Tight Chamber

[MrGoodHammer]

Relatively new reloader seeking wisdom...

Here's the scenario...
Just purchased a Christensen Arms MPR, chambered in 6.5 Creedmoor.
I've ran 20 rounds of factory ammo as part of the barrel break-in process.
Collected that fire formed brass, and took some measurements for load dev.
After measuring head space and base to ogive, I mixed in some other once-fired brass of various head stamps, for de-capping, resizing, and cleaning.
I resized all this brass with a .002 shoulder bump, based on the head space measurement I took from the fire-formed brass.
Then ran all pieces through my Lyman case gauge.
Most of which, are kinda sloppy in the gauge.

This is where things get sticky.
SOME of the brass would not chamber far enough to close the bolt.
A few pieces that would chamber, were hard to extract.
On the pieces that would not chamber, I noticed some scrape marks just above the case head.
In measuring case diameter, just above the head, I found the pieces that measured .4680 would chamber, and extract.
.4685 would chamber, but difficult to extract.
.4690 would not chamber, and incurred scrape marks.
SO...this tells me my chamber is .0034 under SAAMI spec of .4714.

As a result, I drop my resizing die down for max cam over.
Now my shoulder bump is .005+, but the head diameter is now my desired .4680.
Lesser of two weevils I suppose.

Finally...my question...
What resizing die can I use that will give me the .4680 (or less) case head diameter, while maintaining my desired shoulder bump?
I currently have a set of Lee's and Hornady standard dies.
I've been told by one person, a RCBS MatchMaster FL resizing die should solve my problem.
I'm not opposed to ordering a custom die, but would rather not.

Which brings me to my next dilemma...
Since I don't yet have aspirations of PRS competitions, I try to save a few bucks and reload once-fired brass.
Some day I'll "bite the bullet", and drop a couple hundred on nice new Lapua brass, but not today.
This means, in a typical reloading session, my mixed brass isn't a consistent thickness at the neck walls.
Should I use a mandrel die, that should give consistent neck tension no matter neck wall thickness...
Or will a bushing style die, such as the RCBS MatchMaster give me better results?

Sorry for the long read, but wanted to give as accurate a picture as possible.
Thank you in advance for your input.

[FLIGHT762]

I had this same issue with a Styer SSG 69 in 308. .469"case webs wouldn't chamber. I tried two RCBS small base dies that i already had and they couldn't do it. I called Redding and was told their S/B body die would likely work. I bought the S/B body die and it worked perfectly, sized the web to .468". My issue was with brass that had been fired in other bolt guns and I was sizing them to use in the SSG 69.

I don't believe Redding makes a S/B body die in 6.5 C/M. Might have to custom order it. RCBS makes an AR set of S/B dies in 6.5 C/M, but I don't know if that will work for you. It didn't for me. I don't know if the RCBS Match Master dies would do it. You will have to call RCBS.

I don't think you're going to ruin your brass if you bump them -.005" from their fired length.

Are you using a comparator tool or a mic type like the RCBS precision mic or the whidden one to measure your base to shoulder length?

[pacrat]

Before you start forking over for custom dies. Do a bit more checking. Can you identify your fire formed cases. If so, they are likely the ones that chamber/extract OK with .002" bump.

As a result, I drop my resizing die down for max cam over.
Now my shoulder bump is .005+, but the head diameter is now my desired .4680.
Lesser of two weevils I suppose.

Since you now have cases that fit your chamber web diameter. Go ahead and load them. Then fireform them. They should be OK. And you can then go back to a .002" bump without further issue.

I currently have a set of Lee's and Hornady standard dies.

Have you already tried both? You didn't say. And first lesson of reloading is "NOT ALL HOLES ARE CREATED EQUAL". Something you have already discovered an example of, because you said;

Most of which, are kinda sloppy in the gauge.

Sloppy in the gage, but won't fit chamber. Means that the gage is just a useless piece of steel, with a hole in it, that you wasted money on. Which is why I don't use them.

This means, in a typical reloading session, my mixed brass isn't a consistent thickness at the neck walls.
Should I use a mandrel die, that should give consistent neck tension no matter neck wall thickness...
Or will a bushing style die, such as the RCBS MatchMaster give me better results?

Underlined response ........... "NECK TURN THEM". That makes them consistent thickness. And consistent neck tension.

