Short Chamber?

[The Old Salt]

Chamdered a reloaded 308 cartridge that measured 1.625" case head to Datum line, and had a hard bolt closing. Removed cartridge, marked the case shoulder with a majic marker and re-chambered. Another hard bolt close. Removed cartridge and sure enough, the majic markered case choulder showed signs of contact. SAAMI spec shows 1.630 min to 1.640 max chamber dimention. Mine seems to be a tad short. Does explain why I have reloads that don't chamber. This chamber is also tight above the ejector ring. 0.471" is tight. At the shoulder anything over 0.450 is very tight.
Will the Redding bushing dies fix all this?

 

[F. Guffey]

Will the Redding bushing dies fix all this?

When it comes to spending your money on a fix I'll bet there are many dies available.

But first, allow me to ask why you insist on sizing a case for a SAAMI chamber. You fired a case in your rifle then reloaded it. Now? It will not chamber without difficulty when closing the bolt.

I size cases for short chambers, WHY? When I cut a chamber I want to know the length of the chamber from the shoulder to the bolt face before I start, I want to know the length of the chamber while I am cutting the chamber. AND it comes in handy when I purchases a barrel or rifle that was chambered by someone that insist on short chambers and does not understand how threads function.

You fired a case, I will assume you were firing new factory ammo, if so you passed up a good opportunity to determine the length of ammo that will chamber in your rifle. You could have measured the distance from the shoulder to the case head, you could have measured the diameter of the case head above the extractor groove.

I believe other reloaders are going to insist you purchase a small base die. I have small base dies, I do not use the because they do not size the base of the case. It is the base of the die that is small not the base of the case. Then there is the shell holder, the deck height of the shell holder is .125" meaning the die can not size the base of the case.

I would suggest you use a feeler gage to raise the case head off of the shell holder, I would suggest you start with .005". The shim will increases the dies ability to shorten the length of the case and the shim will also increase the presses ability to overcome the cases ability to resist sizing.

I do not know what press you are using, it is possible your case is whipping your press and then there is your lube.

F. Guffey

 

[cw308]

What die's are you using now, are you F/L sizing. I also have a custom barrel, 308 cal.Rock Creek 5R M24 barrel, chamber is on the tight side. Tried the Redding S type bushing dies, went back to my old RCBS F/L die with the competition shell holders, worked best for me. Run out is .001. Set my cases from base to datum .001 case head space, I don't neck turn my brass, I also use the expander ball,I clean the necks & shoulder with 0000 steel wool. I bench shoot only. Your chamber must be kept clean, shooting with a high round count without cleaning will give hard bolt lifts & ejections. Customs have to be babied.

 

[overthere]

Fwiw, I have three 308 rifles and for all of them I get resistance on the bolt when they get to around 1.624. I just resize to 1.619 - 1.620.

 

[F. Guffey]

went back to my old RCBS F/L die with the competition shell holders,

If I had a tiny chamber and using a competition shell holder I would get my money back from the smith that cut the chamber or from Redding, if you are using Redding competition shell holders. The deck height on the Redding shell holders are on the plus side of 'ZERO' when the deck height of the shell holder is .125", to go on the negative side of .125" grind the top of the shell holder or bottom of the die. OR! get a feeler gage, nothing like measuring twice and cutting once.

F. Guffey

 

[Unclenick]

The Old Salt,

Are you measuring the case shoulder position with a Hornady LNL case comparator insert? If so, unless you calibrate the readings by comparison to a headspace gauge of known shoulder position value (use a good quality one), the comparator zeroed by closing the caliper jaws is typically going to give you a reading anywhere from about –0.004" to –0.010" shorter than the actual. This is because of the small radius at the mouth of the comparator's hole that protects it from dulling and from marking a case. The trick here is the name, "comparator". It will accurately compare two cases to find an accurate difference between them, or accurately compare a headspace gauge and a case to find an accurate difference between them. It will not make accurate absolute measurements, though. You need to use a headspace gauge as a reference to get such a number. Zero on the gauge. Measure the case. Add the difference to the headspace gauge length to get an absolute value.

The RCBS Precision Mic gets closer to an absolute measurement because its steel material needs a smaller radius, but it can still read a couple thousandths shorter than actual on a headspace gauge or a case, so the calibration to the headspace gauge is still needed for absolute measuring.

