Load selection questions for longer ranges..

[1stmar]

I have a couple of theoretical questions, theoretical because my range is distanced challenged is I can not practice this myself. For those who shoot long distances (600-1000), do you:
-Initially start load selection/ testing at 100 or 200 yards to minimize outside factors? (Wind, mirage effect..)
If so:
- I would assume that your selection process begins with a max group size (moa) you are willing to accept as you move to longer distances, is that correct? Ie groups that are 1 moa are not going to be 1/2 moa at 600 yards so if your goal is 1/2 moa you would exclude this group.
- have you found that the load you have settled on holds mostly true to form (given outside variables) out to longer distances?

I get the smallest group or seemingly the best load at 100 may not be stable at 600, it's not a question about the smallest group, it's a question about the most consistent group.

 

[Bart B.]

I've never worked up loads for long range accuracy except for one cartridge for which nobody had data for and one bullet that was a new weight and shape. Load recipies given to me by people winning the matches and setting the records have always done well in my rifles using the same cartridges they use. But the loads I developed started with a near maximum charge for the bullet then went right to the long range (600 to 1000 yards) and shot them. Never wasted any time testing at short range (100 yards) except to get a boresight zero on the sights with one or two shots. Then set the sights for the approximate bullet drop at the longer range and shot test groups.

The spread in muzzle velocity alone prevents groups from being the same subtended angle (in MOA) all the way to the longest range you'll shoot them at.

Another issue is how much unbalanced are the bullets when they leave the barrel. More unbalance means more wobbling in flight which means the BC for those more unbalanced is lower than if perfectly balanced. This adds to vertical shot stringing; the longer the range, the more stringing there'll be.

Both of these will easily open up a 100 yard/meter group about 10% to 15% more for each range further by that one all the way to the target. A 1/4 MOA group at 100 can easily be 7/8 MOA at 1000.

The two times I worked up a load was done with 1 grain increments in powder charge weight. I shot 20-shot groups with each so they would be statistically significant. The smallest one was retested 1/2 grain below, above and at its charge weight to verify it was the best, but again with 20-shot groups. One of them would be a bit smaller than the other two and that's the one I used. Same load in several barrels performed equally accurate.

 

[1stmar]

Interesting. I've always read how every rifle is kinda unique to itself. I would have expected a lot more experimenting.

 

[4runnerman]

I shoot out to 1200 yards. All my load development is done at a min of 300 yards. Not sure if that is what you were asking. I always use Newberrys load instructions and they work great. I try to pick very calm day's and go early in the morning to avoid the mirage. I will start with a known good load,work up 10 rounds in .3 grains difference. FYI- never found a accurate load in the higher end of speed. Find the best group,then just mess with the col. I have found a load that shoot's sub moa at 300 will hold good ( for me any how ) as far as I shoot.
As for Mirage-For me I find that shooting a little low seems to be the ticket. I never dial back on power setting. Right now for me doping the wind is my greatest challange.

 

[Jimro]

Most of the "winning recipes" that Bart B. talks about are no secret, at least in 308 and 30-06 circles.

You could say that those loads have been proven Optimal Charge Weight loads in multiple rifles, much like Fed GMM or Black Hills Match ammo.

If you substitute a component however, you may need to adjust the powder charge up or down slightly to compensate for differences in brass, bullet, or primer.

Jimro

 

[Pathfinder45]

Inconsistant MOA

The best shooting recipe at 100 yards may or may not be the best at longer ranges. What works well at 100 yards can really scatter at 300 yards. Oddly, (and counter-intuitively), some load recipes in some rifles will group to a substantially smaller MOA at longer ranges. I once thought that it was not possible; but seeing is believing. The only way to find a load that works well at long range is to shoot at long range. You can't rely on what looks promising at 100 yards to not let you way down at 300 or more yards. But what do I know when I just use a 270 and think that 450 yards is a long ways out there?

 

[hooligan1]

Patfinder, usually a load that has proven to be consistant at 100yds will be consistant at 300. That being said, Im talkin about stuff from .223-.30 cal. Its the choice of bullett that makes the difference out there...

 

[Bart B.]

hooligan1, if a load that has proven to be consistant at 100yds will be consistant at 300, why do group sizes in benchrest matches at 100 through 300 yards get bigger in minutes of angle at each range beyond 100 yards?

Even with the best smallbore rimfire 22 ammo and rifles, the accuracy at 100 yards is about 3 times that at 50 yards when measured in minutes of angle.

 

[4runnerman]

I have maybe 10 loads in 223 and 308 that shoot one hole at 100 yards. Push them to 300 and not a chance. 100 yards is not far enough to judge what a load will do at 300 or farther.

 

[hooligan1]

Bart, 4runnerman, don't misinterprit what i said, Of course groups open up at distance.
Maybe I incorrectly said that a load that is consistant at 100 yds will be consistant at 300, and what I mean is when you get say 3/4 moa consistancy at 100, then at least 3/4 moa should be expected to 300 with most calibers... And I speak only from my experience which is .270, .243, 7mm rem mag, 3006, 25-06, .223.

I didnt mean for a second that samehole groups at 100 mean samehole groups at 300. I forgive you guys this time....

 

[Brian Pfleuger]

I have never been able to maintain the same MOA as distance increases. Roughly speaking, my loads that shoot 1/3-1/2 MOA at 100 will shoot maybe 3/8-5/8 at 200 and by 400 they're at about 3/4. Every error has more time to work on the bullet during each multiple of flight distance.

