New Rossi 92 .357...Zeroing Question

[Charles4400]

Hello All!

Been following for awhile but this is my first post.

I have a Rossi 92 in .357 and will be mainly using 158 gr. American Eagle rounds with it.
I read that the trajectory of the bullets should be pretty flat out to 100 yards and should have enough velocity to hunt deer at that distance.

Question is to get that nice flat trajectory what distance should I zero the rifle in at?

It's a 20" barrell if that makes much of a difference.

Thanks and any help is appreciated!

[AJMD429]

Personally, if I were planning on up to 100-yard shots and wanted minimal hold-over or hold-under, I'd sight in about 'dead-on' at 65-75 yards. You'd not need to hold over or under significantly until out beyond the maximum reasonable (for deer) range of 100yards with that cartridge.

If the ammunition/skill/circumstances were different, the maximum range would of course be different. Myself, I sight dead-on at only 50 yards with .357 Mag 'deer' rifles, because I live in deer-dense country, and turn down lots of shots, so I'd not likely shoot past 75 yards with the .357 myself. That said, I'm sure my grandfather used his .32-20 to kill plenty of deer farther than 75 yards...!

You may already be fully aware of it, but the term "point-blank range" is so often used in the general media to imply a range from zero to a few feet, and actually defines what you're looking for. After defining a 'vital zone', the for any given load/trajectory, and knowing sight height above the bore, you can calculate a 'window' where the bullet would always be within that area. Technically, it includes windage/conditions, but most people only consider it in the vertical direction. The line-of-sight is not necessarily in the center of the maximum and minimum bullet height-of-impact. I mention the concept because some reloading software does an excellent job of helping calculate that - it might say for a given load/trajectory, sights/scope 1.75" above the barrel, and a 6" diameter target, you have a 'point blank range' of 234 yards, and go on to tell you the bullet would cross line of sight (going downwards) at 192 yards and (going upwards) at 18.3 yards, then tell you that if your paper sight-in target is at 75 yards, you should be 1.8" high there. Really cool stuff. I use RCBS's software "RCBS.load v. 3.0" and it is awesome.

[Griff]

and Welcome to the Forum. While I agree with AJMD's logic, I draw a different conclusion. Although Federal's website seems to be malfunctioning, let's assume that their 158 gr. Am.Eagle ammo outta a 20" barreled Rossi would be close to 1530fps, the following chart shows what that trajectory might look like. If your rifle gives a little more velocity the chart would flatten out, if a little slower, a little more arch would be present.


As you can see, the highest point above the line of sight is 2.07" at about 50 yards... it doesn't fall below the LOS until your bullet is about 115 yards downrange. BUT, and this is where I choose my dead-on point based on the greatest degree of error in my range estimation, between 85 to 110 yards, the bullet path is only approximately 1-¼" above or below that line of sight; that's a 2-½" margin of error for your target area. Yet it gives you a 35 yard window of error for range estimation. And, with the bullet path never being over very slightly over 2" above the line of sight, you're still within minute of deer at any closer range!

As they say... "decisions, decisions... decisions!

[Old Savage]

As with Griff's chart, I would sight dead on at 100 yds.

[kimwcook]

As with Griff's chart, I would sight dead on at 100 yds.

Me too.

[Charles4400]

Thanks for the replies this is extremely helpful.

Thats a great program Griff which ids it? Is it the one AJMD429 mentioned (RCBS.load v. 3.0).

OK so it seems that the point-blank range should be at 100 yards...now question is, how do I dial that it on iron sights that far out
? I've done it with scopes but zeroing irons at 100 yards? I can't even see the bullseye on paper that far out!

I am using a Bullseye Ghost Ring rear sight (http://store.stevesgunz.com/index.php?m ... ucts_id=44) with a bead front sight I got from stevesgunz.com. Love the sights just don't know how it will be dialing them in at 100 yds.

any suggestions? Is there a closer point-blank range that will give a similar trajectory or should I zero in 2" high at 50 yards?

[Griff]

Program is the "LEE Shooter" program. Provides for firearms inventory, reloading logs and several calculators.

...or should I zero in 2" high at 50 yards?

Yep, that's what I would do. Then shoot at 100 yards to confirm. Remember, that your ability to shoot at any range will increase the margin of error for a non-vital zone hit by that margin, at a minimum.

[earlmck]

One more thing, Charles. If you can't see the bulls-eye using your iron sights, you need to use a larger bulls-eye. Your eye will do an amazingly good job of centering things, so long as you can see 'em. But it can't center what it can't see! (I use pistol targets at 100 yards with the iron sights, or make my own with nice large bulls).

[AJMD429]

I agree with Griff, in the case that you may be shooting beyond 100 yards without necessarily intending to. I still-hunt the same places every year, and know the ranges well, so hadn't given that due consideration.

Is there a closer point-blank range that will give a similar trajectory or should I zero in 2" high at 50 yards?

Theoretically you can do the sighting-in at ANY range, just offsetting to the proper height above your line of sight, but the geometry is such that if you're 1/2" off of where you thought you were at 50 yards, you'll be 2" off at 200 yards, whereas if you sighted in at 200 yards, that 1/2" mis-reading of your group-center would translate to only 1/8" error at the 50 yard distance. So, even if you do the initial sight-in close-up, you should confirm and fine-tune it out at the longer distance. The other factor is that real-world ballistic coefficients are seldom as predicted (and even vary with velocity!), so that error introduced will be multiplied when you extrapolate to longer ranges vs. interpolating to shorter ones.

