10mm Auto throat specs? Barrel will take 1.393" OAL.

[Whistler]

I just got a 10mm Auto upper back from my gunsmith where he used a long throat .40 S&W reamer to make the chamber. From what I understand the .40 S&W reamers many gunsmiths use are made so that they can use 10mm Auto OAL to get better feeding in STI/SVI guns. He did this to my .40 and it works great. Then he used the same reamer for the longer 10mm Auto and there is no possible way I can get the long OAL needed for the 10mm chamber to fit in my mags. I made dummies to see how far out I'd have to seat to touch the lands and the cartridges came out 1.393" with 200 grain RF lead bullets sized .401.


Was this really the proper way to ream the 10mm chamber?
Is there a .40 S&W "normal" as well as a ".40 S&W long throat" reamer standard?
The short throat that my .40 had before he used this reamer is how I believe the spec for the 10mm is, of course with the added case length. Now we have a long throat 10mm chamber for a cartridge that still use the same OAL as the long throat .40.


As it is now I cannot get any decent accuracy out of the gun and I am willing to blame the long throat...

The GS has measured his reamer and the chamber and says it is within spec of CIP. I am having a hard time believing this since the bullet has a rough 0.118" freeflight before it engraves. At that point the bullet still has support from the case, so it should steer up OK, but this was not how I imagined a $1600 accuracy monster conversion upper.

And I have done all the usual tests.. Alloy, sizing, expander evaluation, soft load, hard load, fast powder, slow powder and bullets from 145gn to 210gn. It all yields about 10" groups at 50 yard, from which I expected about 1". As it is now, the 5" .40 S&W barrel for the same gun outperforms the 6" 10mm Auto.

What I'm asking for here is help to present hard facts that the GS made a barrel out of spec, rather than compromise fixes at the loading bench.

[Pinsnscrews]

According to the SAAMI Spec sheet; The chamber should be 1.322 (+.012)
http://www.saami.org/PubResources/CC...0Automatic.pdf

[Whistler]

Yes, both the GS and I have the specs sheets from SAAMI and CIP. He claims his reamer is within that spec and that the job done is within tolerance. I however, claim that there is no possible way that a chamber that can take 1.393" cartridges is within spec. Especially not with a bullet profile that engages the lands as early as a RF bullet!

Therefor I am looking for hard evidence on what OALs are possible on a verified within spec chamber. If someone with access to such a barrel could take a couple of bullets, drop one at a time into the chamber and measure the distance from the bullet base to the end of the barrel hood, that would give us something to compare with.

[FLYCUTTER]

I would do a chamber casting with Cero-safe. That will prove your point to the gunsmith. He might have to buy you a new barrel if he got careless and removed to much metal.