Friday, May 21, 2010
The Whole AR Gas Piston Hype
1. Does a gas piston AR run cooler than a direct-impingement AR?
First, it depends on what gas piston we are talking about. There are currently a lot of different designs out there and they are not all equal. Some of them are worse than the DI systems they are trying to replace.
Second, it depends on what part of the AR you measure. The bolt can be cooler on a piston AR (and the handguards/gas block will be hotter); but I haven't yet seen any evidence that it makes a difference. Some have claimed that running the bolt cooler improves bolt life and cam pin life; but it seems to me that more modern manufacturing techniques, proprietary bolt designs, and different loading has more to do with differences in bolt life than the temperature. As evidence of this, DI AR15s like the Knights SR15 that use a proprietary improved bolt and barrel extension seem to last longer as well.
2. Does a gas piston AR have a cleaner upper receiver than a DI AR?
Absolutely. The less clear question is "Does it make any functional difference?". I believe Pat Rogers just had a Bravo Company Midlength (DI AR) go 28,905 rounds in training classes with no cleaning at all. It did require some parts replacement as parts wore out; but all they did other than that is add more lube periodically.