44 magnum diameter tolerances?

I

idigg

New member
i had a custom barrel made for me by SSK.

on its maiden voyage to the bench, i realized that one type of ammo doesnt chamber. my father's hand loads work, and 2 other types of factory ammo works. the fiocchi 240 jsp were the only ones that wouldnt chamber. i scribbled some sharpie on the side, and confirmed that it was a width thing, not a length thing. the issue is about 1/4 of the way back from the neck of the case. this ammo works fine in my SW 629, in fact, its been a great hunting round for me with that gun.

im trying to figure out if the issue is with a chamber that is too narrow, or the ammo that is too wide.

i have a set of digital calipers on the way. but thats only going to tell me the diameter. im trying to figure out what the diameter of the casing should be, and if it is in spec, i can reach out to SSK and have them fix the chamber, or if it isnt in spec, well... i know that i need to avoid that ammo. from what i can see in various places... they list:
Neck diameter .457 in (11.6 mm)
Base diameter .457 in (11.6 mm)

i also found the saami specs
https://saami.org/technical-information/cartridge-chamber-drawings/
if you click pistol, it is on pg 54(pdf page 63)


the ssk experience has been quite the disappointment. to say the least. but im not going to go into that right now. suffice to say, if the chamber is out of spec, that just means the quality of the product will end up matching their lack of customer service.
 
looking at the saami specs,

it seems as though the dimensions of the cartridge should be .4569 at the base, and taper to .4561 at the front.

it says "unless otherwise noted body dia -.006... so am i reading that correctly in assuming that the .4569 and .4561 are maximum #s and it can be smaller by .006?
 
First point, generally speaking, unless marked otherwise, the dimensions on case drawings are considered to be the max numbers.

I'm sorry, but the SAAMI drawing confuses me a bit. I have no idea exactly what they mean by "unless otherwise noted body dia -.006"

And in the drawing the arrows for the case body diameters at base and mouth seem to be inside the case, not outside.

The drawing of the .44 Mag case in my Hornady manual has those arrows on the outside of the case, and gives the diameters as .457" at the base and .456" at the case mouth.

im trying to figure out if the issue is with a chamber that is too narrow, or the ammo that is too wide.
Click to expand...

Generally speaking, when 3 other "brands" of ammo fit, and ONE doesn't, its the ammo, not the gun. What you may have is a case where the SSK chamber is cut to min spec, and the Fiocchi ammo is max spec, and do remember that there is a tolerance range to all the specs, and sometimes the +/- amounts "stack up" in just the right way to interfere with proper function, and still have BOTH the gun and the ammo be "in spec".

I think you're "jumping the gun" assuming that SSK cut a "bad" chamber and it needs fixed when only ONE brand of ammo has an issue and the rest do not. Maybe they did, certainly it is enough different from the chamber in your S&W that the Fiocchi ammo won't fit. But that doesn't automatically mean the chamber is out of spec, and if it is within SSK spec, there is nothing they need to do to "fix" it.

I know someone who has had several different Walther 9mm, none of which would take Cor-Bon ammo. Every other brand of ammo fit fine, just not Cor-Bon, and Cor-Bon fit fine in all his other 9mm, just not his Walthers.

While you may not like it, the practical answer is simply don't use the ammo that doesn't fit in the gun it doesn't fit.

Go ahead and measure, get all the info you can, talk to SSK, they might be willing to polish the chamber and that MIGHT solve your problem.

suffice to say, if the chamber is out of spec, that just means the quality of the product will end up matching their lack of customer service.
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From the information provided, its possible the chamber is not out of spec, and if you haven't even talked to SSK about the issue, yet, its hardly fair to bash them for a lack of customer service.
 
I think you're "jumping the gun" assuming that SSK cut a "bad" chamber
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honestly im not even assuming that, other than just being so dejected with the ssk experience up to this point, that it would be an "of course it is" moment.

ive got absolutely no problem not using this particular ammo in this gun. to be honest, most of what i will end up using is our handloads, but we havent worked up a load for 44mag yet. i just have some leftover reloads from when my dad reloaded wad cutters for my grandfather to practice with the 629 that i inherited. once i go through those, and get enough spare brass, ill be shooting 90% reloads, which wont have a problem.

the concern with the fiocchi not chambering is just that i dont want to find out years down the road that many different brands dont chamber, and at that point its too late to call up ssk to fix their work.

but ill take some measurements with the calipers tonight and see what i end up with. obviously, if they are out of spec, well, i wont worry about it. if its at the edge of spec, probably reach out to ssk and have them open up the chamber a hair. its a custom barrel, and i want it the way i want it, and they've already messed enough that im done settling.
 
