Chamber Measurement Problem

[Velocity]

New Build and have only fired 2 rounds so far, just to get a couple of fired cases.
I purchased the Sinclair Bullet Seating Depth Tool to get some measurements of the chamber.

The problem is I can't get the fired brass back in the chamber even when pushing with my finger.
Everything I've read says use a fired case.

What about resizing with out the expander ball?

Will polishing the chamber help with this problem?

[Klem]

Velocity,

If the case came out of that chamber, it will go back in.

By the time cases extract the pressure has dropped and they do not expand any more. In fact they have shrunk slightly to aid extraction, which is what brass is designed to do - it's called 'springback'. For really hot loads it will be difficult to extract but if your cases extracted normally you can pick them up, wipe any dirt off and feed them straight back into the chamber.

Bolt gunners often use neck-sizing only which means the body doesn't get compressed, only the neck to hold the next bullet. With auto-loaders there is less compound leverage feeding rounds so you bump .003" min to guarantee the gun is reliable.

The only way what you are saying is possible is if the case changed shape after it was extracted.

[Velocity]

Hi Klem,

After shooting the round it does not eject the brass because I have the gas turned off. When I grab the charging handle to eject, it takes a very hard pull to get the brass out. When I try to put the case back in, it slides in then stops with about 5/16" to 3/8" of the head sticking out and it will only go back in when I put Bolt against it and slap the end of the BCG with the heal of my palm. I use the BCG to get the case in the chamber without the extractor installed so I can leave the case in while removing the BCG so I can use the Sinclair Bullet Seating Depth Tool to finish my measurement.

To remove the case afterwards I either use a dowel rod or the BCG with extractor installed. Is this problem happening because it's a new barrel?

2 Fired Cases
Neck O.D. .298
Case Length 1.533

[Klem]

Velocity,

That all sounds perfectly normal.

When you turn off the gas completely you will not get any primary unlocking so the case will be stiff to extract. You might have to palm the charge lever or even gently use your boot. If you want the gas to unseize the case but not extract then you can turn it on the lowest setting, say 1 (but not completely OFF).

Cases can change shape slightly if they are extracted with the usual violence. Necks can be dinged on the upper's deflector or hit the ground hard. But it sounds like you are babying them out of the gun.

You have to push hard or smack the BCG the final 1/8" because the extractor claw has to be forced over the rim against spring pressure, while the ejector is resisting all this as it is compressed - perfectly normal.

Not all the case sits in the chamber. The web and base is held by the bolt. Brass down the web and base is extra thick for this reason, so the case can withstand more of its pressure without needing the support of a chamber.

Your spent neck at .298 is fine. SAAMI spec for a Grendel neck is .300".

It all sounds fine.

[Velocity]

Klem,

I do baby the case, I eject it on a piece of carpet. I use a BCG minus the extractor to seat the case that sticks out about 3/8". I think the confusing part to me is when I watch videos where they say use a fired case from your gun as they slide their case right in the chamber with no tapping to seat it, it just slides right in and mine doesn't (hence ?). The barrel has only had 4 shots fired through it, case 1 and 2 then those case two cases are reloaded and fired again just to make sure they have done all their stretching, these are the cases I have been using.

What about a lite polishing of the chamber just in case there is some micro roughness which shouldn't be for a $365 barrel?

[Klem]

I wouldn't bother, unless you can't get it to eject at any gas setting. Obviously give it a good clean and it should wear in by itself..

[Velocity]

Klem,

Thanks for the help, I think I will just run about 75 - 100 rounds through it and then take some measurements. Just thought I'd get some measurements before the first 100.