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 Rifle Zero sonic vs subsonic. 
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So, I am venturing into subsonic reloading for my bolt gun. One of the challenges I am curious about is how to zero the rifle so I can switch back and forth from supers to subs easily which has me curious.

Where is the "break point" where subs and supers begin to follow significantly different trajectories? From 0 to XXyrds the bore of the gun is pointing below the scope bore. regardless of speed the bullet will not cross the plane of the scope before that point. The question is, does the subsonic start to lose it's climb rate before that point?

Lets say I set Zero @ 100yrds with supers. Will the subsonic round still hit pretty much the same point? I am not worried about it being maybe .25" lower @100yrds, I am curious about more significant variations.

The reason I am wondering is I am setting my gun up for a hunt in a few months. Primary will be supers for the deer we are after, but if I tag out early then I am free to hunt other game like Coyotes or anything else I can get to come into a call, but do it quietly so I do not have shots blasting off the canyons while others are hunting a few draws over. I will have a suppressor installed for all hunts so muzzle noise is a non issue. I would like to develop a bunch of subsonic rounds to use for this second option without having to go out and rezero the rifle during the hunt.

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Tue Sep 25, 2018 8:13 pm
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Do you have a ballistics app on your phone? If you use a ballistics calculator (website or app), you should be able to get specific numbers for different bullet types and velocities.

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Tue Sep 25, 2018 8:15 pm
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MadPick wrote:
Do you have a ballistics app on your phone? If you use a ballistics calculator (website or app), you should be able to get specific numbers for different bullet types and velocities.

I do, but I believe when you tell it the zero on the weapon it is assuming the zero with the round you are having it calculate? Hence my question, is zero, zero (within reason) regardless of the round being fired?

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it's too plastic, even for me.
it's like old, overworked, plastic everywhere old pornwhore amounts of plastic.


Tue Sep 25, 2018 8:24 pm
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Well, I'm playing with the Federal ballistics calculator: https://www.federalpremium.com/ballistics-calculator

If I plug in 25-yard zero, and then 150-grain bullet at 2300 fps with 0.5 BC, it tells me that it's going to hit 1.9" high at 100 yards.
If I do the same thing with a 220-grain bullet at 1050 fps, it tells me that it will hit 7.8" low at 100 hards.

So I'm seeing an almost 10-inch difference at 100 yards.

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Tue Sep 25, 2018 8:37 pm
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MadPick wrote:
Well, I'm playing with the Federal ballistics calculator: https://www.federalpremium.com/ballistics-calculator

If I plug in 25-yard zero, and then 150-grain bullet at 2300 fps with 0.5 BC, it tells me that it's going to hit 1.9" high at 100 yards.
If I do the same thing with a 220-grain bullet at 1050 fps, it tells me that it will hit 7.8" low at 100 hards.

So I'm seeing an almost 10-inch difference at 100 yards.

I just did similar with Gundata.org. 100yrd zero the subsonic round was actually on it's downward slope before 100yrds, so it's zero was short to and dropping in to make the "100yrd zero" Darn. I will have to make sure to calculate the dial from my supers to subs so that if I swtch I know I have to dial up xMIL for my subs to be zero'd @ 100yrds or whatever I calculate MPBR to be for that round.

Thanks Steve.

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Talons wrote:
it's too plastic, even for me.
it's like old, overworked, plastic everywhere old pornwhore amounts of plastic.


Tue Sep 25, 2018 8:45 pm
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Whenever you switch ammunition (even lots) don’t expect to stay zeroed. What you’ll want to do is choose which round will be your primary: super, or subsonic. This is what you will truly zero the rifle for at 100 yards for windage and elevation, and also set your zero stop if applicable.

Next, print your secondary rounds.

Open up a ballistic app (highly recommend “shooter”) and set up 2 cartridge profiles: one for supersonic and one for subsonic. Ensure that the secondary round set to be zeroed with a vertical offset: for instance, subsonic is -4” at 100yd. That will influence the remaining range data and prove to be quite reliable.

The thing I would note: beware of zero stops and selecting a round that drops more than the zero stop is set to. You may never be able to twist the elevation dial far enough.

