Tight Chamber #2

[JMUPT]

Ok so it looks like my last thread got deleted because it got a little off topic. So hopefully this one goes a little better.

For those that didn't see the previous thread, here's the short of the previous thread. A new to me rifle was hard to chamber new brass, factory ammo and full length sized brass. The brass was showing a shinny ring around the base of the case. The recommendations were to check the headspace as well as try a small base die. Well I ended up turning my FL sizing die down a little more and the brass chambered easier. I got my headspace gauge in today and took some measurements. This is where the last thread ended. The measurements that I came up with are

Factory ammo
1.7995"
1.800
1.800

Fired factory ammo
1.799"
1.7995
1.798

FL sized brass
1.799"
1.7985
1.799

So I assume that I need to size the brass a little more to give me .001-.003 headspace from what was said previously. Also I shot a few rounds out the rifle yesterday and I had 2 case that had a normal bolt lift until the last 1/3 of lift then it was extremely hard to lift and I had to take my palm and bump the bolt the rest of the way up. Pulling the bolt back to extract the case was normal. I put the case back in the chamber and it was the same way. The load was a mild load 52gr of Reloader 22 with 129gr Nolser long range accubond seated 15 thousandths off, according to the nosler book this should be a mild load. The case showed no other pressure signs. I color the shoulder area as well as the base of the case with a sharpie and chambered the case. It was even more difficult to chamber and some of the marker was rubbed off the base of the case, nothing at the shoulder. Another question then, is this caused by the lack of headspace or is it a whole different issue. Thanks for helping out again.

 

[jonbearman]

What cartridge are we discussing?

 

[JMUPT]

Sorry, that may help. 6.5X284

 

[bigedp51]

You were told to lap the shell holder .002 or .003 and see what happens.

If you are measuring your cartridge headspace correctly, you're saying the fired case is shorter than a new case????

Now measure the base of the case above the extractor groove on a new unfired case, the fired case and a resized case. This will give you more information on the ring around the base of the case.

The biggest complaint you see about headspace on rebarreled Savage rifles is from the headspace being set too tight and the resizing die failing to push the shoulder back far enough. And it sounded like your rifle has a custom barrel and you need to find out if it is chambered too close to minimum headspace.

Now study the drawing below, the highest probability is your not pushing the red dotted line back far enough to fit your chamber properly. And this is where lapping the shell holder comes into play and pushing the case further into the die and shorter than the red dotted line.

The second probability is the rear diameter of your chamber in relation to the base diameter of the case.

Your posting was deleted because fguffey wanted to argue about headspace and cartridge case headspace gauges and didn't like being told he was wrong. And the moderator could have just removed the objectionable posts and not the entire thread.

 

[mikecr]

This is where the small base die(excess near web sizing) never made any sense to me..
Your chamber is your best die, and firing is sizing while clearances are large enough for brass yielding.
So a small base die will cause brass yielding inward followed by firing in a chamber that will cause brass yielding outward. And you're going roundy roundy..

The cases that are causing popping extraction are in interference fit with your chamber. So when you re-chamber the web area is still in interference fit, which is holding the case shoulder away from chamber shoulder(holding the case back against the boltface).
Now you can size the ever lovin crap out of cases, and then they'll chamber well, but firing is just gonna undo it.

A while back I wanted to find out about this. I measured a bunch of WSSM cases and filled out a reamer print to provide 1thou total clearance, over new/unsized cases, at the webline/shoulder. Necks are turned to fitted 13thou thickness. This for a 6.5WSSM, and my intent was to see if a fully fitted improved cartridge ever needed sizing(ever, any kind of).
What I found is pretty much what I set out for -up to a certain pressure. For my cartridge that pressure ended up just over ~65Kpsi by QuickLoad. I settled on a node QL puts at ~64.4Kpsi(3025fps w/139Laps 28"barrel) with my lot of IMR4350.
Over 30 reloads later, and zero body or neck sizing, the cases remain exactly as I had formed. However, since I had set my shoulders at only 35deg, I do still have to bump to maintain ~1thou HS. This after 9 firings. My bump die is a JLC custom that does not do anything else.
Next reamer will take shoulders way higher in angle(~60deg), but no other change. I'm confident that will remove the last of any sizing need.
One prerequisite to this, is sufficient barrel steel around the chamber. I went with a BAT magnum diameter action to provide this.

How could this be? Everyone suggests FL sizing is inevitable..
It's because my cases don't yield on firing, but stay within spring back. There never was enough clearance to allow yielding, or resulting interference fit.
Now WSSM cases are actually WSM cases(cut short & formed), so this would work with WSM cases as well. It should be easy enough to get sufficient barrel steel around smaller cartridges, and case improvements and custom chambers have been done forever.

When I was young, shade tree mechanics thought more & more clearances were needed for racing engines. The truth was just opposite.

