Bullet Comparator (Homemade)

[Ivan the Butcher]

If you are loading ammo for a bolt action or break action rifle and wish to get the best accuracy from the ammo you make, you need some form of bullet comparator. This works for Thompson Center and bolt action pistols also.

This bullet homemade model will tell you where the lands start in relation to your chamber. Then when seating your bullets, you will know if they are touching or how many thousandths off the lands they are. I have found that Remington 700's and Cooper 21's like touching the lands. (Along with Schnider Target Barrels.) Other brands seem to prefer some distance from the lands, I start with .005" and shorten the OAL by .005" back to .025". I have found that if none of those lengths work, go to a different model or brand of bullet.

The simplest model of Comparator is made from a case fired in your rifle, and only BODY Full Length SIZED! This is done with a "Body die" that you own or borrow. (Be sure to lube the case first!) Redding sells these in almost every bottle neck cartridge there is. This type of die does not ever touch the neck. So, the bullet free floats.

To use: Simply insert the bullet you will be loading into the case in a horizontal position. Chamber slowly in the rifle with the chamber also in a horizontal position. Close the bolt or action. Then remove slowly and do not allow the ejector to throw the case out of the action. I always repeat 4 more times to be sure I did it right! Now carefully measure the overall length. This tells you the maximum length this bullet can be seated at in this rifle only. When you change to another bullet start over! I use 50 grain bullets in most 22 center fires, but if I switch to a 55 or 60 grain bullet, they often require a different set back!

I leave the case in the loading die box. (If you used a trimmed to length case, it is also a jig to set your case trimmer with.) It will work and all rifles in this cartridge.

I have made these for 221 Fireball, 223 Rem, 22-250, 22 BR, 6 PPC, 6x284 Win, 308 Win, 300 Win Mag, and 338 Lapua mag. (every body die I have) They only cost a fired case, and can use cases that are worn out or have expanded primer pockets!

Hornady makes a kit that is expensive and only is available in common cartridges (They bought out Stony Point)

I hope this helps you load rifle ammo that shoots tiny group!

Ivan

UPDATED> See post #10

 

[Nemo288]

For my break action rifles, which are either .445-SM or 444 Marlin, I have always just used a fired case that I squeeze the "neck" some with my fingers enough to create some friction with the bullet.
Put the bullet in the case (fairly long) and slowly shut the action.
Then slowly open the action and take the dummy cartridge out and measure the length.
Like you, I do this several times to make sure the bullet has not stuck to the rifling and pulled back out of the case.
This happens with cast bullets a fair bit because I don't have much neck tension.

I have also used this method with the lever action 444 but that requires a little more patience.
But I discovered it shoots best with some bullets touching the lands.
Unfortunately some of those rounds are now too long to load in the side gate.
One of the advantages of the break-actions:
S&W/TC/PacNor/Bullberry Encore .445 SM 12" and 17"
Rizzini BR550E 444 Marlin 60cm

With the wide variety of nose styles, sometimes you don't end up crimping in the cannelure or crimp groove.
In those cases I use a taper crimp on jacketed and plated bullets and the Lee collet crimp on cast numbers which will create a kind of shallow crimp groove on it's own under the mouth of the case.

 

[Jaco1234]

For 30-06 I use a fired case, full length sized, and I split the neck with a fine Dremel cut off wheel. The split acts like a spring. Put a bullet in, chamber the round, remove and measure.

 

[oysterer]

For 30-06 I use a fired case, full length sized, and I split the neck with a fine Dremel cut off wheel. The split acts like a spring. Put a bullet in, chamber the round, remove and measure.

That sounds very great. Thanks for telling me after I ordered hornady modified cases for my 2 new Mausers, Swede and 8mm, could have saved the money

 

[mtgianni]

I had a friend with a lathe tap several cases for me to use in my Stoney Point gauge.

 

[Miracle Man]

I have an old Stoney Point I've used for years. Really helps shrink groups. If you have an older bolt gun that's losing some accuracy they can really help get a few hundred more rounds out of them by getting the bullet closer to the lands, less jump.

 

[cmj8591]

Don't forget that different bullets have different ogives so you will need to measure for each style of bullet that you intend to use.

 

[toad67]

Don't forget that different bullets have different ogives so you will need to measure for each style of bullet that you intend to use.

Yep, and don't forget to make sure that they fit into your magazine, if your rifle is so equipped, before you load up a bunch and wait until opening morning to find out that you made a big oops. Also make sure of the fit in both areas if you run out of bullets in a box, and get a new box of the same old ones. Bullet manufacturers do change the ogive once in a while, even on the same bullet.
I ran into both of the above problems on an opening morning elk hunt. Talk about having your *** in a bundle trying to figure out what to do when all of your buddies are leaving, and you're sitting on your cot trying to figure out what ammo fits, and what doesn't...

 

[DWalt]

Stoney Point makes such a gauge. I have used one for at least 15 years. I made up my own threaded cases, but they can be purchased. Indeed you must use the exact same bullet you will be firing.
Stoney Point OAL Gauges | Free Shipping over $49!

 

[Ivan the Butcher]

For 30-06 I use a fired case, full length sized, and I split the neck with a fine Dremel cut off wheel. The split acts like a spring. Put a bullet in, chamber the round, remove and measure.

I made one like Jaco's today in 223. I think it is an improvement over my own! Thank you Jaco!

Ivan

 

[Nevada Ed]

A fired case is a great tool to fine tune your loads to the gun it is used in.

As mentioned, to use with a case trimmer adjustment/setting,

to learn the OAL of your bullets used,

to find out how much powder in a pistol case is a compressed load,

and a trimed shotgun hull, to see how a wad fits, with certain powders and hulls.

A good looking re-load is a prize to add to the ammo box.

 

[Miracle Man]

Another thing to keep in mind. If you seat the bullet touching on very near the lands you may want to back off a bit on charge and work the load back up. Pressure can rise.

 

[DWalt]

Tests by the bench rest community have shown that finding the correct bullet jump distance from the cartridge to the rifling lands is the most important single factor in getting the tightest grouping from a rifle. Although not the only one - case length uniformity Is nearly as important.

 

[Nevada Ed]

Tests by the bench rest community have shown that finding the correct bullet jump distance from the cartridge to the rifling lands is the most important single factor in getting the tightest grouping from a rifle. Although not the only one - case length uniformity Is nearly as important.

Some go nuts finding cases with centered primer holes and even
take a x-small drill bit to make them 100% round, to get their groups even tighter !!

It's all fun, if you like that sort of thing.