I'm having an issue with a custom Rem 700 in 300 RUM. The gun seems to have a very tight chamber. Fully resized cases (fired from another rifle) do not chamber. The body hangs up about 3/8" from the case head. I can't find any 300 brass or rounds locally.

Can someone measure the diameter of an unfired 300 RUM round about 3/8" from the case head? Thank you!

quote:

300 RUM.

did you get a set of custom dies? tight chambers I have had to take of .015 to.030" off the shell holder to get the die to go far enough to size the case. try a different shell holder if you have one.
base on mine measure .550 at about 1/4 to 3/8 iget .4495 using a micrometer.

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I have had to take of .015 to.030" off the shell holder to get the die to go far enough to size the case.

Yep, not all dies are compatible with all chambers. I have a couple of rifle/die combinations which require using a shellholder that has had the lips thinned to allow the case to enter the die further. Grinding a little off of the shellholder is easier than taking the same amount off of the much harder and more expensive sizing die and doesn't cost much to replace if you screw it up.

And not all shell holders are the same too either!

I find that the topic of tolerances within rifle chambers, reloading dies, brass, and ammo, is widely misunderstood, with regard to the allowable tolerances within the industry.
If you look at the SAAMI specs, which BTW, no maker is bound to follow (this is not Europe and you don't want it to be), it is a miracle that anything ever fits. Especially so in a custom chamber, and I admit I often cut them to absolute minimum, depending on how much I trust the owner to know how to reload.
Also, I Never alter a shell holder. I always alter the FL sizing die, and that die goes with the rifle, no matter where it goes. It is very easy and precise to machine off the amount required in your lathe with carbide tooling.
If you make a shell holder too thin, it will break off. And just grinding them is not the way to do it.

quote:

Originally posted by dpcd:
I find that the topic of tolerances within rifle chambers, reloading dies, brass, and ammo, is widely misunderstood, with regard to the allowable tolerances within the industry.
If you look at the SAAMI specs, which BTW, no maker is bound to follow (this is not Europe and you don't want it to be), it is a miracle that anything ever fits. Especially so in a custom chamber, and I admit I often cut them to absolute minimum, depending on how much I trust the owner to know how to reload.
Also, I Never alter a shell holder. I always alter the FL sizing die, and that die goes with the rifle, no matter where it goes. It is very easy and precise to machine off the amount required in your lathe with carbide tooling.
If you make a shell holder too thin, it will break off. And just grinding them is not the way to do it.

Altering the FL die or altering the shell holder achieves the same result. I don't know why you are so adverse to altering a shell holder. As I have posted before in response to you advising to alter the die and not the shell holder, not everyone has a lathe or access to a lathe. Yes you could send the die to someone who does have a lathe but then they need to have the rifle and some cases to hand to check they have removed enough from the die mouth.

Any competent reloader can shave off a shell holder top surface by hand with some wet and dry paper on a good flat surface, working away until they can size their cases to a good fit in their chamber. The shell holder can go with the rifle just as easily as the die can. Even when I did have access to a lathe, I altered the cheap shell holder not the die. Yes if you thin down the shell holder too much there maybe a danger of it letting go when resizing cases but it is going to take way more than just a few thou before that happens.

To quote what you often say dpcd, it's not rocket science, keep it simple - for those who only have access to simple tools

Someone brought a custom 338 Lapua Magnum rifle.

I have several dies, from different makers.

Non of them would load ammo that will fit in it.

I thought of trying a trick, by shaving off part of the shell holder!

Worked.

I then took several shell holders, from different makers.

And the difference in the thickness was quite significant.

Some of these holders are from makers no longer in existence.

I don't usually say it's not rocket science.
I say it's not Rocket Surgery.