[ar15barrels]

In measuring case diameter, just above the head, I found the pieces that measured .4680 would chamber, and extract.
.4685 would chamber, but difficult to extract.
.4690 would not chamber, and incurred scrape marks.
SO...this tells me my chamber is .0034 under SAAMI spec of .4714.

As a result, I drop my resizing die down for max cam over.
Now my shoulder bump is .005+, but the head diameter is now my desired .4680.
Lesser of two weevils I suppose.

The 0.4714" spec is derived from the 0.4703 cartridge maximum but since you can read a SAAMI print, you would also see that the cartridge minimums are 0.008" under maximum and it's common for makers to chamber guns well under maximum dimensions since factory ammo all comes much smaller than maximum.

Your issue is only related to re-loading brass that was fired in a larger chamber.
You would not have this issue with new brass or new ammo that was only fired in your tighter chamber.

The answer is to get new brass, not a die to try to re-size the oversized cases.
The expansion you are dealing with typically won't be fixed by most sizing dies because of the radius of the sizing die mouth not allowing sizing of that area of the case.

You could roll-size those cases or use a push-thru sizer to fix them for your gun and they should not be a problem after that.

[ar15barrels]

Sloppy in the gage, but won't fit chamber. Means that the gage is just a useless piece of steel, with a hole in it, that you wasted money on.

His gauge is NOT setup to gauge OD.
It's probably only setup to gauge shoulder length.

Some gauges are made that way so you can gauge FIRED cases.

[divingin]

I've ran 20 rounds of factory ammo as part of the barrel break-in process.
Collected that fire formed brass, and took some measurements for load dev.

It may take 2 or 3 firings to accurately form to your chamber. Check to see if the brass chambers easily after firing; it it does, you can't say it's actually "fireformed".

After measuring head space and base to ogive, I mixed in some other once-fired brass

I resized all this brass with a .002 shoulder bump, based on the head space measurement I took from the fire-formed brass.

SOME of the brass would not chamber far enough to close the bolt.
A few pieces that would chamber, were hard to extract.
On the pieces that would not chamber, I noticed some scrape marks just above the case head.

Second sentence: see the first bit of info. You likely didn't need the bump.

First sentence: I see a problem (albeit not uncommon.) Mixing brass is fine, though not ideal. Mixing brass from different chambers can be a PITA.

This does not show that you have a tight chamber; the other rifle may have a loose chamber, or may have yanked the brass from the chamber while under pressure.

As a result, I drop my resizing die down for max cam over.
Now my shoulder bump is .005+, but the head diameter is now my desired .4680.
Lesser of two weevils I suppose.

Lesser until your brass starts falling apart upon firing.

What resizing die can I use that will give me the .4680 (or less) case head diameter, while maintaining my desired shoulder bump?
I currently have a set of Lee's and Hornady standard dies.
I've been told by one person, a RCBS MatchMaster FL resizing die should solve my problem.

Small base full length sizer. Or a set of Redding dies (bushing neck sizer, plus a body die.)

I'll throw one other option into the mix: Run the brass through a 30-06 sizer set to fully contact the shell plate/holder. Base diameter is the same, but the shoulder is much further up. You'll hit the base of your 6CM case without moving the shoulder.

This means, in a typical reloading session, my mixed brass isn't a consistent thickness at the neck walls.
Should I use a mandrel die, that should give consistent neck tension no matter neck wall thickness...

Do you think that's different than a die with an expander ball? The primary difference is that the mandrel opens the neck up as the ram comes up, while the expander ball opens the neck as it's dragged up the die (ram downstroke.) But you end up with the same neck inside diameter with either
(assuming mandrel and expander are the same size.)

Or will a bushing style die, such as the RCBS MatchMaster give me better results?

Bushing dies only work the outside of the neck. Neck thickness between pieces of brass has to be uniform or you get different inside neck diameters.

[MrGoodHammer]

Thank you all so VERY much for the wisdom!
I think I now have a path to successful reloading for this rifle.

Are you using a comparator tool or a mic type like the RCBS precision mic or the whidden one to measure your base to shoulder length?

I'm using a Hornady head space, and bullet comparotors.
I may see if I can track down a Small Base die, and see what I get.

Have you already tried both? You didn't say.

Yes, in hopes the Lee die would give me a smaller web diameter, I tried both.
Same results.

Sloppy in the gage, but won't fit chamber. Means that the gage is just a useless piece of steel, with a hole in it, that you wasted money on. Which is why I don't use them.

