Testing loads at short ranges.

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morsetaper
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Testing loads at short ranges.

Post by morsetaper » Thu May 01, 2014 2:26 am

Living in Northern Virginia, I'm somewhat limited as to the number of ranges that I have convenient access to. The rifle range that I like (C.F. Phelps in Sumerduck), is most convenient-and free. It's a 100yd. DGIF facility, but only open Sept.-Mar. This leaves the local indoor range, and the NRA range, which isn't too bad of a haul. But the local range is only 25yds. The NRA range is 50yds, but my schedule doesn't work very well with their operating hours. And they will limit you to one hour on the range at a time.

Here's my problem:
I have a number of rifle loads that I want to work up in various calibers. Does it make any sense to test these loads at 25, or even 50yds? Or would it just be a waste of my time and resources, causing me to have to start all over again when I am finally able to stretch the distance out?

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Erik
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Re: Testing loads at short ranges.

Post by Erik » Thu May 01, 2014 6:24 am

Chris knows this a lot better than I do, as do others on this board, but I thought I'd share some of my experience.

We have a competition event here where we shoot magnum revolvers out to 200 yards. I was once pressed for time in doing the proper tests at all ranges, so I did a quick zero at 25m, used a chronograph to get the velocity of the rounds and did the rest of the calculations with a ballistics program. So when I got to the competition I adjusted the sights to what the ballistics table said I should. It was good enough to get all hits, and I only lost by not having good enough scores on the point targets.

When we first zeroed our ARs, we didn't have access to the real rifle range, only a 100m range. So we zeroed at 50m (which should theoretical be the same as a 200m zero) and used the ballistics program for the rest, after confirming that the trajectory was what the table said it would be at 100m. Once we got access to a 300m range we only had to confirm the result. I didn't have to adjust anything for the 200m zero, my friend only adjusted a few clicks.

So while I would never try to claim that 25-50m is a good alternative to sight in for longer ranges, in my very limited experience it's been good enough to get me on target and pretty decent hits up to 300m, enough to hit a competition target or a plate. I'd imagine the same thing goes for group sizes, you'll be able to get a rough estimate at short ranges and pick out the really bad and the promising loads, but you'd still need the longer ranges for more accurate results.
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Jered
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Re: Testing loads at short ranges.

Post by Jered » Thu May 01, 2014 7:16 am

Erik wrote: When we first zeroed our ARs, we didn't have access to the real rifle range, only a 100m range. So we zeroed at 50m (which should theoretical be the same as a 200m zero) and used the ballistics program for the rest, after confirming that the trajectory was what the table said it would be at 100m. Once we got access to a 300m range we only had to confirm the result. I didn't have to adjust anything for the 200m zero, my friend only adjusted a few clicks.
Shouldn't that be 25 meters?

At least that's the distance we used in the Army, if memory serves.
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HTRN
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Re: Testing loads at short ranges.

Post by HTRN » Thu May 01, 2014 8:16 am

CByrneIV wrote:25 yards is too short for a full power centerfire, as the deviation hasn't had chance to spread things out enough to rise above the baseline plus noise.
20-25 yards is a good short distance to do initial sight in, because the bullets trajectory more or less match at 200 yards for most centerfire rifles.
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Erik
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Re: Testing loads at short ranges.

Post by Erik » Thu May 01, 2014 12:34 pm

Jered wrote:
Erik wrote: When we first zeroed our ARs, we didn't have access to the real rifle range, only a 100m range. So we zeroed at 50m (which should theoretical be the same as a 200m zero) and used the ballistics program for the rest, after confirming that the trajectory was what the table said it would be at 100m. Once we got access to a 300m range we only had to confirm the result. I didn't have to adjust anything for the 200m zero, my friend only adjusted a few clicks.
Shouldn't that be 25 meters?

At least that's the distance we used in the Army, if memory serves.
Not with a scope. A scope is higher above the barrel than irons, so if you want a 200 yard zero it will also be POA=POI at 50m. Give or take depending on ammo and scope, but with most ammo and the scope 7cm above the centerline, it's close enough that my 50m zeroing got me a confirmed zero at 200m, and hits 10inches low at 300m as the table predicted.
As I said, I wouldnt rely on it without confirmation, but it was good enough for us to hit a target at 300m with very little adjusting.

A fun story. After we confirmed the 200m zero we moved to 300m. I told my friend that the ballistics table said we would now be 10inches low. So my friend aims at the top of the target, and fires 6 shots, which ends up in a less than 3inch group 10 inches down from the top. A sub-MOA group with the cheapest ammo we could find, and using a 1-4 scope...
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morsetaper
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Re: Testing loads at short ranges.

Post by morsetaper » Thu May 01, 2014 4:59 pm

That's all good information, and I appreciate the time given to post responses. But I don't think it quite answers my question. What I'm wondering is, if I'm developing a load, is it reasonable to extrapolate that the charge that gives the smallest group at 50, or even 25 yards, is the one that will produce the smallest group at greater distances? I should have been a little clearer :oops: .

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randy
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Re: Testing loads at short ranges.

