What would cause a semi auto to loose muzzle velocity???

uncledillers

uncledillers

Regular
Rating - 100%
30   0   0
Location
Comox Valley
I have a sl8 and it shoots 300-400 fps slower than it should. That is comparing it to expected mv from factory ammo, hogdon reloading data, and mz stated by other sl8 owners. Does anyone know what might be the cuase of this??

Dylan
 
Expected mv and reloading book mv could be measured out of a longer barrel and the other owners might not be telling the truth. They might not have a chrony and are only using the numbers they read on boxes and in books
 
uncledillers said:
I have a sl8 and it shoots 300-400 fps slower than it should. That is comparing it to expected mv from factory ammo, hogdon reloading data, and mz stated by other sl8 owners. Does anyone know what might be the cuase of this??

Dylan
Click to expand...

In order, the answers are likely:
-the factory ammo has a number on it that only relates to the factory's own barrel, not yours.
-ditto for the reloading data, they used their barrel, not yours.
-other owners that shot the same ammo across a chrony, or read that same number off the ammo box? In either case, they didn't measure it out of your gun.

Yours will likely be different than theirs for a bunch of reasons, including, but not limited to, the size of the chamber on your gun, the diameter, smoothness of finish, and the perfection of the rifling in your barrel, the altitude density differences between whee you shoot and they do, and a horde of 'other' possible causes.

Does the stuff work, and does it work consistently? If so, fuggetaboutit. Otherwise, work up your own loads, for your own gun.

Cheers
Trev
 
Your description is vague. Are you shooting factory ammo and chronographing it or shooting reloads and chronographing the results for comparison to published data from factory loads and reloading books data? What length is your barrel compared to the ones used for the published data? You can expect to lose 50 ft/sec for every inch the barrel is shortened and many reloading data are based on results from 24" or even 26 " barrels. Need to tell us more details.
 
IIRC it was Tom Roster wrote an article on this recently(Reloading for Consistent Velocities, Handloader Magazine), the short version is this, SAAMI allows a 20% variation from published speed(this is partly why DR.EQ has lived this long), the standards are measured in a barrel of a specific set of standards for bore size, length and choke dimensions. Afterall that then you have to account for temperature variance. So under the right conditions that 1330 fps screamer load tested in July in southern ONT could equate to 1090FPS out of a different gun in January in NB. Clear as mud eh?
 
You must log in or register to reply here.
Back
Top Bottom