QB78 .177 MV- okay @ 600fps?January 27 2017 at 2:17 PM
cobalt (Login cobalt327)
New .177 QB78 bought 12-2016. Totally stock. Tested using a chronograph. First CO2 cartridge, getting ~600 fps w/Crosman Premier HP 7.9 gr, want to know if this is reasonable or abnormally low- I've seen reports of QB78 velocities being higher but little/no info on what, if anything, has been done to these guns to get the higher MV. All that I have done is clean the barrel prior to shooting it the first time.
Thanks in advance, Mark
|January 27 2017, 5:55 PM |
How cool was the rifle (lets assume it was whatever the air temperature was)?
Seems a little low to me, asuming your were shooting in air temperatures above 60F
|January 27 2017, 9:03 PM |
According to the website Scott referred you to...
|January 28 2017, 1:36 AM |
...a stock QB78 .177 should do about 625 fps.
But what the other fellow said: CO2 is highly sensitive to cold temperatures.
|January 28 2017, 3:11 AM |
It was around 60-65 deg. F. when I tested the MV. If 625fps is about "normal" @ 75 deg. F, my gun is about where it should be, maybe a touch low, so I guess I can live with 600fps @ the temps I was shooting at. Thanks everyone.
|This message has been edited by cobalt327 on Jan 28, 2017 3:15 AM|
Easy enough to test...
|January 28 2017, 9:41 AM |
...rifle won't cool down super fast, so if you set it in a warm room for a half, then quickly chronograph a couple of shots.
Good news is that all the QB's so far have gotten a little faster as the moving parts "mated up" and ran smoother.
|January 28 2017, 9:28 PM |
According to a very reliable source, Steve Archer of Archer Airguns, "The muzzle velocity of QB78-type guns varies by about 2 fps per degree Fahrenheit". So my gun is right where it should be. Guess I'll have to find something else to worry about!
Thanks for the help, everyone. I appreciate it.
Re: No worries
|February 7 2017, 3:23 PM |
Yes, 600 FPS for a stock QB78 in .177 caliber is right on the nail for muzzle velocity at 65 degrees F.
And yes, my experiments showed a difference of around 2 FPS per degree F in temperature change.
Archer Airguns Inc.