[CliffinSouthLa]

Hi Gang, I got back from the range today and was looking at my targets. The wind was really whipping and I wasn't really happy with all my groups. I was shooting my CZ 204 ......doing something dumb like breaking in the barrel....and experimenting with two loads. I measured the five shot groups ...outside to outside and they range from just under an inch to one and a half inches. Is the correct way to measure from the outside to outside and take away the caliber or middle to middle? Thanks...-Cliff-

 

[samspade]

You have it correct to measure the outside and subtract the caliber. If your group was 1" outside to outside the group would be called .8".

 

[CJ in Wy]

Well

If there are prairie dog parts all over and the grass is red......it shoots good
If dust is flying and dogs are runnin for thier holes............The load needs a little more work
What can I say it aint easy being a ******* BDB

 

[Kyle]

Pocket change

I'm happy when I can cover 5 with a dime. On bad days, I measure outside to inside.

 

[Wingman26]

 

[Ackman]

Center to center. If there's space between the holes, outside edge of one to corresponding outside edge of the other works too. Measuring between extreme outside edges and subtracting bullet diameter is just kidding yourself, but it's a good way to fudge and get a smaller group.

 

[Don in WA]

I like the method in the other post about groups.

Put one on the paper away from the group and measure it for the amount to subtract. Heck, you need a fouling shot anyway right? At least it would give me an excuse for those fliers that are always there, as others say, all day long!

I am now using a ream of 110lb paper to copy for targets that gives cleaner holes. It is almost post card thick.

Works for me.

 

[bcp]

groups

You are measuring holes, so subtract a hole diameter, not bullet diameter. You will probably find that holes are smaller than the bullet. Kind of strange.

Most all of my groups are under 0.10

Bruce

 

[ArtinNC]

This is THE only way to measure groups

Its all a bunch of BULL . This is the only way to measure a group ONE shot Groups .

 

[Paul Workman]

That's why I so often shoot one outside the group...

Center to center. If there's space between the holes, outside edge of one to corresponding outside edge of the other works too. Measuring between extreme outside edges and subtracting bullet diameter is just kidding yourself, but it's a good way to fudge and get a smaller group.

...so I can have a clean view of a single bullet hole to measure for reference and subtract the diameter from that one-hole goup next to it! Isn't that the way it works??

 

[Paul Workman]

Put one on the paper away from the group and measure it for the amount to subtract. Heck, you need a fouling shot anyway right? At least it would give me an excuse for those fliers that are always there, as others say, all day long!

I am now using a ream of 110lb paper to copy for targets that gives cleaner holes. It is almost post card thick.

Works for me.

We think alike (See my response to Ackman )

Yeah, YEAH! I always shoot a couple outside the "real" group for reference purposes! Yep. In reality, fliers can go INTO a group as well as OUT of a group, I recon!

This whole discussion prompted a postal match by joeniv several years ago. It was quite a sobering ordeal. I did quite down the braggin' for a while tho. Mebby its time to do another one!

P.

 

[Paul Workman]

Other have pretty well said it - just to add a (pic)

Hi Gang, I got back from the range today and was looking at my targets. The wind was really whipping and I wasn't really happy with all my groups. I was shooting my CZ 204 ......doing something dumb like breaking in the barrel....and experimenting with two loads. I measured the five shot groups ...outside to outside and they range from just under an inch to one and a half inches. Is the correct way to measure from the outside to outside and take away the caliber or middle to middle? Thanks...-Cliff-

Center to center is the conventional measurement and what BR matches refer to. (Otherwise it would be reeeeeealy hard to shoot a goup in the teens with a .308 if one was measuring from edge to edge, huh?)

To decide winners and loosers of a match to a center to center measurement to .000s really requires a concentric circle gauge fixture like those used in most BR matches, complete with some magnification to assist in getting it set up "perfectly". However, measuring from outside edge to outside edge and then subtracting the average bullet hole measurement (almost always smaller than caliber, for some reason!) will get ya pretty close - close enough for load development for dang sure!

If, as Ackman points out, if the holes are descrete (scattered and clearly distinguishable), one can measure the two outside holes at the same relative location on the holes - perpendicular to a line drawn thru both holes - and that way a direct center to center measurement is aquired w/o having to subtract the diameter of an individual hole. (The parallel lines in the diagram(s) are suppose to depict the location of the jaws of a dial caliper, for example.)

For load development, what maters is consistancy; outside edges or center to center, as long as it is consistant. Center to center removes the bullet diameter from consideration, which is preferable when comparing groups of different calibers, especially.

FWIW,

P.

