What do you folks use for bullet comparators? I have some old ones from Sinclair, but they don't fit on my new Mitutoyo calipers. The groove is just a few thou too tight. I could open them up a bit, but instead I went shopping.

Hornady's is aluminum. Too soft in my opinion for repeatable measurements. I bought 3 in different calibers from Whidden Gun Works and was severely disappointed. They're going back. Horrible workmanship and bare aluminum. If they had been anodized as shown on the website, they'd be hard enough I suppose. Even so, the workmanship is intolerable.

So I just bought this from Creedmoor: Creedmoor Sports Multi-Caliber Bullet Comparator, Creedmoor Sports: Creedmoor Sports Inc.

I'm encouraged since it has thumbscrews. I have a similar one from years back, but it's a three hand operation to hold the calipers, the bullet and the comparator. The thumbscrews are an elegant solution to that.

I'm interested in your experiences in this area. Setting bullet jump in precision rifles is a big part of the game, IMNHO.

The simple Sinclair nut has worked perfectly for forty or so years. I've never found a need for another such tool. Any 6" dial caliper should work fine and leave plenty of room for adjustment.

I normally use the Sinclair "Nut", they made two different sets of calibers (I have them both!)

I also just make one from a sized case and split the neck, then carefully chamber with the exact bullet you are using on that batch of ammo.
The sized and split neck has plenty of grip to keep the bullet in place (as long as you don't eject the dummy and it flies out and lands on the bullet tip, BTDT-been there, done that!

All of my long range rifle cartridges have Redding Competition Loading Die Sets, so Micrometer adjusted seating. I also use the Collet sizers with or without the micrometers. For a good "Red Neck Target Gun": Just size the neck about half its length. This centers the bullet with the bore on non-match chambers. It has made an improvement on every rifle I tried it on. When developing a new load, I have found that just kissing the lands works best on over 65% of rifles (never had a Rem 700 it didn't work on!). For rifles where you must use the magazine and that won't allow for long enough bullet seating, Berger makes a whole series of target and most of their bullets that are designed for long bullet jump. You won't get VLD or Hybrid BC's, but you will get the best that rifle can do! (AR's for longer range varmint shooting come to mind!)

Ivan

I only mess with bullet jump on bolt action single shot rifles. It often does make a difference. Kissing the lands is a good starting point. Lapua recommends you start there with the starting powder charge and increase bullet jump until you find the sweet spot. Then, adjust your powder charge for its sweet spot.

Other folks say to find the powder charge sweet spot with perhaps 20-30 thou of jump, then mess with bullet jump.

Some pundits have said you need to work in 3 thou increments to find the bullet jump node (sweet spot). Yes. 0.003" I doubt the measurements can be that precise. Just kissing or touching the lands is tough to detect. A little more pressure and the bullets goes in farther yet by several thou.

I use Wilson inline dies in an arbor press. I'm confident my cartridge base-to-ogive setting is repeatable. Measuring a cartridge with a comparator is repeatable. Judging bullet jump in the chamber is tough. So I just pick a reasonable base-to-ogive measurement, call it "relative" and work from there. But to my original post, I need to find a good comparator that fits on my new digital calipers. My old trusty Sinclairs don't.

On your new caliper, which way does the comparator not fit? Can you file or sand the caliper notch to the proper dimension? And last suggestion: Have you tried Brownell's (the people that bought Sinclair International)?

Ivan

Last resort: Hornady's replacement for Stony Point.

I use the Hornady comparator for .264 and .223 bench rest. I'm very happy with it. After seating with an LL Wilson micrometer die and arbor press, I get consistent results to half of one thousandth cartridge base to ogive length. I don't think being aluminum is a drawback.

I have generally found the sweet spot in my guns between 20-30 thousandths jump. I check in 3/1000 increments as well.

__________________
What could possibly go wrong?

Good questions, Ivan. The jaws on the new calipers are thicker than the old one. The grooves on my all of my Sinclair comparators are too narrow to fit. You're right, they can be opened up a bit. Unfortunately I'm a bit of a hack. I used a file and carefully opened up the groove. The one I modified does fit now, but I didn't get a clean corner at the bottom of the groove. I also managed to mess up the bottom of the groove since the file I used cuts on its sides as well as its faces. The comparator fits, but it rocks on the calipers. Either I need a different file or a machinist buddy with a mill.

I did check with Brownells. So far they haven't answered. The old Sinclair items are one piece. They have a specific hole size and attachment groove in a solid piece. Brownells' new approach is a grooved comparator body that accepts inserts for different cartridges. Seems like a good idea but the comments indicate it also doesn't fit some calipers.

You may recall in post one I stated my trouble with some old Sinclair bullet comparators. They fit on my ancient dial calipers, but the jaws on my new digital calipers are a fuzz too thick. In the picture below, you can see what I'm describing. The dial caliper has one of the old Sinclair comparators on it. They are one-piece, slip over the jaws and are secured with a setscrew. I have them with several hole diameters suited for specific bullet diameters. They served me well until I got new calipers.

I looked at several solutions and settled on Sinclair's newer offering. This is shown on the digital calipers in the pic. A call to Brownells helped greatly. Say what you will about Brownells, but they've always been great to me. They assured me the groove in the comparator was wide enough to handle my new calipers. Indeed it is.

I am pleased. The new caliper is a two-piece affair. You buy the body and suitable inserts. The inserts are nicely machined and have the appropriate angle inside the hole - not perfectly cylindrical, but with a very slight taper to mate with the bullet ogive. A plus is that shoulder bump gages are also available to use in the same comparator body. So I bought some of those too. Shown in the pic is their XL comparator body. They have a shorter one, but you might have issues with long slender bullets or measuring cartridge base to shoulder on loaded rounds.

This is definitely an improved setup. Digital calipers make relative measurements easy. Just close the jaws on the comparator, zero the calipers, then measure the bullet's base to ogive dimension. Works the same way to measure cartridge base to shoulder, or base to ogive.

Enthusiastically recommended!

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The photo clears things up. I thought you were talking about the Sinclair "nut", a very simple device I've used for forty years. It works fine on any caliper. I assume it's still sold by Brownells. The gadgets you have may work okay, but you might find you like the Sinclair nut much better.

I've had a Sinclair nut for years. It seemed to take three hands to make it work, though. I can be quite the fumble-fingers at times, so the nut has just been sitting. Creedmoor has an equivalent nut, but with thumbscrews to attach it to the calipers. I ordered one but it hasn't appeared yet. Admittedly, I have a lot of toys that were tried and stashed. It's a sickness!

Yes, it's awkward at first, but very simple and the measurements are 100% repeatable. I wouldn't consider any other such tool.

I use the Sinclair nut and I realized long ago that shooters like gadgets, maybe more than any other hobby or sport.