In order to participate in the GunBroker Member forums, you must be logged in with your GunBroker.com account. Click the sign-in button at the top right of the forums page to get connected.
Any way to check a scope?
dcloco
Member Posts: 2,967
Need to check a scope for accuracy and if the dials move L/R & U/D like they are supposed to.
I have a scope, that I have placed on two different rifles (same caliber) and the groups that I "achieved" are nasty.
I am suspecting the scope.
Thoughts? Suggestions of what I could do at home?
Thanks in advance.
I have a scope, that I have placed on two different rifles (same caliber) and the groups that I "achieved" are nasty.
I am suspecting the scope.
Thoughts? Suggestions of what I could do at home?
Thanks in advance.
Comments
Pete
Lacking that, the above suggestion is a good one.
Use the graph paper and actually watch the crosshairs as you adjust the dials. Go back and forth with adjustments and be sure the crosshairs move.
I tis possible to have the erector tube in a bind...moved to far right or left....because of improper mounting...and the verticle will drift upon adjustment.
Optically center your scope before mounting...mount in a v-block (could be as simple as a 'v' cut in a 2x4) and rotate the entire scope, crosshairs lined on a target downrange. The crosshairs should be pasted on the target...adjust till it happens.
Boresight your rifle...using the adjustable rear mounts till you are VERY close to crosshair/boresight.
Only use the windage for MINOR adjustments....
They're cheap when compared to wasted time, ammo, and give plain good ole satisfatction of having fun. Fun, fun, fun is the word.
Additional MUST DO test of variable power using a collimator/sighter.
1. Start test with maximun magnification, at grid center. Following Just C's 1" click movement test (called "Shooting a square")carefully noting results. Put each test (4) down on paper. Hopefully you'll return to the Grid Center/
2. Retest by starting at the Grid Center AND reducing power so you can still just see the grid clearly.
Carefully note results. If adjsutments return the reticle to the same positions....adjustments....W/O recoil are good.
If not at the same points, internals are off somehow. Can be defective, worn parts....yes they do break in & wear out, and last but not least scope tube stress from incorrect mounting. If present...it absolutely will affect internal movements when changing power, and when making adjustmnents. POI will keep shifting.
3. Explore mounting system for movement at rest, and under recoil.
4. Check scope alignment via dowl pointed indicators, or by placing an tube cylinder accurate both in diameter, and straightness in the ring halves looking for proper fit. Any gaps/light show misalignment.
A collimator will point out several things.
By turning the power ring thru the complete arc, One can tell if the reticle is optically centered....most are not. That is why the rifle will hit 6 inches away at 9 power then 3 power.
One other thing that is amazing....ALL variable power scopes are slotted...nearly 2/3 rds of a circle. Then that heavy occular lenses (the eye piece) is hung off that aluminum tube..well weakened by that slot
They break and bend. One can put the scope in a 'v' block and rotate it while watching carefully for that 'up and down' movement that signifies 'bent'...and time for a scope overhaul....
THANK YOU for ALL of the info.
The scope that needed checking is going back to manufacturer - does not hold zero...
Squeeze two five shot groups with the scope mounted on a 204, left it on 10 power for the first five and 20 power for the second five - adjusted for parallax...and kept same point of aim. 3" groups +. Installed a new, but cheap, scope - 1/2" groups, consistently...with the exact same rounds. Rounds were loaded at the same time and I pulled each round at random out of the box of 100.
Draw this out on a paper and mark each target as stated, you end up with targets TWO inches apart at the top NOT ONE. I think your IDEA was great but your instructions need re-written... Not being an *, just always up for kewl ideas to help me with problem areas.
Lee
set a target at 100yds, then shoot. Mark POI and make a sqaure of 4 targets. The first target being 1" left of POI and the other being 1" right of POI. the next 2 targets are 1" above the other 2, thereby making a square. Now, click in 1" in the left directionto be impacting at the left target,..then go up 1" and shoot again to hit the high left target, then dial in 1" right, and shoot to impact at the high right target, then dial 1" down to hit the low right target, then dial in the 1" left to hit the original POI. (all of this is while aiming at the center or original bullet hole) That is the "box test". If the scope can make these adjustments and hit correctly after each adjustment, then it is tracking correctly.
Shoot the target one time. Adjust your scope to change the point of impact 1" to the right. Aim at the SAME spot on the target as your first shot. Adjust your scope to change the point of impact 1" higher. Aim at the SAME spot on the target as your first shot. Adjust your scope to change the point of impact 1" to the left. Aim at the SAME spot on the target as your first shot. Adjust your scope to change the point of impact 1" lower. Aim at the SAME spot on the target as your first shot.
This is the only true test of a scopes ability to track and hold zero correctly. This takes into account the movement of adjustments, their integrity, and their ability to stay put under real world recoil forces.
The suggested "box test" makes a 2" SQUARE of 4 targets and one in the center. Once you get on at the center,..you track the scope in a 2" sqaure to see if each change in setting corresponds to the target square (all while aiming at the center to eliminate that variable) If the scope "tracks,..it will hit all 4 targets and then come back to the center target.
This is the only true test of a scopes ability to track and hold zero correctly. This takes into account the movement of adjustments, their integrity, and their ability to stay put under real world recoil forces.
Nice addition JC (the diagram)[:D] That should clear things up![;)]
quote:Originally posted by JustC
The suggested "box test" makes a 2" SQUARE of 4 targets and one in the center. Once you get on at the center,..you track the scope in a 2" sqaure to see if each change in setting corresponds to the target square (all while aiming at the center to eliminate that variable) If the scope "tracks,..it will hit all 4 targets and then come back to the center target.
This is the only true test of a scopes ability to track and hold zero correctly. This takes into account the movement of adjustments, their integrity, and their ability to stay put under real world recoil forces.
Nice addition JC (the diagram)[:D] That should clear things up![;)]
See the flyer below "& the center"???? LOL!
Lee
I figured the picture was worth a thousand descriptions, so I threw that one on the scanner. Writing instructions can be a PITA to get 100% straight and understandable for everyone,...so it was "back to the drawing board" (punn intended)[:D]
dcloco,..that flyer was someone else's bullet that strayed over on to my target,.....yeah that's it, that's what happened[:p][:D][^]
They were shooting a 338 belted mag or a 35 Rem?? LOL!
Agree - picture IS worth a couple thousand words.
I like the drawing, great information...but who shot that great big miss[:0] down at the bottom of the page?[;)]
Edit:
Or is that your test group of 5?[:D]