Tx for all the replies. A go gauge enters the chamber, so I am a little reluctant to grind the shellholder or the dies as that might make resized cases too short. I tried 2 shellholders (including the one that came with the Lee dies) and there was no difference.

hivelsity- are those die dimensions or unfired case dimensions?

yes new Norma brass.
maybe this will help. There are really no two chambers the same, they may be from one end of the tolerance to the other. Like was said above it is not exact new reamers cut smaller than a worn or resharpened reamer. The head space gauge measures from a data line on the shoulder to face of the bolt
Who cut the chamber or were you just told it was a custom. Can you supply some case diminutions' and are the RUM cases? personally I have a box full of failed experiments. A few dollars for a modified shell holder would be the least of my worries. Do this pull the bolt check for a ridge or a rough surface at the mouth of the chamber. the chamber may need polished if there are burrs. blacken a case and chamber it see if there are any brass being shaved. Double check OAL of the brass against the SAAMI specification. let see what turns up.
Buy a good reloading manual like Lyman its hard to beat.

Nosler custom 0.546
Remington 0.545

But that's with a dial caliper "about 3/8" from the cartridge base" as I don't have a precision micrometer.

None of this means anything. Too many variables involved as I said above.
One question and test will tell all; will factory ammo fit into the chamber? Preferably more than one make of it.
I can make it work if you send the the rifle and the EXACT brass you want it to fit.
Not rocket surgery. Simple processes involved.

quote:

Originally posted by dpcd:
I don't usually say it's not rocket science.
I say it's not Rocket Surgery.

Noted correction

quote:

Originally posted by sjmci:
Tx for all the replies. A go gauge enters the chamber, so I am a little reluctant to grind the shellholder or the dies as that might make resized cases too short. I tried 2 shellholders (including the one that came with the Lee dies) and there was no difference.

hivelsity- are those die dimensions or unfired case dimensions?

With respect you have asked for help in trying to resolve the issue you are having in sizing fired cases from another rifle to fit your custom rifle but are reluctant to try anything suggested. If a go gauge fits your chamber then it is highly unlikely that there is anything wrong with your chamber.
Sizing cases fired in other rifles can be problematic especially if the other rifle chamber is oversized. The spring in presses and in the case brass can prevent a fit even when fully sized in a die. Sometimes it just needs a little extra sizing in a die which can be achieved as myself and most other posters here have indicated, skimming the shell holder the easiest.

Although your cases are hanging up in the chamber by 3/8" inch .0005" or a little more extra sizing of the case walls can make the difference between no go and go. That same .0005" setting the shoulder back is not going to make a dangerous situation.

I load for 4 different 7mm-08 rifles with the Rem 700 having a slightly tight chamber compared to the other three. I have had to skim the shell holder to size cases to fit that chamber but cases sized with the same die setting, a good hard bump of skimmed shell holder to die mouth, work perfectly in the other 3 rifles with long case life and loaded ammo fully interchangeable in all 4 rifles.

Nobody can help you if you are not prepared to take advice and try. Nothing attempted, nothing gained.

Yes of course we are all assuming factory cartridges fit, that is usually the first requisite to try when having reloading problems.

Right, that.
Here is a technique I use for sizing cases for tight ish chambers; Make sure your shell holder cams up HARD against the die. Don't use too much lube, and of course, not too little.
Run your case into the die two or three times; I all it "milking" the case into the die. Not just once.
Hard to explain but it does make a difference because I think it might make the brass size more.
Come over and I'll show you.

I had the same problem with a 264Win barrel. I just kept setting the die so that the brass was seated deeper into the sizing die until it would chamber.

Again tx to all who responded.

I tried what dpcd recommended: when resizing I fully seated the case 3 times rotating it 120 degrees each time. I also let the case sit in the die 10 seconds before withdrawing it, and also tried a different shellholder.

Nothing helped. Here is a picture of the resized case after trying to chamber it:


What I do find interesting is that cartridges/virgin brass measures .545-.546. That's a big difference from what my resized cases are measuring (.550). If that's correct why don't my Lee dies resize the brass down to those numbers?

Next step is to get some factory rounds or unfired brass.

Those numbers mean nothing without a reference, which is your chamber; how do you know it is the OD, and not the length?
Again, yes, try a factory round. And/or other dies.
I assume someone fired it before you? Or is the rifle new?
This is all an easy fix...don't fret.

You've lost me there a bit sjmci. From what you have said in your first post you have no other/virgin brass or rounds but you are now quoting measurements of .545-.546 for cartridges and virgin brass, where did this come from?

The base measurement for the 300 RUM cartridge is .550" which you say is what your resized cases measure.