 

[The Old Salt]

Lets see I’ll try to address everything that was asked.
I am using RCBS FL dies and a Hornady comparator gauges. The comparator is attached to a Starrett No. 120A, 6” caliper. The other caliper I use for all measurements that don’t use the comparator gauge set is a Brown & Sharpe 599-579-4, also a 6”.
The info about the small radius at the mouth of the comparator insert makes since that it would impact the measurements. DA! It a comparator not a measurer! Got it!
Not trying to size to a SAAMI chamber, just trying to figure out what mine is.
Reloaded rds that don’t chamber weren’t fired in the custom barrel chamber. I might not have paid close enough attention to my FL die set up when reloading these rounds some years back. But above the ejector ring these cases are over 0.470+” and at the shoulder are 0.450+”. That’s why I asked if a Redding S Type small base bushing die might work.
Instead of using a feeler gauge under the case head, I have a ground down shell holder so I can just put the feeler gauge between the shell holder and the die when I set up the dies. Haven’t done this yet but I see it coming. I did run a couple cases through with the die set flush with the reduced shell holder. Shoulders got set back TOO much, but above the ejector ring did get reduced to 0.470” or slightly less. They did chamber but are too short at the shoulder.
The Redding S Type bushing die (on my wish list), used with my ground down shell holder, might allow me to shrink the base with the bushing removed and then FL size to get the shoulders set correctly. Lot of work to save brass that isn’t all that high quality to start with, but I am learning A LOT about the entire process and that is why I engaged you all with the question. Thanks to all for taking part in the dissuasion.
I have brass that was FL resized, then fired in this chamber, to use with my comparator. New brass will be tried next.
Reloaded cases that measure (w the comparator) 1.623” head to datum chamber just fine. Once you get to 1.624” or just a hair over, the case shoulder is rubbing the chamber shoulder.
Thanks for the heads up on need for clean chambers on a custom barrel. I have XXX rds since the last cleaning. Have just wiped the chamber with a dry patch and only when I have had rds pull apart in the chamber due to sticking during chambering. (Very Long C.O.L.s) No need to comment on my lack of cleaning. There are reasons for everything, but it sounds like I am at the point where it needs to happen.

Hope to get loaded up today and shoot tomorrow. Once again, thanks to everyone.

 

[PA-Joe]

I did run a couple cases through with the die set flush with the reduced shell holder. Shoulders got set back TOO much, but above the ejector ring did get reduced to 0.470” or slightly less. They did chamber but are too short at the shoulder.

Go back to your last setup with the reduced shell holder and screw the die out 1/4 turn and see if they will chamber and if the shoulder got longer. Keeping backing out 1/4 turn until it chambers correctly.

 

[F. Guffey]

Instead of using a feeler gauge under the case head, I have a ground down shell holder so I can just put the feeler gauge between the shell holder and the die when I set up the dies. Haven’t done this yet but I see it coming. I did run a couple cases through with the die set flush with the reduced shell holder. Shoulders got set back TOO much, but above the ejector ring did get reduced to 0.470” or slightly less. They did chamber but are too short at the shoulder.

The companion to the press (the feeler gage) is the humble tool of the modest releaser. The feeler gage can be used to size cases for short chambers, I can size cases for chambers that are .012" shorter from the shoulder to the case head than a go-gage length chamber. I can size cases that are .014" longer from the shoulder to the case head than a go-gage length chamber, and everything in between. That is 26 different case length when measured from the shoulder to the case head.

The sizing die is solid, meaning there are not many tools a reloader uses that can shorten the die from the top of the die to the bottom of the die. When the die is adjusted off the shell holder the top of the die raises above the press. If a reloader chooses to raise the die off the shell holder they can use a height gage or a dial caliper to measure the height of the die above the press.

Same for seating bullets, it is possible to make a transfer as in transferring the dimensions of the chamber to the seating die, the tuff part? Convincing them it can be done.

And as always there are Redding Competition shell holders. Problem, they only go one way. I have one set, 3 of the shell holders are off by .001" each. Not a problem, I paid $5.00 for the set, now all I have to do if find another set for the belted magnum cases. I then can add the 3 that are off by .001" each and then grind the other two to make up a completer set that covers everything from minimum length/full length size +.001 to +.010". OR! I can use the humble feeler gage.

With the feeler gage I can form 7.7 Japanese from 30/06 cases and a 308 W forming die.

F. Guffey

 

[mehavey]

Reloaded cases that measure (w the comparator) 1.623” head to datum chamber just fine.

Therein lies the secret. (And unless you have a full set of Forster/Clymer headspace gauges*)
therein also lies the comparator measure to use as your sizing baseline.

*Don't sell your chamber short yet (pun intended) unless/until a true headspace gauge says it's so.

 

[The Old Salt]

Today was range day! Are there any better days than Range Day?
But last night I cleaned her up, bore and chamber!
First rounds fired chambered easy but had extraction problems. The old CAVIN brass loads have an appointment with the impact bullet puller. They might work OK for milder loads, but only after some case work.

All my loads in LC brass did just fine. Only one or two stiff extracts. Everything else was just fine. I took measurements on all the brass before chambering and will again now that they are fired. I did measure above the ejector ring as I extracted them. Measurements were made aprox 0.060" above top of ring. most any case swelled was 0.001". FL die should take care of this. They are individually identifiable and I will track each case. Best group is in the 3/4" range at 200 yards. I am not a competitive shooter, so I'm proud to have it. All rds loaded 0.010" off rifling +/- 0.002". The micro die is also on the wish list!

When I get my problem children rounds pulled down I plan to put some of those great suggestions to work.

Once again, thanks to all.