Thread: Tight chamber and marks on projectile

Been loading my grendel for a while and it's been easy 1/2 moa working beautifully. Then all of a sudden tight chamber when closing bolt and tried a few rounds left scratch marks on them. and the scratch only happens on one side.
Unsurprisingly the few rounds I shot were flying everywhere.
COAL is 2.260, same recipe haven't changed a thing. So I'm really scratching my head wondering WTF happened?
I clean my rifle pretty diligently and I made damn sure there are no debris in the rifle.
Need some experienced lads to help me troubleshoot. Would appreciate any ideas aye.

Check for carbon ring/buildup in the neck/throat area

What's your load and velocity?

Greetings,
Looks as though the projectiles are seated too long. The marks are from the rifling. Either the adjustment on your die has moved or if you have just started a new box of projectiles then they are a different shape. This does happen from time to time and the seating depth needs to be adjusted to suit. If it is a compressed charge then your projectiles may have crept forward.
Regards Grandpamac.

As has already been said, carbon ring. Normal cleaning will not budge it in my experience.

Originally Posted by grandpamac

Greetings,
Looks as though the projectiles are seated too long. The marks are from the rifling. Either the adjustment on your die has moved or if you have just started a new box of projectiles then they are a different shape. This does happen from time to time and the seating depth needs to be adjusted to suit. If it is a compressed charge then your projectiles may have crept forward.
Regards Grandpamac.

grandpamac has identified the issue. The COAL is too long as pics 1 and 3 show rifling marks on the bullet. Looks like the bullets were pushed a fair way into the rifling when chambered. As gpm says when changing to a new pack of bullets, supposedly even the exact same profile and weight, there can be subtle changes that sometimes allows bullets contact the lands and you need to adjust the COAL to prevent jamming bullets. I have found this mostly happening with Hornady bullets. Other makes, not so much.
Another possibility ( recently discussed here on another thread ), but I don't think is the case here yet, is if you neck size only it eventually leads to case lengthening to the point that rounds become tight on chambering. You will then need to FL size the brass to return to easy chambering and a perfect chamber fit.
Finding bullet marking on only one side can be due to the extractor holding the bullet slightly off centre line as it's chambered, or due to a bolt face not perpendicular to the boreline causing the same thing. Or it may just be the chamber throat ( leade ) that is cut unevenly meaning one side of the bullet contact lands before the remaining surface. This is not uncommon in non custom rifles. But obviously your rifle shoots very nicely so no point in worrying about any of this. Get the COAL sorted as gpm says and you should be back to business as usual.

In your pics it appears that the neck isn't sized all the way down and the case shoulder looks rounded as though it hasn't been sized back.
Wind your sizing die in further to bump the shoulder back a little and I think the issues will go away.

Those projectiles definitely look to be jambing in the lands. As pointed out above.

Originally Posted by Dazzh

Those projectiles definitely look to be jambing in the lands. As pointed out above.

But only on one side? So shouldn't really be jammed in the lands. Maybe the case isn't concentric anymore or sized enough and pushing the bullet into one side of the bore?

Those scratches are also on the brass case mouth and appear to line up with those on the projectile, indicating maybe not the lands...

Can you confirm that the shoulders gets pushed back 4 thou?

How many times have these cases been sized and reloaded.

I do not think the projectile is seated out to far. I'd say the cases either does not get sized enough or the fact that you I dont see a champhering on the casemouth indicates that the cases gets deformed during bullet seating.

Hi team

Lots of great feedbacks and things I can check, kinda busy during week days so it might take me a few days to go through them all. Here are a few quick responses.

1. carbon ring, not sure if this one applies, I've cleaned quite regularly and this rifle has only shot about 200 rounds. but still, how would i check for these?
2. seated out too long, don't think this one applies either, I think I tested up to 2.275 and shot well with no issues, this was seated deeper already.
3. rifling mark, this was probably confusing for a few people, I forgot to mention that I pushed these rounds into the chamber a few times to test, so some of them have repeated/multiple marks, now i see that looks a lot of rifling marks
4. Load data, 123gr ELDM, 28.5gr 8208, CCI SR primers, around 2600fps, previously worked a treat. I deliberately used once fired hornady black cases so I assume they shouldn't be too deformed? But they were fired from this chamber so I could be wrong. Btw, factory ammo fired fine but lost accuracy as well, so frustrating.
5. Sizing for neck & shoulders. I use redding FL sizing, follow the rule to get die to touch shell holder then another quarter turn, not sure what more to do, also got myself some headspace gauge kit, will test to see if shoulders are bumped back properly.
6. concentricity, I suspected this, will try to borrow some gauge and test it.

Thanks a ton team! Fingers crossed I can get this to shoot again. It's been such a good rifle and got me most of my deers.

1) borescope. teslongs are good and affordable (129 bucks from a nz supplier) alternatively ask a friend or gunsmith.

At the same time check for marks in the chamber area where you see the marks on the bullet

Point 5 - That will be what Im suspecting is the issue.(You confirmemed my suspicion on this)

The age old thread it in till it touches the shell holder then.... does not always mean the die has been set up correctly.

Ive got a very good suspision that your FL sizing die aint pushing the shoulder back far enough.

Easy enough to test. Size a case and stick it in a case gauge - It will immediately show if the shoulders have been pushed back far enough.

1) my 6.5 develops a carbon ring after around 150 rounds.despite normal cleaning. You might be able to feel it running a dry loose patch slowly down from the muzzle and feel it snagging slightly down at the chamber end. Patch out with accelerator, bronze brush and a good scrub concentrating on the chamber end. Bore paste another good option, if it’s a carbon ring they can be stubborn, I’ve used a cordless drill on slow speed to good effect also.