44 AMP said:
I have no idea exactly what they mean by "unless otherwise noted body dia -.006"
Click to expand...

It means that any diameter dimension you see without its own tolerance listed next to it will have a tolerance of -0.006" (+0.000 is assumed). So, for example, the case mouth and body diameters have no separate tolerance given next to their values, so they are all -0.006" tolerance. The head, however, has its own tolerance of -0.010" given, so that's an example of "otherwise noted".


Idigg,

I am going to guess that you will find your cartridge case exceeds the SAAMI diameter right over the base of the bullet. This would happen if the case wall's internal taper started to thicken a little too close to the case mouth. In that instance, the seated bullet under that thick spot would produce an excessive diameter. If I assume that the base location is about 0.375" into the case mouth, at that location, any diameter over about 0.4584" would interfere with a SAAMI minimum chamber. The properly dimensioned cartridge should not exceed 0.4563" at that location.

If the cartridge dimensions appear never to exceed 0.4584", then you may have a tighter-than-SAAMI chamber, which is usually a good thing for velocity and accuracy but can cause compatibility issues as you describe.

Keep in mind a digital caliper, despite often resolving half a thousandth, has accuracy limited to about 0.001" in most users' hands. For the problem you are having, and for bullet and slug diameter measurements, you really want to use an OD thimble micrometer that resolves 0.0001". There are a number of inexpensive ones on the market. This type if you know how to read a Vernier scale, and this type if you don't.
 
If you happen to have a Lee Factory Crimp Die you could try running the ammo through it to see if it will chamber then. I’m talking about the die with the sizing ring, not the collet crimp die.
 
https://imgur.com/a/pb7T8Od

Ok, back with an update. Seems as though the ammo is well within spec. At the top of the case, 0.455 was the biggest I found. But my concern is that even the ones that were 0.454 wouldn't go in. (edited to fix 445->454)

Do you all think I should keep it as is? I could see if it didn't work with something at the edge of spec, but it seems like it should accept anything that far in spec.
 
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Call SSK if your barrel is under warranty. If not, a local gunsmith that does chamber work. Include a round of ammo you mentioned and have him correct it.
 
Any chance you measured the rounds that DO fit and work??

Generally speaking ammo makers produce ammo that is slightly below listed min chamber specs (and below listed ammo max specs) so that the ammo fits in everything. Usually this works fine. Once in a while, an individual gun and ammo fit is a problem, which is what appears to be the case, here.

Also be aware that the regular calipers are fine for measuring to the nearest thousandth, but if you need accuracy to the nearest ten thousandth (0.000X) you need a different tool, for best results,
 
Take the decapper out of a full length sizing die and run the ammo through it.

And/or wrap some steel wool around a bore brush screw it into an old cleaning rod then attach that to a drill and polish the chamber.
 
Idigg,

I assume that the last dimension you gave has the last two digits transposed. But clearly from the marks, now that I can see them, there is a chamber issue. You could try Bluetopper's polishing approach, but in your shoes, I would want to look in there with a borescope to check for gouges and to drop some pin gauges in to find out if you simply have raised ridges from the chamber reamer having chips in its edges, or if you got a chamber made by a roughing reamer with the finishing reamer follow-up having been missed.

If you don't have the tools for those, I would email the maker and say your gun won't let some commercial ammo chamber, and here's what happens when I try, adding in that last photo with the scuff marks. They will likely ask you to send it to them to fix. Obviously, they should never have let it out of the factory that way.
 
first off. thanks everyone for the replies. i appreciate it.

I assume that the last dimension you gave has the last two digits transposed.
Click to expand...

oops, correct. i edited it. 0.454 wouldnt chamber.

Any chance you measured the rounds that DO fit and work??
Click to expand...

i did, but no photos. 0.451-0.452 was what the other ammo was.

so to be honest, there is something else wrong with this barrel that i already wanted them to fix/make right. and it seems like the general consensus is that, while i can live with it, it is within reason for me to want it fixed. the other thing is nitpicky, and, while it's nitpicky, i spent over $450 on a custom barrel... i want it the way i want it. (damnit, lol)

my thoughts are basically that its a 16" 44mag barrel. its not a free floated 26" creedmore bench gun. i dont need to worry about 1/10th moa and having a super tight chamber to maximize accuracy. its a utility rifle, meant to be light, compact for dragging through the woods to shoot deer. id much rather be confident that all ammo is going to fit in it.

it definitely sounds like it is something i could live with, and just avoid that ammo... but when it comes down to it.. if y'all think it is within reason to want it fixed, that's the route im going to go.

so... many thanks to all again. nice to have a community to have help from.
 
You can always live with it and just avoid the ammo that doesn't fit, but I see no harm in talking with the barrel maker, explaining what is going on, and seeing if they will fix it.

And, if possible, I recommend actually talking with their tech people over the phone. Emails are handy and relatively permanent records, but may be handled by office staff who might not be as technically competent as you desire.

And if there is something else about the barrel that you need fixed/desire changed, absolutely talk to the maker!
 
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