Long Range scope set-up help

[barthmonster]

I've done just enough reading on here to get me in trouble. Don't know what to search for so I'll ask.

I have a Savage model 12 F/TR in .308 and I wanted to learn to shoot first then longer range (why I chose the rifle). I put on a Ken Farrel 20 MOA scope base and put on a scope I already had. It's a Burris Signature 6-24x (1" scope)

With the scope all the way down, the gun shoots ~ 8.5" high at 100 yards. Do I need a 30mm tube scope ? Or just ditch the 20 MOA base ?

Just had target knobs put on the scope too...

 

[SBruce]

Sounds like you'll have plenty of up adjustment left!

One thing you can do without changing the base is to use a set of the Burris rings with the inserts. If I remember correctly, they will give you up to approx 10 minutes in any direction you choose. They should get you close to dead on at 100 without the expense of a 30mm tube or new 0 minute base.

If it were strictly a Long Distance rig, it wouldn't bother me to be 12" high at 200 and dead on at approx 400, but that would bother some others.

 

[LouBoyd]

The older 1" Burris Signature series scope had a very small range of vertical adjustment.
I don't know the exact model you have, but I had one wich ddin't have +/- 20 moa of adjustment.
it also had target knobs where the number of clicks didn't match the number of makrings per revolution. (60 vs 56). That got real confusing. My advice would be to get a different scope.
Even the $200 Burris 10x40 mil-do0t 3200 series scopes have about 90 MOA of vertical adjustemtn. The Leupold Mk 4 M1 16x40 has 140 moa of vertical adjustment, more than is needed for most cartridges which will reach 2000 yards supersonic.

Before you buy a scope or a base run a ballistics program on the ammo you plan to shoot. I don't want any scope on my rifles which won't zero from 25 yards to whatever the maximum supersonic range of the bullet is. Also subsonic cartridges like the 300 Whisper and 300 BLK need lots of vertical elevation adjustment if used to their maximum effective range. As rule of thumb don't used a base with more than half the moa of the adjustment range of your scope. I leave at least 10 MOA so the scope never bottoms out.. That assumes the scope is symetrical.

Scope knobs don't have to be symetrical. Not all scopes need tapered bases. For example in the Horus falcon the reticle is already offset by 20 MOA.

 

[barthmonster]

It's a 6-24x44 Posi-Lock Signature. Sucks since it was nearly $500 a few years ago and I just had $80 target knobs put on at burris..

I've got the Burris Signature Zee rings with inserts on it now, I can probably buy just the 'offset' inserts and take 10 MOA back out reducing my 20 MOA base to an effective 10 MOA, that should take care of the 8.5" high thing. Hopefully the scope will still have enough adjustment to get my little .308 to 1000' even if it's only target shooting.

I'm not ready to hunt past 250 yards without more practice. I'll get there though. Probably use the 7mm RUM if I do it.

 

[SBruce]

It's a 6-24x44 Posi-Lock Signature. Sucks since it was nearly $500 a few years ago and I just had $80 target knobs put on at burris..

I've got the Burris Signature Zee rings with inserts on it now, I can probably buy just the 'offset' inserts and take 10 MOA back out reducing my 20 MOA base to an effective 10 MOA, that should take care of the 8.5" high thing. Hopefully the scope will still have enough adjustment to get my little .308 to 1000' even if it's only target shooting.

I'm not ready to hunt past 250 yards without more practice. I'll get there though. Probably use the 7mm RUM if I do it.

How many total minutes are available in the scope, from lowest point to highest point?

I can run the ballistics for you if you want, gotta tell me the bullet, velocity, altitude/temp, and where you want to zero at.

If you've got 40 usable minutes of "up" left from where you are now, and you get the offset rings to get you -10 minutes, then in theory you'd still have about 37-38 minutes left to play with after zeroing at 100. That's enough to get you to 1000, but maybe just barely (according to the numbers I am looking at now).

 

[barthmonster]

how do I tell, count the total clicks ?? Or try to 'look it up' on burris site ?

30" .308 barrel. 168 gr A-max. Mild load of 43.0 Varget, I got it from an article about Brad Suave on 6mmbr.com supposed to be accurate. Don't have a chrono, sorry..

My 175 Gr. A-max load is H4895 and is hotter. H4895 about 1.5 gr. below max I don't have my load-data with me.

 

[SBruce]

Yes, count the clicks or minute marks from stop to stop on the elevation dial.

We can go off of factory advertised velocity using those bullets, but still need to know the altitude of where you plan on shooting 1000 yds.

 

[barthmonster]

I'm sorry, I live at about 1350 feet.

I was AMAZED at how the ballistic co-efficient made a huge difference in elevation of impact. Those loads I listed are slower with the 168 A-max (they are a light load) plus a heavier bullet, however they printed higher at 100 yards than Federal 150 grain hunting (flat-base semi-spitzer) bullet factory ammo. Those sleek bullets really make a bigger difference than I thought...

 

[SBruce]

The difference you're seeing at 100 yds likely isn't because of the BC of the bullet. That usually doesn't have much effect till you get out past 300 yds.

I couldn't find the BC of the 175 A-Max, but I did find one for the 178 A-Max.

OK, just based on advertised factory ammo velocities; the 165 should be able to get about 2800'/sec. The 178 should maybe get 2650.?

We'll assume 100 yd zero and standard atmosphere at 1350' elevation.

The ballistic program says you'll need 33 minutes to get to 1000 with the 168 going 2800'/sec. Same program says you'll need 36 minutes to get to 1000 with the 178 going 2650'/sec. The BC of the 178 is only slightly more than the 168 according to the program, so it doesn't help enough to make it worth while. If you could push it at 2750 or so, it would be better.

 

[barthmonster]

I'm going to need a chrono I guess. I know the 30" barrel gives me more velocity, just not sure how much. I'm loving my first-ever try with Lapua brass btw, stuff is purty..

Thanks for the help. I'm going to order burris' off-set inserts to take back 10 MOA and check the full MOA-range of the scope. Hopefully that will do the trick.

really I just need to practice. My groups suck and I know it's me ! My .223 encore-barrel with blue-dot reduced loads I can almost make all the holes touch at 100 yards. Guess I'm a wuss about recoil, if you can call a .308/.270 recoil..

 

[barthmonster]

Looking at ordering the set which includes various offset inserts. Counted clicks, but might have lost count a couple of times.

Refurbished 6-24x44 Burris Signature Select Riflescope Plex Reticle Matte PA Posi-Lock - Natchez Shooters Supplies

This is my scope, says 22-inches of 100 yard adjustment (~22 MOA), which won't do 1000 yards. That's okay for now.

I'll get the inserts, then maybe zero at 200 yards and do some practice at 500-600 yards, I need it !

The (mis-counted) clicks were at or near 200 (multiply by .125 or divide by 8) gives 25 MOA so possibly the 22" is conservative, we'll see.

Maybe the 8.5" high at 100 will only be 5" high at 200 and I can use the 5 MOA offset inserts, that will help too.