 

[Bart B.]

hooligan says

what I mean is when you get say 3/4 moa consistancy at 100, then at least 3/4 moa should be expected to 300 with most calibers.

If that suggests a 3/4 MOA group at 100 will be a 3/4 MOA group at 300, I disagree. If it means the 300 yard group will be bigger than 3/4 MOA, then you're on the right track.

From what I've seen of benchrest aggregate records (agg's are meaningful, smallest group records are insignificant), they seem to open up about 1/10th MOA for each 100 yards past the first 100 yards through 300 yards. This applies to the cartridges they shoot at these short ranges. Long range benchrest groups open up about the same amount going from 600 yards to 1000.

 

[4runnerman]

I agree with Bart here. Just because you are always shooting 3/4 MOA at 100 yards does no way mean you wll be shooting 3/4 MOA at 300 yards,sure would be nice if that was reality though. If I am shooting 3/4 MOA at 100 yards,I am back to load development for sure. Now this is going on a target rifle. 3/4 Moa for your run of the mill deer rifle would be ok ( I think).

 

[Jimro]

I would like to point out that groups can get smaller as well, then open up again, then get smaller again, in terms of MOA dispersion.

Sometimes you can point the cause of it to barrel whip, as in the SMLE or M14/M1A rifles. Sometimes you can point the cause of it to bullet flight stability dynamics changing with velocity and stabilization.

Other times you are just left scratching your head going "what the heck?"

I've had a load group just over 1 inch at 100 yards group 1.5 inches at 200 yards. Was it scope parallax throwing me off? Was it bullet instability in the first 80 yards of flight? Don't know.

A sniper I know tested a 7mm Magnum sniping system out to 1600 yards, and noted that there were three accuracy nodes in the load they tested by range. The groups would get larger, then inexplicably get tighter again at 900, 1300, and 1600 yards (if I recall the ranges correctly). I don't have access to his data, but his experience jives with my own (although not to such extreme ranges).

Still, if your groups aren't tight at 100, adding distance won't help in my experience. Although anything I can get under 1 inch at 100 has stayed "sub-MOA" at further distances (not going into the transonic range anyways).

Jimro

 

[cryogenic419]

I start at 100 just to see what the load is doing overall, but don't really pay too much attention to that. I am more concerned with what the ammo does at its intended ranges. My thought is yes 100 yards will give you an idea, but if you base everything you do off of just testing at 100 yards and only 100 yards you might be missing out on some real world factors that will come into play at longer distances. Say a load is super accurate and consistant at 100, but at 200 and a slight breeze its not staying so consistant, and at 300 its all over the place. I guess I'd rather sacrifice a little bit of accuracy at 100 for improved results further out.

I got into service rifle shooting and matches last year and one of the things I did with load development was start out with 52gr SMK loads. Super accurate at 100, and from a rest those things could Xring all day at 100. They seemed to lose a bit of their magic at 200, at 300 I kept asking myself what the hell happened? Bumped up to the 69 SMK and while the 100 yard was not as tightly grouped as the 52's it wasn't that much more of a bigger group, my 200 groups improved greatly as did the 300. I went on to the 77 SMK and again, 100 was not as tight as the 52's, but the 200 and 300 looked amazing.

Obviously if you can't get somewhat decent groups at 100 it's not going to get better further out.

 

[Bart B.]

I've had a load group just over 1 inch at 100 yards group 1.5 inches at 200 yards.
---------
...a 7mm Magnum sniping system out to 1600 yards, ... The groups would get larger, then inexplicably get tighter again at 900, 1300, and 1600 yards...
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...anything I can get under 1 inch at 100 has stayed "sub-MOA" at further distances...

Unless all the bullets producing the longer range groups are the same ones making the shorter range groups, the test isn't valid. A valid test of how a 5- or 10-shot group performs at different ranges is to have sensing elements at each range that the same bullet from each 5- or 10-shot group goes through. Otherwise, you're comparing groups shot with different rounds of ammo.

In other words, you shoot only 10 rounds and they make a group at each down range point and those groups are compared. If you've got sensors every 100 yards all the way to 1000, you've got ten 10-shot groups all made with only 10 shots. This is what Dr. Mann did in the early 1900's shooting lead bullets through paper screens placed every few yards all the way to 100 yards. Each bullet fired in his tests went through 10 sheets of paper.

 

[Jimro]

Bart B.

Would tracking the bullet flight on doppler radar count? That's what the USMC does when evaluating experimental sniper systems. It allows them to note points of bullet instability as velocity drops off.

Which is the reason why the USMC passed on the 408 Cheytac, the bullets had the same flight profile issues with the transonic zone as the 50 caliber bullets already used for long range sniping, so there was no benefit for the USMC to adopt a proprietary sniping round for anti-material purposes.

Jimro

 

[Bart B.]

Doppler radar would work well if it precisely measured bullet position relative to the line of sight at several range increments. Most Doppler radars measure target speed but none's accurate enough to detect a bullet's position within half an inch several hundred yards downrange that I know of.

 

[Jimro]

Well, I do know that the military has access to millimeter wavelength radar, and that the base of a bullet has a larger cross section than the front ogive.

But that is the extent of my knowledge, so whether or not the radar system used could track both location and velocity will remain a mystery until someone who was there can tell me how the bullets flew on the radar screen.

Jimro

 

[reynolds357]

I load develop at 200 yards. A load that is good at 200 may or may not be good at 1000. A load that is trash at 200 will most assuredly be total trash at 1000. Why do I develop at 200? My private range is 200 yards long before it gets to a creek. Anything longer than 200 has to pass over the bad air over the creek.