measuring groups?

[bkjeffrey]

What is your standard for measuring groups? Extreme outside diameter of group? Center to center of the furthest apart holes? THe center to center method seems almost impossible IMO.

The reason I ask is I quote this phrase from another thread:

custom built Remington 700 by Tactical Operations, model X-ray 51. It wears a Schmidt and Bender PMII 4-16x50mm scope / has 3rds in .08".

Assuming this is a .30 caliber bullet, this group would actually be impossible. Even if all the fired rounds traveled through the same exact hole the group would still technically be .30.....correct? Unless there was some way to measure the exact center of the point of impact of each round fired to establish the deviation.

Also, while typing this I figured that you could fire 3 rounds at 3 seperate targets while having the same exact point of aim on each target and establish deviation based upon measurements taken from each target.

Just curious.....

 

[LoonWulf]

i use CTC. measure the whole group, then minus bullet diameter. Ive never shot a group small enough to have an issue LOL...if i remember correctly my smallest was about .26 for 4 rounds and last pushing it out to .5 and something, LOL

 

[Tim the student]

CTC.

 

[bkjeffrey]

Ah, that makes sense....brainfart.

 

[briansmithwins]

Just to point out, three round groups are meaningless when talking about a weapon's accuracy. Ten round groups start to tell you something but multiple ten round groups are even better.

With careful three round group selection I've owned several .8 MOA AK-47s.

BSW

 

[Steve H]

Extreme outside edge to opposite outside edge minus bullet diameter.

 

[jmr40]

The easiest way to get center to center measurement is to find the 2 holes the greatest distnce apart. Measure from the outside edge of one hole to the inside edge of the other. Assuming all are from the same diameter bullet this gives you the center to center measurement without any math, or guessing exactly where the center of the holes are.

 

[jmr40]

Just to point out, three round groups are meaningless when talking about a weapon's accuracy. Ten round groups start to tell you something but multiple ten round groups are even better.

I disagree. Five different 3 shot groups tell me just as much about the rifles accuracy as three groups of 5 shots or one group of 15 shots.

Long strings of 5 or more shots tell something about how well the rifles barrel dissapates heat and a little about the concentration levels of the shooter. But little about the rifles accuracy potential. For a hunting rifle 3 shots are about the max anyone will ever need.

Want to find out how accurate your rifle is. Put up a target and fire the first shot of the day at it. Take it down and put it up until the next range visit. Put it up an fire 1 more shot. Repeat until you have 15-20 shots on the target.

 

[esheato]

I like to put up two targets on top of each other...swap the top target at every 3 or 5 shots...at the end of the day you have your group targets and a composite target accounting for all the groups. Of course this only works on the same load, distance, etc.

 

[TonyAngel]

Although I do measure groups using the above described method, I have recently come to the conclusion that shooting groups is a total waste of time. Three shot groups or ten shot groups, you aren't learning anything about the capabilities of the rifle/shooter combo.

Just this past weekend, I was trying out some new (to me) Berger Hybrids. I put 5 rounds into a group that measured something around .05" CTC. At a glance, it appears to be a single .308 hole. My buddy that was spotting for me said that he would have called BS on it, except that he could see the target paper moving as the bullets passed through the hole. Do I consider that to be a representation of what I am capable of with the rifle? Nope.

If you really want to know what you and your rifle are capable of, you need to shoot dot drills, having to acquire a new target for each shot. If you want to know what your group size was, then do a composite. I use target sheets that have a series of 25 1/2" target dots on them and this is what I practice on. Having to shoot through transitions will give you a better idea of what you and the rig are capable of in a real use environment.

 

[Carl N. Brown]

Since the 1950s I have read/heard groups are measured center to center of the bullet hole in the target.

You are actully measuring/recording the accuracy of the gun and ammo, not the size of the hole in the paper.