Measuring groups

[butchlambert]

Need to get this away from another thread. Some of you have been around for a day or two and didn't fall off the turnip truck.
My question is a group that has 2 bullet holes with a bullet hole distant between them or 2 bullet holes distance between them. If you are shooting a 17 cal and you had 2 bullet holes with a bullet hole between them it would be a .354 group, or a 223 would be .446.
Am I wrong?

 

[CatShooter]

Need to get this away from another thread. Some of you have been around for a day or two and didn't fall off the turnip truck.
My question is a group that has 2 bullet holes with a bullet hole distant between them or 2 bullet holes distance between them. If you are shooting a 17 cal and you had 2 bullet holes with a bullet hole between them it would be a .354 group, or a 223 would be .446.
Am I wrong?

17 centerfire bullets are 0.172" - so it would be 0.344"

223 bullets are 0.224", so it would be 0.448"

 

[Patch700]

Lol.... I've been wondering when this would pop up.

I'm going to say that yes butch , you are on the rite track... no need to get your meds adjusted

 

[butchlambert]

Lol.... I've been wondering when this would pop up.

I'm going to say that yes butch , you are on the rite track... no need to get your meds adjusted

Patch700,
Unfortunately for a lot of you I'm not on MEDS.

 

[mikecr]

Depends on how big the bullet holes are(regardless or fired bullet diameters).

 

[Jay Christopherson]

I take the lazy way out and use OnTarget, but when I measured groups physically, I measure the furthest two shots outside to outside and subtracted a bullet diameter, so I guess I would agree with CatShooter's assessment, based on Butch's scenario.

If you check out this Bulletin article, it shows a raw target, then measured by OnTarget:

http://bulletin.accurateshooter.com/2013/01/ontarget-program-measures-group-sizes/

If I were eyeballing that target, I'd be tempted to say the group is about "4 holes" vertical (4 .177 caliber holes since that is what was being shot on target), but I'd be wrong... it's not quite "3.5 holes" vertical (3.378 holes to be exact), which is quite a bit of difference. For my money (which is none, since it's free), OnTarget is the best tool out there for measuring groups. Resolves a lot of arguments...

 

[jonbearman]

You take the 2 furthest outside dimensions minus the diameter of one bullet and that is your group.

 

[Joe Salt]

I always measured the widest part of the group then subtract the diameter of the bullet.

Joe Salt

 

[jonbearman]

Most times I have measured targets , if you flatten the paper you will see a little black ring on the paper and that is from soot on the bullet and even though the hole is smaller the soot on the target will measure the actual diameter of the bullet. They take this into consideration when measuring for matches. It may be soot as has been told to me or just a copper swipe as the bullet passes through the target. This is why I always try to use card stock targets like at sinclairs so it shows up.

 

[Lazer]

I believe this is one of the groups butch is struggling with. Shot from s .223 rem at 100yds , any guesses as to group size?
Crap, sorry its sideways

 

[jimcasey01]

I have been following some of the threads on the forum. I would never have suspected that there was any confusion on how to measure group size until recently. Oh well, we all have to learn.

 

[jimcasey01]

I believe this is one of the groups butch is struggling with. Shot from s .223 rem at 100yds , any guesses as to group size?
Crap, sorry its sideways

I would suspect in the area of .557 if it is from a .223

I originally did very quick computations in my head, which may or may not be accurate. After reading Otter's post, I believe that his figures are more accurate than my own, as posted above.

 

[181backup]

Need to get this away from another thread. Some of you have been around for a day or two and didn't fall off the turnip truck.
My question is a group that has 2 bullet holes with a bullet hole distant between them or 2 bullet holes distance between them. If you are shooting a 17 cal and you had 2 bullet holes with a bullet hole between them it would be a .354 group, or a 223 would be .446.
Am I wrong?

Butch I would also agree the pic of the original groups in question don't seem the size posted, but I have seen the actual target in person held it in my hand looked at it with calipers and it is as stated it was measured the same way as the groups on my post that I asked you to look at on the 100 yard challenge that you said looked fine. The pic just does not do it justice

 

[SS427]

At first glance I would say that is around 1/2 inch.

Upon closer inspection I see about a 3.5 bullet width in the group. My .223 punches a hole that measures about .215. That times 3.5 = .7525 minus .215 gives me a group of about .538 inch.

 

[butchlambert]

Doesn't matter as I do not shoot a 17 any more. Thought it was a .177. Maybe they are .172, but it really matters not. My point is a group of 3 bullets distant would measure .446 or there about for a .223. The young man should be able to see the group that he posted above is not a .359. The group is pretty good for the little rifle that he is shooting and he should be proud of the group. Jim Casey has shot a group or 10 and understand that some groups you can eyeball pretty closely.

 

[LHSmith]

Why would anyone make it so difficult to measure bullet holes by using crappy target paper fastened over a poor backer? If you want accuracy in measuring groups get some quality target paper and fasten over clean (unshot) homosote ( the best IMHO), coroplast, or rigid insulation board. There is no hard and fast rule on what diameter a bullet measures on targets.......if one is " in tune" they will look 1 caliber smaller .....if one is shooting with a bad crown or running on the outside edge of stability they will look 2 calibers larger.
I hope this helps....the last thing I want to do is mudder : up your thread Butch.....and I also think you can be very hallarious ???

 

[Lazer]

So we have a .557 and a .538. And for butch your guess ?? After calling me out on a friendly 100 yd challeng and all of the pm"s about it ?? Basically calling me a liar??? When I posted 30 and the qualifications are for 20, and when I shot from sand bags on a gravel road prone. with a cartridge that's not "known" to be benchrest accurate. Your guess ........?

 

[LHSmith]

Those "friendly" keyboard competitions never turn out well.

 

[Jay Christopherson]

So we have a .557 and a .538. And for butch your guess ?? After calling me out on a friendly 100 yd challeng and all of the pm"s about it ?? Basically calling me a liar??? When I posted 30 and the qualifications are for 20, and when I shot from sand bags on a gravel road prone. with a cartridge that's not "known" to be benchrest accurate. Your guess ........?

To be fair Lazer, Butch never "called you out" in your thread - he suggested that you might want to re-measure your groups because he had a difference of opinion over your stated group size. Which is pretty fair given you posted the raw targets with no information on how you measured them. For your friendly competition thread, my recommendation would be to post your targets with OnTarget overlays. It's dead simple and it precludes people questioning your method.

And you never came up in this thread until you jumped in... just saying you might want to ease off the throttle a bit.

 

[Syncrowave]

I always measured the widest part of the group then subtract the diameter of the bullet.

Isn't that the way everybody does it?