When I'm dialing in my 260Rem with 120 gr ttsx or 30-06 with 165 gr tsx bullets, I generally zero at 200. Then I know I"m good out to 250 without thinking and I should aim a few inches low if 100 or closer.
Where I hunt is mostly dark timber, except when chasing antelope which is still often only a 200 yard shot so 200 zero takes care of 99% of my hunting requirements.
I've not yet worked up a hunting load for my 6.5 G, so I might do that differently, depending on results, but since my known hunting ranges won't change, I'm guessing I'll use the same technique until proven not K.I.S.S.
09-30-2017, 01:55 AM (This post was last modified: 09-30-2017, 02:56 AM by Klem.)
Those advocating a 200yd zero might find that a Point Blank Range (PBR) calculation is a more efficient way to zero for hunting.
I think we all agree that the ultimate goal of hunting is to land a hit within a critical circle on an animal. If you work back from there using the ballistics of your gun and ammunition you can find the zeroing range where the dangerous space is maximised. This zeroing range is unlikely to be exactly 200yds. By maximising, I mean maximising the possible ranges that a point-and-shoot will result in a deadly/humane shot.
For example, using;
a 120NBT @ 2,460fps to hit a 6" diameter circle on say, a deer.
PBR Zero.
Plugging these number into JBM Ballistics online give us a PBR zero of 219yds. With this zero we can shoot out to 255yds and hit within that 6" circle.
For ease of zeroing JBM tells us if we zero 2.7" high at 100yds then this is the same as a 219yd zero.
200yd Zero.
JBM tells us we can shoot out to 240yds before the bullet drops below 3" (3" is the radius of our 6" diameter kill-circle on an animal).
Result.
With a calculated PBR zero you get 15 more yards of dangerous space than an arbitrary 200yd zero. It's not much but it's still undeniably better and depending on your gun, ammo and kill-circle it can be a lot more. Sure, if you don't have 15 minutes to plug your gun's data into JBM, or are in a place where the internet doesn't exist, go with the convenient 200 zero... but most people on this forum are a lot more particular about precision, so you may as well be precise about your zeroing as well.
I would add to that, I have yet to see anyone eyeball a distance to an animal or object and be within 30 yards. Unless you have a rangefinder, that extra 19 yards makes a difference with the adrenaline.
I spent a lot of time looking at the "Maximum Point Blank Range" idea.
In the end, I concluded that it makes sense if the ONLY shooting one does is at medium game or paper.
Th high trajectory -- 5 to 6 inches above the line of of sight for intermediate ranges -- adds a lot of detail to be remembered when practicing, plinking or casual shooting at those distances. The 1.5" high zero at 100 yards means that I can hold centre of mass for most varmints or casual targets to a tad past yards. Raising the crosshairs then works out to about 300 yards.
Going further than 300 yards moves one into choosing one of the various options for getting the right point of impact.
Am I the only guy that uses meters? Makes a lot of sense for a scope set in mils generally, keeping it metric. ;-) Seriously, though...
50/200m zeros are the lazy man's answer to PBR zeroing. Anyone that has spent time w/ 5.56 has undoubtedly come across the 50/200m recommendation. I use it myself on my iron sighted or RDS 5.56 ARs. It's easy and, in my opinion, a better option that the 25/300m standard many of us were taught.
As regards actual PBR-zeroing - it IS a useful tool. I first encountered the concept years ago on Chuckhawks. My biggest issue with PBR is that people accept, for my taste, far too large a "vital zone." Way back when I first read about it, Chuckhawks used a +/- 3 inches (or a 6" vital zone) - often, if I use software like JBM, I do the same if considering ethical game harvesting. That's a level of error I am willing to tolerate under the assumption that I am going to hold my POA on my desired POI - which is the whole point of the PBR zero anyhow.
It's only my opinion - but, if you have the skill and the DOPE to consistently hold over/under, then a PBR zero isn't really for you. It's utility is lost at that point.
DJL2 Wrote:...It's only my opinion - but, if you have the skill and the DOPE to consistently hold over/under, then a PBR zero isn't really for you. It's utility is lost at that point.
Very well said!
A large majority of our forum are either actively practicing those skills or are developing them. On the other hand, there are some very good to excellent shooters who know they will avoid shots at medium game at ranges beyond about 300 yards (meters too).
The vast majority of us should put ourselves in this class. Wind doping is a real challenge and even 5 mph winds can take one out of the vital zone at 300 yards with some bullets. Going out to 500 yards ups the odds of a miss for all but the best dopers.
Hence, the PBR method -- independent of one's choice of zero -- should be the starting point for everyone.
If one wants to progress beyond the 250 - 300 yard/meter range for medium game, one must shoot enough to become familiar with wind doping and note carefully the circumstances where the shot drifts outside the 6 - 10" diameter circle we view as the vital zone size. Only when one develops the experience to routinely place the shot into the right spot should he or she consider a shot 'way out there'...
