• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Measuring Groups on back side of paper?

Does measuring group size on the back side of the paper, center to center make sense to anyone else? Because in this case the holes are much smaller and easier to see than from the front. Of course if the 2 outside bullet holes touch then it's harder. But if the don't...thoughts?
 
I use Imperial sizing wax. Even though I use it very lightly and I wipe off the cases after sizing, the holes have a gray discoloration that could come from the wax. More likely it is carbon residue from inside the case necks. I almost never tumble my cases. I just wipe them off after sizing and I run a brush inside the case necks.

When a hole has tears, when I flatten it out I can see exactly where the bullet hit from the grey discoloration.
 
Last edited:
Does measuring group size on the back side of the paper, center to center make sense to anyone else? Because in this case the holes are much smaller and easier to see than from the front. Of course if the 2 outside bullet holes touch then it's harder. But if the don't...thoughts?
front side outside to outside subtract bullet dia . as said here .
 
I probably need to start using better paper because the imprint of the bullet on the paper isn't as big as the bullet diameter. Therefore, using the method of measuring outside to outside makes my groups seem smaller than they actually are.
 
I probably need to start using better paper because the imprint of the bullet on the paper isn't as big as the bullet diameter. Therefore, using the method of measuring outside to outside makes my groups seem smaller than they actually are.
That's not uncommon and the marks should be consistent in size.

Measure outside to outside, and subtract the diameter of the mark instead of the bullet. Example a 30 caliber might leave a .295 mark.
 
FWIW - a friend showed me a few years back that the cardboard from regular brown boxes seems to allow the bullet to cut a much sharper hole that it would in typical printer paper. I always have some boxes lying around, so I started cutting them up for use as targets, and the edges of the bullet holes really are much sharper than with printer paper, unless you buy specialty heavyweight stock.

Because the bullet holes are usually smaller than bullet diameter as you noted, measuring bullet hole/group dimensions center-to-center is the better method. Further, software such as OnTarget that measures groups center-to-center is readily available, often for free if you choose an earlier version.
 
I use one of those Neil Jones tools to measure both club and IBS targets at Manatee. I put that tool under a large magnifying glass and center holes of different bore sizes around one hole in the target. Then there is a straight line in that plastic line of hole sizes. If you place it in the center of the far hole you are measuring to then move the proper size hole to go around that far hole, the readout is within a couple thousandths.

Hard to describe above but simple if you have the tool in your hand. Measing with a plain caliper is tough as there is often bullet yah and the holes may not be round, finding center is still a guess and there can be paper issues. Edge to edge or center to center is fine for casual measurements. To do it right takes that Neil Jones tool or the like.
 

The IBS record committee has used something similar for decades. Three different people can measure the same target and very seldom differ by more than a few thousandths so something must be working correctly.
I use one of those Neil Jones tools to measure both club and IBS targets at Manatee. I put that tool under a large magnifying glass and center holes of different bore sizes around one hole in the target. Then there is a straight line in that plastic line of hole sizes. If you place it in the center of the far hole you are measuring to then move the proper size hole to go around that far hole, the readout is within a couple thousandths.

Hard to describe above but simple if you have the tool in your hand. Measing with a plain caliper is tough as there is often bullet yah and the holes may not be round, finding center is still a guess and there can be paper issues. Edge to edge or center to center is fine for casual measurements. To do it right takes that Neil Jones tool or the like.

Our club NJ tool came with a screw-on magnifier....
1632968956745.png
 
Here are a couple of photos showing the grey marks on the target which I believe are coming from carbon residue, but some sizing wax is also a possibility. The photos are after flattening out the tears from the back side of the target and placing a piece of tape on them to hold them flat. The grey circles are very close to the same diameter as the bullet caliber.
 

Attachments

  • D33C4702-4CBB-409A-A976-90A01126837E.jpeg
    D33C4702-4CBB-409A-A976-90A01126837E.jpeg
    220.6 KB · Views: 8
  • 95954AAB-2E57-43F3-8584-FC7AFBCCFDDD.jpeg
    95954AAB-2E57-43F3-8584-FC7AFBCCFDDD.jpeg
    230.8 KB · Views: 8

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Forum statistics

Threads
166,276
Messages
2,215,452
Members
79,508
Latest member
Jsm4425
Back
Top