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Zeroing tips needed.


mpmo

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Trying CO for the first time. Would like advice on considerations for zeroing.

 

-Shooting USPSA and Steel Challenge

-Reloading 124gr, 128pf for USPSA and 115gr (PF TBD) for steel.

 

Longest target I have seen in my area competitions is around 25 yards. For sure not the norm.

 

CZ S2 OR w/ SRO. Right now all stock but have some grips and springs on order.

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Trying CO for the first time. Would like advice on considerations for zeroing.
 
-Shooting USPSA and Steel Challenge
-Reloading 124gr, 128pf for USPSA and 115gr (PF TBD) for steel.
 
Longest target I have seen in my area competitions is around 25 yards. For sure not the norm.
 
CZ S2 OR w/ SRO. Right now all stock but have some grips and springs on order.
25 yard zero all day

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31 minutes ago, mpmo said:

If I zero to 25yds, How far off if any can I expect it will be at 35 and 5 if at all?

depends on your gun and load.  shoot it in 5yd increments 0-50yds so you know what if any holdover/under you need to do at a match.

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When you guys zero are you standing, seated, supported, unsupported? 



I get a different point of impact supported than I do standing and shooting at USPSA speed... not a lot, but enough that I zero the same way I compete.

Zero at 20 yards. I also like to hang a piece of steel and then walk back in 5 yard increments just to see where it hits.


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Agreed, at 600' elevation, it's cutting it close for matches at sea level.

Right now just starting and shooting local level 1 matches. I have a U classification and will be a C once I shoot 2 more classifiers (first 2 were C’s and I’m progressing.) Don’t think travel outside of my area is in the cards anytime soon nor shooting higher than level 1 for the next 6-8 months.

All rounds chronoed fall between 126-130 with most at 128. Obviously a different chrono or different conditions could change that. But by how much?


I live 900ft above sea level. I had no idea that was a factor! But if you were going to a match at a vastly different sea level, wouldn’t you just load to that environment? So if I am shooting for 128 and I am going somewhere low, add an extra 0.2gn of powder.

I could also see if I was working up to a match where I felt it was the safest to load 130-135, load and run that a few months in advance.
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From my understanding, it seems easiest to load to around 130 PF at sea level. That way, you don't need to adjust loads depending on elevation. Your gun will react roughly the same as well.

 

Personally, I just put 4.0 gr of titegroup for 125 gr blue bullets and call it a day. No idea what it actually chronos, but it should be good...

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3 hours ago, terrapin said:

 

 


I get a different point of impact supported than I do standing and shooting at USPSA speed... not a lot, but enough that I zero the same way I compete.

Zero at 20 yards. I also like to hang a piece of steel and then walk back in 5 yard increments just to see where it hits.


Sent from my iPhone using Tapatalk

 

 

I do as well, that's why I was asking. I do it initially seated with my arms supported but not the gun. Then I stand and do something like the doubles drill to see where I'm hitting. Although I've been setting mine up to shoot a tick low at 15 yds because I can't seem to put together really good groups at 20. 

Edited by promtcy
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13 hours ago, mpmo said:

All rounds chronoed fall between 126-130 with most at 128. Obviously a different chrono or different conditions could change that. But by how much?

You only have 3 units of cushion (let's just call them "PF units"). At 124 grains for your bullet, every 10 feet/second is 1.24 units. You have about 25 feet per second cushion. 

 

How much does your velocity vary? How much will it change with temperature and air density? That's why you don't load that close to the limit, particularly since you're already shooting minor and if you dip below the threshold you'll be shooting for no score. The "wimpy major" at least pushes you only down to minor...

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13 hours ago, mpmo said:

I live 900ft above sea level. I had no idea that was a factor! But if you were going to a match at a vastly different sea level, wouldn’t you just load to that environment? So if I am shooting for 128 and I am going somewhere low, add an extra 0.2gn of powder.

No, that's how you end up in all sorts of trouble when you have the potential to mix rounds or mess up the powder measure. 

 

Just add a bit of powder and settle on a higher PF. You won't be able to tell a difference between 128 and 132, yet you won't have to worry about chrono ever again. Anything starting with "12x" in minor and "16x" in major is looking for trouble. It might work and you can push it that low, but it's all risk and no reward. 

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15 hours ago, terrapin said:

I get a different point of impact supported than I do standing and shooting at USPSA speed... not a lot, but enough that I zero the same way I compete.