Post by randy » Thu May 01, 2014 5:04 pm

Jered wrote:
Erik wrote: When we first zeroed our ARs, we didn't have access to the real rifle range, only a 100m range. So we zeroed at 50m (which should theoretical be the same as a 200m zero) and used the ballistics program for the rest, after confirming that the trajectory was what the table said it would be at 100m. Once we got access to a 300m range we only had to confirm the result. I didn't have to adjust anything for the 200m zero, my friend only adjusted a few clicks.
Shouldn't that be 25 meters?

At least that's the distance we used in the Army, if memory serves.
During the 80's using the then standard 55gr ammo, multiple military manuals and targets were set up for a 25 meter Battlefield Zero. That round out of the M-16 would have the same POI at 25 and 250 meters (in elevation, not accounting for windage), with the rise and drop at ranges between those two ranges would impact within an area the size of a human torso when using a center of mass aimpoint. I have copies of the targets used at that time intended to be used at 25m with reduced sized human silhouettes.

Whether this is still valid, considering the mass issuance of the shorter barrel M-4 and heavier bullets, I don't know, but I use this process to do initial zero on my ARs and any issues are on my end, not the rifle's.
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Erik
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Re: Testing loads at short ranges.

Post by Erik » Thu May 01, 2014 6:49 pm

randy wrote:During the 80's using the then standard 55gr ammo, multiple military manuals and targets were set up for a 25 meter Battlefield Zero. That round out of the M-16 would have the same POI at 25 and 250 meters (in elevation, not accounting for windage), with the rise and drop at ranges between those two ranges would impact within an area the size of a human torso when using a center of mass aimpoint. I have copies of the targets used at that time intended to be used at 25m with reduced sized human silhouettes.

Whether this is still valid, considering the mass issuance of the shorter barrel M-4 and heavier bullets, I don't know, but I use this process to do initial zero on my ARs and any issues are on my end, not the rifle's.
I checked this in my ballistics table, and if I assume iron sights that are 2inches above the centerline of the barrel, a 25m zero would have the POI within 4 inches from POA up to 300m. So it seems very plausible.

My scoped rifle with a 50/200m zero is within 2 inches from 15metres out to 220m. So in competition conditions, we can pretty much assume POI=POA up to 220 metres or so. Given there's no wind of course.
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Vonz90
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Re: Testing loads at short ranges.

Post by Vonz90 » Thu Jun 26, 2014 1:47 pm

morsetaper wrote:That's all good information, and I appreciate the time given to post responses. But I don't think it quite answers my question. What I'm wondering is, if I'm developing a load, is it reasonable to extrapolate that the charge that gives the smallest group at 50, or even 25 yards, is the one that will produce the smallest group at greater distances? I should have been a little clearer :oops: .
Here is a method which is different and I think better way to do what you are asking about. When I am working up a load for a new powder/bullet combination I typically do a small DOE. I usually do it at 50 yards, because you get better differentiation at 50, but there is no inherent reason it cannot be done at 25, the results will just be less clear and it might take more rounds to verify the results.

1. Do four loads with the new powder/bullet. I typically keep the OAL the same for all of them as that eliminates a variable. For one bullet size, they should be the smallest load you would consider and the maximum you would consider and two evenly spaced loads in between. I typically do 10 per load, although maybe only 6 if is a very initial look at it.
2. Sight in your rifle at the range you will be shooting (with a known load, could be factory ammo for instance) to make sure it is centered and to give you a base line group.
3. On four separate targets, STARTING WITH THE LIGHTEST LOAD AND MOVING UP FROM THERE, shoot all of your rounds. Do not adjust the point of aim at any point. Check the brass of each shot to verify there are no signs of over pressure before moving to the higher load. Note on the targets of each if there are any external issues (action does not cycle on autos, excessive flash, kicks like a mule, whatever).
4. Measure group size for each load, eliminate any known flyers (if you flinched or whatever) as part of that process. {If you want to do a bit more work, measure the distance of each round from the point of aim, calculate the average distance from POA and standard deviation of the data set (any spreadsheet will do this for you easily) the average distance + 3xSTDEV will give you the radius of the group size for 99% of a population at that load.}
5. Graph the data with the load size on the x axis and the y should be either group size or maximum radius (average distance + 3xSTDEV). Mark off any sections of the graph which you might need to eliminate due to external issues (maybe the bottom loads if does not cycle, or top loads if you see overpressure, etc.)
6. Pick the load that gives you the best accuracy in the otherwise acceptable round. Sometimes that is easy as it shows a clear trough, other times it is relatively flat through a section and you can reasonable pick anything in that range.

You need to follow that up with either another DOE centered around the load the graph indicates is the most accurate but with smaller increments and using more rounds (typically I do 20 of each one on either size interpolating to the loads which are at either side of the range you are looking at). If the data points very firmly at a given load (like if the maximum load is also the most accurate, and you are developing it for hunting) then it might be reasonable to just try that single load. It depends on what your goal is.

I like to do my second work up at a longer range than the first (typically 100 yards if I did the first at 50). If you cannot do that, I would at least try it at some point to make sure your results correlate.

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