I tend to agree for the most part, that since most mass produced case gauges are reamed to SAAMI spec, and many barrel chambers are under spec, they don't give an accurate picture of how the round will cycle.
BUT...I have gauges for many of the calibers I load, and they have saved me some headaches in a few instances. So, it's kind of a wash on their worthlessness.

The answer is to get new brass, not a die to try to re-size the oversized cases.
The expansion you are dealing with typically won't be fixed by most sizing dies because of the radius of the sizing die mouth not allowing sizing of that area of the case.

Yeah, this is probably the right way to go.
2 or 3 firings should give me truly fire-formed cases for my chamber.

Again, I sincerely appreciate your input.
I will probably report back in a few weeks as time allows me to shoot and load for this rifle.
Really looking forward to stretching this MPR out, and seeing what I can do with it.

[FLIGHT762]

I'm using a Hornady head space, and bullet comparotors.
I may see if I can track down a Small Base die, and see what I get.

If you have access to a 30/06 die, you can try what pacrat suggested to take a 30/06 sizing die and run your cases through it with the die set @ the shell holder with light cam over and see if that helps. 308 reloaders do that with some success. You won't hurt your brass.

Redding does make a 30/06 S/B die, but I don't know if that's a route you want to take with the brass that wasn't fired in your Rifle.

Bottom line is you need to segregate brass fired in your rifle from brass fired in someone else's C/M.

[pacrat]

Originally Posted by pacrat View Post
Sloppy in the gage, but won't fit chamber. Means that the gage is just a useless piece of steel, with a hole in it, that you wasted money on. Which is why I don't use them.

I tend to agree for the most part, that since most mass produced case gauges are reamed to SAAMI spec, and many barrel chambers are under spec, they don't give an accurate picture of how the round will cycle.
BUT...I have gauges for many of the calibers I load, and they have saved me some headaches in a few instances. So, it's kind of a wash on their worthlessness.

first bolded .... Yes they are. But as you have discovered and Randal explained. That factoid pretty much means nothing. The issue with making a quantified statement such as this. Is that it makes no room for the problem you are experiencing. There is this creature that lurks in all standardized manufacturing processes called "TOLERANCE STACKING". This creature rears its ugly head and bites many reloaders on the butt. And it is what you are experiencing. SAAMI specs are "GUIDELINES" and those guidelines have included, "acceptable tolerances" in dimensions.

second bolded .... OP, please remember that "NOT ALL HOLES ARE CREATED EQUAL". [aka as mentioned above "tolerance stacking"]. Until a case gage is PROVEN to match a firearm chamber. It is useless. The only way to confirm that proof is to BUY IT then TRY IT. It it doesn't match your chamber, it is useless, but OOPS too late you already bought it trusting it would be a viable tool. And it failed you.

In reality only two holes matter. [1st hole] is rifle chamber. And it is also, the only hole that truly matters.
[2nd hole] Is the sizing die. If it doesn't match the [1st] hole you have a problem.

Both holes can be within SAAMI spec, but still the problem exists. Because of that aforementioned creature. You can't resolve, or even diagnose the ACTUAL problem, by introducing a [3rd] hole into the mix. Which you have already shown to be true.

You diagnose the problem by chamber checking cases/ammo in [1st] hole. Since I already paid for and own [1st] hole. I don't go out and buy an unneeded [3rd] hole, and hope that it may prove useful in a "few instances".

FLIGHT762 said;

If you have access to a 30/06 die, you can try what pacrat suggested to take a 30/06 sizing die and run your cases through it with the die set @ the shell holder with light cam over and see if that helps. 308 reloaders do that with some success. You won't hurt your brass.

Actually that was member "divingin" that made that bolded suggestion. I can't definitively say if that would work. Without checking the math differences between 06 and Creed cases as to diameters and tapers.

As to the underlined. I definitely disagree with that. A 308 case is shorter than 06 and shares head dimension. But it is also fatter at the shoulder. And that would definitely SQUISH the case shoulder of a 308 case to be undersized in a given 308 chamber. Just as you can't take a 308 rifle barrel, and simply run an 06 reamer into it, to make it into an 06. You have to "set back" the barrel first. Or wind up with an "oversized ring" at the location of the previous 308 shoulder.

[fguffey]

Finally...my question...
What resizing die can I use that will give me the .4680 (or less) case head diameter, while maintaining my desired shoulder bump?
I currently have a set of Lee's and Hornady standard dies.
I've been told by one person, a RCBS MatchMaster FL resizing die should solve my problem.
I'm not opposed to ordering a custom die but would rather not.