How many of you have put a BPZ elevation on your rifle and actually shot groups on paper from about 25 yards to the max distance of your theoretical PBZ just to see what your trajectory and group size really looks like? It will be an eye opener because it won't be what you envisioned via your ballistics computer. It will show you what reality is which ought to give you a lot more confidence in using such zero's.
Also, how many of you have recorded your zero about twenty or thirty times to see how much it may change from session to session? If you regularly shoot at a specific distance, record your zeros and after about twenty shooting iterations using the same load, shot at the same distance, you will find that for reasons unknown, you end up adjusting zero periodically and up to a minute on average. I know one minute isn't much but it is when you deal with using battle sight or point blank zeros. Again, it will present you with another reality that you can use to your benefit via increased confidence in using PBZ's.
...Also, how many of you have recorded your zero about twenty or thirty times to see how much it may change from session to session? If you regularly shoot at a specific distance, record your zeros and after about twenty shooting iterations using the same load, shot at the same distance, you will find that for reasons unknown, you end up adjusting zero periodically and up to a minute on average. I know one minute isn't much but it is when you deal with using battle sight or point blank zeros. Again, it will present you with another reality that you can use to your benefit via increased confidence in using PBZ's.
LR55
Elevation and windage changes for me from session to session.
Off-topic sort of.. but I have a 260 Rem R700 build for me by Clerance Hammond that is the only rifle I've owned that absolutely retains its perfect zero.. Even with multiple loads, projectiles, and temperatures the 100byard zero remains bulls-eye.
I've had many different companies do many different rifles, but Clerance is the man. Older Grentleman from Red Lion Penn, and his techniques are old school. I believe he was a rather well known bench rest shooter in his day..
If anyone is looking for a custom bolt gun, I simply cannot recommend him enough.. the tolerances and "trueing" he puts into his rifles is stunning.
I'm a new Grendel shooter, but I've built limited data from 25-200m. My observations are thus.
I used a 25m target to get rounds on paper, and centered, before moving to 100m.
@100m, I was about somewhere between .7-1 mrad low (hard to remember, because I had no intent to keep the 25m zero, just adjusted).
@200m, I confirmed that I needed .7 mrad (123 gn ELD-M @ ~2470 fps) of adjustment.
On the flip side, using my 200m zero, I'm only about ~2 inches high @ 100m/150m...
Honestly, under field conditions, that's inside my margin for error as a shooter from anything other than prone supported. As mentioned here, my optic has a zero stop and I am toying with whether to leave that @ 100m or move it to 200m.
Now, all that being said, my greatest experience attempting to shoot multiple distances with one zero is actually using my issue rifle/carbine. I have a healthy appreciation of free-float handguards from the same. Part of the problem is that a 25m zero is poor practice in general, because it can mask errors if you're not shooting dime sized groups. However, if we look at the theoretical PBR 25/300m PBR zero, we note that your best case is being about 5 inches high at your 150 and 200m targets. I admit to not being the best shooter, but I found this not to be an effective PBR zero/trajectory. Just shooting at Ivans w/ either RDS or irons, I needed to make a conscious effort to aim at the base of the target to maximize my hit potential. That's not an ideal hold, either, but I needed/wanted a clear POA reference and "estimate five inches low on this relatively featureless, monochromatic mass" wasn't it.
A 50/200m zero ended up providing me a far more useable trajectory, with far less input required on my part as a shooter. Part of that is because the projectiles is within +/- 3 inches of POA all the way to 250 meters and is no lower (about -5 inches) @ 300m, than a 25/300m zero is high at 150-225m. Accounting for 5 inches of drop between 250-300m is a lot easier for me than accounting for +5 inches in my short-mid range shooting.
These are big targets. An Ivan is, arguably, a much easier target to hit than a deer (for example). I found the +/- 5 inch trajectory tolerance to be far too generous for even this type of shooting, based on my level of skill. It required me to make hold under corrections on the most common targets I was engaging to score hits reliably. I wanted to be able to hold POA centered on my target and make hits - which is what a PBR zero is supposed to support. Moving to a +/- 3 inch 50/200m zero supported that for me. The 300m targets being the least common, it was much less hassle to just hold at the neck/shoulder for that one presentation.
Sorry for the TL/DR...that's how I arrived to my own conclusion on the utility of the PBR zero and what sort of trajectory I'm willing to accept in a PBR zero.
LR1955 Wrote:Guys:
How many of you have put a BPZ elevation on your rifle and actually shot groups on paper from about 25 yards to the max distance of your theoretical PBZ just to see what your trajectory and group size really looks like?
Also, how many of you have recorded your zero about twenty or thirty times to see how much it may change from session to session?
