How would you interpret these down range results?

[Nature Boy]

Shooting one of my most accurate loads yesterday netted results that I though would be worth a discussion.

My rifle is an FN SPR .308 with a Leupold Mark 4

Range is 100 yards. I'm shooting 168g Berger VLDs, new Lapua brass, 44g varget, federal 210M primers. All rounds measured for run out with less than .001"

I've been playing with group size, trying both 5 shot and 10 shot groups to see which tells me the most about me, my rifle and my loading process. Here's the results:

After warming up, I fired this 10 shot group. Shot sequence noted:

I then shot 2 groups of 5 shots thin the sequence noted

I honestly have no idea how to interpret this.

Random observations:

The aggregate of the second set of 5 shots is probably pretty close to the 10 shot group.

What the heck happened tho the last 5 shot string.

I try to be as consistent as I can in my shooting technique and my loading process but I really don't know what to take away from this that will help me improve other than load up some more and try it again.

Curious to hear what you guys think

 

[jak67429]

how long between shots? How much cooldown between groups?

 

[macgrumpy]

Something is moving.

Is your bipod on something soft? When shooting from a bipod the feet should be on something soft, I put an old piece of carpet under mine.
Is there clearance between the scope and the barrel? How much room do you have between the objective bell and the barrel?
Is there clearance between the scope cover (objective lens) and the barrel?
Are the action screws tight? The screws that connect the stock to the receiver.
Does the stock properly clear the barrel?
Does the receiver fit the stock tight?
Are you placing your trigger finger the same way every time?
Are you placing your trigger finger so the you pull straight to the rear when you squeeze off the shot?
Have you properly adjusted for parallax?
Are you using the same cheek-weld for each shot?

 

[Hastings]

I typically get good accuracy but poor grouping when I use a bipod. Sounds contradictory, I know, but it's what I experience. If I'm taking shots at a woodchuck or coyote the first shot will likely be the only shot needed. If I try for really tight groups on paper, the result is less exemplary. Take the bipod off and try the same strings from a sandbag. Quickest way to narrow the options.

I've owned 308's that required total cool-down between shots if I wanted same point of impact. It was not always the result of a thin barrel or poor bedding.

By the way, your first photo looks to me like shots 3, 6, and 8 were the product of a slightly different point of aim, (operator error) or a different powder load from the other seven shots. I get that sort of consistent elevation deviation with just a fraction of a change in total powder grain-weight. What powder are you using, and are you loading the powder with a powder drop tool or weighing each charge with a scale?

The second photo showing two separate groups of 5 looks to me like shots 6-10 show a more random variation more typical of barrel heating up or bipod bounce.

When I see flyers with consistency in windage I check my trigger control. Consistency in elevation and I check my loading techniques and chronograph for extreme spread. Erratic flyers is usually me, the bedding, or the barrel heating up.

By the way, you are a much better shot than I am.

 

[Llama Bob]

My first thought was to question whether the Berger 168 would stabilize in the 1:12" twist barrel. However, according to Berger's twist rate calculator the stability factor is 1.55 at 59degF temperature and 0ft elevation. So I believe the bullets should stabilize.

The next thought is to question whether you have an accuracy load for that rifle. Have you done a charge weight ladder to see if things improve? What about a OAL ladder? Of course, since the rifle has proven it CAN shoot a solid 5-shot group, the ladder results might be difficult to interpret - you'd probably want to shoot 10 of every configuration.

What does the rifle do with 168gr FGMM?

If FGMM has problems, then it's down to either shooting mechanics or rifle problems.

I would look at two things for mechanics:
- Natural point of aim. When you get on target, if you close your eyes, relax, and take three breaths where does the rifle end up pointed? If the answer is not "exactly on target" then you've failed to achieve natural point of aim, and the rifle will drift towards the point it goes to when you're relaxed during firing.

- Downforce into the bipod. Despite their current popularity, bipods are well known for producing groups like that. The problem is usually eliminated by putting more force on the bipod legs. This can be achieved by pushing your shoulder into the stock more, or putting downward pressure on the scope with the non-trigger hand. I know it's out of fashion, but I have always gotten better results with a ruck than with a bipod.

As far as the rifle, check the torque on all mount, scope, and action screws. Check that the barrel is free-floated. The FN barrel and rifle SHOULD be OK (they tout 1/2 MOA) but I've never felt that hard chromed carbon steel was a good choice for an accurate barrel so color me a tad bit suspicious.

