New Reloader Question - Bullet Comparator

[Dixie Reckt]

Hello,

Trying to set up my bullet seating die for jam-0.020" but my when I have my bullet comparator in my calipers I cannot get a consistent reading. For example: I seated an empty case in my action so I have at bullet seated a jam. If I zero the calipers with the comparator on it and then put the exact same unadjusted cartridge back into the bullet comparator I get different non-zero readings. I cannot trust my zero on my comparator/calipers. The calipers I trust, the comparator is just a hunk of metal - so I don't think that's changing... how do I set the cartridge into the bullet comparator/calipers right every time to get back to zero? I'm getting +/- 0.050" depending on how I place the cartridge into the comparator. So I'm stuck I can't set my bullet seating test because I can't accurately measure my bullet seating depth. I have the Hornady brand comparator.

 

[MikeRu]

If you measure something as a control without the comparator attached, like an empty rifle case or a steel block (eg a weight standard), is it reproducible?

If your neck tension is too light it could be the bullet is being moved by the calipers? Put a fine sharpie mark on the bullet just above the neck.

 

[Dixie Reckt]

If you measure something as a control without the comparator attached, like an empty rifle case or a steel block (eg a weight standard), is it reproducible?

If your neck tension is too light it could be the bullet is being moved by the calipers? Put a fine sharpie mark on the bullet just above the neck.

Yes it is reproducible. I don't believe the neck tension is too light - I'm not putting a lot of force on the calipers and I cannot move the bullet in/out by hand. I have 3 thou neck tension.

I'm almost certain that its the fact I cannot precisely put the cartridge back into the exact same position in the calipers/comparator each time for measurement. Its as if I need another comparator with a shell holder on the other end of the calipers to get it into the same position every time is what I'm thinking...

 

[MikeRu]

Yes it is reproducible. I don't believe the neck tension is too light - I'm not putting a lot of force on the calipers and I cannot move the bullet in/out by hand. I have 3 thou neck tension.

I'm almost certain that its the fact I cannot precisely put the cartridge back into the exact same position in the calipers/comparator each time for measurement. Its as if I need another comparator with a shell holder on the other end of the calipers to get it into the same position every time is what I'm thinking...

That’s going to be solvable, but best if you could have someone there to see the issue.

Possible issues:

Avoid the flat Hornady base, it causes issues —just use the naked caliper blade and the correct comparator.

Hold the blades closed against the empty comparator with your fingers, and then tighten the set screw.

Spin or wiggle the case/bullet until it’s base is flush on the caliper blade, giving the smallest length reading.

If there is play or wobble in your calipers then check the tensioner screws that hold the arms in alignment. The screws should be just snug and it should slide with light pressure.

One higher $ option is to use the Hoover Accuracy One bullet trimmer housing as a mount for your calipers. They slide back and forth in the mount, much less of an issue with thumb pressure as a variable.

Mitutoyo calipers are a nice upgrade. More $…

 

[Webster]

Hello,

Trying to set up my bullet seating die for jam-0.020" but my when I have my bullet comparator in my calipers I cannot get a consistent reading. For example: I seated an empty case in my action so I have at bullet seated a jam. If I zero the calipers with the comparator on it and then put the exact same unadjusted cartridge back into the bullet comparator I get different non-zero readings. I cannot trust my zero on my comparator/calipers. The calipers I trust, the comparator is just a hunk of metal - so I don't think that's changing... how do I set the cartridge into the bullet comparator/calipers right every time to get back to zero? I'm getting +/- 0.050" depending on how I place the cartridge into the comparator. So I'm stuck I can't set my bullet seating test because I can't accurately measure my bullet seating depth. I have the Hornady brand comparator.

You don't need an accurate number. No reason to jam exactly 0.020". I consider any number you get as a starting reference for OAL Just try shorter and longer in maybe 0.005" increments to see what shoots the best. I never jam because I don't want to stick a bullet in the bore if I have to extract a loaded round. It would dump powder all over the chamber and trigger mechanism. No reason to think jam would give the best accuracy. If it's a varmint huting rifle the OAL isn't critical. The rifle and your skills may not be good enough to see a difference.

 

[ELR LVR]

1) try closing the calipers by pinching the jaws shut
dont use the thumbwheel
2) if these are electronic calipers, ditch them and get some manual B&S calipers
--- Even my fine Mitutoyo digital can show different numbers every time due to metal, magnets, motor freq's, etc.
If the batteries are not in good contact, also throws number readings off
I wish I never bought digitals, including Mitutoyo
They are now my "Beater" calipers
My B&S manual calipers - are my "accuracy calipers" with never a deviation and always read zero when closed

 

[FTR_Mojo]

Hello,

Trying to set up my bullet seating die for jam-0.020" but my when I have my bullet comparator in my calipers I cannot get a consistent reading. For example: I seated an empty case in my action so I have at bullet seated a jam. If I zero the calipers with the comparator on it and then put the exact same unadjusted cartridge back into the bullet comparator I get different non-zero readings. I cannot trust my zero on my comparator/calipers. The calipers I trust, the comparator is just a hunk of metal - so I don't think that's changing... how do I set the cartridge into the bullet comparator/calipers right every time to get back to zero? I'm getting +/- 0.050" depending on how I place the cartridge into the comparator. So I'm stuck I can't set my bullet seating test because I can't accurately measure my bullet seating depth. I have the Hornady brand comparator.

