quote:

Originally posted by sigfreund:
It doesn’t demonstrate much except for the difficulty some of us have in maintaining a consistent tight group for 10 rounds. The “flyer” at the bottom was the last shot fired.

You've hit on an important concept, and one that I've unfortunately demonstrated way too many times when I've shot groups or dot drills. We often get all excited when we see tiny groups through our scopes. We're shooting well that day. Just one more round, hold my beer, watch this, I'm putting it right in the center. Ruh-roh.

Instructors from Grayguns, Rifles Only, and Snipershide have all told me the same thing. We sometimes go brain dead on trying to force another great shot, and then forget the fundamentals that worked so well for the prior "X" number of rounds.

quote:

Originally posted by fritz:
... forget the fundamentals that worked so well for the prior "X" number of rounds.

Without a doubt, and I will try to keep reminding myself of the fact.

A sort-of 10 shot group. What I found interesting (once again) is that each two shot “group” after the first one was fired with the same point of aim at the bottom of the inner circle, but even though each pair was very small (the largest was 0.446" center to center), the points of impact were different from target to target.





Rifle was a JP Precision JP-15, ammunition Berger 77 grain OTM Tactical, fired from the prone at 100 yards. Because prone is so uncomfortable for me these days causing me to raise my head off the stock and I had to reposition my support hand after every pair, that’s no doubt the reason for the wandering groups.

(The .30 hole at the upper left was a friend’s confusion about which target was his.)

Something I learned today, which is relevant here: Apparently the accuracy standard for the HK PSG1 was fifty rounds inside 1MOA at 300M. Wow.

I do not know at what rate of fire this was achieved. A bore cleaning regimen being included (or not) would presumably have an impact too. Surely it was at some sort of steady rate of fire, or it wouldn't be meaningful. Seems, to me, that if a gun can put ten round inside 1MOA at 300M, it'll put forty more in there too, so long as heat and fouling doesn't become a factor.

quote:

Originally posted by KSGM:
Wow.

Wow! Indeed.
I remember reading long ago about the 1 MOA at 300 meters standard, but had no idea that it was for 50(!) rounds. And I can only wonder what factory-loaded ammunition at the time was capable of delivering that result as well.

I first became intrigued by true foreign-made precision sniper rifles when I was in Germany in the 1980s, and the PSG1 attracted my attention early on. Although I brought back an SSG 69 (and it’s one of very few guns I wish I still had), I could only cringe when I learned the price of a PSG1. It’s probably just as well that I couldn’t begin to afford it, but ….

I will say that, though I have seen it mentioned a few different places, I have not seen the 50rd 1MOA standard stated in any capacity that seems truly "official". I intend to keep looking.

quote:

Originally posted by KSGM:
Something I learned today, which is relevant here: Apparently the accuracy standard for the HK PSG1 was fifty rounds inside 1MOA at 300M. Wow.

I do not know at what rate of fire this was achieved. A bore cleaning regimen being included (or not) would presumably have an impact too. Surely it was at some sort of steady rate of fire, or it wouldn't be meaningful. Seems, to me, that if a gun can put ten round inside 1MOA at 300M, it'll put forty more in there too, so long as heat and fouling doesn't become a factor.

Amazing accuracy! It's interesting how the standards for shooting are determined and achieved. The consistent rate of firing and the maintenance of the bore cleanliness is sure to have a significant role in achieving this tight association. It conveys a lot about the quality of these firearms.

I recall discussions in another site on the H&K PSG-1. And no, I haven't shot or handled one.

It is a very accurate rifle, especially for a semi-auto that's 50+ years old. Understand that it's a German rifle, and especially back then, MOA metrics likely meant nothing to H&K. It was designed to put "a group" of rounds in an 80mm circle at 300m. Meaning, accuracy of just under .3 mils. Now .3 mils just happens to be really close to 1 MOA, the North American pseudo-standard of accuracy. The guys I've met who truly deal with targets ranged in meters have mil optics, refer to angles in mils, refer to accuracy in mils.