The lowest printing round should be your primary, which will enable your zero stop to avoid the issue described above

Sent from mobile while falling asleep.

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Tue Sep 25, 2018 10:48 pm
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VantageReloading wrote:

The thing I would note: beware of zero stops and selecting a round that drops more than the zero stop is set to. You may never be able to twist the elevation dial far enough.

The lowest printing round should be your primary, which will enable your zero stop to avoid the issue described above


A zero stop works the other way. It could prevent zeroing a round that impacts too high. When you dial dope on a scope, you're adjusting for lower impacts at longer range; dialing back toward zero raises the point of aim, it doesn't lower it.


Wed Sep 26, 2018 7:53 pm
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lamrith wrote:
So, I am venturing into subsonic reloading for my bolt gun. One of the challenges I am curious about is how to zero the rifle so I can switch back and forth from supers to subs easily which has me curious.

Where is the "break point" where subs and supers begin to follow significantly different trajectories? From 0 to XXyrds the bore of the gun is pointing below the scope bore. regardless of speed the bullet will not cross the plane of the scope before that point. The question is, does the subsonic start to lose it's climb rate before that point?

Lets say I set Zero @ 100yrds with supers. Will the subsonic round still hit pretty much the same point? I am not worried about it being maybe .25" lower @100yrds, I am curious about more significant variations.

The reason I am wondering is I am setting my gun up for a hunt in a few months. Primary will be supers for the deer we are after, but if I tag out early then I am free to hunt other game like Coyotes or anything else I can get to come into a call, but do it quietly so I do not have shots blasting off the canyons while others are hunting a few draws over. I will have a suppressor installed for all hunts so muzzle noise is a non issue. I would like to develop a bunch of subsonic rounds to use for this second option without having to go out and rezero the rifle during the hunt.


You're forgetting the fact that the subs will shoot to a very different point of aim from harmonics and barrel movement. That's a much bigger difference inside 100 yards than what a ballistics app will tell you. You'll have to shoot and find out, but you should expect your subsonic rounds to impact well below point of aim at all distances. Do not expect to be able to zero both subs and supers to the same point at any distance; not gonna happen unless you get really lucky.

The best you could do to have a zero for each is to use a mil/mil scope and record the dope needed to zero the subsonic rounds.


Wed Sep 26, 2018 7:57 pm
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Yondering wrote:
VantageReloading wrote:

The thing I would note: beware of zero stops and selecting a round that drops more than the zero stop is set to. You may never be able to twist the elevation dial far enough.

The lowest printing round should be your primary, which will enable your zero stop to avoid the issue described above


A zero stop works the other way. It could prevent zeroing a round that impacts too high. When you dial dope on a scope, you're adjusting for lower impacts at longer range; dialing back toward zero raises the point of aim, it doesn't lower it.


Yondering, I was getting ready to type up a response and explain why you're wrong . . . but then I twisted it in my brain for a while, back and forth, and I finally concluded that you're right. :bigsmile:

So yeah, I would say that your highest-printing round should be your primary. That way, if you switch to a round that hits lower, you can always adjust the scope "up" which is typically dialing the knob counterclockwise.

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Wed Sep 26, 2018 7:59 pm
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Thanks guys. Makes more sense now, and being able to use the verticle offset is something I had failed to catch in my app. That will be perfect for what I want to do.

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Talons wrote:
it's too plastic, even for me.
it's like old, overworked, plastic everywhere old pornwhore amounts of plastic.


Wed Sep 26, 2018 8:02 pm
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VantageReloading wrote:
Whenever you switch ammunition (even lots) don’t expect to stay zeroed. What you’ll want to do is choose which round will be your primary: super, or subsonic. This is what you will truly zero the rifle for at 100 yards for windage and elevation, and also set your zero stop if applicable.

Next, print your secondary rounds.

Open up a ballistic app (highly recommend “shooter”) and set up 2 cartridge profiles: one for supersonic and one for subsonic. Ensure that the secondary round set to be zeroed with a vertical offset: for instance, subsonic is -4” at 100yd. That will influence the remaining range data and prove to be quite reliable.

