MVA Sights

[Matt Muir]

I just got my MVA #107 sights and they sure are a sight to behold. Just a few questions to those that shoot them.

1. How often do they need shimed to get a plumb fit?

2. What is the average number for 100 and 200 yards (moa).

3. Do most take them off when not shooting? They have the thumb screw so it does come off easy, just dont want to loosen up the locking notch by doing something stupid.

I just want to cut the trips down range to check targets during the sight in period. I have loaded test rounds but not that many sighters.


Thanks, Matt

Oh, its a 45-70 with a 34 in barrel

[JSnover]

Hi Matt.
It's not uncommon to shim them.
What do you mean by 'average number'? If you're asking about average group size, your rifle is probably capable of 1MOA (2" @200 yards).
If you're asking about sight settings and zeroing for 200 yards, your group can be as much as 10" high at 50 and 15" high at 100. If you were to bore sight the rifle at 100 yards (so the sights and barrel were both pointing at the X ring), you could need to raise your rear sight as much as 15 minutes to hit the X at 200. Higher velocities will flatten things out a bit.
Take the sight off when not in use if you worry about damaging it. As long as you don't over tighten the hardware you should be ok but I think if you fold it down and handle the weapon carefully while you're off the line you shouldn't have any trouble leaving it in place.

[405]

Matt,

Sure hope they work well for you after all the hub-bub! Don't take all this verbage as "the only way" or "you must" directions.... just some thoughts on what has worked for me.

The first thing of course is getting the staff as plumb as possible with the axis of the rifle. A good straight edge and some shim stock is all that's needed. I've used all variety of very thin copper, brass, alum. etc. for that depending upon the thickness needed and sources on hand. How often do they need truing up when first attaching ?? Dunno. Sometimes all the stars line up and no shim needed.

Even if perfectly plumb with the rifle after checking and/ or shimming there is no guarantee that it will be plumb with the flight of the bullet :-D... have to start somewhere tho.

As far as removing staff assembly from base?- as long as you are careful shouldn't be a problem. I imagine if done many times over a very long period of time it might loosen the pin/yoke fit. I just fold mine down and call it good. Since I clean from the muzzle it's never in the way. I either put a cover over the sight or glue a small piece of leather to the stock or sight so it doesn't ding the stock.... just depends on the fit.

As far as MOA?- There are those out there that can quote those numbers forwards and backwards. I can't. The vertical is somewhat meaningless because the trajectory of each load is so variable. Windage can be done but doesn't mean a lot because once the staff is parallel to the flight of the bullet only the conditions will dictate changing the windage. MOA per mark depends on too many things and some of them will change each time the gun is shot. Once you shoot enough at the different ranges with a given load you can record the MOA numbers for the elevation and windage marks on the sight for that particular load.

If your loads are accurate to the extent of bullet stability and reasonable group size out to the distances you intend to shoot it's just a matter of taking time at the range, making the adjustments and recording the results.

Take a wild guess at your bullet BC. You know the weight. You have a pretty good idea of velocity. Then go to a ballistics calculator like Norma's (link below) and play with the numbers..... that should get you "on paper" out to a few hundred yards.
http://web.archive.org/web/20060206153811/http://www.norma.cc/htm_files/javapagee.htm

If for example you have a good load that you will use for a while and plan to shoot at 100, 200 & 300 yards .... take a supply of ammo, cleaning equipment and large cardboard backer and targets with big enough black bulls to see at the longer ranges to the range and plan an outing.

Set a bull target at maybe 25yds. Bore sight with the action open on some steady bags, etc.- adjust sight to center with bore and bull. Shoot to see if close. Set target at 100 and sight in. Shouldn't take but a few. Clean bore. Mark elevation index on sight with ultra fine felt tip pen. Set target at 200. Bore sight to give approximate elevation as indicated by ballistics program like Norma. You should be at least on paper or the large backer. Sight in. Mark sight elevation index with felt tip. Clean bore. Repeat at 300 and so on. That pretty much describes how to do it. You will see then if the sight elevation staff is parallel to the flight of the bullet. If not, you can either shim to correct or simply correct on the windage adjustment for each range and mark or record the correction. If you try to do all this in bad conditions there is no way to make sense of the exercise.... same holds true when load testing! Should try for good conditions to do this first run. Some shooters use a bubble front sight to maintain perfect gun plumb for the longer ranges. I use one only on the really long ranges or just to correct my hold if a habit of canting creeps in. Depends on how "over the top" you want to take the Sharps shooting game :)

