hot is to hot
Comment by martin — July 17, 2009 @ 12 pm
No easy answer on that! What IS known is that heat kills barrels.
Rapid-fire (OTC) shooters know their barrels will suffer from the necessary 10 shots-a-minute, two or four times a match (or more, if alibis are involved) but that’s part of the cost of playing the game.
You need to know what your “comfort level” is for barrel lifespan and safety margin when shooting loads near the limit on hot days. I’ve gone as far as to take my ammo boxes to the long-range line in a small ice chest when the sun’s out and the temp’s already 90+ if the load I’m shooting was tested at 60.
Comment by Steve Clark — July 17, 2009 @ 1 pm