New Rifle & Brass Question

[PhilM]

After some advice, to what may be a silly question, but I have not come across it before!

So my reloading experience has so far involved Tikka T3s in 223 and 308, reloading for both using Lapua Brass, and no problems on about 6 firings (223) and 10 (308).

After firing a case I deprime, throw them in the SS tumbler to clean and then I will check the length/chamber the empty cartridge to check it chambers well and doesn't have a stiff bolt.

usually this is all fine and I necksize using a collet die. If they don't chamber easily or are too long, I will full length size them and trim. Either way I then chamfer as required, prime, throw powder and seat the bullet. Never a problem.

So I bought a new AI AT with a 6.5 Creedmoor barrel. I have done some load development and have settled on one that is quite some way back from showing any pressure signs. Velocity and accuracy are good.

So my brass is new Lapua, small primer stuff. I have 100 cases once fired. During my normal reloading prep I deprimed and cleaned them, and then measured/chambered them.

Now the case length is fine, below the trim length - all good.

When I chamber the empty case however, there is no stiffness to the bolt closing, all good.

However I am seeing some 'swipe marks' on the base of the case, which is taking material off (can clearly see it's brighter than the rest of the case). I am assuming this is being caused by the ejector during the bolt opening/closing. It is causing slight material loss (tiny brass flakes on the bolt face).

This is concerning me somewhat, am I right to be worried?

The rifle now has about 100 rounds though is, maybe it's just a stuff ejector spring marking them? I am concerned it may be a headspace problem (too little?), but other observations don't tie up for that (and the 6.5CM barrel was checked with go/no go gauges when I picked it up at the same time as I bought the rifle).

I was hoping someone can give some advice anyway as I haven't come across this before in all my reloading for my previous rifles!

 

[mdmp5]

The marks you are seeing are round right? Those are ejector marks and signify some over pressure. If that is all you are seeing with no other signs, I wouldn't stress over it. Shouldn't have a headspace issue with a factory gun.

 

[PhilM]

Thanks for the reply.

They are not overpressure marks. I did get some during load development but then backed the charge way off.

The marks are not even there after cleaning. They only appear when I chamber a fired, but cleaned case to check the bolt shuts on it ok.

The mark isn't round. It looks like the ejector dragged around the 60degrees of bolt rotation.

My main concern is that it is removing brass in small amounts from the case base, and also those flakes are then sitting on my bolt face.

Maybe it's nothing to worry about - I think it's a little OCD I chamber the fired cases anyway after cleaning to judge whether they need a FL size or not.

 

[MtnCreek]

Any chance the brass shaving is from closing the bolt on brass that have protrusions from the ejector hole from overpressure on the previous firing? Try a piece that never had high pressure to see if it does the same.

 

[spife7980]

Got pics?

 

[PhilM]

I don't think it is from the protrusions of any brass that was exposed to higher pressure during load development - the marks are much wider than the area of the extractor during firing (the circle mark), it is also very uniform 'polishing' in appearance.

 

[spife7980]

Hmmm, not familiar with an AI bolt, can you easily remove the ejector like you can on a rem 700? If so chamber some clean sized cases and see if they still show up. If not install it back in and see if they are there then. That would pinpoint it as the ejector.

I agree that it isnt a pressure sign if it is only on clean sized cases. But it does have a radius to it on the ends like a ejector might leave so thats a good place to start looking to. Does it do it with a bullet seated? I can only think that maybe it goes in crooked without a bullet to guide the tip in and is jamming on the shoulder or something its jamming up on closing and forcing them against one another. But you say it chambers fine so that wouldnt be it. So nvm

 

[prcomte]

Could that be a mark from the where the extractor hits the back of the case when chambering? It almost looks like it has the same shape.


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[L.R.Novice]

The AI bolt has smooth robust locking and some mechanical advantage. You could have a stiff bolt indicating oversized brass and not realize it if you're aren't used to the AI.

If I understood you correctly, you are using the chamber to check fired brass. Try checking headspace with a gage and see if its long. Also try full length sizing the brass and see if it still leaves marks.

 

[shoot4fun]

Now, the AW/AX bolts are a Sako-style extractor with a spring loaded plunger-type ejector. It is possible your ejector spring is just a wee bit tight (it is a new rifle & not just new to you?) and that could cause the marks you see. If your primers appear to show no sign of flattening which leads one to believe you are not over pressure on the loads. My advice would be to forget the mark and move on. Nothing to worry about.
Now, let's address this chamber-check on fired brass you're doing.
When I first started loading 6.5 Creedmoor I called Hornady to see which of the comparators were to be used to measure case length to datum line. They said it fell between .375 and .400 so use either. I use the .375 but recently saw reamer prints showing the datum at .400.
Using the datum measured with the .375 (C) comparator I get 1.544" for virgin Lapua 6.5 Creed. In my new T3X TAC A1 I measure once fired Lapua brass at 1.548". These measurements are much more useful than "chamber-checking" fired brass. If you don't have the comparator set then get one. Check your fired brass against new brass for growth. Set your die up to bump the shoulder back 2 to 3 thousandths from the fired case measurement.