string left to right (or right to left)

[Tn Tom]

What generally causes a group that is acceptable elevation wise (.400" @ 100 yds) mesure 1.300" windage. (5 shot group)

The scope has been checked for tight mounts and rings. Both have been loctited. The scope is a new Bushnell 6x-18x-40mm. Mounted low but not touching the barrel (.010). Rings are lapped.

I've rechecked the pillar screws (action is also bedded). Everything is tight.

The wind was less than 3 mph maybe a gust to 5mph? Chrono has the velocity at 3008. This is a .220 Rocket in a Ruger 7 MkII action. 69 gr Nosler HPBT, 33 gr Varget.

I took of my Redfield 10x when I noticed my turrent was clocking slightly and I would put it back on if I can secure the turrent somehow. Permanent Loctite didnt hold. Maybe I'll try some superglue.

I'm going to shoot a string of 10 in a day or so maybe it was me just getting "hanky".

Normally shoots .3 - .6 MOA. Hard question to nail down.

 

[wally]

Lets see, 5MPH wind is about 7ft/sec, 100 yards at 3000ft/sec means time of flight about 0.1 second so drift could be 0.7ft or ~ 8" worst case.

I've of course ignored the "acceleration factor" as the bullet velocity accelerates to match the cross stream velocity (which you'd need to get from a detailed bullet data and ballistics software) but it doesn't take a lot of wind variation to open up a tight group laterally as even if the bullet hit only a tenth of the cross stream velocity it could still be 0.8" drift between no wind and 5 MPH

Note that 3MPH is about walking speed so if you can feel any wind it will have an effect that is maximum when at right angles to your line of sight.

--wally.

 

[Ghost Walker]

Barrel rubbing on stock might have something to do with it too.

 

[Tn Tom]

I think I can rule out barrel / stock as the barrel is free of contact with the stock at least before firing. The action is glass bedded and I can slide a business card between the barrel and stock all the way back to the receiver and its free.

I going to shoot it again tomorrow if its calm. .7"+.7" would be 1.4" so maybe.

I've got some other ideas but that it is all lateral gets me scratching my head. If it were in the loads themselves wouldn't the variation tend to be horizontal as well?

My best groups have been with brass (.220 Swift not yet fire formed meaning still new and F/L sized). My problem groups are fire formed plus 3 firings, neck sized. I'm going to try some of the unfired Swift brass again and see where I end up and I know my best groups were on very calm days. It sure is hard sometimes to be objective.

 

[DoubleTapDrew]

Consistent cheek weld? Maybe try firing with your firing hand's thumb wrapped around the stock and then without.

Also read this even though it's mostly about vertical stringing: http://www.6mmbr.com/verticaltips.html
Here's a bit from that article in the bags and rest section:

• If the channel between the Rear Bag's ears is not in line with the barrel, but is twisted left or right, this can affect recoil and vertical consistency. If the bag is off-axis quite a bit, you will get horizontal stringing.

 

[rizbunk77]

You have addressed the only factors I could think of. It its assembled correctly, and floated, all I can say is shoot it again and see what happens. Also I am assuming you are holding the rifle the same way each time you shoot with regard to cheek weld and shoulder position. If you were canting the gun or had parallax it could make some difference.

 

[Tn Tom]

I'll check my bags and see if I can improve the set-up. I was prone and the front and rear seemed secure but I'll relook at it when I get it set-up.

Cheek weld is a problem I think a pad might be in order.

Parallax in the back of my mind with the new scope may be playing into it to. I wasn't comfortable in that area.
Thanks again for all the input. I'll let you know how the next round come out.
Tom

 

[Ghost Walker]

If everything else checks out, I can think of one more thing: Based on my past experience using them ...... that new Bushnell scope.

(After the first or second went down on me, I haven't tried another one in, at least, the past 20 years.)

 

[Tn Tom]

I'm going to be looking very closely at the Bushnell. Never had one before. I've used my 10x Redfield for many years and broke the adjusting knob off by accident and hoping to get it repaired. I was always very pleased with it. I know there are much better scopes available but the prices have gotten way too much. I know I get what I pay for. I just cant put out $1k bucks for one any more. We'll see what happens.

 

[Ghost Walker]

Naa, you don't need to spend a grand; but, yeah, I hear ya! All of my excellent scopes are made by Leupold. Take a look at THIS ONE.

You can, probably beat the price if you shop it.

 

[Tn Tom]

I saw this Leupold 6-18x40 VX-II Waterproof & Fogproof Riflescope (2.8-1.3 Degree Angle of View) with Fine Duplex Reticle and An Adjustable Objective - Matte Black * Price: $ 419.95 and the same one again for 399.99. Whats the difference between the VX-II and the MK2?

Let me ask you this I just returned a Weaver T-24 that I found new for $359 but after I mounted it I discovered the the locking ring for the AO was eccentric and would strike my barrel when tightened or loosened. Other than that it seemed a nice scope. I just didn't want to discover other problems after I had used it a short while and not be able to refund. The 24X was exciting but realistically probably more than I needed.

I'm really thinking that after reading an article regarding the parallax issue I may have been dealing more with that. I re-examined my front rest and the bag was far from tight. I got that fixed and the gun now sits very nicely.Still haven't shot the Bushnell. The wind hasnt stopped blowing for 2 days and its howling again.

I have a Leupold on my handgun (old Ruger 3 screw .44) and they are so nice. Theres no arguing the quality.