When a gunsmith receives a new chamber reamer is it usually a requirement to hone the reamer down to match the tolerance of the supplied brass?

My gunsmith recently cut a chamber with a reamer that l supplied and ended up with a looser chamber than he likes. Relative to new unfired RWS brass it has about 7 thou slop at the base of the case and around 4 thou at the neck. Calibre is 9.3x64

Obviously, the rifle may still shoot fine and l don't want to blame anyone but l want to understand the conventions involved in ordering up a reamer and supplying it to a gunsmith.

Do people simply pick their brand of brass and specify a reamer to the exact dimensions of the case? Given that there will be a bit of run out (both on the reamer and the lathe) l would imagine there will naturally be a thou or so difference anyway.

I sure can't say what most do. I have had reamers cut to minimum clearance to the brass I was using. I've also tried different brands of brass until I got the tightest base fit.

My opinion is the reamers are cut closer to standard a lot of the brass on the market not so much.

You also so should consider the size of the resized brass produced by your reloading dies.
I think a lot of people like .003 clear at the base compared to the solid head of the brass.
The diameter at the shoulder has to accomodate factory ammo but you should checked resized cases too. Resized cases may be larger or smaller depending on the loading die. If necessary you might have to test several dies to find a fit you like or you may have to make your own sizer.

quote:

Originally posted by gk1:
When a gunsmith receives a new chamber reamer is it usually a requirement to hone the reamer down to match the tolerance of the supplied brass?

My gunsmith recently cut a chamber with a reamer that l supplied and ended up with a looser chamber than he likes. Relative to new unfired RWS brass it has about 7 thou slop at the base of the case and around 4 thou at the neck. Calibre is 9.3x64

Obviously, the rifle may still shoot fine and l don't want to blame anyone but l want to understand the conventions involved in ordering up a reamer and supplying it to a gunsmith.

Do people simply pick their brand of brass and specify a reamer to the exact dimensions of the case? Given that there will be a bit of run out (both on the reamer and the lathe) l would imagine there will naturally be a thou or so difference anyway.

Very hard (impossible) to hand hone a reamer and keep it true so most smiths do not. (and should not) Best to grind it at the factory where it was made. I have designed and had made, lots of reamers with tighter specs than SAAMI allows. Check the specs on both chambers and ammo; there is quite a bit of tolerance allowed between them from a min brass and a max chamber, so .007 is within spec. If you want a tight reamer to match your brass, you should order it that way. People usually do not specify the reamer diameter, sometimes they do.. SAAMI has already done the interface work for us (custom or match reamers are another story) You could have custom dies made to match your new chamber. now that you have a chamber bigger than you wanted. But do not blame your smith; he just the tooling YOU supplied.

SR4759,
What the dies do is the big question. I have a feeling my FLS will squeeze it down again. I was lucky enough to order Neck sizing die when l ordered mmy dies from CH-4D. There a not many die companies that do dies for the 9.3x64

I make my own sizing dies. I spec them .002 at the shoulder undersize and .003 undersize at the base. If you do not indicate your bore before chambering correctly your chamber will be larger at the base and the shoulder. I had rather spec and chamber my rifle chamber a little oversize and have my die reamer make my dies a couple thousandths smaller.

dpcd,
I'm definitely not wanting to blame the Gunsmith as l feel he was being very honest with me and a bit hard on himself. He also charged me about half of what he originally quoted me and has offered to re-size the reamer in his tool grinder (apparently a couple of hours work) if l want to get do another barrel in the future.

This was my first reamer that l have ordered and l suppose l'm a bit surprised that the specs allow for so much clearance.

Is there some reference that specifies the maximum allowed tolerances. I can only find info of min chamber and max cartridge.

I remeasured the clearance as headspace by placing packaging tape at the base of the case and l think it's closer to 0.005"

I think you are going to find that you will need the chamber specs that have been cut with this reamer to get the velocity that you desire for the 9.3x64 if the base and neck are any tighter you will be loading to 9.3x62 levels just so you can remove cases from the chamber. I'd be more concerned with the lead OD and length of the throat..004 at the neck is pretty tight. Before you have a floppy shoot the damn thing. I have been down this road with the 9.3x64

Thanks for all the replies, l feel a bit better about it now.