Check the length of your resized cases and have a look at the mouth of a resized case after trying to chamber one. If the cases have stretched the mouth maybe being crimped when trying to chamber a case. Trying different shell holders is not necessarily going to work as the the shell holders maybe the same dimensions. Better to take one holder and shave down a thou to see if pushing the case further into the die is enough to solve the problem.

This might be a dumb question, but is the rifle a 338RUM? That would explain why a 300RUM case won't go in all the way...

If he is measuring 3/8" from the base of the case, and it measures .550", and the rifle closes on a go gauge, sounds to me like the dies are at the high end of tolerance and are a bit too large- the case does taper to 0.525 at the shoulder.

I suppose he could black the case and try and chamber it 4-5 times to wear the black off and see where it is contacting the chamber- but if a go gauge chambers, I doubt its the rifle that is the issue here.

A die can be out of spec. It happens. It could also be the brass is too long, as RUM's do stretch quite a bit in my experience.

If he can/has chambered factory ammo, it could also be a stacking of tolerances, but then the go gauge shouldn't close, should it?

quote:

Originally posted by crbutler:
If he is measuring 3/8" from the base of the case, and it measures .550", and the rifle closes on a go gauge, sounds to me like the dies are at the high end of tolerance and are a bit too large- the case does taper to 0.525 at the shoulder.

I suppose he could black the case and try and chamber it 4-5 times to wear the black off and see where it is contacting the chamber- but if a go gauge chambers, I doubt its the rifle that is the issue here.

A die can be out of spec. It happens. It could also be the brass is too long, as RUM's do stretch quite a bit in my experience.

If he can/has chambered factory ammo, it could also be a stacking of tolerances, but then the go gauge shouldn't close, should it?

I assumed his measurements were of the true base of the cartridge, trying to do comparative measurements of cases some distance down from the base is an exercise in futility.

I agree case length could be the issue and needs carefully investigating.

All of this discussion is an exercise in futility; no measurement in a vacuum tells anyone anything no matter where it is located. It is all relative to the mating components.
Spec? There is NO specification that is mandated, or checked, by anyone, in firearms in the US. And we don't want it to be. Mismatches are actually rare, and are usually due to operator error; yes, sometimes dies and chambers are incompatible. Rare.
I could determine the cause of this issue in 10 seconds. if I had the rifle and dies in my hands.
All this internet discussion is an excessive in futility. Someone else said that.

quote:

I don't usually say it's not rocket science.
I say it's not Rocket Surgery.

My mom use to say curiosity killed the cat, and If you dont stop im goin slap you a bug huntin.
Looking at the caSE in the picture there are a few bright spots and the neck does look strange? it will be hard to determine with out the correct information.
Wonder if the die is just a neck sizing die?

eagle27: The .545 number is from crbutler's post.

If correct then it looks like the sizing die is not doing it's job.

Looking around for some 300 RUM ammo. Nowhere to be found, and in NY you can't mail order it, so I'll keep looking.

Another question: I've always assumed that virgin brass is the same dimensions as a cartridge (if so I could try to get virgin brass). Am I correct?

quote:

Originally posted by sjmci:
eagle27: The .545 number is from crbutler's post.

If correct then it looks like the sizing die is not doing it's job.

Looking around for some 300 RUM ammo. Nowhere to be found, and in NY you can't mail order it, so I'll keep looking.

Another question: I've always assumed that virgin brass is the same dimensions as a cartridge (if so I could try to get virgin brass). Am I correct?

Virgin brass should be the same dimensions as a cartridge but the quality today is not always good so some reloaders run new brass through the resizing die before loading. I have done this on occasion with some lots of new brass where QC hasn't been good.

Plan B:

1 - Get a 300 RUM full length sizer

2 - Cut die off in back of shoulder. Not sure how far back, maybe start just in back of shoulder.

3 - Insert resized case then use a vise to push case further in.

4 - Repeat pushing in case additional 1/8" every time until case enters chamber.

Comments?

What???
OP, please come back on and tell us if a factory round fits.

If you can get a different die set, try resizing a case in that.

Cutting up the die to fiddle with it is pointless.

If you are convinced it’s the chamber, get some cerrosafe and make a casting of the chamber.

If you are convinced it’s the dies, getting a new die set should fix it.

