Tight chamber.

[oso grande]

I have heard, that, if a bullet won't easily slide into the mouth of a fired, un-sized case, the chamber is too tight.
Any truth to this?
A dangerous situation?
OG

[Turo]

With the variation of case thickness, especially one that has been fired and not resized, I'd say it's a fairly inaccurate way to diagnose a problem with the gun.

[swifty]

Compare the chamber dimensions with SAAMI specs.

[oso grande]

Compare the chamber dimensions with SAAMI specs.

Gosh, I don't know how to measure the chamber.

[swifty]

A chamber cast would need to be poured then measured. Cerrosafe from Brownells is the common material to use, though sulfur works fine.

[chim-chim7]

Long tipped inside micrometer.

[bruceflinch]

Is the OP having an issue or just scratching an itch?

[rsrocket1]

Chamber that fired case. If it is a snug fit, take the measurements of that case. Is it too big?

[CSACANNONEER]

Is the case so long that it has grown past the chamber thus, pinching the case mouth closed? If so, that's why we trim or brass.

[huckberry668]

Let's think about this, the chamber cannot be tighter than the cartridge or it won't load.

1. Chamber is the entire barrel portion that actually contacts the cartridge. What you're describing is just the 'neck' portion.

2. The neck portion of the chamber should be at least .003"+ larger than the factory/loaded ammunication (bullet diameter + (2x neck thickness)). When fired, the brass will expand to .001"-.002" smaller than the actual chamber neck diameter. It actually first expand to seal the chamber as the bullet leaves the mouth then 'spring' back .001"-.002".

So if the original cartridge you're describing actually 'fired safely'. that means the neck portion of the chamber is less than .002" larger than the diameter of the loaded cartridge at the neck. That's too tight of a chamber neck for commercial ammo. I've only seen chambers like that on custom guns (mostly bench rest rifles) where the shooters 'turn' the necks of the brass to closely match the chamber neck.

3. I fired some military rounds out of my customed .336" neck (if I remember correctly) 308win match gun and had some difficulty sliding a bullet in the fired case mouth. but that's due to the heavily crimped mouth. once I trimmed off the crimped area the bullet slides in with no tension.

So, if I had a gun with a chamber as you described, I'd be careful with the choice of ammunition I shoot out of it. 'Pinching' of the bullet at the chamber neck or leade/throat can cause catastrophic failure (blow up) from high chamber pressure.