Advanced Marksmanship Canting my rifle?

[m1ajunkie]

I posted a thread in the optics forum thinking this issue was optic related. However, Now I feel like the issue is rifle cant.

Shooting yesterday on a calm day, I got windage data that didn't make sense with the conditions. Conditions were extremely calm with wind blowing right to left at most 3mph.

However, I came up with this windage data in moa:
300yds- .75L
400yds- .75L
500yds- .75L
600yds- 1.5L
650yds- 2L
675yds- 2.25L

At first I was thinking my issue was my scope out of level. I have since verified that it is good to go, via level on scope cap, rifle rail and plum bob method.

I ran the data through JBM's ballistic calculator and found data for a 5 degree cant matches my data exactly. Is it possible that I am canting my rifle 5 degrees consistanly? I go windage data exactly matching that posted above from two range trips exactly a month apart.

I have not been running any kind of anti cant device but now I feel it is needed to get solid data. Is my theory correct about consistant cant?

 

[Redmanss]

Re: Canting my rifle?

A five degree cant is pretty significant, and something I think you would notice while shooting. The question here is are you noticing you having an obvious cant, and are you calling the wind by observing a mid-range mirage? Could be a swirling wind, but I don't know what your range design is.

Honestly, while it's hard to diagnose a problem like this over the internet and I don't know your shooting background, I'd be more looking to trigger control and proper position behind the rifle than I would to a cant for the cause of this anomaly. But of course you can always try an ACD to take that possible error out of the equation.

 

[Greg Langelius *]

Re: Canting my rifle?

Red's right, the Internet is a lousy diagnostic tool. Rather than quantifying the problem, fix it.

Here's how I square up my reticle.

I rest my rifle so it's relatively stable, and pointed out a window at a house with siding. The scope rings are loose enough to permit the scope to rotate.

I level the rifle by aligning the butt plate screws with a plumb line.

I level the reticle by aligning the horizontal wire with the siding.

Tighten the rings and repeat both steps to ensure nothing crept during tightening.

This method is easy, straightforward, and essentially foolproof.

It bases its effect on the principle that one should be able to trust the accuracy of environmental artifacts that were already leveled by professionals. Professional builders install siding with a level. Building corner edges, etc, are also pretty reliable.

When I go shooting, I level my target top edge by looking back at the covered shooting line's roof and aligning the target's top edge with the roof ridge. Then, on the line, I align the horizontal reticle wire with the target's top edge.

I do other things relative to this too, but most of you good folks might consider them obsessive. I have found that making an overt effort to deal with parallax and verticality can shrink my dispersion by around half.

Greg

 

[TOP PREDATOR]

Re: Canting my rifle?

bubble levels, ACD, cosine indicator links

 

[m1ajunkie]

Re: Canting my rifle?

I agree that 5 degrees is a lot of cant. I had my rifle bagged here at the house and added the five degree clockwise cant and it seemed noticable to me. However when I shoot at that range, the targets are 20"x30" rectangle steel that aren't level themselves so it is hard to tell when I have the reticle level and I feel I may have been over compensating. Obviously a ACD would have helped me from the beginning.

FWIW, today I am going to try the method of leveling off of something like an edge of my house. Would a plum bob line hanging say 50yds away be an effective tool to use to level so long as the rifle is level?

Right now I have the rifle leveled and the elevation cap lid is what I used to level but it appears to be .3 degrees off level. Would I be better off to trust the reticle method than the scope cap? I want the scope to track perfectly verticle and horizantal.

 

[TooTall]

Re: Canting my rifle?

If your rifle is level, a plumb bob works good. Level your rifle at the lug shelf.