Rifle Scopes A "Bay Window Report" and beyond

Magnumdood

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Dec 28, 2001
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I took delivery of my S&B 5-25x56 last week. I'm waiting for the mount from Near Manufacturing. It's going on my 30-378. I put the Henny 6-24x72 on my R.E.P.R. (it's in a Near Mfg. 20 MOA Alpha mount).

I'll be shooting them side by side until it gets too dark to see. That information will be used in my Bay Window Report.

Once I've established a 100 yd. zero on both rifles, I'm going to shoot the box. How large should the box be in order to reveal a tracking problem that a 10 MOA box would not reveal?
 
You should test 100% of the range you intend to shoot! but 20 MOA is about the least to go. Errors can show anywhere along the travel. There is no pre-determined spot. For most problems you need to compound the errors to add up to a number beyond the size of your shooting. Do you really think you'll see a small error shooting a REPR?

Shortcuts serve no one, especially the owner. Today it's a half ass "test" tomorrow you're complaining your software doesn't line up and you can't figure out why.
 
You should test 100% of the range you intend to shoot!
How? Instead of making fun of me, tell me what I should be doing.


There is no pre-determined spot. For most problems you need to compound the errors to add up to a number beyond the size of your shooting.
Again...how?

Do you really think you'll see a small error shooting a REPR?
My REPR, in informal bench shooting at the range, regularly cloverleafs 3 rounds at 100 yards and stays under 1 MOA at 200 yards with Federal Gold Medal Match 175's. I'm limited by the club I belong to; the farthest we can shoot is 200 yards. Also, this is the 2nd AR platform rifle I've ever owned in my life. The first was a Colt AR-15 that I bought in 1994 and flipped it for double what I paid. The clinton crime bill brought about this same sort of buying frenzy that we're seeing today. Most of the other patrol deputies were carrying some AR variant, and no, I wasn't impressed with the lack of precision. Even the H-Bars didn't shoot anywhere near as well as a tuned bolt rifle.

So, what is a small error?

Shortcuts serve no one, especially the owner. Today it's a half ass "test" tomorrow you're complaining your software doesn't line up and you can't figure out why.
What's "half ass" about what I'm doing? You're always preaching about getting out and shooting your scope rather than counting the ridge caps on your neighbors roof with it, and proclaiming scope A is better than scope B because scope A can resolve the bird shit on the neighbor's privacy fence and scope B can't.

I assure you I am more than intelligent enough to grasp the concepts in your answer if I were conversant in the lexicon of "Rifles Only".

I really would appreciate some help rather than having a simple test, that everyone does, shit on because I'm the one doing it.
 
I am not letting you off the hook that easy.

First off I have not worked at Rifles Only for more than 3 years, so any conversant lexicon is mine and mine alone.

Next if you are serious about these question, you are missing the basics, and really you need to not do any bay windows reviews or offer advice to anyone regarding scopes, period. This is day one stuff.

To test your scope you can do it in a variety of ways:

1. Mount a 4ft level on your target board at 100 yards. Place the reticle on the top and then run the elevation up until the reticle reaches the bottom and count how many clicks it took to reach 48 Inches, then do the math.

2. Create a target board with at least 30 inches of vertical. Have a fixed aiming point at the bottom and use that to sight in on while dialing up the elevation. Measure the strikes and also make sure the strikes track level with the fall of gravity. You may find some scopes have a curve in the top end, and will veer off the line.

Checking the scope across 100% of its travel means one of two things.

1. Checking it out to the max effective range of the rifle it is on, like 1000 yards. If you rifle needs 38MOA to 1000 you use that, if it needs 11 Mils you use that.

2. Check it across across all the elevation left in the scope. If you can reach 20 Mils use 20 mils.

Compounding errors means that errors in a scope can be small, so you need to compound them in order for them to show up. So say you think you have an MOA adjusting scope but really have an IPHY one, you need to add up to see the .047... which means 10 inches is only about a 1/2 inch. So 20 inches would be 1 inch and so on... you would not know the difference between an MOA or IPHY adjusting scope if you only tested it across 10 inches. This is why a 4" or 8" box test is useless. you cannot see the errors. Generally speaking 24" would be bare minimum like using a poster board from Staples. So a 1 MOA shooting rifle would hide errors that are only a 1/2" in size, any shots inside that 1 MOA would be considered normal for the rifle.

This is basic scope calibration stuff. It's what you should do automatically when you mount one, especially if you plan on using a ballistic computer of any type. Scopes are generally the weak link in the system, and not because of glass quality but because of the internals. Not doing this I consider being half assed. There are more than enough videos of me doing this stuff on YouTube with a variety of scopes. I even show how to calculating the adjustments using Field Firing Solutions as it has a tool for doing it.
 
No more By Window reviews.

...Next if you are serious about these question, you are missing the basics, and really you need to not do any bay windows reviews or offer advice to anyone regarding scopes, period. This is day one stuff..

I want to sincerely thank you for the time you took to answer my questions. I first level the mounting rail while the rifle is on the shooting rest and rear sandbag rest. Then I hang a plumb bob at 100 yards and get the vertical stadia lined up precisely with the plumb bob while keeping the level on the mounting rail centered. I use a kit that I purchased from Darrell Holland to level the scope reticle in relation to the mounting rail on the rifle. Then I set my scope level when I have the rifle plus the scope level/plumb. Then I carefully tighten the cap screws and and the level and finish off the mounting with a Seekonk 20 inch/lb torque wrench. We get to the same place using different methods.

Regarding me offering advice regarding a scope selection to someone on this site advice regarding scopes I sure don't remember it. If you find where I offered advice on which scope another SH member should use I'll retract my advice and offer an apology to the victim of my ignorance. If you prefer I don't do a "bay window review" I won't. If you don't want me to share the my results from the box test I won't. I know I'm not qualified to provide military advice to other posters regarding anything on this board. There are so many guys who have been there and done that on this site I would feel foolish giving advice on a scope to a man who was a real world military sniper. Guys like you have been taught what it takes to run a scope and the rifle under it.
 
My mistake; I reread what you posted above and we weren't heading to the same place, just by different means. I'm going to run both of my scopes through what you laid out above.

Thanks again for the detailed response. It has helped me tremendously already in that you have shown me what needs to be tested in a scope and a way to quantify the results of the testing.
 
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Here's a pic of one of the scope test sheets I have made over the years. I go out to 40 MOA or 10 mils. At 100 yards a mil is 3.6" so put the marks 3.6" apart starting at your aiming point and work up. For MOA I start at 10 MOA, 10.47" at 100 yards, and then go every 5 MOA.

To touch on what Frank said you do need to go out a good ways. Example, I had a Leupold scope that was fine to 15 MOA and then it started going off and then at 25 MOA it went off more. Testing to 10 or 20 MOA or 3-5 mils won't tell you what you need to know. Also with a MOA scope don't forget those little .047s as Frank said. They add up.