Sighting in a .308

[Swift]

My son brought home his latest acquisition. A used Winchester Model 70 Stealth II with a Harris bipod and a BSA Stealth Tactical scope. He tried sighting it in and wasn't having much luck before he got cold. It's about 20 degrees here in Iowa. Actually much warmer than it has been! He left it here for me to play with. I set up at 35 yards, bagged it solidly and pulled the bolt to boresight it. It was close enough to try it. I shot three shots, bagged under the rear, tripod under the front. Three shots were touching each other about 1/4" above the bullseye. I then went to 100 yards and shot three more. Target was a paper plate with a 1" bullseye. None of them hit the plate. I wasn't sure I liked the hold I had with the bipod so I folded it up and bagged the front and back solidly. I shot three more and missed the plate entirely again.

My next step is to get a bigger target, but shouldn't they still be on paper since the 35 yard group was essentially touching the bullseye? I love my Leupold scopes, but I don't have a spare laying around to swap and I don't want to screw up a well sighted rifle yet. The BSA is tight in the mounts, but feels like the occular bell wiggles a little bit. What do you guys suggest?

 

[Doc Samson]

Always start with the scope, particularly if any of it's parts are wiggly.

 

[JackSprat]

I would think they should hit the plate, but they would be high,because your scope is higher than your barrel,and in essence you have the hairs,and the point of impact meeting at 35 yards.In theroy any thing inside of 35 yards would hit just a little low,and any thing beyond would hit progressivly high.If by some chance you have see thrus,or something high this would be magnified.

 

[jmr40]

You are missing just a little high at 100, probably just enough to be off a paper plate. With a 100 yard zero you'll be 1-1.5" low at 25-35 yards.

 

[Jackal]

The first and only BSA scope I've owned could not be zeroed. Turns out the crosshair was moving around inside the tube. Nearly drove me nuts, trying to track down the issue, then I shook the scope and heard the rattle...

 

[Robert101]

I typically use 25 yards, then 50, then 100 yards just for the reason you explain. Just because it appears all is good at 25 yards doesn't mean the end result will justify it. Seems to me that you are probably missing high.

 

[Gtscotty]

I pretty much always boresight at 100 yds. Try picking a corner of the target or some other visible but suitably fine aiming point, it's not hard to get pretty close at 100yds if you have a decent rest to sit the rifle in.

 

[Nature Boy]

Get a good solid position pointing at you 100 yard target, then pull the bolt and look down the bore from the breach end. Line the bore onto the target, then keeping the rifle steady look through the scope and see where your crosshairs are. Adjust from there to put them on target.

 

[Art Eatman]

Generally, dead-on at 25 yards is about three inches high at 100, assuming a low-mount scope. One or two inches either side of the vertical.

For most "deer cartridges" that are faster than a .30-30 but not magnum, 2" high at 100 is right at dead-on at 200 and roughly 6" low at 300, give or take an inch.

 

[Geno]

I recently gave my M70 Stealth II, 308 Win with Nightforce 12-42X56 to my nephew as an heirloom. Here is the load and zeroing I used. Your ammo (projectile weight and velocity) will make a difference in trajectory.

Load:
Brass: Lapua
Projectile: Lapua 155 grain Scenar
Powder: 47.1 grains of Varget (**Max loaded was 48 grains)
Primer: Win LR primer
COL: 2.909" (Does not fit in the max well...single round feed only)
Muzzle Vel: **3,010 FPS

Zero at 25 yards: appx -0.75".
Zero at 100 yards: appx +1.0".

It sounds like an optics issue. Congrats on an awesome rifle! For fun targets, we shoot shotgun primers at 100 yards. Great rfiles!

Geno

 

[NeuseRvrRat]

a very large piece of paper will save you a lot of frustration in these situations

 

[Swift]

Thanks for the replies guys. I did bore sight at 100 yards as well (by looking down the barrel and looking through the scope while solidly sandbagged) and it should have been on paper. My paper plate target is 9" diameter so I figured I'd be on paper with the 35 yard group being so close to the bullseye. I will try shooting at a larger clean target tomorrow to verify where the group is. I think I've got another cheap scope around to swap with the BSA to see if that's the problem. I'm really suspicious of the scope. Thanks.

 

[BigBore45]

It's the scope, BSA is junk

 

[Jackal]

It's the scope, BSA is junk

I've got to agree. Even Leapers would be an upgrade over BSA My BSA 3-9x shot the crosshair loose mounted on my 10/22 after about 200rds......

 

[Robert]

BSA is total junk. Try a different scope if you can.

 

[JackSprat]

I'm no fan of Chinese glass,but In this case I think it's just physics..I don't think you would have been consistant at 35 yards with the scope being bad ..You do need your target on something big enough to let you know were you hit if you are off the paper though..I would adjust the scope to shoot about 5 inches lower,at 100 yards,before I even shot.

 

[Nature Boy]

I'd just get a better scope and start over. You're going to eventually do it anyway because that rifle deserves better.

 

[Sunray]

"...crosshair was moving around..." Had a Tasco that did that. Couldn't actually see it until I put a bore sighter on. Every time I opened and closed the action, the vertical reticle would bounce left or right. You could try doing that with the rifle securely tucked into your sand bags. Tuck the rifle in tight and look through the scope while cycling the bolt.
If you've bore sighted at 100 the rifle absolutely should be on paper. 1/4" above the bullseye shouldn't be that much too high at 100 to be off a 9" pie plate. A big hunk of paper behind the plate will show you where it is shooting though.

 

[Swift]

I tried shooting it again with a bigger target tonight. The first shot was about 6 inches high and six inches left. The next three were in one ragged hole 6 inches high. I adjusted the scope to shoot six inches lower. The next shot was two inches below the bullseye, eight inches lower that the last three. I corrected the scope back up two inches and shot two more. The first one was an inch above the bullseye. The next one was four and a half inches high and an inch right. These were all shot from a front rest and rear bag from a portable shooting bench. I shot three from my .220 Swift with a Leupold VX3 and shot a 3/4" group. I think it's the scope! Thanks for the help guys.