You should not have any trouble finding help with things like case head space and .002" Bumping because; when they finish you will be no better off now than when you started.

When sizing a case, the head of the case is not sized. The case protrudes from the sizing die is .125" meaning none of the case head from the head of the case to .125" above the case head can be sized. And then someone should consider how much pressure is required to expand the case head. The case head is not supported by the chamber.

And then there is that thing about shoulder bump; it is impossible to move and or bump the shoulder back when using a die with full body support. The shoulder can only be moved forward. There is something about sizing a case reloasders do not understand. When sizing a case part of the case body becomes part of the shoulder and part of the shoulder becomes part of the neck and if a reloader keeps doing it enough the neck requires trimming.

Bumping is a function of the press, I have cam over presses, all of my cam over presses are bump presses; and I have non cam over presses, my non cam over presses do not bump. My cam over presses bump twice, the ram bumps the top of its travel and it bumps again on the way down.

Reloaders had trouble comprehending the concept of cam over 60 years ago and as reloaders are not doing any better today. I have 3 Rock Chuckers, none of them will cam over. Adjusting a die in a cam over press is different than adjusting a die in a non- cam over press.

F. Guffey

[jager56]

Something

[fguffey]

As to the underlined. I definitely disagree with that. A 308 case is shorter than 06 and shares head dimension

Pacrat, I form 308 cases from 30/06 cases, after forming I have to trim .479" from each 308 case. I would never form less than 100 cases when trimming that would be close to 46 inches of trimming, so the 308W is shorter than the 30/06 in length by .479" from the end of the neck to the case head.

I have two sets of 30/06 dies that are very small base dies. they keep ever case I have tried to size in the two sets of dies. I have some 'no-name case lube, there is no lube that comes close to being better, I do not use my no-name lube with these dies because reducing the case head diameter is a waste of a good case and the case has no purpose.

I have suggested reloaders place the case head into the open end of the die to determine if the open end of the die is too small in diameter or to determine if the cases have been fired with heavy loads, and there are other ways.

F. Guffey

[ar15barrels]

please remember that "NOT ALL HOLES ARE CREATED EQUAL". [aka as mentioned above "tolerance stacking"]. Until a case gage is PROVEN to match a firearm chamber. It is useless. The only way to confirm that proof is to BUY IT then TRY IT. It it doesn't match your chamber, it is useless

The best case gauge is one made by your gunsmith with the same reamer that chambered the barrel and using the piece of barrel blank that was cut off at the muzzle.
Now you have the same person using the same tool cutting the same barrel material.
You won't get a chamber gauge any more similar than that.

[fguffey]

Had a stuck case from using reloaded shell in bca barrel. Sold and replaced with a bull barrel and handled reloading cases nicely. Sometimes barrels need breaking in before using reload cases but depends on the brand. Also learned not to use once fired brass from another rifle. Should use the brass casings from specific rifle shooting out of.

Years ago I would go a firing range in Garland, Tx, there were times I went to the range to find brass. I wanted cases that were fired in ugly chambers. If there was a component manufacturer that sold cases to reloaders that knew what they were doing the practice of purchasing used/fired cases would not have been necessary. Knowing how to measure the length of a case and the distance from the shoulder/datum to the case head made it possible to size the case to fit the chamber if the reloader knew/understood how to measure the chamber. I know chamber casting is suppose to solve all the answer and of the questions; there are two reloaders that can cast a chamber in such a way as to get All of the answers.

One of the best tools available to a reloader is the Wilson case gage. Reloaders claimed the Wilson case gage was a drop-in gage, I do not know their motive except they always had their favorite tool.

F. Guffey

[mofo1111]

I had the similar issues with 2 different 6.5 Creedmoor barrels from 2 different quality manufacturers. The chambers were tight in both. I honed out the chambers very carefully with a honing brush from brush research manufacturing. BRM. They had to custom make one for me with a long shaft to use on a AR-10. I didn't want to take the barrel off. I only honed the chamber enough to leave a slight drag when hand extracting brass(I left the rest for break in and chamber erosion). Also check your factory ammo. After I honed the chamber, Winchester value pack ammo was failing to chamber. The ammo was out of spec. Winchester made good and sent me a voucher for more ammo purchase. When I used Hornady ammo, all ammo functioned without issues.

Maybe try the honing brush. But be very careful! You do not want to remove too much material from the chamber and make it sloppy. The honing removes tooling scars and reduces any drag. Good luck.