20 or 15 MOA rings?

seblambang

seblambang

seb
Gentlemen,

I would like to make a set of rings for my switch barrel rifle (6ppc / .284win) in a few days and need your input here.... the scope is just a Sightron 36X fix (can't buy/use a better one at this time being)....planning to use this scope both for the short range (100/200) & 1000 yds BR...i.e. without changing the rings/scope. --- (I guess it can be done...but I might be wrong?)
Problem is, I still don't know the trajectory of the .284win / the bullets @ 1,000 yds?....planning to use/try Berger 180gr hybrid & 162 gr AMAX....barrel is 30" long - 1:9, if this help.
I think Sightron 36x has 40 moa internal adjustment (maximum), and "want to optimize" the optic - either for 100/200 - to 1,000.

My question is, should I make 20 moa rings, or just approximately 15 moa?

(Actually I must be able to determine the spacing/slope etc between the rings once I know the trajectory).
(I know there are rings set that I can buy in the market...I just would like to make one myself b'cause I like experiments).
(I don't have a Davidson style base overhere but I have a standard/non moa Kelbly rings set for my reference).

Thanks you for your help,
seb.
 
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Seb,
The rule of thumb seems to be .001" equals 1 MOA [ the Sighttron instruction sheet may have a chart showing this ]. A .020" shim under the back of the base would be a 20 MOA correction. A .015" shim would be 15 MOA. Not a lot of difference and you probably wouldn't be able to tell the difference in actual use.

How about an angled riser base that slides onto your action's existing dovetail? The trick will be making the adaptor as low as possible so your scope doesn't end up so high that it's awkward. Due to time constraints I have used some absurdily high setups on my 200 yd 22lr's and having the scope real high seems to have no negative aspects when actually shooting the rifles in competition from a bench.
 
Crb, thanks for the reply.

I just find a "trajectory chart" of the .284 win / bullets in 6mmbr.com.... http://www.6mmbr.com/7mm284.html :cool:

180 gr Berger VLD drops about 270" at 1,000 yds.
Let assume it's 27 moa (approx 282.69" at 1.000)....bigger # is safer in this case.
1000 yds is 36,000 inches.
If the CTC between the rings is 5" (Stolle Panda has approx 6" davidson base) - the ratio is 36,000 / 5 = 7,200 X.
To compensate approx 283" drop at 1,000 yds, the rear ring must be 0.03930" taller than the front ring....=(283" divides by 7200)
I wouldn't use shim myself as it's not a good way to create moa rings...I want my rings set to be as straight/inline as possible, I don't want to lap the rings at the time, etc.

According to my math, a 0.02" shim would give 20 moa (approx 209.4" at 1,000 yds) ONLY IF the ctc between the front & rear rings exactly, or very close to 3.6". It would give much less moa amount if the ctc between the rings is more farther apart. -- I want the rings to be as far as possible to reduce/minimize scope flex....most likely between 4.8" to 5.2", ctc. --- (I have had the stock with proper length of pull, comfort zone / eye relief of the scope etc already).

Now, the scope has 40 moa internal adjustment....let's assume 20 moa the best (10 moa up, 10 down)... if (say) I make 20 moa rings it would give "benefit" for the long range but not so good for the short range.

I think I will go with 15 moa or a bit less....

Re: Angled riser.
I have limitation on the ring's weight etc (i.e to make weight for LV)....my stock is already heavy (@ 860 grams, because of the dual purpose).
I was planning to make a one piece base moa rings before this (from one solid alum billet), but it will weigh more than 5 oz.... so two split/separate rings with moa is my only choice now.

*The reason I don't want to change the rings/scope from 100/200 to 500 or 1,000 is for "practical use" only.

Thanks & Best Regards,
seb.
 
Using the Quick Target program, and 2,800 fps for the .284 the total drop to line of bore at 1,000 yards is about 320". For a typical warm PPC load, it is 7.5" at 200 yd. With this you should be able to work it out. It seems to me that if you start with a centered reticle, 15 MOA in the rings comes the closest to splitting the difference, but either should work.
 
Thanks you Boyd.

.......

Just a little experience...:
I just broke my Sightron a moment ago! :mad:. (bought it several years ago, never shoot it, it's "tuckerised" by someone I admire). After close inspection tonight, using a flashlight I found some alum debris inside the tube (I believe it came when it was drilled)...I then open the eyebell to try to remove the debris & to learn the mechanism inside....knock it several times on a wood block since the debris was hard to remove, but then I found the crosshair dissapeared!!! (I believe I have broken the crosshair).
Well, learning "is expensive", lol.... only to know how the internal scope works and to know that its windage adjustment has about 9.1 full turns max (theoritically 68 moa) and its elevation has about 9.6 full turns (theoritically 72 moa), and that the inside turret is not supported by the side & top screw from about 3/4 part of the max adjustment (rattles beyond approx. 3/4 of the max adjustments)...and that scope reticle is really fragile - it cost me almost $ 400, just within several minutes! :D
Interesting experience, anyway...:D

I need another scope now.

seb.
 
