Steyr Steyr LG110 HFT

[cavedweller]

When switching barrels, it's likely that your vertical zero changed. One barrel is likely to shoot higher or lower due to the inherent radial runout. This will affect your apparent trajectory. I say apparent because it's the combination of scope height in relation to the exit path of the muzzle that will alter the trajectory you are seeing.

The part I'm trying to convey is that the actual flight of the pellet is the same ...but the way its its perceived can be altered by scope height. You can change "scope height" by rotating your barrel.

makes sense an "got it". looking forward to the FALL :} forgot to mention the Alpha or Delta wolfs like the Ghosts have a one grub barrel orientation point... not rotating these bad boys. Love me a Thomas though.

 

[Smok3y]

Cavedweller,
I like the Alpha Wolf picture! Does that scope rail have a built in MOA? There is a reason I ask.

Where do most folks measure scope height? I ask that question for a reason. In playing around with various ballistics programs and trying to understand how they calculate trajectory I realized what an important role scope height plays. For my FX Crown MkII with a 500 mm barrel shooting 13.4 gr pellets at 820 fps a 1/10 inch change in scope height gives a .25 MOA difference in POI at 30 yds. That is two clicks on my Falcon scope. Maybe not terrible in FT but I have been shooting a lot of AGN 30yd Challange cards and that 2mm difference could change an X into a 9.

All of the programs I looked at use "barrel angle" to set your zero. Barrel angle is the angle between the scope centerline (moved down to the center of the muzzle) and the angle of the barrel. Move the scope up and the barrel angle must increase (measure as positive if the muzzle moves towards the line of sight of the scope) in order for the projectile to hit your zero because the angle must make up for both projectile drop and scope height.

Now if you have a scope rail with one of the now common 20 MOA (or more) built-in "positive or up" barrel angle you can dial less clicks on your scope to make up for the projectile drop and scope height. But what many folks miss is that the 20 MOA barrel up angle actually decreases the scope height. That is because (IMHO) scope height needs to be measured at the muzzle! It is only after the projectile leaves the barrel that gravity begins to do its work. And if you have a 20 MOA scope rail and a 500 mm barrel I am willing to bet the "effective scope height" has decreased by about 0.1 inches. That results in the afore mentioned .25 MOA change in POI.

OK now, am I getting this wrong? Happy to discuss.

Cheers,
Greg

PS - I love your member photo. It always seemed funny to me how the girls loved our dress whites! The collar was a pain, but they did make us look good!!

I shoot to measure scope height instead of trying to measure with a ruler/caliper on some scopes. Target about a foot in front of the rifle and then measure the distance between aim point and impact. This is your scope height. This allows for the MOA you mentioned in the rail. Can be very hard to do this because you can’t really focus that close (so I haven’t been able to do this will all scopes). Have to cover scope and put a pin small hole to see through (Google it).

Either way you can figure out the exact scope height that works for your ballistic app and your parameters by continuing to shoot. Found that out here. Whether you start by ruler, calipers, or shooting, the apps (Strelok for example) will allow you to update your scope height to a more accurate setting after you see how your actual impacts relate to what the app says or should be.

It has been a while since I’ve updated mine (over a year), but it works something like this… (you can search to find this too. Seems like I remember CCut or someone sharing this a few years ago.)
Enter your info (scope height, pellet, speed, etc) into the app closest you can get it. Zero your rifle at your 25, 30 , or whatever yards you want for your zero. Shoot at a closer range, like 10 yards and see how far off you are from what the app tells you. Adjust your scope height in the app until you find a match for the adjustment you should have at 10 yards based on your actual impact. Test and see if the rest of your scope dope works now based on the app.

 

[cavedweller]

I shoot to measure scope height instead of trying to measure with a ruler/caliper on some scopes. Target about a foot in front of the rifle and then measure the distance between aim point and impact. This is your scope height. This allows for the MOA you mentioned in the rail. Can be very hard to do this because you can’t really focus that close (so I haven’t been able to do this will all scopes). Have to cover scope and put a pin small hole to see through (Google it).

Either way you can figure out the exact scope height that works for your ballistic app and your parameters by continuing to shoot. Found that out here. Whether you start by ruler, calipers, or shooting, the apps (Strelok for example) will allow you to update your scope height to a more accurate setting after you see how your actual impacts relate to what the app says or should be.

It has been a while since I’ve updated mine (over a year), but it works something like this… (you can search to find this too. Seems like I remember CCut or someone sharing this a few years ago.)
Enter your info (scope height, pellet, speed, etc) into the app closest you can get it. Zero your rifle at your 25, 30 , or whatever yards you want for your zero. Shoot at a closer range, like 10 yards and see how far off you are from what the app tells you. Adjust your scope height in the app until you find a match for the adjustment you should have at 10 yards based on your actual impact. Test and see if the rest of your scope dope works now based on the app.

@Smok3y - good post.. the last paragraph is pretty much my method at this point but once in a while one of my too many guns and scopes likes to mess with the methods that leak out of my brain bucket.