{"id":948,"date":"2010-10-11T01:00:51","date_gmt":"2010-10-11T08:00:51","guid":{"rendered":"http:\/\/www.airgunsofarizona.com\/blog\/?p=948"},"modified":"2010-10-04T10:41:59","modified_gmt":"2010-10-04T17:41:59","slug":"powerplant-pellets-and-footpounds","status":"publish","type":"post","link":"https:\/\/www.airgunsofarizona.com\/blog\/2010\/10\/powerplant-pellets-and-footpounds.html","title":{"rendered":"Powerplant, Pellets, and Footpounds"},"content":{"rendered":"

For years, I have heard things like \u201cspring-pistons don\u2019t like heavy pellets\u201d and \u201cCO2, pre-charged pneumatics and pump guns are more efficient with heavy pellets.\u201d I guess I just accepted these truths as an article of faith and never really thought much more about them.<\/p>\n

But recently I have been testing several .25 caliber \u2013 quarterbore \u2013 air rifles, and the tale that the chronograph tells is interesting. Put simply, when it comes to power generation \u2013 that is, foot-pounds measured at the muzzle \u2013 springers tend to like light pellets and pneumatics prefer heavier pellets. Of course, it isn\u2019t always a straight linear function, because there are other variables, such as how tightly the pellet fits in the bore.<\/p>\n

It all started when I was chronographing a trio of break barrel .25 cal. springers. I was using Gamo Pro Magnum 21.91 gr. pellets to chronograph them, because I had a plentiful supply of those pellets. One of the rifles was slinging the Gamo pellets at 565 fps average, which works out to 15.53 foot-pounds average. I mentioned this to the importer, and he suggested trying JSB Kings<\/a> (25.4 gr.). Somewhat counter to the \u201claw\u201d about springers, the heavier pellet did better in terms of power but slightly worse in velocity: the JSB Kings averaged 555 fps for 17.37 foot-pounds at the muzzle. But the real surprise came with the lightest pellet. 19 gr. Milbro Rhino<\/a> pellets rocketed through the traps at 667 fps for a sparkling 18.7 foot-pounds. In this case, the law about springers proved right: the lightest pellet did generate the most power in this .25 cal. spring-piston powerplant.<\/p>\n

Okay, I thought, but what about the pneumatic airguns, do they obey the \u201crules\u201d or not? It was raining when I thought about answering this question, and I usually need to do my chronographing outdoors, so I turned to the respected varminter Cliff Tharpe. Cliff, whose online handle is VarmintAir, is producer of the Airgun Hunting the California Ground Squirre<\/a><\/span>l<\/span> DVD. He has deep experience in hunting and clobbering vermin with air rifles.<\/p>\n

Cliff has a factory stock .25 Benjamin Maraude<\/a>r that he routinely uses to pop prairie dogs at 50-100 yards. He sent me some data on his experience chronographing different weight pellets through the Marauder, with the following note: \u201cThese were all shot at the factory settings, whatever those may be.\u00a0 All velocities were taken with the start screen 12 inches from the muzzle.\u00a0 I use a CED M2 Chronograph set up indoors, with the infrared screens.\u00a0 Two mags, for sixteen shots with each pellet.\u00a0 All pellets were weight sorted.\u00a0 This is with a 3000 psi fill.\u00a0\u201c<\/p>\n

And here\u2019s the data:<\/p>\n