60 yards need calculations to 50 uards

[Jefferson]

getting a buddy to test some REAL rimfire benchguns for ammo liking

his home range has target frames at 60 yards and we wish to convert the results to 50 yard targets

is it just the simple math division ir is,there a newer formula based on rimfire speeds and so on?


am I missing something

 

[grauhanen]

Use basic math to convert from 60 yards to 50. If you are converting group size, multiply the size at 60 by 0.833 to get what the size would be at 50.

 

[Jefferson]

Jeff

 

[homer76]

I would suggest a ballistic app and knowing the ballistic coefficient of the ammunition you are using. A chronograph helps as the posted muzzle velocity is not always correct for your rifle.

However the difference is minimal for the distances you inquiring about.

I'll use one of my rifles as an example using a chronograph and Strelok Pro. I have a Ruger 10/22 with 16" barrel zeroed for 50 meters using CCI AR Tactical. At 60 meters it drops 1.5 cm and the velocity drops approximately 20 fps.

 

[Blastattack]

Multiply your group size by 5/6. It’s that simple.

 

[Snider shooter]

Better yet just go and shoot and find out what your group size is. Nothing beats actually doing it.

 

[Jefferson]

Better yet just go and shoot and find out what your group size is. Nothing beats actually doing it.

see post 3 buddy

 

[struff55]

well i would just set a target up a 50 yds and shoot and why would you have a target at 60 to begin with
rimfire sighting
zero at 20 yds 1 inch high @ 50 ten it zero's at 75 yds 3-5 inch low at 100 yds
basic rimfire sighting adjust a bit for ammo velocity

 

[_Shorty]

Shoot at 50. What you get at one distance doesn't translate to another distance. Positive (and negative) compensation is distance-specific.

 

[Jefferson]

Shoot at 50. What you get at one distance doesn't translate to another distance. Positive (and negative) compensation is distance-specific.

100 % correct and most not only don't know this

but never will and certainly will not understand it fully

 

[_Shorty]

To clarify, you're not going to see earth-shattering differences between 50 yards and 60 yards, but the point is that what you get at either distance is not going to be a directly-relatable amount. It's going to depend on what distance the gun is tuned for versus the distance you're shooting at. In most instances, rimfire benchrest competitions are shot at 50 yards, so it makes sense to test at 50 yards. You're going to want that gun to be tuned for 50 yards if that's where your competition distance is, and playing at other distances won't tell you as much as you want to know about 50 yards. Multiplying by 5/6 is correct as far as translating one size at 60 yards to what it would be at 50 yards *if* it shot the same at 50 yards. And I'm just trying to point out that it isn't going to shoot the same at 50 yards. Again, it isn't going to be 1" at 50 yards and 10" at 60 yards, as we are only talking about a 10-yard difference, but it isn't going to be exactly 5/6ths when you go from 60 down to 50 because there is also going to be a small difference in how it shoots at both distances. You're not going to learn nothing at 60 yards, but you will be better off to just pace off 10 yards closer and temporarily put a target holder there at 50 yards. In most scenarios you might not care all that much, but when you're talking about getting serious with serious bench guns, you're better off actually shooting at 50.

 

[grauhanen]

There is little information accompanying the chart shown above in post 3. So that readers can be on the same page, so to speak, some clarity on what the chart shows might be helpful.

Although there is no distance given, presumably it is 50 yards. The column on the left appears to show different rifles that shot the 13 different ammos as shown by the various ammo labels across the top row.

The columns of numbers for each rifle and ammo appear to represent results. Are these outside-to-outside group sizes in millimeters? Ten-shot groups? Do they represent the average size of the same number of groups or a single group?
_____________________________

With regard to the question of converting results from 60 yards to 50, if groups are being compared a simple conversion will suffice. If a shooter were ammo testing at a testing facility such as the Lapua test centers in the U.S., all results would be at 50 meters (very close to 55 yards) and 100 meters.

Experienced BR shooters who use testing facilities don't worry about getting results from 50 meters rather than 50 yards. Whenever shooters ask what the results are in yards they are provided with a simple conversion. That ought to be satisfactory here.

Ammo that shoots at 60 will shoot at 50. The difference in distance between the two is small enough to make no appreciable difference in how the ammo performs. When comparing results at more significant distances then a simple conversion may not always be valid because, except for unpredictable and unusual circumstances, group sizes become increasingly larger as distance increases.