Thread: Concentricity issues after deburring

I bought a basic lyman 'ammo checker' (case gauge) which is basically a sammi cut hole to help ensure you arent about to load a deformed case). Been using it quite a lot in order to weed out any mistakes.

Had straight cases right upto the neck trimming and deburring. All cases were slippin in and out of the block before deburring. After..... bent as shit.

Thats using a typical deburr double ended tool. The bad news is, ive been ruining my concentricity for 10 years. Good news is, it hardly matters because im under 1moa almost always.

BUT. It will be interesting to see how the cases turn out when loaded. Shoving the brass into the case guage seemed to strighten it out after putting each piece in and out till it didnt grip.


But who knows if its buggered the neck tension. Guess that will become clear shortly

So maybe TRY using said deburring tool while bum of case is locked into holder from lee case length tool so it's spinning in drill to deburr. That way it's even pressure around entire case mouth as it's spinning????

What tool and how are you using it?
I struggle to how see how it could be bending your brass?

Unless you and your rifle system are capable of genuine 1/4 Moa groups or less I wouldn’t sweat about it. I would venture that most people wouldn’t notice any accuracy issues unless upper echelon target shooters. Remover, a lot of these gadgets are like chronographs in that they’ve spoilt many a good load when you see the numbers aren’t what was expected.

Non concentric ammo may or may not shoot well relative to what you expect or want. You will have to shoot some to see. I used to go to lengths to ensure handloaded ammo was as concentric as I could make it, and it shot acceptably. Then got some Norma factory ammo which I checked ouf of interest. Concentricity was all over the place but it shot much better than my "perfect" handloads in the rifle I used. So, I no longer checking concentricity but load everything with Redding dies which does the job well enough for me.

Originally Posted by woods223

Unless you and your rifle system are capable of genuine 1/4 Moa groups or less I wouldn’t sweat about it. I would venture that most people wouldn’t notice any accuracy issues unless upper echelon target shooters. Remover, a lot of these gadgets are like chronographs in that they’ve spoilt many a good load when you see the numbers aren’t what was expected.

Post of the month....

Originally Posted by woods223

Unless you and your rifle system are capable of genuine 1/4 Moa groups or less I wouldn’t sweat about it. I would venture that most people wouldn’t notice any accuracy issues unless upper echelon target shooters. Remover, a lot of these gadgets are like chronographs in that they’ve spoilt many a good load when you see the numbers aren’t what was expected.

And if you want to add a whole pile more stress to your system, buy a bore scope.

Originally Posted by T.FOYE

Good news is, it hardly matters because im under 1moa almost always.

that is good news, but, of course, for how many shots, how frequently?

I don't think the Lyman case checker checks for concentricity. It is only a go No Go gauge for case length, headspace and body size. I suspect you have not chamfered your cases properly to remove the burrs from trimming. You can check this with your thumb nail. If it hangs up on the case mouth there is more to do.
GPM.

I dont think concentricity is hugely important. After reloading I push all my projectiles through a long tube at High velocity. That plus the 200000 RPM seems to make them all go pretty much the same place.
If a rifle case after resizing is 2 Thousandths smaller its sitting in the chamber at a lean isnt it? When the charge goes off, to me its like a sprinter coming up out of the blocks. The case straightens, the bulet starts into the lands and force takes over the rest.

If concentricity mattered a lot then when i shoot a crooked round at say 1000 yds, I should see it fall well out of the group. So say my rifle is 1 MOA capable at 1000yds it will throw 10 inch groups. So now I put a crooked bullet in that has .005 thou run out.... how much will my group open up to? Im no mathematician but if it meant that i lost 1/2 MOA and my group is now 15 inches. I would revisit concentricity If we work that back to 100 yards and the rifle is still 1 MOA capable then my crooked round is going to make the group 1.5 MOA.
I've never seen it.
Just like using a loose fitting die in a Co ax press We get a lot of self alignment . I think things like neck wall variance, bullet tension / release, powder charge and wind all have more impact on our shooting systems than concentricity.
Sure its nice to eliminate it as a variable but I know of more Conc gauges sitting in boxes on shelves above the reloading bench than sitting on the reloading bench.

To the OP, maybe try a VLD chamfer tool? Also you could throw the brass back in the tumbler after chamfering to polish out any roughness the deburring did?

Originally Posted by grandpamac

I don't think the Lyman case checker checks for concentricity. It is only a go No Go gauge for case length, headspace and body size. I suspect you have not chamfered your cases properly to remove the burrs from trimming. You can check this with your thumb nail. If it hangs up on the case mouth there is more to do.
GPM.

As you shove the case in it, if anything is off then it wont freely drop into it. Thats what i was noticing after deburring.
Most were requiring a good shove to get them in which can only mean one thing if you dont have a lip on the outside of the neck (carefully checked them prior)

My usual concentricity guage isnt Nasa worthy but it does work. Thats the hornady sewing machine looking boat anchor .

Originally Posted by woods223

Unless you and your rifle system are capable of genuine 1/4 Moa groups or less I wouldn’t sweat about it. I would venture that most people wouldn’t notice any accuracy issues unless upper echelon target shooters. Remover, a lot of these gadgets are like chronographs in that they’ve spoilt many a good load when you see the numbers aren’t what was expected.

The insane reloader in me hopes that ALL guns are capable of .5MOA.

I would like to check if deburring is causing anything
- what con guage is best for empty case measuring?

Originally Posted by T.FOYE

I bought a basic lyman 'ammo checker' (case gauge) which is basically a sammi cut hole to help ensure you arent about to load a deformed case). Been using it quite a lot in order to weed out any mistakes.

Had straight cases right upto the neck trimming and deburring. All cases were slippin in and out of the block before deburring. After..... bent as shit.

Thats using a typical deburr double ended tool. The bad news is, ive been ruining my concentricity for 10 years. Good news is, it hardly matters because im under 1moa almost always.

BUT. It will be interesting to see how the cases turn out when loaded. Shoving the brass into the case guage seemed to strighten it out after putting each piece in and out till it didnt grip.


But who knows if its buggered the neck tension. Guess that will become clear shortly

Measure the neck in two places preferably with a micrometer. ....seems like you are creating a burr. Put it through a full length resizer and it should establish a burr or no burr pretty quickly.

Im struggling to figure out how you bend brass de burring it. I did a you tube clip where I shot some un concentric brass and It shot fine