ButchL
I will use the neck sizer for now but a custom FL die will be on the cards. I don't have too many options on brass suppliers for this case, but l might also get lucky.

Darcy,
Could you please elaborate a bit on how having a bit more clearance will help achieve the higher performance? Will it help drop the pressure a bit? You are definitely right in telling me to fire it first.

George

George,
If I'm reading this correctly, the chamber is .007" LARGER in diameter than the brass you have. Correct?
If this is the case, then I have to bring this to your attention. Of all the chambers I have cut, most if not all standard reamers have cut around that much difference due to the brass running .003-.005" under what they are supposed to. Magnum belted brass, '06 based brass seem to be the worst offenders. This is why I tend to insist on match chambers. You must remember that the differences between min chamber and max brass can add up, especially with new reamers and undersize brass, .007" is not that much of a big deal and a standard FL die adjusted correctly to bump the shoulder .002" should size the case correctly just above the web.

In regard to tight chambers, it is sometimes not desirable because of function, for example I would not want a tight chamber on a DG rifle, even if it was only ever used with factory ammo, even factory ammo has been known to lock up a bolt for no other reason than a tight chamber and hot weather.

Cheers.

416RigbyMauser,
Yes, your interpretation is correct.
7thou difference at the base and 4thou at the neck when comparing the reamer to the new unfired rws brass.
It is re-assuring to hear that this is normal and even desirable for a big game rifle.
Thanks
George

George having you chamber cut as it is now will not enhance or degrade any accuracy potential for that particular cartridge in my humble opinion. You're not building a competition rifle. You may find that another brass manufacture's 9.3 cases will be larger on average than your RWS brass. If you want your cases to center the loaded rounds "better" in your chamber you could Neck Size your fired cases but I personally would not. I realize you want to build as accurate a rifle is as possible but a 9.3 is not a 6XC or 6PPC. With the variations of brass currently on the market I'd rather have a chamber that would except most anything than a custom tight spec chamber as you may arrive in Arusha and your "special match grade" ammo goes to Rome on a different connecting flight. At that point you are going to hope and pray to be able to roust up any ammo to use on your hunt and hope it will chamber. It is after all big game hunting rifle to be used out to 300 yards, at least I assume this is the case. In this case don't sweat the chamber specs.

gk1

CIP standard drawings are available on line,
If you cannot find them send me a PM. I can email a file directly to you.

It pays to study the drawings. You can compare the drawings to the brass and ammunition that is available. You can then plan your reamer and chamber around the brass and ammo.
One thing about starting with a smaller reamer.
It is always possible to polish a chamber a little larger if needed.

CIP Publishes the specs. It is as Dave Manson said, there can be a wide range between chamber max and brass min.

It seems to be that more and more often brass is found on the smaller side. Costs less to make I guess.

Cutting a chamber to match your brass is done often but has its own problems. It is wise to lay in a lifetime's worth of brass. If that brass runs out, other brass may not fit, especially factory loads. And what if your handloads ever get mislaid? Factory ammo may not work.

On a hunting rifle one has to wonder if the effort is worth it?

My 9,3x64 was chambered using a CIP minimum spec reamer. I use RWS brass. It will shoot MOA all day long. Plenty good enough for 300 yd or longer shots.

Like D'Arcy said, its a hunting rifle, not a match rifle.

I personally wouldn't try to resize a chamber by polishing it. To make it a thou larger will take,maybe, 320 paper and I doubt it would be round and concentric to the neck and throat.

Some people fret over the smallest things when life is short and it doesn't matter anyway. Don't lose any sleep over it; and next time you will know. You said you found the CIP chamber dimensions and the cartridge dimensions. Well, just do some math and you will see the possible clearances you can create. If you want to design a custom reamer from your brass, go to the PTG web site and you can make it any dimension you want. I do it all the time.