The 50-round accuracy requirement appears to be an internet myth, retold enough times that some now think it's gospel. 50 round accuracy is an admirable, but ludicrous, test. I can't believe any manufacturer -- large or small -- would even consider it. Just try to find a human to shoot 50 rounds with repeatable results. The only place I'm aware of such tests is at Lapua for match-grade 22lr ammo testing. Lapua clamps your action (you keep the stock) into a vise of sorts to perform the testing across various lots. As I've demonstrated in this and other threads, wind affects accuracy. If H&K (or anyone else) wants really good accuracy at 300 meters/yards/whatever, an enclosed range is necessary. Could be a tunnel, could be a building, but the air needs to be stagnant. JBM ballistics indicates that for 2800 fps MV with SMK 168 at sea level, the lateral drift is 3/4" for every mph of wind from 3 or 9 o'clock. At 300 yards, a 4 mph crosswind produces 1 MOA of lateral drift. Wind hoses real-world accuracy -- just ask any F-Class competitor.

The few real-world accuracy targets I've seen posted indicate that the PSG-1 can shoot five-round 1/2 MOA groups at 100 yards. Which means that five-round 1 MOA groups at 300 yards should be expected with the right rifle-ammo-optics-shooter system. There definitely are AR10-type rifles today that can shoot this well. GA Precision's GAP-10 is near the top of the list. Plus KAC SR25, Wilson Combat, JP Rifles, LaRue OBR, and some others. My Black Rain based AR10s exhibit this kind of accuracy. As for the AR15, I have a handful of uppers/rifles that will do this. In the middle of page 4 on this thread, my Rock River based AR15 did 1-1/2" of vertical variation at 335 yards (about 1/2 MOA vertical) -- with horizontal wind drift of 9.5" to 16.5". This RR held verticals to around 1 MOA at both 375 and 470 yards, again with substantial lateral wind drift, and after a total of 40 rounds on 3 different targets.

Posted for KSGM.

Nosler 168gr HPBT “Custom Competition”

Thank you, sigfreund.

I'll provide a bit more detail. I wanted to isolate the first shot, as I have been frustrated with first shot deviation in the past. I sent the first round at the left target, and the remaining nine at the right target. I then inserted that first round into the overall group, using a marker. I was pleased with the lack of deviation.

I actually came off the gun and rolled back onto my haunches twice, inside the ten-shot string. This scope is a not very forgiving, when it's cranked up to 25x, and my eyes were straining pretty good.

I am happy to have a 10rd group for record at 300M. I have a record of 10rd sub-MOA (barely) performance at 100M, and it's good to know the system can maintain that out to a further range. Though this 300M group is technically just over 1MOA, I can feel good about stating that my system is capable of 1MOA performance out to 300M.

The LGS has a Ruger AR trigger at a very good price. It'd be a decent upgrade, and might help me bring the 300M group beneath the 1MOA threshold. I know there's nicer stuff out there, but the budget only allows so much at the moment, and I'd like to maintain more of "combat trigger" anyway.

I still intend to do the internet-approved 6x5 performance evaluation, but it was honestly too intimidating for me today.

That one round at 12 o'clock could have been a goof; or it could have been that 10th round that tells the whole story. If I could reel him in, the max spread would be 3.25", which would be sweet. Maybe I'll get that trigger and try again.

Someone like fritz has the depth and breadth of experience to say for sure, but I think this gun does pretty darn good for a chrome lined barrel not advertised as anything special. I guess you could say the 901 is more of an exceptionally accurate battle rifle, than a SPR. It serves the DMR/SPR role in my small arsenal though.

Thanks again, sigfreund, for the image posting assistance.

This message has been edited. Last edited by: KSGM,

You're welcome, and the results are definitely good. We don't know for certain unless we actually fire the shots.

The Rock River's Doublestar barrel is showing wear, but is trying to hang in there. The throat wants to develop a carbon ring, but regular cleaning is keeping it from occurring. MV with FGMM has dropped from the normal 2800 fps to 2756, which is a typical indication the throat has a fair amount of cracking. Elevation dope for longer distances has changed a bit.

It's now our weed killing season in the pastures. This means my shooting time is limited to when storms are coming through, and there's a high risk that rain will wash off the herbicides -- making the spraying futile. And this means wonky winds. Upper atmosphere wind patterns were from my 6 o'clock (West), but while shooting the ground winds were mainly from my 1-2 o'clock. First up was confirming muzzle velocity with my Magnospeed, and confirming that the optics were still zeroed at 100 yards. I had JBM dope tables for 2800 fps, so I was guessing a bit with the lower MV. I shot prone, at a fairly good clip. I wasn't really counting rounds shot or fully loading mags -- just shooting between storm clouds, trying to avoid rain and lightning.