Al,
I think I can make it without the need of lapping or bed it.
I have no doubt that the davidson base of Stolle Panda is perfect/straight. What I need is only to make correct spacing (between the rings) & the slope & diameter.
I'm now thinking to make the rings (i.e. "the base") from one solid billet, as I just realized that I still have about 6 oz left for the rings, assuming I still use a Sightron.

seb.
 
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Does anybody have any evidence that lapping, bedding, etc.. of scope rings actually improves the system or is everybody going with it sounds like something that needs done?
 
Depends entirely on what you start with. Should you start with a Panda and paired rings, probably not much difference. Begining
with a 40x or 700 remchester, it can be agreat improvement
 
Personally I think lapping/bedding scope rings wouldn't improve anything but only to grip better & to not marr the scope's tube. As long as the base & rings are perfect/properly built, anyway. We are talking about BR receivers with close tolerances here.
But who am I? I'm just a newbie in BR shooting.
seb.
 
Seb,
I have mounted a fair number of scopes, and the only way that you will know how much tolerance stack and distortion from tightening rings to bases is to take a few strokes with a lapping bar, and see how evenly it is cutting. Also, it has been my experience that the inside parting edges and corners generally need some work. A couple of years back, it was my responsibility to mount three March scopes for the fellow that owned the company that I was working for. I did not want any modification of the scopes' finishes to show up if they were taken off their respective rifles. The rings were as good as they get, one f the actions had a one piece base, and another was with Kelbly rings and bases on a BAT. The third involved BAT rings on a BAT. While the two benchrest actioned jobs weren't bad, they were not perfect. The other one needed some work even with the one piece base. Later when we had reason to take take one of the scopes out of its rings, there were no marks...none. I am not satisfied that this would have been the case if I had not done the work. Why guess? I would rather know.
 
Well, I have managed to make the rings today. It's done, only need to be polished. (see pics bellow...hope the pics are clear enough)
-Base angled approx. 14 moa (one piece base), total weight approx. 3.1 oz only (88 grams)...I'm happy it's much lighter than expected before!
-I also make a dummy receiver (Panda Short footprint) which helps me to make the stock's inletting & the Davidson style dovetail.
(I'll also show you my stock after finishing in a few days).

http://
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http://
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I put my damaged Sightron & tighten the screws (standard metric M4, 4 screws per ring) very tight. No any ring mark on the scope tube when removed.
The dovetail is also real tight (total four standard M5 are used)....I'm sure it wouldn't move under .284win recoil, as I've bumped the dummy receiver + the scope on a wood block for many times & real hard! I use the same alum alloy I use on my rests (aircraft grade series 7000).

I'll make another one for 30mm scope tomorrow.... just in case...:D. I'll probably use other scope (NF) for the long range match.

Thanks for the help gentlemen,
seb.
 
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Wilbur said:
In what way is there an improvement?
Click to expand...
Wilber, given a 700 action , add bases and check with a straight edge . You will find notoriously that the two bases are
not in alignment. It is comon for the rear bridge to be tilted backwards and often neither one will be level because the
rear bridge may be tilted to one side or the other. While the gun is very stable on bags, loosen a screw on the ring caps
and your crosshairs move also. Changing the tension can give a different POI. Those changes reflect a stress we don't need.
The machined in rib on something like a panda give far better alignment with much less stress. Other custom action are also
much better for base alignment. We want to eliminate variables and a Rem can be the worst.
 
Seb...do you plan on making various MOA taper rings? I run 20 MOA rings on a standard panda rail and I'm able to run back down to 100 yards on a NF NXS 12-42. I'm not far from bottoming out at 100 and would like to raise the scope a little. 15 MOA should her perfect.
 
Thanks for the link, Stonewall.
It's a good read, anyway it's not my skill to make a fine crosshair.... I got another scope (a B&L 36) several days ago.

...............

Can't wait to try/shoot my new 6PPC/.284win!!!
Will be leaving for the "Harry Madden C/ship" in Brisbane tomorrow....will also get BRT course for the 2nd time before the match.
Have shipped my stuffs & the stock two days ago and plan to glue-in the action on Tuesday.

seb.
 
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