Cartridge checkers

[Smithjdsr]

Tell me about cartridge checking devices. Some are individual, knurled cylindrical things with a “chamber” and they seem to have a stepped mouth end with different lengths. Some are rectangular and have “chambers” for half a dozen different cartridges. Some, like my old Herter’s, are just a stepped aluminum thing marked with the max case length for lots of calibers. (My old one lacks .223, I was surprised to discover. I guess when I was a kid, .223 wasn’t nearly as ubiquitous.)
 
I know they are designed to save time over using calipers. Are they all of equal value? Do the same thing? They must all be for the brass only, since different bullets have different C.O.A.L.?

[Publius]

Very useful tools. I use ones made by sheridan for two calibers I load for and will eventually get one in 450BM as soon as I start loading for it. Don't know if sheridan makes one in 450BM though.

[Bmt85]

Tromix makes one for the 450. I thought about picking one up, still might.

I started with a few of them for bottleneck cartridges, but found that they aren’t that useful (for bottlenecks anyway). I set all my dies to just bump the shoulder a few thousandths (usually around .003”), so I just use a headspace comparator. No need for a case gauge at that point. The way some people use the gauge (set it so the bottom of the case ends up flush with the gauge), will usually end up with brass a lot smaller than the chamber. That leads to overworked brass and reduced case life. With the 450, it might still be useful, but I’ve done fine with out one.

[Publius]

I admittedly don't use mine all the time, but they do come in handy when needed, and I like having a tool to do the job rather than not having the tool and wishing I had one.

Last time I used it was about month ago when I went to the range with a friend. He was having cycling issues. After a quick look at what was going on I concluded it was his ammo and it wasn't chambering fully or getting stuck in the chamber, but he insisted his buddy was an expert reloader and there was absolutely no way that could be possible. A quick drop into the chamber checker showed almost half the ammo wouldn't drop freely into the gauge under gravity, nor would some release without a firm push to remove it. Was getting stuck on the case heads.

Sure there are other ways to figure that out, but the convenience of having a tool that can do that in literally a couple of seconds far outweighs the cost. JMO

[Thom28]

Tromix makes an excellent chamber gauge. As stated by other posters, I don't use mine every time I reload but it comes in handy when/if problems present themselves.

[CJP1]

I recently bought one made by Lyman. This really cuts down on the number of cases that I have to resize. If my empty cases don't fit in the checker I then use a modified shell holder (Thanks Hoot) to take out minute bulge left in cases closer to the head that were fired in AR or Bolt Action platforms. I have used the checker on my reloaded rounds but the bullets are set too far out so rounds don't fit into it. It is a handy tool to have on your bench, especially if you have both a single shot CVA Scout and a Ruger bolt action like I do.

[Smithjdsr]

I recently bought one made by Lyman. This really cuts down on the number of cases that I have to resize. If my empty cases don't fit in the checker I then use a modified shell holder (Thanks Hoot) to take out minute bulge left in cases closer to the head that were fired in AR or Bolt Action platforms. I have used the checker on my reloaded rounds but the bullets are set too far out so rounds don't fit into it. It is a handy tool to have on your bench, especially if you have both a single shot CVA Scout and a Ruger bolt action like I do.

So, the Lyman gauge just showed up. (My reloading room is about to become a guest room for 2 weeks, so one quick playtime then closed for business until after Tax Day... Good thing I love my daughter and her wedding is not a burden, and good thing I love my mother-in-law). Anyway, all the .223/5.56 cases I had resized drop right into it just by gravity. No pushing necessary. the. Base is inside the top step at the back and slightly above the bottom step (I think that’s what Lyman wants- between the steps). I trimmed them and they’re all at, or slightly inside, the other end of the gauge.

This is all according to Hoyle, right? If the case drops in the gauge and is right at, both ends, I can load them and they should cycle through our AR’s just fine (clearly some range time is required before making that hypotheses a fact). After I get some bullets stuffed, I’ll do it again. You’re saying that they might not chamber in the gauge, but will still work in the rifle?

[plant_one]

You’re saying that they might not chamber in the gauge, but will still work in the rifle?

SAAMI always gives a min/max for both cartridge and chamber specs. it establishes a safe tolerance range.

soo....

most of those cartridge gauges are cut for minimum chamber, which is just a smidge - yes thats scientific measurement term - larger than maximum cartridge.

so yes - its possible for a cartridge to fail the gauge and still chamber in an in-spec chamber thats above minimum but not exceeding maximum chamber dimensions.



hth

[Hoot]

Barrel manufacturers buy chamber reamers by the case-full. When they're new, they cut more generous chambers. As they wear, the chambers get smaller and at some point the worn one is tossed into the scrap box and a new one is grabbed. How long the manufacturer uses the too small reamer depends upon the barrel's price point. Reamers cost money. Value manufacturers will actually order their reamers oversized to the max allowable dimension to make them last through the most cuts before they are too small. I myself have seen chambers that were very generous and ones that were too narrow. Its the luck of the manufacturing draw, which one you end up with. The other possibility is chambers cut with NC boring bar lathes. Straight walled caliber chambers are the most easily cut using that method. Not many complex steps in the NC program. Same conundrum however. The NC program steps that set the cutting location don't change but the cutting head insert will wear from barrel 1 through 100, or whatever number they produce before rotating the carbide insert.



Tungsten Carbide Inserts cost money too.

You get what you pay for.

Hoot

[Smithjdsr]

That is... the best explanation I have heard. Thank you.

I’m not a machinist, just a 6th grade social studies teacher and has-been chemist who likes punching holes in paper- and deer (and quail, if I can afford to get to Kansas in November). I’ve milled out several 80% lowers and, so far, all my builds go “bang” and not “BOOM” but I’m no machinist. Sometimes they’re not beautiful.

That would partly explain why some barrels are sub $100 and others are a LOT more. I guess If you get one in the middle of the run, you get a good one! So far the gods of bushmaster must be smiling favorably upon me because my $100 18” BCA barrel groups 1/4” tighter than my buddy’s $250 20” barrel.

My almost-defunct chemistry skills don’t resonate with machinist “tolerance” because in chemistry, one typically can’t distinguish, with any human sense, the difference between 10 ppm and 25 ppm (parts per million), let alone ppb or ppt. But similar differences in barrels, or powder charges, can mean “Yep! That works!” -vs- “That didn’t work and the deer got away!” ...or even “Yep! That works!” -vs- (KABOOM!) “Has anyone seen my right pinky finger around here?”

So, I have a cartridge checker, the current set of cases all look good. Going to try a few (maybe Friday) and we will see... That’s .223. Will I be needing one for 450B? .45 ACP? 9mm? (I have a .30-06 and I won’t even start .243 without one).