10-02-2017, 08:13 PM (This post was last modified: 10-02-2017, 08:17 PM by LR1955.)
Kilco Wrote:Off-topic sort of.. but I have a 260 Rem R700 build for me by Clerance Hammond that is the only rifle I've owned that absolutely retains its perfect zero.. Even with multiple loads, projectiles, and temperatures the 100byard zero remains bulls-eye.
I've had many different companies do many different rifles, but Clerance is the man. Older Grentleman from Red Lion Penn, and his techniques are old school. I believe he was a rather well known bench rest shooter in his day..
If anyone is looking for a custom bolt gun, I simply cannot recommend him enough.. the tolerances and "trueing" he puts into his rifles is stunning.
Kilco:
So you are saying that every single time you went to the range with that rifle and shot at 100 yards, it grouped exactly where it grouped the previous X number of times? Not that it held a bulls eye every time. But that it shot to the same zero every time and you have never had to touch the sights.
DJL2 Wrote:I'm a new Grendel shooter, but I've built limited data from 25-200m. My observations are thus.
I used a 25m target to get rounds on paper, and centered, before moving to 100m.
@100m, I was about somewhere between .7-1 mrad low (hard to remember, because I had no intent to keep the 25m zero, just adjusted).
@200m, I confirmed that I needed .7 mrad (123 gn ELD-M @ ~2470 fps) of adjustment.
On the flip side, using my 200m zero, I'm only about ~2 inches high @ 100m/150m...
Honestly, under field conditions, that's inside my margin for error as a shooter from anything other than prone supported. As mentioned here, my optic has a zero stop and I am toying with whether to leave that @ 100m or move it to 200m.
Now, all that being said, my greatest experience attempting to shoot multiple distances with one zero is actually using my issue rifle/carbine. I have a healthy appreciation of free-float handguards from the same. Part of the problem is that a 25m zero is poor practice in general, because it can mask errors if you're not shooting dime sized groups. However, if we look at the theoretical PBR 25/300m PBR zero, we note that your best case is being about 5 inches high at your 150 and 200m targets. I admit to not being the best shooter, but I found this not to be an effective PBR zero/trajectory. Just shooting at Ivans w/ either RDS or irons, I needed to make a conscious effort to aim at the base of the target to maximize my hit potential. That's not an ideal hold, either, but I needed/wanted a clear POA reference and "estimate five inches low on this relatively featureless, monochromatic mass" wasn't it.
A 50/200m zero ended up providing me a far more useable trajectory, with far less input required on my part as a shooter. Part of that is because the projectiles is within +/- 3 inches of POA all the way to 250 meters and is no lower (about -5 inches) @ 300m, than a 25/300m zero is high at 150-225m. Accounting for 5 inches of drop between 250-300m is a lot easier for me than accounting for +5 inches in my short-mid range shooting.
These are big targets. An Ivan is, arguably, a much easier target to hit than a deer (for example). I found the +/- 5 inch trajectory tolerance to be far too generous for even this type of shooting, based on my level of skill. It required me to make hold under corrections on the most common targets I was engaging to score hits reliably. I wanted to be able to hold POA centered on my target and make hits - which is what a PBR zero is supposed to support. Moving to a +/- 3 inch 50/200m zero supported that for me. The 300m targets being the least common, it was much less hassle to just hold at the neck/shoulder for that one presentation.
Sorry for the TL/DR...that's how I arrived to my own conclusion on the utility of the PBR zero and what sort of trajectory I'm willing to accept in a PBR zero.
DJ:
Had to read it a couple of times. I doubt your trajectory would be low at 100 given a 25 point of aim / impact. More like about five inches high but won't argue it.
Agree with having to hold low at the 150 and 200 targets with a 300M BSZ. Shouldn't be that way given computer generated data and there are reasons why you had to hold low other than just danger space issues. And high for the 300's. However your experience is more common than not. Which is why I asked how many put paper up from about 25 to the end of their computed danger space and shot a group on each target using a center hold, to actually see what is happening both in terms of trajectory and group size.
Also think your 200 zero would give a higher hit probability given a center hold until you get to 300. Then like you said, a high hold on the 300 targets.
I have nothing useful to add, but greatly appreciate y'all freely sharing your wisdom.
As a slacker, and because there's no good spot to do a correct PBR between 200 & 300 yards where I shoot, I use a 200 yard zero. Klem makes great points about sacrificing a few yards with that though.
Reading some of ther recent posts, especially the ones by LR55, reminded me that the zero "drift" from session to session might be a manifestation of the true dispersion of one's rifle, especially if calm winds are present for each session.
On average, a 3 - 5 shot group is much smaller than 10 or 20 shot group given the same intrinsic dispersion. Most of us don't want to 'waste' ammo on 20 or 30 shot groups, especially when all those 'flyers' make the group much bigger.
Add to this changes in wind, temperature and light and the group grows slightly more.