The thing I would note: beware of zero stops and selecting a round that drops more than the zero stop is set to. You may never be able to twist the elevation dial far enough.

The lowest printing round should be your primary, which will enable your zero stop to avoid the issue described above

Sent from mobile while falling asleep.

So that -4 you refer to would be where the subsonic (assuming it is the secondary round) hits target in relation to the primary? So if the subs hit say 2" down and 1" left of the supers I would enter -2 vertical, -1 horizontal?

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Talons wrote:
it's too plastic, even for me.
it's like old, overworked, plastic everywhere old pornwhore amounts of plastic.


Mon Oct 01, 2018 7:17 pm
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lamrith wrote:
VantageReloading wrote:
Whenever you switch ammunition (even lots) don’t expect to stay zeroed. What you’ll want to do is choose which round will be your primary: super, or subsonic. This is what you will truly zero the rifle for at 100 yards for windage and elevation, and also set your zero stop if applicable.

Next, print your secondary rounds.

Open up a ballistic app (highly recommend “shooter”) and set up 2 cartridge profiles: one for supersonic and one for subsonic. Ensure that the secondary round set to be zeroed with a vertical offset: for instance, subsonic is -4” at 100yd. That will influence the remaining range data and prove to be quite reliable.

The thing I would note: beware of zero stops and selecting a round that drops more than the zero stop is set to. You may never be able to twist the elevation dial far enough.

The lowest printing round should be your primary, which will enable your zero stop to avoid the issue described above

Sent from mobile while falling asleep.

So that -4 you refer to would be where the subsonic (assuming it is the secondary round) hits target in relation to the primary? So if the subs hit say 2" down and 1" left of the supers I would enter -2 vertical, -1 horizontal?


I'm not aware of any ballistic app that allows you to enter a zero offset in mil or moa, which is what I think Vantage was getting at. However, once you know the zero offset for your subs (say 1 mil down and 0.3 mil left for example), you can add those values to your dope chart. That 1 mil vertical offset will be consistent at all ranges, meaning if you dial 1 mil vertical to zero your subsonic load, you can just use the dope chart values from that point to correct for distance.

That is easier, in comparison to measuring your offset in inches at a certain range, and trying to correlate that for longer distance. For example, if your subs hit 3.5" low at 100 yards, but your shot is at 70 yards, your point of aim won't be 3.5" high, it'll be something less. (3.5"x70/100 plus trajectory compensation) If you measure in mils, it'll always be that 1 mil plus the trajectory, regardless of distance.

Does that make sense?


Mon Oct 01, 2018 7:50 pm
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Touching back on this one as I was finally able to get out and test things. Yes the trajectories due to fps and barrel harmonics are so different that they do not track together past a few yrds from muzzle.

One thing of note however is that strelok DOES handle offsets from a given zero, if you document the information and then enter it. So if you gun shoots supers consistently and in a set group set that as your primary zero. If it also shoots subs in a good group but that is offset from the supers enter that offset information, then when you change rounds to a known round it will factor that offset in when calculating elevation and windage for a shot.
http://www.borisov.mobi/strelokpro/ios/cartridges.htm

I will post up data on results for my gun tonight when I get home.

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Talons wrote:
it's too plastic, even for me.
it's like old, overworked, plastic everywhere old pornwhore amounts of plastic.


Mon Oct 29, 2018 1:53 pm
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Results:
BASE ZERO: 165Grn Sierra GameKing's, @2600fps
POI offsets (where hits in relation to Base Zero):
  • 165Grn Sierra GameKing's, @2600fps plus 10" 30cal Suppressor: .1MIL down, .6MIL right
  • 165grn Maker's REX subsonic @ 970fps: 3.8MIL down, 3.6MIL right
  • 165grn Maker's REX subsonic @ 970fps plus 10" 30cal Suppressor: 4.3MIL down, .5MIL right

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Talons wrote:
it's too plastic, even for me.
it's like old, overworked, plastic everywhere old pornwhore amounts of plastic.


Mon Oct 29, 2018 5:14 pm
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