Now wind and conditions. Again the Norma site will allow you to play with some numbers as will any number of printed tables. Then more range time to see what, for example, a 30 mph wind at 3 O'clock does to the POI at the different distances and how much "Kentucky" to give it or how much to change and remember and record the windage adjustment needed on the sight. The other method is to have someone act as spotter to "call and guess" on bullet impact in the dirt :mrgreen:.... then "walk" your bullets into desired POI. Some shooters are good enough and have enough repetitions of all this to lock it in memory. Then in conditions they simply adjust the sight or "Kentucky" a hold and bingo. Looks like magic but is just a lot of experience and dedication and good memory.

Good Luck!

[Matt Muir]

Jsnover, sorry for not being clear. What I was looking for is the starting number for 100 yrds, such as 19 or 27 , whatever other 45-70's shoot. Then how many MOA is a good starting point for 200. I would love to play and figure it out but I only have around 10 rounds loaded as sighters. The rest have different powder and bullets for test groups. I will need to cast some more after I see what shakes out on the range. I just need to get on paper in as few rounds as possible. My bore sighter is "loaned out" so I would need to try the old fashion way of just looking down the barrel and adjusting.. and hope I'm close.

Is the 15 min an average between 100 and 200?

Sorry for the dumb questions, I'm used to 1 click being 1/4 inch @100 and 1/2 at 200 through a 20x scope. I can see where these sights can be very accurate after you get the hang of em.

Thanks 405, I will head to lowes or NAPA to buy some shim stock. In theroy if you know the BC and FPS you should be able to use a chart and adjust min to get real close at any distance, if I understand what you said,right? That is pretty slick for a sight that is 134 years old !

[waksupi]

Sight settings will depend on barrel length.

I don't like removing the sight, unless absolutely necessary. If you have a good rifle, get a GOOD hard case, and transport it inside each trip.

[JSnover]

No dumb questions, Matt. And this is the best place to ask, anyway.
An initial sight setting is almost impossible to nail down from one rifle to another. As 405 said, find your bullets ballistic coefficient and figure your velocity as near as you can. Then use the calculator (a trajectory table will do in a pinch) to find out how high your bullet should be at a given distance. Gravity is consistant. Wind is a whole 'nother story.
A bore sighting tool isn't necessary, your method of eyeballing it will work. With the bore and the sights centered on the bullseye at 100 yards, come up .150" on the rear sight. I've used two bullseyes in the past; one as an aimpoint and the other about a foot higher, since that will be the point of impact at 100 if you're sighting in for 200. Do yourself a big favor and start from the 50 yard line. This is important because if the calculations are far enough off, you can completely miss the target at 100. In that case you'll have wasted the shot and have no idea where it went. Bring a spotting scope if you can. Write down or print out the trajectory table for your load.
Fire a group, measure the distance from the group center to the point of aim. Adjust your sights up or down according to the table. If the next group is in the right place, move to the 100 yard line.
Good luck, Matt!

[Don McDowell]

Matt to get close on the initial 100 yd setting just peer thru your MVA and adjust the elevation until it and the barrel mounted sights are lined up. If you've fired the ladder at longer distance you can also get close by setting the ladder to the desired yardage, and then adjusting the vernier to align with those sights.

[405]

Matt,
Just to clarify- make use of bore sighting by"eyeball" not a boresighter. Given a good steady rest/cradle you can do this clear out to longer ranges given a trajectory table as JS suggested. If you're POI zeroed at 100 and the table says 5 ft of bullet drop between there and 300.... you can put two large black bulls at 300yds one five feet higher than another (or whatever the table says)... put the bore center on the top bull while adjusting sights to center on the bottom bull- should be close enough for POI on paper or large backer. Just some suggestions to save a bunch of shooting into the OZONE :mrgreen:

Here's a pic of a midrange vernier tang mounted on a highwall to show how to "cheat" or shortcut the vernier adjustments for a particular load sighted in at those ranges. Makes it easy to see and adjust on the range. The three black marks on the right side (fixed staff) are the yardages... bottom=100 yds, middle=200 yds, top=300 yds. The single black line on the left is the index mark on the moveable vernier (attached to the eyepiece). The pic shows about a 225-250 yd setting.

For load changes... the right side marks are simply wiped off with alcohol. For really good or often used loads just record in a log the readings for each yardage on the right side (fixed staff) scale and use the same index mark on the vernier.