 

[ArtinNC]

Paul,
I got into a argument one time and measured it from center to center and got a whopping .009 differance, so why is everyone making such a big deal . So for posting on the board I think measuring from out side to out side and subtracting diameter of the bullet is good enough. And that is all I will be doing and if everyone wants to flame we that ok with me .
Or we can shoot one shot groups ( like just did ). And the pictures on the screen is not full scale so you can't measure on the screen . So why is every one want to flame anyone that wants to show a group that they are proud of, and most of the ones that are doing the flaming never show pictures their groups. just my .02. Art

 

[Paul Workman]

Paul,
I got into a argument one time and measured it from center to center and got a whopping .009 differance, so why is everyone making such a big deal . So for posting on the board I think measuring from out side to out side and subtracting diameter of the bullet is good enough. And that is all I will be doing and if everyone wants to flame we that ok with me .

I don't think there is a "big deal", until and unless a contest is at stake. Then a target fixture, like those used at a BR match (I don't have one or I'd post a picture) will get down to .000" center to center as accurately as one can, I suppose, given the differences in paper and conditions, etc.

However, there was a guy who used to post pictures of groups shot with his .223 where there was clearly un-burnt paper between the holes and he would mark them as groups waaay below caliber - some in the mid to low teens, as I recall. When challenged, this character (like some do) took it as a personal attack and get really ignorant - stoopid, in fact. I saw him brag about some of the same groups on the benchrest.com board and get flamed to a cinder for it (and deservidly so!). It made for some humorous reading for sure!

Having said that (coma!) someone made mention of the paper between holes as evidence the groups couldn't be as small as claimed. There was a time when I might have agreed. However, in order to get a better view of the actual burned outside hole edges, I push the curled (burnt) edges of the hole back to the hole center and put some tape on the back of the group to hold the paper in place. Then I can clearly see the hole edges to take a measurement.

But, this process does sometimes push paper fragments between some holes. The burned edges don't change position, and that is what is being measured. However, the shards of paper that appear the center of the group do give rise to someone not knowing what has happened to question the measurement results, especially if there is paper showing between the holes and results are sub-caliber. The shards present a distorted result - not the truth - but do give rise to questions, sometimes. (The group on the lower right shows what I mean. After ironing the edges out, it looks like one can see several "rings" which might be misconstrued as circles depicting the actual holes, which may or may not be true.)

Also, as someone mentioned, using card stock or heavy paper for targets results in much cleaner holes and aids measurement consistancy a lot, I find too.

I agree w/ you: Center to center via the distance between the burnt edges of the group, minus the average distance between the burnt edges of one or more discrete holes is what I use for my own records and what I'm referring to when posted here. I realize it ain't perfect, especially when taken to .000. However, for the sake of discussion which is usually load development results, they are fine, and I won't question anyone elses measurements, even if I'm dubious

 

[Paul Workman]

Measure some holes from edge to edge and see how often they are smaller than caliber. I have seen some holes that measure considerably smaller than caliber, and I feel like I'd be foolin' myself to use caliber diameter as the amount to subtract to get center to center group size.

Anywayz, try it and see if you don't agree.

P.

 

[varminter22]

Hi John,

This subject comes up often. And no one means to cause flames - I certainly don't.

But in reference to your group (posted), either I'm missing something or ...

The extreme spread of bullet holes appears to measure under three bullet holes, or approximately 2.6 times .224" which equals approximately .582" or so.

.582" minus .224" = .358" for a group measurement (approximately).

What am I missing?

Again, NO flames intended. Just wondering what I'm missing!

 

[CliffinSouthLa]

Okay, I Think I have It.....

shoot a five shot group and measure edge to edge and subtract the caliber....since this is a five shot group shouldn't I subtract the caliber five times ...Thanks -Cliff-

 

[samspade]

I got into a argument one time and measured it from center to center and got a whopping .009 differance, so why is everyone making such a big deal . So for posting on the board I think measuring from out side to out side and subtracting diameter of the bullet is good enough. And that is all I will be doing and if everyone wants to flame we that ok with me .

I agree with Art, mostly you are measuring groups for your own evaluation. For personal evaluation and on these forums I only speak of outside to outside when refering to a rifles accuracy. To me it makes little difference of how you measure as long as you measure and don't use terms like "My rifle shoots MOA", "minute of prairie dog" or "It's a Tackdriver" those terms say nothing.

 

[Rocky Raab]

Hey varminter, I like that. "Appears to measure..."

I think that's how I'll do it from now on. Let's see, stand back a couple of yards, raise my thumb, squint and say, "Yup, that appears to measure, oh...call it point three one inch. Nice group!"

Of course, there are those who believe all gun writers (I humbly include myself) do it that way all the time, right? Grin.

 

[Paul Workman]

I agree with Art, mostly you are measuring groups for your own evaluation. For personal evaluation and on these forums I only speak of outside to outside when refering to a rifles accuracy. To me it makes little difference of how you measure as long as you measure and don't use terms like "My rifle shoots MOA", "minute of prairie dog" or "It's a Tackdriver" those terms say nothing.

Yep. What really matters is how one does it for their own records. But, I wouldn't say MOA means nothing - MOA is well defined. However, even tho a minute of angle is the same no matter what the range, it is one thing to shoot MOA at 100 yards and quite another to be able to shoot MOA at 1000 - at least it is for me!

P.