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Mentolio · Veteran Member

Hi, I own a Benjamin Marauder now in .22, and an Umarex/Browning Leverage, also in .22. The Leverage likes JSB Exact 14.35gr domes, and the Mrod seems to like JSB Exact 15.8 domes. Needing to re supply on pellets, I opted for some heavier JSBs (18.13gr Jumbo Heavy and 25.39gr Jumbo Monsters, both domed), and some Benjamin 14.3gr HPs. The Mrod grouped better with the 15.8s than the 14.35s, so I figured I'd try even heavier.
Now I haven't tried them out yet in my Mrod. I did try them out in the Leverage. It seems that the heavier the pellet I shoot thru the Leverage, the higher it's point of impact becomes (this being the opposite of the behavior exhibited by my Crosman Vantage NP when going from 7.33gr to 10.5gr. The 10.5s all hit several inches lower on the target than the point of aim). All shots are from 27 yards, and in groups of five. 14.35s point of aim/impact are the same (zeroed). Switching to 15.8s makes my point of impact about 2 inches higher than point of aim. The 18.1s still group tightly, but impact the target about an inch higher than the 15.8s. The 25.39s make for a sloppy group, and strike even higher! The heavier pellets do seem to fit a bit tighter in the breech, but so do Benjamin 14.3gr hps, and they group poorly and don't hit much higher than the 14.35 JSBs. My question is: doesn't this seem odd? I would think that the heavier pellets would strike lower on target as they should be, by their nature, traveling slower? Anyone else encounter this, or am I experiencing something normal?
I'll Chrony the pellets when the weather clears a bit, and see if indeed the heavier guys are traveling slower.

rsterne · Moderator

Barrel Harmonics....

Bob

longhunter · New Member

not really harmonics, more so the point in the recoil cycle at which the pellet leaves the muzzle. heavier or tighter fitting pellets take longer to exit the barrel than lighter or looser pellets, hence, the tendency to strike the target at a higher point relative to the point of aim.

Slavia · Moderator

As for interior ballistics, rsterne's answer is right on, but it's a combination of several factors. Barrels do indeed "flex" with harmonics, and the barrel's attitude at the exact moment the pellet exits depends on when the pellet gets there. Mass and pellet "fit" will influence that. So will powerplant characteristics - maybe the heavier pellet is a tad more efficient at soaking up energy from the spring/piston/transfer port.

Then there is the question of exterior ballistics. Maybe the heavier pellet has a higher ballistic coefficient and bleeds less energy (and therefore velocity) than the lighter pellet.

Or all of the above. I noticed the same thing with my G1 at 100 yards. I was surprised to see that 8.3 grain RWS Superdomes had almost the same P.O.I. as 10.5 grain Crosman Ultramags. In the end, it doesn't matter much. You pick the pellet that does what you want it to do and learn its behaviour at different ranges.