That is why I advocate multiple trips to the range using the same zero for all of them. Then set the sights to capture the composite group center.
Next look at the composite group size and extend it to the range where it would be about the size of the vital zone of interest. That defines the maximum tange where one should attempt a shot under conditions similar to what were seen on the range over the multiple trips.
If the winds ere stronger than seen on the range, don't attempt the shot unless you have confidence in your doping and offset.
murfvol Wrote:I have nothing useful to add, but greatly appreciate y'all freely sharing your wisdom.
As a slacker, and because there's no good spot to do a correct PBR between 200 & 300 yards where I shoot, I use a 200 yard zero. Klem makes great points about sacrificing a few yards with that though.
murf,
You don't need a 200-300 yard range to zero with a PBR. Calculate your PBR on the computer and it will also give you the impact point on the target at 100. For example, it might be 3.1" high at 100. You then zero at 100 so that the point of impact is 3.1" higher than what you are aiming at. Then you are PBR-set for all the further ranges.
If you want to send me your gun's info (muzzle velocity, bullet etc) I can do it for you.
10-03-2017, 11:05 AM (This post was last modified: 10-03-2017, 11:07 AM by Kilco.)
LR1955 Wrote:Kilco:
So you are saying that every single time you went to the range with that rifle and shot at 100 yards, it grouped exactly where it grouped the previous X number of times? Not that it held a bulls eye every time. But that it shot to the same zero every time and you have never had to touch the sights.
LR55
Yes, exactly the same spot. Given the round count with this rifle is relatively low, (below 500) but my handloads with the 143 ELD-X, 140 ELD-M, Berger 130 AR Hybrid and 140 VLD hunting POI are all within .5 moa. 120 TTSX was the furthest from said POI, at 1 moa to the lower left.
Ive never had results like this with any other rifle whatsoever.
My father has a 6.5-284 build on a stellar action by Clarence, and he has similar results.
I've only neck sized Lapua brass for it, and I've yet to have to trim the brass. It shrunk slightly on the first firing, and with 10 reloads on the same brass (neck sizing only) i have to seen any growth.
It sounds like horse s***, but every time I've taken this rifle out, at 100 yards with my pet load of H4350 under the 143 eld-x at 2800fps it is absolutely in the center of the target.
The rifle also wears a Nightforce SHV F1, so I'm very confident in the scopes repeatability as well.
Kilco Wrote:Yes, exactly the same spot. Given the round count with this rifle is relatively low, (below 500) but my handloads with the 143 ELD-X, 140 ELD-M, Berger 130 AR Hybrid and 140 VLD hunting POI are all within .5 moa. 120 TTSX was the furthest from said POI, at 1 moa to the lower left.
Ive never had results like this with any other rifle whatsoever.
My father has a 6.5-284 build on a stellar action by Clarence, and he has similar results.
I've only neck sized Lapua brass for it, and I've yet to have to trim the brass. It shrunk slightly on the first firing, and with 10 reloads on the same brass (neck sizing only) i have to seen any growth.
It sounds like horse s***, but every time I've taken this rifle out, at 100 yards with my pet load of H4350 under the 143 eld-x at 2800fps it is absolutely in the center of the target.
The rifle also wears a Nightforce SHV F1, so I'm very confident in the scopes repeatability as well.
Kilco:
I ask, not because the rifle may change but because the shooter may change. Am curious to know how much and how often. I have sometimes gone five training sessions without any change but the sixth session, same range, same conditions, shows a change. Whether the change is minor or major depends on the standards one has set. I bring it up only because sometimes people can get consumed with trying to figure out why instead of just accepting it for that day and continuing on.
I ask, not because the rifle may change but because the shooter may change. Am curious to know how much and how often. I have sometimes gone five training sessions without any change but the sixth session, same range, same conditions, shows a change. Whether the change is minor or major depends on the standards one has set. I bring it up only because sometimes people can get consumed with trying to figure out why instead of just accepting it for that day and continuing on.
LR55
Massive truth to this, and even regarding this rifle you are 100% correct.
Even though this is a 15 lbs bolt gun and relatively easy to shoot, every few outing with it I'll find myself shooting inexplicably low 1/2 to 1". Seems to be a Trend with me and all my rifles.
With my Grendel (16" 7.3 lbs rifle) I find if my concentration is off or I've had one too many coffees I'm usually puilling to the low right.
I know this is an old thread, but here goes. Have finished my project, A-2 left handed clone 6.5 grendel. We have no ranges in the area worth messing with, better to find an open area and set up a target. My question: Need POI vs POA for a 36 yard zero as in Marine Corp zero. There are sites that discuss this for the 5.56, but not for the Grendel. Appreciate the replies...and plz don't be too hard on this noob... Had fun building it...and looking forward to building the next one for hunting. This one is for defense.
