Problem with MOA

[Mike 243]

I have a 1000 yard bench gun in 243 win. Scope is Sightron 6x24x42 with 52 moa. Base is Ken Farrell 20 moa. I can't get a zero at 300 yards it still 7" high when out of adjustment. I have this same setup on 2 other guns and can zero at 100 yards. Anyone have any ideas as to what could be the issue.

 

[gme]

if the base/rings are correctly machined and installed it's probably that the barrel has a fair amount of "hook" in it and on installation was clocked so the muzzle is "looking up" which will want to shoot high, I've seen this several times

 

[CaptainMal]

So take the 20 moa base off. That would still give you over 30 moa to do the 1,000. Change to a 10 moa base. Shim the rings say 3-4 moa.

You may also consider a set of Burris Signature rings with the adjustable inserts. Use the old base, if compatible with the rings, and make the elevation adjustments with the different-sized inserts. Simple.

 

[Mike 243]

Have you exhausted your windage left or right therefore restricting elevation

Yes I have. The scope has a minimum of 40 moa. This scope has 417 clicks in elevation or 52 moa.

 

[Mike 243]

So take the 20 moa base off. That would still give you over 30 moa to do the 1,000. Change to a 10 moa base. Shim the rings say 3-4 moa.

You may also consider a set of Burris Signature rings with the adjustable inserts. Use the old base, if compatible with the rings, and make the elevation adjustments with the different-sized inserts. Simple.

I forgot to mention I do have the Burris Signature rings on.

 

[Mike 243]

I can make the adjustments with the inserts. I'm just interested into why such a drastic difference with the same setup as other rifles.

 

[Mike 243]

Just remember a scope is a tube in a tube therefore if you are not reasonably centered on windage your elevation is effected.

Sorry I miss replied. My windage is pretty much centered up. I was thinking have I checked movement left and right.

 

[Curmudgeon]

What caliber are the other rifles? What are the barrel lengths?

 

[Mike 243]

All barrels are 28" problem rifle 243 win 106 gr eps bullet at 3030 velocity.
284 win 168 gr Berger at 2960 velocity
300wsm 210 berger at 2850 velocity all have
Burris Signature rings medium height

 

[ED3]

I can make the adjustments with the inserts. I'm just interested into why such a drastic difference with the same setup as other rifles.

If one assumes you are using the insert rings, it then begs the question: 'Are they set up correctly?'
Double check the values, and positions of the inserts.

 

[Mike 243]

Yes they are set up correctly

 

[JMayo]

On my 22 to get from 25 to 200 With burris rings its -20 on front and +20 on rear
... not +20 +20 ....

 

[Mike 243]

Interesting
That’s the scope with the 1 inch tube IIRC
Others have had problems with those. I would send it back to Sightron.

SPJ, the scope is advertised as having 40 MOA. I called Sightron from top to bottom of adjustment this scope has 417 clicks / 52 MOA. it hold a true at 1000 yards. I believe it has something the barrel bore curve. It's going to the Gunsmith this weekend.

 

[Mike 243]

On my 22 to get from 25 to 200 With burris rings its -20 on front and +20 on rear
... not +20 +20 ....

Thanks for you reply. I've used a few set of these rings. I know how the + and - work

 

[MattPeetz]

Your barreld action is bedded upwards. Not parralel to the stock.

 

[ED3]

Your barreld action is bedded upwards. Not parralel to the stock.

How would that affect the relationship between the bore of the rifle, and the sight line of the optic?

 

[mikeeg02]

When you say the other rifles have the same setup just different barrel, are you screwing other barrels onto this action ? Or they are a separate action/scope set up the same ?

If it's one action and scope with a different barrel, it could just have a big bow in it like the others have said and when this barrel is on you're going to have to offset the bushings in the rings.

Otherwise.....

SPJ, the scope is advertised as having 40 MOA. I called Sightron from top to bottom of adjustment this scope has 417 clicks / 52 MOA. it hold a true at 1000 yards.

The thing to remember about this, is from a centered reticle, you have half that down. Which is just a little less than what you need for 1k *if* your scope was centered at 1k.

If you're 7" high at 300 bottomed out. Then you're ~5 minutes high from 100.

Your come up to 1k from bottomed out is probably around 18 minutes ? Is that about where you are when you're on target at 1k?

Either way, if you have the rifle/ scope sighted in at 1k I bet you can adjust the elevation approximately 52-18= 34 minutes higher before it stops.

If the bushings are correct, you may need to try a 10moa base instead of a 20 for this barrel. Theres always a chance you got a 30 moa base. You could compare measurements to your others.

EDIT: Fixed a few things. I outsmarted myself a few times.

 

[MattPeetz]

How would that affect the relationship between the bore of the rifle, and the sight line of the optic?

ED3

Take a small piece of heavy card stock. Like an index card. Maybe two pieces. Put the pieces under the rear of action. Tighten action back down then shoot. Watch how much your zero changes. Then put the pieces in the front. Repeat process. Then you will know how it affects it. I’ve actually done a couple guns bedded this way. Barreled action pointing slightly up from paralell to gain some moa.
Its not the barrel

 

[ED3]

ED3

Take a small piece of heavy card stock. Like an index card. Maybe two pieces. Put the pieces under the rear of action. Tighten action back down then shoot. Watch how much your zero changes. Then put the pieces in the front. Repeat process. Then you will know how it affects it. I’ve actually done a couple guns bedded this way. Barreled action pointing slightly up from paralell to gain some moa.
Its not the barrel

Isn't that simply warping the action?

 

[MattPeetz]

Isn't that simply warping the action?

No