[4060MAY]

best place I have seen on how to read a vernier
http://www.uslink.net/~tom1/vernier.htm

look around the site, lots of good stuff

[Matt Muir]

Thanks guys, I am itching to get to the range, freezing rain today may put a damper on the fun. At least it's good weather to cast!

Casting, now that's a whole new set of challenges.

[EDK]

I don't know if you've cast BIG boolits before. I hadn't done anything bigger than 300 grain 45/70s in a 2 cavity RCBS or LYMAN; mostly 357--44--45 pistol boolits.

Casting 500 grain LYMANs and 620+ BROOKS for LEAH (the 50/90 SHILOH) is a whole different ball game. The low tin alloys and heavy weight boolits need to be fairly hot. Hollow base for paper patch is supposed to be a little finicky also.

You learn a little every time you cast...good luck

:cbpour::redneck:

[405]

Matt,
There are probably too many cooks in the kitchen already but oh well. If it gets too thick just give us all a "time out" :roll:

The terminology of MOA really causes problems especially with tang sights and some of the graduated military sights. There very well may be a table listing what each tic mark on your MVA tranlates into in terms of Minute Of Arc (Angle) but it would have to be specifically calibrated for that sight ON that rifle (sight radius). [waksupi pointed that out]

It's purely coincidental that MOA is roughly equal to 1 inch at 100 yards. The confusion comes when the terms are used as meaning the same thing. Two completely different things.

The easiest, direct way to see what "1 inch POI change" on target at 100 yards means in terms of tics or markings on your sight and rifle combination is to shoot a 3 shot accurate load at 100 yards. Move your rear sight one graduation tic up (or down) and move the windage one graduation tic left (or right). Shoot three more on same target. Using the group's centers, measure the POI change both for elevation and windage. Then you'll have some solid data on what the graduations mean. On the elevation portion- the major graduation tics (marked 0 up to 3,4 or5) are usually subdivided in tenths with half-tenths marked as the smallest subdivisions. Use the tenths for the test. Windage scales may be different - just use one graduation change for the test.

There's no magic in the vernier system. On most sights it simply allows precise adjustments or readings to .01 of a major graduation. You can eyeball almost as close and for sure the gun and ammo and shooter would have trouble justifying the precision... except in unusual cases of extreme accuracy and/or VERY long ranges. For example: You eyeball an elevation setting of 1.3 but by using the vernier you get a reading of 1.29. Whether or not the increased .01 precision makes a difference... maybe, maybe not?

Hope you get some decent weather. Have shot once in the last 3 weeks and it's driving me crazy!

[Don McDowell]

Matt you might want to carry a pocket notebook, and everytime you shoot the rifle note the load and the sight settings for the various distances you shoot. Even if you shoot on the same range at the same targets time after time the sight settings will change a bit due to mirage, or lack of, head winds and tail winds can also give some fits at distance with these big slow chunks of lead.

[crossfireoops]

What McDowell said,

Uniform to unpredictable / wierd shifts,.....with day to day conditions,

Barometrics, ...elevations,...lot to lot variations in powder quality ( WHAT a joke THAT is)

unforgivable,...albeit tragic,....flinching / poor breaks.

.001" obsessions stalkin', and maiming.....

Like the fellows that put your rigs together were lame brained.

Lotta' Ya'll already down,...on that one.

Probly' should not have dumped all this crap over Don's disertation,...

I'll be "Fired" accordingly

GTXC

[montana_charlie]

The standard vernier breaks an inch of elevation into a hundred parts. Most guys call those 'points'.
If the sights are 36 inches apart, each point is equal to 1 MOA of change in bore angle.
A Sharps rifle with a 30-inch barrel will have that 36-inch sight radius.

Dividing your actual sight radius into 36 will give you a constant that you can use to convert the 1 point = 1 MOA rule.
For example, on a Sharps rifle with a 32-inch barrel the sights are 38 inches apart. Therefore, 1 point equals .94 MOA.

All of the above is pure mathematics, therefore undeniable. However, a dozen other variables will intrude to disrupt the purity of the math...when you actually send that bullet downrange.
CM

[Matt Muir]

Thanks MC.

[freedom475]

Was just shooting my 74 45-70 34" sharps with 500gr. Lee over 70Gr 2f BP.

Sight setting for 200yrds was .45.....40 is about 10in low and .50 is about 10 inches high.

this may help get you close. Good Shooting:Fire:

[Just Duke]

:bigsmyl2: