308 brass warp issue

[armymedic.2]

On the fourth reloading of my brass (.308 - 41.5 gr IMR4064 Standard primer pushing 178 amax) im starting to notice about 5% of rounds not chambering easily.

All friction is on the edge of the base of the brass, next to the primer where the headstamp is.

The bolt will close fine, just a little harder than it should.

What is the cause of this? i am no where near the max load.

Are these cases now discards or should i run them through again? Brass has be be giving somewhere

I use rcbs comp dies, which is a full length rezizing and micro seater.

Thanks for all replies.

 

[vman]

Re: 308 brass warp issue

Curious to see replies to this as I also get the same thing happening every now and then. Brass had also been trimmed to correct length

 

[MitchAlsup]

Re: 308 brass warp issue

I see the condition of your cases very similar to my cases. The area down near the web has expanded and needs a good push to make the web smaller in diameter. I happen to Neck Only size most of the time, and when my cases get to this point, I pull out the body die and compress the web.

Since you are already using a FL die, I wonder if it might be a little on the generous size near the web. Time to get out the micrometer and give it some measurements.

As far as using the cases, I would, but do inspect the web for thinning (paper clip trick). When the primer pockets loosen up, or any precursor to cracking; they are done.

 

[armymedic.2]

Re: 308 brass warp issue

these cases are micro-metered and trimmed to length. They are absolutley the right overall length, what i don't know is if they are warped somehow or what. It is disconcerting to think i will only get 3-4 reloads out of some of these cases. just don;t want to proceed until i know why it is happening............

 

[lanwickum]

Re: 308 brass warp issue

How do you setup your FL die in the press, what press are you using. I set my dies up to bottom on the shell holder with the hodler all the way up. Then 1/4 turn further.

 

[gcoulsey]

Re: 308 brass warp issue

Armymedic,
are you able to run your cases over a concentricity gage?
If you stand them up on a flat surface do they stand up looking crooked?

Or try rolling them on a flat surface (mirror) to see if the cases are banana warped..??

What brass are you using mate?

 

[oneshot onekill]

Re: 308 brass warp issue

It sounds like your cases are too tall at the shoulder. OAL can be fine but if the shoulders are not pushed enough when you size they can be tight. I had some wind up too tall at the shoulder by .015". You can check them with a Case Gauge. You just drop the sized shell in and if it sticks out the back at all it's too long at the shoulder. Should also let you know if it's warped because it won't fit all the way in. I would expect it to bind way short.

 

[JeffinTX]

Re: 308 brass warp issue

"On the fourth reloading of my brass (.308 - 41.5 gr IMR4064 Standard primer pushing 178 amax) im starting to notice about 5% of rounds not chambering easily.

All friction is on the edge of the base of the brass, next to the primer where the headstamp is.

The bolt will close fine, just a little harder than it should."

Trim length has nothing to do with the problem you're describing. You say that you are using a FL sizing die and I presume that you have it set up to bump the shoulders minimally, say .003" for reliable feed (and not set up to only neck size).

However, your description of the problem sounds like the base of the brass case is not adequately sized down. This is independent of overall trim length, neck sizing, or shoulder bumping during the sizing operation. You'll need to find another sizing die that will do size down the base. At least you're shooting a bolt gun, which has enough camming leverage to extract the case from the chamber. An autoloader may not be so kind and will have failure to extracts. Ask me how I know...Either way, another brand of dies (I went from Redding to Hornady in .223 to work in a CLE chamber) to get adequate resizing of the base. This is where the "smallbase dies" are sometimes needed.

 

[oneshot onekill]

Re: 308 brass warp issue

I still say it sounds like the shoulders aren't bumped back enough. I check every shell after I size/de-prime them and I always have variations in how they fit in the Case-Gauge based on how fast or slow, hard or soft I was with the arm of the press! Sometimes I have to run them through a second time with a little more authority so they fit the Case-Gauge properly. It's probably my press or dies that are just sloppy but I don't know...

 

[Grump]

Re: 308 brass warp issue

Read the whole thread and the OP identifies factors he believes to be correct so us Helpful Harry types won't waste his time guessing about things it's NOT.

Axial shifting of the casehead due to incomplete sizing of the case body just ahead of the web sounds like the most likely culprit. However, this can be imitated by burrs on the extractor rim which rub on the inside radius of the boltface's SIDE.

Long headspace (shoulder) on the ammo is unlikely to leave the marks the OP describes. However, I trust that he would have checked that by now. If not, armymedic.2, do that and return and report.

Both problems can be identified by dropping the cases backwards in a Wilson or other case gage. Give it a good twist and then look for the scrub marks.

Try double-resizing the cases, rotating them 180 degrees in the shellholder/shellplate between the first and second passes. Don't scrimp on the lube.

Burrs? I use a file. Unlikely with a bolt gun, but we gotta ask. I use a file laying flat on the bench.

 

[oneshot onekill]

Re: 308 brass warp issue

Ah... I thought he meant on the actual headstamp surface which I had because the bolt face was scratching it as I closed the bolt. My bad...

 

[armymedic.2]

Re: 308 brass warp issue

apologize lads, have not been able to check your theories as i am in the hospital with the wife a month and a half early for my son, trying to keep him in my woman. will report when i have a chance