Burris FF3 ?.

[1iagobblergetter]

My son shoots right handed and is left eye dominate so he's had great luck using the ff2's & 3's turkey hunting...
Now we are trying to set up a .450 Bushmaster with one for Deerhunting...Shoots great at 25,40,&50yds,but out much further than that we can't hit the target..Are these just designed for closer range shooting?? Were shooting off a table&rest...Thx for any help..

[Tail Feathers]

A 3 MOA dot at 50 yards should be 1.5MOA at 50.  That's good enough for a deer gun.  I wouldn't try brain shots with it, but shooting for the heart/lung area which is about 7" in diameter, it should suffice.

[1iagobblergetter]

We had great groups until we got to 75yd and beyond..
That gun should drive tacks at that range...Is it the gun or change the site...We even moved back in at 30yds then right where we wanted it again..Maybe I'll get him a spear instead if it's the gun..? The target is approximately 12×24 and cant get on paper at 75yds..

[WV Flopper]

 I doubt that you would get great groups even with .5 MOA gun at 100yards with a FF3. Just because of it being a 3 MOA dot at 100.

What you describe says to me it's the bullet not stabilized in flight.  I would imagine if you tested some more at extended distances you would find holes in the target not quite circular but oblong. Maybe check your twist rate of the barrel compared to the bullet weight/length/coefficient. You can find calculators online to give you good bullets for your barrels.