This has probably been discussed previously but, if so, I can't locate it. My son is purchasing a LMT switch barrel rifle with a 16"/ .308 barrel and a 18.5"/ 6.5CM barrel. My brain tells me he should be able to zero one of the barrel/ caliber/cartridge at X yards and place that information into a ballistic app. Then it should be possible to figure out what distance the second barrel/ caliber would cross the first caliber's trajectory to learn that particular barrel/caliber/cartridge zero and place that info in the ballistic app as a new profile. Confirming that zero by testing. Again, in my head, this should allow the scope's zero settings to remain unchanged and only the info from the ballistic app profile for the particular barrel playing a role in elevation settings for each shot? Am I making my brain do math that makes no sense? Thanks for any assistance, anecdotes, suggestions or experience. Or wake me from my ignorance please.
- Thread starter Ivaduck
- Start date
its a fine theory but its unlikely to have your true zero line up perfectly on elevation. You'll almost certainly be a couple tenths off at minimum
What is more likely the best course of action, is to get a solid zero with one barrel. and see where your POI is different with the 2nd and have your ballistic app account for a "zero offset".
Depending how far away from each other both zeros are.
What is more likely the best course of action, is to get a solid zero with one barrel. and see where your POI is different with the 2nd and have your ballistic app account for a "zero offset".
Depending how far away from each other both zeros are.
What black snow mentions above is correct. I also have an LMT and switch between a 14" P&W 308 barrel and 18" 6.5 Creedmoor and the offset between the two is not large but is there so you want to make sure your zero offset is properly accounted for, but also be aware that if the device that holds this information goes down and you use some other device for your solution it could be off, so always good to have a hard copy (paper) backup.
Very common for AI shooters“2 barrels, 1 scope” sounds oddly familiar…
@Ivaduck
Could also zero the optic to the primary barrel and log the offset with the other barrel. When he shoots the secondary barrel, just adjust the turrets to the offset and use the reticle for adjustments when shooting.
Then we he goes back to the primary barrel, all he has to do is zero out the turrets.
Could also zero the optic to the primary barrel and log the offset with the other barrel. When he shoots the secondary barrel, just adjust the turrets to the offset and use the reticle for adjustments when shooting.
Then we he goes back to the primary barrel, all he has to do is zero out the turrets.
So long as the barrels return to zero then, yes this is easily done.
The easiest way is to set one barrel as the primary one which is what you zero the scope to, then the other barrel is set up with the appropriate offsets in your ballistic app.
If you get luck your elevation should be pretty close, and with capped or locking windage turret just dial out the wind.
Unfortunately my Tikka 260 and 6.5CM barrels have a 2mil difference in elevation, which isn't ideal.
The other option would be to have two scopes and switch them with the barrels, say a 3-18 for the 6.5cm bbl and a 2-10 for the 308 bbl.
If found with most rings scopes RTZ perfectly, and at time have had 3 scopes zeroed to one rifle and move them around during testing.
The easiest way is to set one barrel as the primary one which is what you zero the scope to, then the other barrel is set up with the appropriate offsets in your ballistic app.
If you get luck your elevation should be pretty close, and with capped or locking windage turret just dial out the wind.
Unfortunately my Tikka 260 and 6.5CM barrels have a 2mil difference in elevation, which isn't ideal.
The other option would be to have two scopes and switch them with the barrels, say a 3-18 for the 6.5cm bbl and a 2-10 for the 308 bbl.
If found with most rings scopes RTZ perfectly, and at time have had 3 scopes zeroed to one rifle and move them around during testing.
Zero barrel 1 at desired starting distance. Reset turrets to 0. Make sure it's the caliber you're gonna shoot the most. Better yet it's the most accurate barrel as well. This is so you can accurate determine how repeatable your system is.
Switch to barrel 2 and zero scope to that barrel but before you reset the turrets to zero, note the 'offset' from your first barrel. Write it down.
From there you can test repeatability between the barrels and true your dope for distance. If it's repeatable just dial the offset between the 2 barrels and there you go.
Works well on my rifle. Luckily half a minute of windage at 100 is my offset from 308 to 223..
Switch to barrel 2 and zero scope to that barrel but before you reset the turrets to zero, note the 'offset' from your first barrel. Write it down.
From there you can test repeatability between the barrels and true your dope for distance. If it's repeatable just dial the offset between the 2 barrels and there you go.
Works well on my rifle. Luckily half a minute of windage at 100 is my offset from 308 to 223..
This is very similar to how I do mine with my LMT. I would also point out that my LMT is pretty good with RTZ after barrel swap (using a torque wrench on the two barrel bolts) but not quite as good as my AI's have been, so I always try to confirm zero especially if I'll be shooting at distance.
Thanks so much, this is a ton of good info. I had forgotten about the zero offset within the app. Can hardly wait to read back through these posts a few times and get ready to play! Again, I appreciate your time and thanks for the encouragement.