I would be very careful about this - if you're not getting the same zero, you have an issue with the trigger pull. Compensating for trigger pull with the sight alignment will cause all sorts of problems as your trigger control gets better. You'll start getting better AND missing... 

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7 minutes ago, IVC said:

No, that's how you end up in all sorts of trouble when you have the potential to mix rounds or mess up the powder measure. 

 

Just add a bit of powder and settle on a higher PF. You won't be able to tell a difference between 128 and 132, yet you won't have to worry about chrono ever again. Anything starting with "12x" in minor and "16x" in major is looking for trouble. It might work and you can push it that low, but it's all risk and no reward. 

 

Yes!

I was working chrono at a level 2 match 3 weeks ago and an open shooter went 164.9 pf and was surprised. He said he shot a match last week and it was 168pf. That's just too close to cut it.

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On 8/28/2020 at 7:29 AM, zzt said:

I zero everything at 25 yards.  It gives me the most flexibility.  BTW, there are several 35 yard targets in Steel Challenge.

This ^^^.

 

KISS - keep it simple. Do NOT zero at close range since you will be seeing quite a bit of the "sight offset effect." Don't do different zeros for different guns (unless you only own a few) since you'll always have to think about how to shoot which gun. Just pick a good distance for a handgun, 25 yards or more, pick a sight picture you prefer, then sight in all your guns the same. (Exception would be specialized bullseye guns, but that's a completely different beast.) 

 

Remember, for pistol distances your bullet drop is negligible (it's all "point blank range"). What makes the difference is the offset between the bore center and the aiming device (iron sights, red dot). For example, if you zero at 5 yards, the bullet goes up the amount of sights offset in those 5 yards, but then goes that much up at 10, twice that much at 15, etc. You add up a lot of inches or half-inches by the time you get to long distance shots...

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FWIW, Altitude has very little difference on velocity for PF at Chrono.  There's not enough air to bash through for all of 3 yards to the chrono to slow a bullet more than 1 or 2 FPS with any reasonable altitude change.

 

But, temperature tends to change with altitude as well and that can make a much larger difference depending on the powder.

 

As an Australian friend said years ago "Put some rounds in an Esker [cooler] with some ice.  Put a couple beers in to stop the ice rattling around.  Go to the range and chrono your regular temperature loads, chrono the cold loads.  Drink the beer."

 

Chronos also vary one to the other.   When you go to Chrono at a major with 2 chronos in one box, they usually show different numbers, and that's two of the same brand in the same setup.

 

 

 

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I went back to my chrono data and found a couple things.

Initial test: 

74deg F, 30.2 in Hg, stock 16lb. recoil spring, handloaded and measured, Avg. 128PF

Most recent test:

64deg F, 30.1 in Hg, 11lb. recoil spring, loaded on LnL AP, Avg. 130PF (2 PF spread)

 

I'm good with that for now.  Will continue to chrono under different conditions.

 

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So when it's 95 degrees you'll be at 124pf. Good to know

Using N320. From what I have read, velocities drop in cooler temperatures. So by that logic, +30deg should increase PF. Am I off on this?

As I said, I will continue to chrono under different temps to see if there is an effect.
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I use 320 also but don't load close enough to the limit to know that answer. I just set something I know will be good in all conditions, check it once and that's it. A day at the range dicking around with the chrono is time spent not practicing

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4 hours ago, shred said:

FWIW, Altitude has very little difference on velocity for PF at Chrono.  There's not enough air to bash through for all of 3 yards to the chrono to slow a bullet more than 1 or 2 FPS with any reasonable altitude change.

 

But, temperature tends to change with altitude as well and that can make a much larger difference depending on the powder.

 

As an Australian friend said years ago "Put some rounds in an Esker [cooler] with some ice.  Put a couple beers in to stop the ice rattling around.  Go to the range and chrono your regular temperature loads, chrono the cold loads.  Drink the beer."

 

Chronos also vary one to the other.   When you go to Chrono at a major with 2 chronos in one box, they usually show different numbers, and that's two of the same brand in the same setup.

 

 

 

 

I was ignorant on the variables to bullet velocity. Thank you for clarifying. It seems temperature and barometric pressure have the greatest effect. Altitude, in and of itself, has no effect. Regardless, it's the wise move to load to a higher PF to give yourself the cushion.

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