I just finished building a 6.5cm with zermatt origin action/26" proof ss prefit. I loaded up a few 5 shot groups with H4350 (36.0gr/36.5gr/37.0gr/37.5gr) and hornady 140gr eld match in once fired hornady 6.5cm brass (There's only 20rds through the barrel before shooting these groups). The shoulder was bumped back 1 thou. I shot the first 3 charge weights but didn't continue bc I noticed that all the fired brass had a scuff looking ring around them (It's not raised up or at least not enough to feel super noticeable) and that's not to be confused with the darker ring below that near the base from the resizing die. Recommended max charge weight is 40.0gr and i stopped at 37.0. Other than the rings the brass looks fine. Primers look good. Anyone know what would cause this mark? Does it mean something bad is happening or dangerous?
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Rings marks on fired brass
- Thread starter JRBullock1987
- Start date
At first glance I would say a imprefection in the chamber is the cause.
- Nov 3, 2010
- 9,632
- 20,057
these primers almost look like they have set back. Are they proud from the bottom the case head or do they sit flush with the head?
Pressure shows at the .2 line this is far above that. this looks like it might be something in a chamber that is less than ideal but won't affect accuracy.
I would hand load a few very clean ones and see if this is actually occuring in chambering. if so call gunsmith but its an easy polish out if so
I would hand load a few very clean ones and see if this is actually occuring in chambering. if so call gunsmith but its an easy polish out if so
When I seated them I had a slight crush but they are now flush with the base. What does that mean?
And your loads of H4350 are kind of puny IMO. “Max loads” are IMO determined by lawyers. Not engineers or ballisticians.
Do you have a chronograph? I’d be looking for good groups in the 2750 and 2850 areas personally.
Do you have a chronograph? I’d be looking for good groups in the 2750 and 2850 areas personally.
Ok. So my prefit passed the go and didn't close on the no go. However my fired brass headspace is the exact same headspace as the go guage. So when bumping back my shoulder 1 thou it is under the go guage man. Would that make anything that's going on here or is that irrelevant? I dotnquite fully understand it but I feel like the go is the minimum correct? So I don't want a chamber that's max Headspace is at the minimum (go gauge headspace) right?
that has nothing to do with this - that brass isn't showing pressure. Does it mark a clean piece of brass when you handload it in.
But also - don't setback headspace on new brass, it comes short. Shoot it, then determine the headspace and set it back from there.
Lol I know its was just testing things out before I start working upm I did low on purpose. I've been reluctant to start doing load development bc I'm stuck on my prefit chamber dimension and I wanted to double check things were ok. My fired brass headspace is 1.534", which is the same at the go guage and it's got me all turned around.
This brass was once fired in my chamber. I used brass from factory ammo i zeroed my rifle with to test things out before i start using my alpha brass. . So my headspace was 1.534 furefirmed in my barrel. Which is the go gauge headspace eith my comparator. So they are the same
Haha. Ok. I get way to ocd about stuff and fixate. If the ring goes completely around the brass is that just a slight defect in the chamber? Is there a way to get that out of there?
you should shoot a few that are very clean and make sure to handload them and see if it still marks them. if so you should send pictures to manufacturer and ask them - it is highly unlikely to effect accuracy at all and is likely no problem as long as brass is extracting fine.
Also what are you supposed to use to clean your 6.5cm chamber? What size brush to fit in there to clean it?
https://www.boretech.com/ This has everything you need for cleaning, including caliber-specific rods, patches, jags, and brushes.
Cleaning is a highly debated topic, and I think most people will say you should clean every 200 rounds or so unless you see accuracy drop off before then (unlikely). Truth is you can do a lot more harm than good cleaning.
Ok. Extraction was just fine. No issues there. I'll have to load them singles and take a look
No. Only when I fire the brass. I don't have a way to look inside the chamber unfortunately
I'd guess there's some sort of mark in the chamber, it'd be nice to have a look at it with a scope, would give you a better idea if you'd be able to nock it out with a light polish
Eh....those BoreTech chamber brushes are really made for AR-15 and AR-10 semi-autos.
Me...with bolt guns....the only thing I'm really trying to clean in the chamber itself is a small amount of brass in the body area. I just take a bore mop, a bit of BoreTech Eliminator or C2 copper remover (and yes, Dorothy...I do like BT products), swab it around a bit in the chamber, and then dry it out with either another mop or a patch. The amount of copper I get out of the chamber isn't very much and seems to mostly come from Hornady crappy brass consistency. I've had some of their ELD-M ammo that I had to horse wrangle to get the bolt closed. Just shitty lot of ammo with the case body not sized properly.
Cheers
I was going to say that's around where my Giraud trimmer leaves a mark when you twist the case in the case holder
clean chamber with .40 or .45 jag with solvent, .50 nylon bristle, .40 or .45 jag with solvent
I use a 10" proshot rod w/ fixed handle
I use a 10" proshot rod w/ fixed handle