The odds of a new die set being bad are pretty small.

Of course, getting a factory round answers as well, usually.

I agree I need to get a factory round, just haven't brought myself around to spending $80 for a box.

Ain’t that cheaper than a new FL sizing die?

If you want to fiddle with loaded rounds in a die, get a Lee factory crimp die. At least it is meant to have a loaded round go in.

Most likely you have a tolerance stacking issue.

A chamber on the minimum side and a die on the maximum side.

I've run into sizing issues with once fired brass from someone else's rifle if their chamber is Maximum (large) and mine is minimum (small).

Yes, you "should" be able to resize them with a FL sizer die but it doesn't always work out that well.

Find a 'smith or a seasoned reloader in your area to help you trouble-shoot. That's my only advice.

Zeke

quote:

Originally posted by sjmci:
I agree I need to get a factory round, just haven't brought myself around to spending $80 for a box.

Just spend 10 minutes of your time and sand down the top face of your shell holder. When I did that to a Lyman shell holder I sanded down until the Lyman imprint on the top face of the shell holder visibly lost some of its depth. Solved the problem of tight chambering cases in one of our 7mm-08's while not causing any issues with chambering the same cases in three other 7mm-08s.

I never advise anyone to alter anything until the actual problem is identified. Which, in this case, it has not been.
Everyone is just chasing solutions; no one really knows what the problem is.
Common among you humans to focus on COA before knowing what the problem really is.

quote:

Originally posted by dpcd:
I never advise anyone to alter anything until the actual problem is identified. Which, in this case, it has not been.
Everyone is just chasing solutions; no one really knows what the problem is.
Common among you humans to focus on COA before knowing what the problem really is.

You're not wrong but unfortunately with no factory ammo to hand the OP can't offer much else in terms of identifying the problem. Anyway, chamber casts, measuring cases, blackening cases, polishing chambers, polishing dies, blah blah blah, is not going to change anything.
For a simple no cost possible solution, one that many hand loaders have experience with i.e. shaving down shell holders to allow a case to go further into the FL die, is something that can be done in a few minutes. If it doesn't work then nothing lost.

I too don't usually advise anyone to alter something until the cause of the problem is identified but where something simple can be tried that very often solves a known issue, better to do something than nothing.
If all else fails I'm sure you can loan the OP a SMALL BASE resizing die which would solve his problem

It ain't the base. No one makes a small base 300 RUM die anyway.
I just hate to see guys thrash around like this and accomplish nothing.
I could determine the problem in ten seconds if I had the rifle and his dies.
I would correctly size a piece of brass for him, in my RCBS dies, but I can't find any 300 RUM brass in my shop. I had some....

quote:

Originally posted by dpcd:
It ain't the base. No one makes a small base 300 RUM die anyway.
I just hate to see guys thrash around like this and accomplish nothing.
I could determine the problem in ten seconds if I had the rifle and his dies.
I would correctly size a piece of brass for him, in my RCBS dies, but I can't find any 300 RUM brass in my shop. I had some....

Yes like you I'm sure a few of us here could solve the problem in short order but if we had the OP's rifle and dies but none of us have them so we can only make suggestions for the OP to try himself.
BTW my reference to a small base die was a play on your known dislike of them, for sure a SB die for 300 RUM would be rarer than the proverbial rocking horse shite

I usually try the lowest cost solutions first. So a used sizing die is about $25 on ebay, a lot less than a box of ammo. I admit I have a mental block about buying ammo since its so expensive and I have only once in my life bought any ammo for cartridges I reload.

I agree with Tom (DPCD) that I still don't know what the problem is.

BTW Lee has offered to look at the dies so I may just send them the sizer and case and see what they say.

Eagle; I knew what you were alluding too!
SJ; I don't blame you actually.

Update: Tx to DPCD who resized 4 of my cases using an RCBS sizer.

All chambered. 2 went in easily, 2 offered some resistance but chambered.

Sent one of them to Lee with another case sized with the Lee die plus the sizer. They sent it back saying that they removed .002 off the die. Tried the die and it was no better than before - you can't even get the bolt handle to start rotating.

So it appears that Lee dies are just oversize compared to an RCBS die.

Still trying to get some virgin brass to try, hard to find a single box.