If youre struggling to use calipers, I would suggest using a tool like this;

Instant Indicator – Headspace and Bullet Seating Depth Comparator Designed for those seeking the utmost from their handloads | Redding Reloading Equipment

This instrument provides an extremely fast and accurate method for comparing the shoulder position of fired and/or sized cases and bullet seating depth uniformity. The addition of the “Range Adapter” makes this instrument more versatile and may now be used at the range or in the field without...

redding-reloading.com

This will take your caliper proficiency out of the equation. There are alternative tools like that on the market from different manufacturers. That one is good as you can just slowly drop your press handle, removing your variable hand pressure.

 

[kelbro]

I prefer the RCBS Precision mic:

Precision Mic

shop.rcbs.com

Much less finicky.

 

[FTR_Mojo]

Im not sure whats finicky about the Redding comparator. You put a case in and look at the dial. Couldn't be simpler.

I haven't used that RCBS one, but it actually looks way more finicky for a beginner. It doesn't have an instant indicator. Plus it looks very slow. You have to take the case in and out every time, screw in the micrometer....
I certainly wouldn't pick that RCBS one if I wanted a fast, user proof option for a beginner.

 

[rwj]

The OP stated variance of +/- 0.050” That is huge and suggests something fundamentally wrong with the tools and/or methodology. I’d recommend identifying the root cause before moving on to the more expensive tools that may not be needed.

 

[L.Sherm]

Change the battery.

 

[60723]

For me to be consistent, I have to rotate the bullet in the comparitor until the needle stays on a number

 

[Coyotefurharvester]

I will second(question) the +,- of 50 thou. Do you mean +,- 0.005? I could see that if the cartridge base isn't consistently positioned on the caliper blade(no anvil). No primer, correct? And case base undamaged/flat? We all assume you are using the matching for caliber bullet comparator?

 

[Dixie Reckt]

You don't need an accurate number. No reason to jam exactly 0.020". I consider any number you get as a starting reference for OAL Just try shorter and longer in maybe 0.005" increments to see what shoots the best. I never jam because I don't want to stick a bullet in the bore if I have to extract a loaded round. It would dump powder all over the chamber and trigger mechanism. No reason to think jam would give the best accuracy. If it's a varmint huting rifle the OAL isn't critical. The rifle and your skills may not be good enough to see a difference.

You don't understand the question.

I will second(question) the +,- of 50 thou. Do you mean +,- 0.005? I could see that if the cartridge base isn't consistently positioned on the caliper blade(no anvil). No primer, correct? And case base undamaged/flat? We all assume you are using the matching for caliber bullet com

I will second(question) the +,- of 50 thou. Do you mean +,- 0.005? I could see that if the cartridge base isn't consistently positioned on the caliper blade(no anvil). No primer, correct? And case base undamaged/flat? We all assume you are using the matching for caliber bullet comparator?

Yes I think you're right its 5 thou variation not 50 thou

 

[Murray Brook]

On my Hornady bullet and shoulder bump comparator I use a case neck chamfering tool and do each cylinder. Just a light bevel gives me a more repeatable number. JME

 

[D-4297]

1) try closing the calipers by pinching the jaws shut
dont use the thumbwheel
2) if these are electronic calipers, ditch them and get some manual B&S calipers
--- Even my fine Mitutoyo digital can show different numbers every time due to metal, magnets, motor freq's, etc.
If the batteries are not in good contact, also throws number readings off
I wish I never bought digitals, including Mitutoyo
They are now my "Beater" calipers
My B&S manual calipers - are my "accuracy calipers" with never a deviation and always read zero when closed

Someone who has a grasp of what is required to get precise measurements with calipers . I still have ; and use both my B&S and Mit calipers twenty years after retiring from Aerospace Die shop .

 

[tdogg]

I didn't read this whole thread but there is technique to getting consistent readings.

Close the calipers on the round and spin and wiggle it to align the base of the case flat against the caliper jaw. If there is a primer in the case remove it (assuming it is a dummy round) or make sure it sits below flush. Practice getting the dummy round to give you the same reading to get a feel for how it needs to sit in the calipers. If the cartridge is slightly tilted in the calipers it will effect the reading.

Cheers,
Toby

 

[Timon]

If you want anything to start right with a comparator, start off using the Short Action Customs comparators. They are cut to match your cases and your bullets, so that you get repeatable numbers. Of course, the caliper has to be working properly.

Scott

 

[MikeRu]

I think Hornady comparators seem reproducible to within +\- 0.0005” or so (that’s 1/2 thousandths), plenty good enough. I hear SAC are better but I haven’t used them. Curt Knitt sells some very nice ones that index a little further out on the bullet nose, I highly recommend.

CTK Precision

CTK Precision was born out of the need for superior shooting equipment and gun accessories at reasonable prices.

www.ctkprecision.com

I doubt if the comparator brand is the issue here.

 

[divingin]

Curt Knitt sells some very nice ones that index a little further out on the bullet nose, I highly recommend.

Not sure that's ideal, depending on what you're trying to accomplish. I'd want the tool to measure as close to the actual ogive (the point in the bullet that first contacts the lands) as possible in order to minimize reading any ogive to nose variation in the bullets.