322 yards -- 3.75 inches vertical, 12 rounds.
I thought JBM dope was 3.2MOA, which I dialed. Dipshit -- it was actually 4.2MOA, but in reality 4.5 for the lower MV. I tried to keep rounds centered on the target, generally holding the 3 o'clock point. Effective bullet drift of 5-10 mph, but higher actual wind speeds due to the 1-2 o'clock prevailing pattern. About 1.1 MOA vertical dispersion. Sorta OK. A few high impacts, which is often my fault.

On to 414 yards. JBM said 7MOA elevation, I dialed 8. Corrected for MV, I should have been in the 7.2 to 7.5 MOA ballpark. I held more-or-less the 3 o'clock point again and tried to center the shots. Not so much -- effective crosswinds of 3-12 mph, based on actual drift. Actual winds were higher. Mirage was beginning to get unpleasant with this target.

6.25 inches of vertical dispersion, or just under 1.5 MOA. Not my finest shooting. I feel this was the start of a barrel becoming tired, due to a few low impacts.

On to 587 yards. FGMM 69 new dope is 1 MOA more elevation than old figures. Actual POI was within 1/4 MOA of new dope. I held 2 MOA below the target "shoulder", which was just below the orange dot. Winds were pretty steady. I figured the effective cross winds were 6-7 mph. Actual wind speeds were 10mph or a touch more. I held windage of 2 MOA right of the right edge of plate. 9 rounds, 6 inches of vertical & only 2.75 inches of horizontal dispersion, right at 1 MOA.

I thought results were pretty decent, especially given that mirage was getting nasty. Lots of dust in the air -- down drafts from nearby rainstorms, and craploads of pollen from just about every pine tree in the area. This older NF NSX 3.5-15x scope is no longer state of the art.

On to 708 yards. Mirage just sucks. Not the best scope for these conditions. Wind is not playing nicely -- effectively 8-14 mph crosswind, based on my estimated drifts. Wind in my face (from 1-2 o'clock) felt more like 15-20 mph. I missed with the first 5 shots trying to figure out elevation and windage, then put 11 in a row on the plate. But I couldn't always see where I hit on the plate -- I guessing on some impacts with sound of the impact and movement direction of the plate. All these hits were with holding 4-6 MOA off the right edge of the plate. I needed the whole width of the 100% IPSC, due to wind variation.

A little under 1 MOA vertical dispersion. Definitely both low and high groupings. Some could be wind differences from terrain. Maybe spin effect -- RH twist with wind from the right. Maybe variation in technique. And maybe some variability from the aging barrel. Actual elevation dope was 1.25MOA more than with the old MV of 2800 fps.

JBM lists the time of flight at just over 1 second. After being in tune to spotting my own impacts at 300-ish yards, it seemed like forever before the bullets landed. A couple of times I'm thinking "Was that a squib? When's the bullet going to impact?"

Not an HK PSG-1, but an old HK SR9. The OEM trigger is ... challenging.

B-Square mount, Burris 1x6 duplex, benched, 100 yards (intended 200 yard range not available).
Federal Premium Gold Medal Sierra MatchKing 168 gr. Bright day, 91°F, quite windy/gusty changing directions.

Group is 2 1/4" x 3/4".

I paid no attention to lighting or windchanges while firing. If this had been standard .22RF from a match rifle, I would attribute the diagonal stringing to wind changes, but 168GR .308 at 100 yards?

No, probably chasing the group with the crosshairs and poor trigger control.
___________

Edited to add:

Thanks for your observations, fritz!

POA: I was aiming at the center of the bull, attempting to see it divided into equal quarters by the duplex crosshair at 6X.

I think: inconsistent rear & front bags and stock in shoulder placement. Will do your suggestion of dry fire with the same setup to see how it affects the sight picture on target. Would be interesting to borrow a trigger pull scale.
___


Quite a few more points to address after reading this article:

https://bulletin.accurateshoot...rom-speedy-gonzalez/

This message has been edited. Last edited by: RichardC,

KSGM -- that's good shooting with an AR10 in 308.

Richard C -- Hard to say exactly what's going on with that group. Wind effects are primarily horizontal at short distances -- the vertical dispersion really don't into play until hundreds of yards down range. Lateral drift for that load with wind from 3 or 9 o'clock is likely around 3/4" for every 10 mph of wind. A 30 mph crosswind would produce about 2.25" of lateral drift.

Vertical dispersion is commonly caused by breathing issues (breaking the shots in different parts of the respiratory cycle), inconsistent cheek weld, or inconsistent rear bag (or front rest) use.

