Strange marks on rim, rounds hard to chamber?

[mattri]

Having some trouble with a 7mm-08, will try to be brief.

New WW brass, weight sorted, trimmed and chamfered, loaded with a well under max load, fired. No problems at all.

Now lets say we take 50 fired cases, neck sized, trim, chamfer and clean. Headspace matches on all rounds, measurements from any point of the case all match up- nothing looks amiss. Sized rounds chamber easily, no stiff bolt or anything.

Except for a few. I don't have an actual count but lets say 4-5 empty cases will chamber "hard". It could be that it takes just a little more pressure than normal to close the bolt, or it can be very very stiff.

When examined the cases that chambered hard will have a dent on the rim, very narrow, and perpendicular to the case body, at a 45-60 degree angle that leaves a tiny bulge, or ridge on the front of the rim. Sorry I don't have a picture yet but imagine that the case were made of wax, and you took a needle and you tapped the side of the rim while slightly drawing it toward the case mouth.

My only guess is that the mark is made from the extractor but the dent is much more narrow than the extractor is wide and the extractor is clean, no signs of damage or debris. Also, there are tiny little brass shavings in the chamber sometimes after a hard extraction.

Thoughts?

 

[mattri]

 

[jonbearman]

Have you measured the od of the rim? It looks like the interference as it goes into the chamber and the extractor actually lets go when it chambers and the rim is slightly smaller and as it goes in it skids on the edge of the extractor.Measure and take an average of the case rim.What kind of rifle is it???One other note,how stiff is the extractor like its binding and wont slide over to actually pick up the cartridge.

 

[Tozguy]

Do the cases that chamber OK also have dents in the rim?

Important to know what rifle we are talking about, type of extractor and ejector. Do you feed from a magazine?

Re the brass shavings, have a close look at the cases with a magnifying glass to see where the case is being shaved.

 

[mattri]

Excellent replies thanks.

The rifle is a Savage PTA with a Criterion barrel.

Will re-measure rims today, don't remember the measurement off the top if my head.

Headspace is measured with a comparator type gauge so the neck/shoulder junction could be different I suppose. I neck size with a Lee collet die and then bump the shoulder with a body die.

Extractor moves freely on un-dented cases, and freely on cases that have the dent as long as it isn't lined up with the actual dent.

 

[bigedp51]

mattri

I'm assuming your Savage PTA doesn't have a magazine, are any of your action bedding screws sticking up inside the action?

If the screws are not sticking up inside the action, do the screw holes have any sharp edges that can grab brass?

 

[mattri]

Good catch, sholud have mentioned that I checked the inside of the chamber, no screws coming through, sharp edges or burrs.

One of the things that puzzles me is that 2 cases with identical measurements at the shoulder and along the body will chamber differently.

 

[Tozguy]

Mattri,

When you get two cases that measure the same but chamber differently, rotate each one 180 degrees then rechamber and see if you still get the same result. The only meaningful way to feel chambering ease is with a stripped bolt (no firing pin) as you already know.

Also, I would give priority to finding and correcting the cause of the dents in the case rim. Those are severe dents and are not doing any good at all.

 

[243winxb]

Extractor problem? Check the blind hole for a burr or replace parts. My guess. http://www.switchbarrel.com/Extractor.htm

 

[mattri]

I suspected the extractoor as well, took it apart, took the spring and ball out, everything looks ok.

 

[K22]

This the typical problem I've noticed at the range with an number of new Remington 700's and it's due to the extractor.

Since you have a Savage it may not be related to the extractor but I'd would look there first. Not familiar with the Savage extractor design but the fix for the Remys is to install a Sako style extractor.

 

[mattri]

Thanks for the reply. If it were an extractor problem wouldn't it show up on more cases?

 

[jrm850]

I would index some cases with a sharpy and cycle until you repeat the problem. The reason I say this is that there is a very slim chance that the dents are happening on the opposite side of the extractor. I've never seen it in a 308 length case before but I have seen it when trying to get 6brs and and a dasher to cycle through a Remington. The case is so short that when the neck clears the chamber the ejector cocks the case so far to the right that the rim clears the opposite boltface wall. When the bolt is retracted far enough for the shoulder to enter the raceway, the case neck is pushed towards the bolt axis causing the rim to re-enter the bolt face. Sometimes the base of the case slips out of the extractor just enough so that the opposite side of the case binds when trying to reenter. I doubt the geometry of the 7-08 will let this happen but it's easy enough to rule out.
good luck.

 

[mattri]

Thanks for the tip I'll check it out. Have some new brass on the way, going to start over with it and see how it goes.

 

[jonbearman]

I am not sure if all the extractors are the same in all savage rifles.Go to savage parts finder and enter your serial number and see what extractor it takes.Then go to brownells and see if it is the same.I am thinking now that the extractor may be out of spec and needs replacement along with the spring and detent ball which is a subject all its own.We usually use a 9/64th's detent ball for better extraction etc.They can be had at brownells by part#080-679-140.You get a bag of 20 for about 5.00.This is an upgrade I found out about on savage shooters.com which I suggest you join just for the help with making them quite reliable.Check the site out and you can see several faq's on the home page.

 

[mattri]

Swapped out the ejector, will post how it does. Thanks to all for the replies.

 

[treeman]

polish the tip of the plunger that holds the extractor in place and the hole on the extractor. it looks to me from your pics that it is sticking and not leting the extractor "slip" over the rim