Sight-wise, your sights will work as well at 1,000 yards as at 50 yards, provided the bullseye is proportionately the same size, so just use one you can see that gives you a visible thing to aim at, yet is small enough that you are going to aim in the same place each time, vs. wandering over a large area. Think of it as just an aiming-point serving as a reference - "barely-but-definitely-visible" is just about perfect for a sighting-in bullseye.

Here is the link to another great ballistics program you can download, and this one is...

• FREE - http://huntingnut.com/index.php?name=PointBlank

It does all you really need, but I bought the RCBS one years ago and just like to mess around with it. If I could shoot well enough to need to know the effect of a 5-degree cant to the right in an 75% humidity environment at 855 ft. above sea level in a 10 mph crosswind, I could take FULL advantage of the RCBS-dot-load...

[Charles4400]

Really appreciate everything from you all... the input is certainly informative and extremely helpful!

Need to get out the range next week and do some sighting in.

Thanks again!

[levernut]

Federal Eagle 357Mag/158JSP from my Rossi 20" measured in my Prochrono gave 1811f/s (average of 3 shots).

[Griff]

Federal Eagle 357Mag/158JSP from my Rossi 20" measured in my Prochrono gave 1811f/s (average of 3 shots).

That's even better!!!


NOW your 2-½" target area stretches from 70 to 115 yards. And, your 50 yard sighting would only be slightly under 1-½" above your line-of-sight.

You'll still need to shoot the load out of YOUR rifle to confirm that it matches that optimum trajectory. These computer programs ain't perfect, but they sure take a lot of "by guess & by golly" out of getting a rifle sighted in for multiple ranges.

[AJMD429]

NOW your 2-½" target area stretches from 70 to 115 yards. And, your 50 yard sighting would only be slightly under 1-½" above your line-of-sight.

THAT's about perfect...!

Two other things to keep in mind as you pick your 'window' range:

• 1. The bullet trajectory is more perpindicular to your line of sight at the 'farther than anticipated' end of the range than the 'closer than anticipated' end, so small errors in estimated yardage lead to bigger misses 'out there'. Unfortunately the need for accurate range estimation 'out there' vs. close-up, is the opposite of our real-world abilities. Then answer as Griff showed earlier is to be sure your selected range to be sighted-in over is generous on the 'out there' end, in case that "100 yard" shot turns out to be 115 yards. If your "70 yard" shot turns out to be really 50 yards, you'll be off by way less.
  
  2. The software may list "minutes of angle" or "clicks" you'd be off at various ranges. Due to the same geometric issues as stated above, being even a couple MOA too high at 75 yards puts you 1.5" high there, vs. a couple MOA low at 150 yards would mean 3" out there. Combine that with the fact that if you're 1.5" high at 75 yards, you're probably 'only' 1.3" high at 50 yards if you've misjudged the distance as being only 2/3 as far as it really was, 'out there' your 3" low could become 15" low if you misjudged your distance as 3/2 of what it really was.

All this theorizing and speculating is fun when the weather is bad, but the REAL fun begins when you get out there at the range and see what the Rossi can do. Whatever load/trajectory/sighting you decide on, you're gonna have lots of FUN.

[Charles4400]

All this distance thought is starting to slowly seep its way into the noggin.... trying to get out to the range this week to try some of this out!

Thanks, this is all allowing me to make more reasons to get out there soon!

Only thing I;m not looking forward to is hammering the dovetail rear sight while at the range (bringing small table vice to do so)... don;t suppose you know of an easy tool that can adjust the windage on these dovetails do you?

[3leggedturtle]

[quote="Charles4400 OK so it seems that the point-blank range should be at 100 yards...now question is, how do I dial that it on iron sights that far out
? I've done it with scopes but zeroing irons at 100 yards? I can't even see the bullseye on paper that far out! :shock[/quote]
Thats desribes the majority of us here I personally put a paper plate up at 100 yards and just start shooting. With my .45 Puma can keep them in a 4" group so far. I hold on the bottom edge of plate. It has the standard open sites.

[Charles4400]

Well got a chance to get out to the range today and I defiantely need to print out some larger targets!

Ended up trying to zero in at 50 yards and found I was shooting too high even using a rest.

Problem is, my front sight cannot be adjusted for elevation and my rear sight (bullseye ghost ring) is already on its lowest setting for elevation.

I can aim it so that the bead sits lower than the middle of the ghost ring but would rather not have to have that type of getting used to and just use the sights as intended. (I have other rifles with irons and don;t want to create a bad habit)

I'll ask in a new thread about the availability of rear iron sights with elevation adjustments attatched by dovetail .

Other than that the gun feels darn nice! The recoil feels good because it just goes straight back and there isnt that much recoil to even speak of. It sounds more solid firing than the sound of 5.56 that I am used to. Fun gun indeed! I was hitting the steel plates out at 100 yards, but just want more precision with my shots on paper before I will consider using this to hunt.

There where some hang ups on loading the round into the chamber sometimes and it got better as the day went on, but I'll just chalk that up to breaking it in. I plan on using the Steve Gunz methods in his video to smooth things out when I get the chance.

Will update as things progress...and thanks again for all the input...it really does help.

[Pete44ru]

I too use American Eagle 158gr JSP's in my Rossi M92, and have taken two deer with it, one @ 60yds (+/-), and the other paced out at 90yds. Both were DRT, using a center hold on the chest/vitals.

The ammo was readily zeroed, using the issue front sight and the peep sight, that I custom-installed - zeroed @ 1" high / 50yds.

Just my $0.02, and no disrespect meant - but those "quick" solution type, dovetail peep, "Bullseye" (BS, IMHO) sights are a waste of time & money.

50 years of hunting/shooting tells me to do it right the first time.

.