Lateral dispersion is often caused by inconsistent trigger pulls. Not pulling straight back. Slapping the trigger. Placing different parts of the finger on the trigger. A classic is called the "Captain Hook" -- placing the finger joint on the trigger, instead of the pad. Also, consider the common issues of the "Glock trigger", where some shooters regularly place shots low and left with a Glock. But with a bad trigger, all bets are off. Dry firing is key here. If you can break the dry-fired shot without moving the sights off POA -- and I mean absolutely no movement off POA -- then the bullet POI should match POA. With a good trigger break while dry firing, if a camera were placed inside the optic, an observer would never know a shot was dry fired.

Inconsistently placing one's eye in the center of the scope will do some wonky things with accuracy. If the eye isn't centered in the scope's eyebox, there will almost certainly be some shadowing or tunneling. This will be even worse if parallax is set incorrectly. Shots could go in any direction.

Ammo/barrel inconsistency usually shows up in POI variation in all directions. With enough rounds -- sometimes with 5, definitely with 10 -- ammo/barrel variations will almost always produce more-or-less circular groups.

Using a target with a better defined POA might help. Assuming you aimed at the 12 o'clock part of the black 7 ring, you should have been able to control vertical POA variation fairly well. But if you don't frequently use the edge of round targets for aim points (as is often done in PRS/steel matches), then your horizontal aiming consistency could have been compromised.

Thanks for that discussion, fritz.

I was aware of some of the factors you described, but not all. In addition to my own shooting, I’ve been asked to help another shooter develop some proficiency with a precision rifle and you’ve given me some things to watch for.

Other points to consider....

We shoot rifles better when our bodies are properly aligned with the direction of the shot. From Rifles Only training -- align your rifle to the target, then align your body to the rifle.

Understand that shooting with a sling is different. If the gun is pointed to the target at 12 o'clock, our bodies will generally be pointed somewhere around 1 or 2 o'clock. But non-sling shooting is different, maybe with the exception of the standing positions used by biathlon competitors. Whether prone, bench, or barrier, our spine should be in line with the rifle. Our shoulders & hips should be square to the target. When the rifle recoils, the recoil forces are distributed along an axis that is in line with the shot.

Now some will say that recoil isn't a big deal. They might say the 308 has mild recoil, and it is easily controlled. Well....these are folks who haven't had their asses handed to them in PRS/steel/precision matches by shooters with comparable abilities using a truly mild-recoiling cartridge such as 6BR or 6 Dasher.

RichardC -- I don't know if you shoot from a bench, but it you do, try squaring your shoulders to the target. Most of the right-handed bench shooters I've seen at public ranges are squared to 2 o'clock, when their rifle is pointed at the 12 o'clock target.

****
Here's another point from Rifles Only training.
Think of pushing one pencil with another pencil on a smooth table. And you use the end of one pencil to push the end of the other. If the 2 pencils aren't aligned straight with each other, the pencil being pushed will twist sideways instead of going forward.

Next up...different ammo, Hornady 75 BTHP Black. I find it interesting that most of my barrels shoot more accurately with the Hornady's "Black" load than the "Match" load. Same bullet, essentially the same MV. "Match" tends to be more expensive, and kinda-sorta implies better match accuracy.

This barrel's regular MV with H75 black is 2780 fps. Magnetospeed now has it at 2727 fps, so this load has slowed down, too. I shot only one target, a 12" plate at 322 yards. 13 rounds, 2.5 inches vertical dispersion, around 3/4 MOA vertical variation. This barrel likes H75 black. This barrel is getting older, but it still hasn't given up the ghost.



I didn't calculate wind speeds based on drift, and I wasn't using my Kestrel. However, for this group the winds started out at my 2 o'clock, then finished at my 11 o'clock. This is a classic example of fishtailing headwinds, which sometimes produces head-scratcher days in steel matches. And yeah, I know I need to adjust dope tables for the decreased MV.

For my first shot, I held the 3 o'clock point, and the round landed center -- yeehaw. The next shots crept towards the right side of the plate, as the wind shifted to 1 o'clock. I then held center of plate, and a few rounds landed just left of center.

A few more rounds, and they started impacting the right side. So I switched to holding the 9 o'clock point -- and rounds landed just left of center. Meaning the wind was now coming from my 11 o'clock. The last round impacted just right of center, meaning the wind picked up speed, or shifted to 10 o'clock for that shot.

This shows a lot of wind effect, for a pretty large target, at a pretty moderate distance.