 

[Nature Boy]

Is your bipod on something soft? When shooting from a bipod the feet should be on something soft, I put an old piece of carpet under mine.

Yes, me too, a piece of carpet

Is there clearance between the scope and the barrel? How much room do you have between the objective bell and the barrel?
Is there clearance between the scope cover (objective lens) and the barrel?

Yes, nothing touching the barrel. Maybe 1/8 of an inch. I'm using low rings

Are the action screws tight? The screws that connect the stock to the receiver.

Yes

Does the stock properly clear the barrel?

Yes, barrel is free floated

Does the receiver fit the stock tight?

Yes, it's fully bedded

Are you placing your trigger finger the same way every time? Are you placing your trigger finger so the you pull straight to the rear when you squeeze off the shot?

I try to do this.

Have you properly adjusted for parallax?

Yes, I always dial out as much as I can

Are you using the same cheek-weld for each shot?

I try to, same position on the stock, same pressure

 

[Nature Boy]

Llama Bob and Hastings,

I think you guys make a good point about the bipod. Next tip I'll shoot off a bag.

I'll also check the scope base to make sure it's secure. I've already verified the rings are good.

This is all good info. Thanks fellas!

 

[farmerboy78]

I think I agree about the bipod issue partially. They don't need to be on something soft, I have that they need to be dug in well and solid to the ground, so you can preload them for recoil control. Which is what I think the problem is. If it's not very stable and preloaded (consistently)it will let the rifle react different

 

[macgrumpy]

Bipods are designed for field use and as such they are normally used on the soft earth but when used on a bench with a hard top you absolutely need a soft surface under the feet or else recoil will bounce the rifle. No amount of "pre-load" will eliminate bounce if the bipod is on a hard surface. I use quotes around that word because I don't feel that pre-load is necessary with high a quality bipod, with my GG&G it's a waste of time, with a new Harris it's not important either but as they wear it'll become more important. Pre-load is more important for creating a consistent setup than it is for controlling recoil.

 

[wally]

I don't feel that pre-load is necessary with high a quality bipod, with my GG&G it's a waste of time

I'm not sure pre-load makes any difference beyond possible recoil control if you want/need fast followup shots. Prone in the dirt (inexpensive Midway shooting mat) with a cheap NcStar $20 bipod we were ringing 10" steel plates at 300 yards with Wolf FMJ 7.62x39 and my new CMMG Mutant with Burris 5X prismatic scope -- by no means a long range rig. The scope BDC worked great, although not quite as designed, center dot zeroed at 100 yards, second dot dead hold at 200, third dot dead hold at 300. After seeing the impacts on the plates I may tweak the windage a bit to move POI a bit to the right, but I was thrilled for first time out. Got to remove some large trees and a lot more more brush to get beyond 300 yards

I was always taught to hold the rifle as loosely as possible -- just tight enough to not get hit by the scope in recoil.

 

[Bart B.]

The way you put the rifle into your shoulder and rest your cheek on the stock can cause all those wild shots to be where they are.

Another common cause is flicking your finger off the trigger the instant the sear breaks and the firing pin starts to fall. That movement can cause fliers to go 1/2 MOA or more away from the center of a few shot group.

Us humans are oft times the biggest variable. Had one on a major USN command rifle team that was flicking his finger off the trigger all the time. He didn't believe me and though there was some other reason he could not keep most of his shots in the 10-ring. So I told him to aim at the 600-yard target in prone, load the Garand then aim without his trigger finger on the trigger. I would watch the muzzle slow down wiggling then still then be calm and steady as I pinched the trigger with my thumb on the back of the trigger guard and index finger on the trigger. We did this exercise for 10 shots. All of them went into the 12" ten ring on the target. He thought it was luck, so we did it again. Same thing happened. Finally, he was a believer and soon was shooting very good scores from all positions.

 

[DRYHUMOR]

One thing. You stated new cases. I'd prep and trim; then weigh. If you have a chronograph, start writing the FPS with a sharpie on them after firing. That will help spot cases that are out of the "norm".

 

[243winxb]

new Lapua brass

Sort prepped brass by 1/10 gr weight.

 

[wally]

... to aim at the 600-yard target in prone ... All of them went into the 12" ten ring on the target ...

Is a 2 MOA 10-ring some kind of standard or do they get smaller at at shorter range and larger at longer range (in terms of MOA)? Would make me feel really good about hitting (~90%) a 3.3 MOA plate at 300 yards with ammo that is widely regarded as 2 MOA "at best", not that I'm not thrilled at the way were hitting first time out which was expected to be little more than function test, sight-in, and some plinking fun.