 

[bigedp51]

This is where the small base die(excess near web sizing) never made any sense to me..
Your chamber is your best die, and firing is sizing while clearances are large enough for brass yielding.
So a small base die will cause brass yielding inward followed by firing in a chamber that will cause brass yielding outward. And you're going roundy roundy..

mikecr

My full length RCBS small base .223/5.56 die only sizes the base of the case .0005 smaller in diameter than my standard RCBS .223/5.56 die and is perfect for my AR15 rifles. On the other hand my Lee full length .223 die sizes the base of the case over .0015 smaller in the base than my standard RCBS .223/5.56 die. Bottom line, we live in a plus and minus manufacturing world and no two dies and chambers are exactly alike.

Bottom line, a small base die brings the case back to minimum dimensions like the case was before it was fired. And semi-autos needs a loose fitting case on ejection.

The OP has bought a small base die and a cartridge case headspace gauge and just needs to bump the shoulder a little more.

JMUPT

Read the link below.

Gauging Success - Minimum Headspace and Maximum COL
http://www.brownells.com/.aspx/lid=11470/GunTechdetail/Gauging-Success-Minimum-Headspace-and-Maximum-COL

 

[Patch700]

Before you get carried away... Is this a 6.5x284 WIN or a 6.5x284 norma..

If your chamber was cut specifically for use with 284 winchester brass it will be smaller in the base area as compared to a norma chamber.

The two are not the same , lapua brass will be slightly larger in the base area.

If you try to size 6.5x284 lapua brass in a 284 winchester die you will see what im getting at.. Things will get tight about halfway through lol.

So it is possible you have a smaller chamber than your dies can accomodate...measure the base

 

[bigedp51]

Before you get carried away... Is this a 6.5x284 WIN or a 6.5x284 norma..

If your chamber was cut specifically for use with 284 winchester brass it will be smaller in the base area as compared to a norma chamber.

The two are not the same , lapua brass will be slightly larger in the base area.

If you try to size 6.5x284 lapua brass in a 284 winchester die you will see what im getting at.. Things will get tight about halfway through lol.

So it is possible you have a smaller chamber than your dies can accomodate...measure the base

American made brass is notorious for being on the small side in base diameter and European made brass is slightly larger in base diameter. Are you saying if the chamber was cut .002 to .005 smaller in diameter for Winchester brass he will need custom made dies? And yes Lapua brass is harder in the base and so is Lake City brass and therefore a little harder to full length resize, But I have never seen special dies made for European cartridge cases that are slight larger in diameter than American brass.

Also the OP bought the Redding Small Base Body Die 6.5mm-284 Norma (6.5mm-284 Winchester) so are you saying this die is also not going to work?
http://www.midwayusa.com/product/385430/redding-small-base-body-die-65mm-284-norma-65mm-284-winchester

In the OP original posting that was deleted he had photos of his cases and a ring around the case in the base area showing rub marks. And it appeared that the rub marks were high enough and well within the small base dies capability to reduce in diameter.

 

[CatShooter]

This is where the small base die(excess near web sizing) never made any sense to me..
Your chamber is your best die, and firing is sizing while clearances are large enough for brass yielding.
So a small base die will cause brass yielding inward followed by firing in a chamber that will cause brass yielding outward. And you're going roundy roundy..

So my chamber is my sizing die?? Cool. And I love the "Roundy roundy" thingie ;D ;D ;D ;D ;D

 

[mikecr]

Yes, your chamber is your best sizing die. It's your upsizing/forming die.
Just measure new, sloppy, high runout brass against the same but fire formed to see it.

I've used mostly 223, 6br, and 6.5wssm lately. Have not FL sized any of them, much less needed a small base die.
The 223 won't because it's relatively thick for area and has plenty of barrel steel around it. Cooper chamber.
The 6br was cut with my reamer, not as tight as the 6.5wssm, but tight neck & body by standards worried about here.
No trimming, no annealing, tight pockets, and the cases will last forever.

I suppose I could go for higher pressure nodes that would send me down the roundy roundy paths. But these guns shoot as good as they're ever going to right where they are. I'm pretty confident in my loads.
For anyone who wants to do this, just do a pressure test for the point where FL sizing will be required(I call it MyMax). Bring a blade mic to the range for measurement at the webline. As you go up in charges you'll see normal growth that will plateau as case springback clear of chamber springback. Keep going up in charge, and eventually you will see a clear step change(+.0005 from the plateau). Log it. Develop your load below that charge/pressure, with any somewhat modern cartridge(not a 30-06), and you will never need a small base die or pocket tightening schemes. Just manage your bumps, and neck sizing, so that you're not in excess with either, and your cases will last the rest of your life.
If you think MyMax/YourMax isn't high enough pressure, next time choose a cartridge with needed capacity and/or put more barrel steel around the chamber(larger tenon/finer thread pitch).

Hell just use Savage WSM actions & appropriate bolt heads for every cartridge!
They know what they're doing.
I know, too late..

 

[matorre]

.........
pffft

 

[Dusty Stevens]

.........
pffft

Is that how you revive an ancient thread?