View Full Version : how to analyze groups?

dust feeder
06-16-2012, 4:48 PM
Begining my venture into percsion shooting and hunting. Just bought a 24" barrel savage model 10 .308 and tried to shoot for gorups for the first time ever last week. Mostly to find a good lower-end training ammo. Shot 8 different brands/grain: PPU 145, 165, 180, Federal 180 vital shok, federal fusion 180, Bishop Ranch 147, S&B 149, Federal 7.62 surpus XM80C.

All shootign was at 100 yards. It was a bit windy, somewhat on-and-off gusty and I really didn't pay too much attention to that.

Now Im trying to analyze the groups. Some rounds seemed to out perform others, but I'm also very new to this and am sure I played a part. Groups were 1.1" (best) up to 4-5".

The 4-5" gorups would all have a few shots within 1" then on or two 3-4" off. I'm assuming most of those were my fault b/c most ammo, (even the cheaper Fed) wouldn't have that kind of discrepancy. Is this a good assumption?

Also, some group's were strung out vertically and others horizontally. Other than my error, can I assume that most of the vertical stringing had to do with ammo charge consistancy if it was within about 1"?

How much of an effect would roughly a 10 mph wind have horizontally? maybe 1" drift? Ammo consistancy shouldn't play a part if horizontal stringing, right?

EDIT; how do I include th epics in the post so you guys don't need to click on them to open them?

I've attached pics of 4 groups for reference. please look at them and see if you can give me any advise as to what might be going on. Obviously, I know I'm the biggest factor but taking me out of the equation, I'm just trying to learn how to analyze what me or my rounds are doing.

You'll see, pic 5 is a almost perfict horizontal line. Does that mean the rounds all probably have a uniform charge and either the wind or I was pulling them right or left?

Versus pic 8 which has 2 shots close and one 2.5" low. Could that be one orund that has a lower charge?

Pic's 4 & 7 seem to just be equally off vertically and horizontally. I'm a ssuming htats just a standard variance each way.

Btw - the cheapest ammo I was shooting was blue box Prvi 145 grain loads (not the white box mill surp loads) at ~$12-13 a box of 20, and those seemd to be the most accurate. Fed XM80C wasn't far behind.

Tired not to ramable much but expalin well. Thanks much guys. I learned alot here when I was just getting into black rifles. Looking foreward to learnign a wehole lot more about his stuff!

06-17-2012, 11:44 AM
Hey, I can't help with your questions on vertical and horizontal dispersion, but I suggest shooting 5+ shot groups to see what you are really working with.

Also, don't waste your money on the 147gr type ammo anymore. I highly recommend either reloading or purchasing match grade ammo (FGMM 168gr or 175gr, perhaps some Hornady 168 and 178 AMAX loads).

Typically Savages are very accurate, and to be honest, your groups are really not super great. This is likely the combination if it being your first time shooting for groups and the ammo that you chose.

Keep practicing and you will develop your skills and print tiny groups, but you MUST get good ammo that your rifle likes.

Also, what scope do you have? Are you shooting with a front and rear rest or a bipod?

06-17-2012, 11:54 AM
Yeah dont waste your time with cheap ammo.


06-17-2012, 12:07 PM
JPach nailed it -- groups don't look good but don't tell anything because the entire lot was cheap ammo.

If not handloading, first buy & test match ammo until you know you have a shooter-rifle-ammo combo that will consistently shoot well. When testing cheap ammo afterwards, posting two control groups (e.g., 1 at beginning, 1 at middle of session) with match ammo for the day will ensure you know it's not you causing the flyers. From here is where you can select what cheap ammo works best in your gun for practicing.

Re: cheap ammo, it flies everywhere because it's cheap -- inconsistent brass thickness, primer pockets, flash holes, primers, charge weight, bullet shape, bullet weight, bullet aerodynamics, etc. And inconsistent charges will cause unpredictable results due to barrel harmonics -- it might be vertical, horizontal or both. If you look up slow motion video or a rifle shot, you will see the barrel whips & torques like a bridge in an earthquake.

Other plug about cheap ammo -- unless shooting paper at 100-200 yards is all you envision doing, you won't enjoy the first time you get out further and realize you can't hit anything unless you're shooting 20" gongs or something huge. It's nice to know what match ammo works great in your gun for this 2nd reason.

06-17-2012, 12:22 PM
I've read and found this to be true, at least for me, 1st one is pretty obvious.

1. If stringing horizontally, your trigger finger is jerking to one side.
2. If stringing vertically, you are holding you breath. Breathing wise, I let all the air out right before a shot.

06-17-2012, 12:25 PM
Problemchild brings up a good perspective contrast.

If plinking for fun, a sub-MOA 100 yard group is generally considered good (<= 1.0472" center to center). However, if you're getting into it with long range/precision in mind, MOA is not good. Then there's benchrest shooters who say anything above 0.1" is bad.

Starting for sub-MOA groups at 100 and 200 is a great starting point until you figure out where you're heading with the sport.

06-17-2012, 2:19 PM
This might be long but I thought it was a good read.


06-17-2012, 3:20 PM
Yeah dont waste your time with cheap ammo.

Yes the OP is clearly having similar results, thank you. We should use what works best in our individual firearms, no matter if it is cheap or expensive.

dust feeder
06-17-2012, 3:37 PM
Thanks all. First I'll make clear that I know I am the main contributor to the inaccuracy and definitely wadnt trying to brag about the groupings. I have a Harris bi-pod in the front and my fist on a sandbag under the back. Basic leupold 3x9 on top.

Next step - ill buy some good match grade ammo and really see what I'm capable of. Any suggestions other than fed Gold metal match? After seeing what it's capable of and until I get done reloading equip I would like to find a cheaper round to practice with and get as much trigger time as possible with. Even if I know the round is 2moa accurate I can know I'm improving my personal skills as long as I'm keeping my groups under 2 moa, right? Since I'm hitting some in the 4's I clearly have some room to improve before ammo is the main limitation.

Joachim - why do you say skip the 147 grain loads? I know they are more succeptable to wind but any other reasons? Less inherently accurate? I ask bc ironically the less than match grade ammo I've used this far the lighter 145 grain PPU, federal 7.62 NATO, S&B 149, and bishop ranch 147 have concistantly been more accurate than my 180 grain federal fusion, fed power shok, and PPU. Maybe just a coincidence since none were extremely accurate

dust feeder
06-17-2012, 3:41 PM
Sorry. That last comment was directed at Jpach and i cant edit the actual post on my phone. Damn iPhone autocorrect!

06-17-2012, 4:08 PM
Honestly, I think you have done well.... For Social Work, if you will, or hunting for food.... You got the job done! Good job...

Now the fun is honing your skill... Like anything else experience will be your teacher and you seem open to 'constructive criticism'... So enjoy!!

06-17-2012, 8:53 PM
Sorry. That last comment was directed at Jpach and i cant edit the actual post on my phone. Damn iPhone autocorrect!

Disregard the 147ish comment then lol. I assumed the 147s were responsible for the ****ty groupings because typically those bullets are used more for plinking rather than for precision. If they are the more precise out of the bunch, using them for cheap fun will certainly not hurt.

The message that I was trying to get across was just to use consistently precise ammo.

Good to hear that you will be reloading. Everyone pushes the SMKs but I have had better results with the 168 and 178 AMAXs, you should try them and see how you like them.