 

[Sav .250]

Absolute concentration on each and every shot is paramount. Plus, spacing of rounds down range. A cool barrel helps reward the shooter.

Other than that your on your own.......

 

[imashooter]

Just curious. What style feet does your bipod have? does the bipod collapse toward the muzzle end or back toward the shooter? Which Mk IV? Magnification (s)? Thanks. Nice setup btw.

 

[Dr.Rob]

Could be as simple as fatigue, breath control or follow through. "Chasing groups" we often have them open back up. Tightening your grip as you squeeze the trigger will give you those slightly low and left shots. Try moving your thumb to the same side of the stock rather than wrapping around the pistol grip.

 

[z7]

Not being nearly as experienced as some here, i would venture to say that the last group is you. When i say you i don't mean you are a bad shot or anything, clearly you punched almost 10 rds into one hole.

I am getting started with my bolt gun ad tiny things make me throw a shot. I would guess that is the cause of your flyers on thr 10 shot group. The 2nd 5 shot group probably started poorly due to inconsistent something, probably bipod pressure or natural point of aim and fell apart after that. I would say your groups are goos, keep shooting and have fun

 

[Bart B.]

Is a 2 MOA 10-ring some kind of standard or do they get smaller at at shorter range and larger at longer range (in terms of MOA)?

Go to page 14 in:

http://rulebooks.nra.org/documents/pdf/compete/RuleBooks/HPR/hpr-book.pdf

 

[Bart B.]

I interpret those groups to be normal for a pretty accurate load in a good rifle. You need to practice good marksmanship techniques as the outliers indicate toure not holding and firing the rifle consistently. A good instructor will see your weak points and help you overcome them.

i would venture to say that the last group is you.

All the groups are that of the shooter, ammo and rifle. There are no fliers. All shots are the result of the system; ammo, rifle and shooter.

Sort prepped brass by 1/10 gr weight.

If that's really important, then powder has to be weighed to .001 grain and bullets to .01 grain. Take apart all the primers then sort their explosive pellet's weights to nearest .001 grain; put them back together carefully.

Come on, that's rediculous. So is prepped brass, in my opinion for commercial rifles. Neither need be done until your biggest groups are about 1/3rd MOA. Best thing to do for commercial barrels is slug them then mic the slug groove (maximum) diameter to nearest .0001". Get bullets larger in diameter than that.

 

[Llama Bob]

I think taking handloading out of the equation entirely and shooting 168gr FGMM is a good idea. It's not really possible to debug the shooter AND the rifle AND unproven handloads all at once. Time to cut down the number of variables and I suspect that's the load the rifle is throated for anyways.

 

[243winxb]

If that's really important, then powder has to be weighed to .001 grain and bullets to .01 grain.

Come on, that's rediculous. So is prepped brass. Neither need be done until your biggest groups are about 1/3rd MOA.

Well Bart, when you fire for score on the wrong target , in competition, it sure dont matter.

 

[wally]

Go to page 14 in:

http://rulebooks.nra.org/documents/pdf/compete/RuleBooks/HPR/hpr-book.pdf

Thanks, it looks like the 10-ring is pretty much ~2 moa and the X-ring is 1 MOA for High Power and half that for F Class.

I'm figuring out steel plate sizes to order as I layout our longer range shooting location, clearly a 10" plate at 300 yards is too large to really improve my skills or be much of a challenge, but it sure is a lot of fun and a great introduction for shooters trying longer ranges for the first time using the cheapest ammo available.

I'll definitely get some 1 moa plates for 3-500 yards, which will require better ammo than I've been using, But 4 moa plates and cheap 2 moa ammo sure is cost effective long range fun.

 

[Nature Boy]

Another common cause is flicking your finger off the trigger the instant the sear breaks and the firing pin starts to fall. That movement can cause fliers to go 1/2 MOA or more away from the center of a few shot group.

I'm positive I don't do that. I follow through and don't release until I visualize the round hitting the target

 

[Nature Boy]

Just curious. What style feet does your bipod have? does the bipod collapse toward the muzzle end or back toward the shooter? Which Mk IV? Magnification (s)? Thanks. Nice setup btw.

It's an Atlas bipod, rubber feet. The legs will fold either way and lock in at various angles

Scope is a Leupold Mark 4 LR/T 4.5-14x50mm