Trimming Rifle Rims

Status
Not open for further replies.
M

mineralman55

Member
Joined
Aug 13, 2009
Messages
64
Location
deep south
I've been doing a lot of case prep for 30-06 and .308 lately, and something I'm noticing is that a significant percentage of the military cases, both standard and especially national match, have rim diameters that are too large. The nominal diameter is 0.473". After resizing, about 8-10% of the case rims are too large in diameter to fit into a Wilson "go-no go" gauge.

Hand trimming the rims by Dremel is do-able, but not satisfying. Does anyone make a jig or fixture that can be used to set the rims to nominal diameter?

I've access to a lathe and mill, so suggestions would be welcome. I suppose I could buy another case gauge, cut off 0.100 inch from the rim end, insert a case, put it into a 3-jaw chuck and trim it, but that seems like overkill.
 
You are correct in your rim diameter being .473'' for both the 308 Win and the 30-06, but have never never heard of a rim becoming out of spec in either cartridge. I load for and shoot two M! Garands and SA M1A and use nothing but LC match cases or FA military cases and have never seen this situation before. Do these cases chamber after sizing ,and if they do, could your gauge be out of spec? I'm sorry that I can not be of further help.
 
I had a batch of military brass, mixed headstamp 5.56.
I was going through it and there was within this batch certain cases that looked like they came from China or the middle east. Primers, even though they had been crimped, were literally falling out!

When I tried to put EVERY SINGLE ONE of those cases into my #10 Shell Holder, none of them fit in, AT ALL! The cases' base rims were too high and I believe too wide. At first, I thought of filing them, but then I thought if they are this bad, I don't even want to run them through my AR.

I ended up tossing at least 100 of these cases, as they were definately NOT within 5.56 or .223 specifications!

It may be you have a bad batch from some cheapo place made by child labor in a sweat shop.

I've reloaded more than about 20,000 rounds and this is the very FIRST time I have ever had any kind of case base rim issues!

If I remember correctly, they had a symbol on them similar to the pi symbol in math.
 
"Do these cases chamber after sizing ,and if they do, could your gauge be out of spec?"

As an experiment, I took a file and carefully trimmed down the rim of several. They dropped right into the gauge, perfect fit. Calipers confirmed several rims were oversized.

These are Lake City national match, or just plain Lake City, not 3rd world junk.
 
I will assume you did not fire the cases in your rifle.


Had you measured before and after you would know when the case head rim expanded, I have test fired rifles with loads that were designed to expand the case head, open the flash hole and primer pocket with a dry chamber, heavy loads that are designed to be safe can expand the case head and rim if lube left on the case, a few years back there was an attempt to eliminate case stretch between the case head and case body, they lubed the cases, I referred to them as 'slide and glide' shooters, all of the thrust was absorbed by the locking lugs and case head, there was no getting through to them, they did not measure before and after, lube on a case is nothing new, the mistake was developed during WW1 by accident.

All comments welcome?

If you have access to equipment and or access to someone that does and that individual can hold tolerance have them to drill a hole through a block, plate etc. that is .373 in diameter. The hole will allow you to drive your cases through it and shear, swage or size the rim, some 30/06 cases are larger in diameter ahead of the rim and below the the case body that is not sized in a FL die, again the bottom .125 of the case is not sized because of the shell holder height of .125 from the deck to the top of the shell holder (I know there are many that SAY shell holders look different), if the deck height of the shell holder is not .125, get your money back.

Avoid sizing the head of the case above the rim, then there are small base dies? Dies that size cases like commercially sized cases and again the base of the case is not sized because of the shell holder deck height of .125.

30/06 cases with .373 diameter case bodies ahead of the rim, when 30/06 cases are formed to 7.7 Japanese and fired, the case expands and forms to the chamber, or when the chamber is worn or oversized.

F. Guffey
 
If they don't fit the proper caseholder or won't chamber in your rifle, you have a problem; otherwise no problem. I load a lot of M72 and M118 Match brass and have never had a problem. Of course, I use the RCBS Precision Mic to measure cartridge headspace and the rim doesn't come into play with that tool.

Don
 
If you want to turn the rims down, you might start with a wilson case holder for their trimmers. Both the neck and the head are exposed when the shell is in the holder.

You might be able to make a custom cutter that would turn them in the Wilson trimmer.

Andy
 
This seems like much ado about nothing!

Obviously, the GI 30-06 National Match cases worked just fine the first time, or they wouldn't be once fired National Match brass, now would they.

If they fit the bolt face of your rifle they are not too big.
And if they do fit the bolt face, and are a couple thousandths larger then .473", it would just insure more reliable extraction.

I have reloaded GI brass in every caliber they made since 1962, and have never seen a case with a too large rim that needed turning down.

If they won't fit your shell holder, it is too tight or has a bur in it, and needs polishing just a tad with a Dremel tool.

As for trimming rims to make them all exactly .473"?
Life's too short to sweat the very small, very unimportant stuff like that!

rc
 
"that is .373 in diameter" should have been .473, sorry about that.

Lost in the last three post is the curiosity as to why the rim is over .473, me? I would know or I would want to know, but I do more measuring than I do talking.

Back to access to equipment and close tolerance, the person that drills/cuts the hole in the block should cut a drift/driver that is .470 thousands in diameter with an alignment pin installed that would be .208 + or - very little, the pin will center the drift/driver in the primer pocket and the case will center in the hole of the swage block, or as suggested, do nothing.

F. Guffey
 
Lost even more, if the case jams up in the .473 hole the case head has expanded beyond .470, if the case head expands from .470 to .473 in one firing that is 6 times the recommended daily expansion of one firing when compared to the case head expansion of commercial ammo (.0005 thousands) then there are all the answers given for the warning signs of excessive pressure, so I am only trying to convince one person, mineralman55, a hole is a gage. I purchase them when I find them at gun shows (cheap) because no one knows what there are.

F. Guffey
 
Lost again is the purpose for having different brands of shell holders, for this stuff I like the older ones, today Lee is loose, then RCBS then the 'good old ones' even now the loose ones have a purpose and an advantage for those that know how to use them.

F. Guffey
 
Glad RC came along to answer this question...

Because I'm sitting here asking my self ... what the yell does rim diameter have to do with a round fitting a chamber ...

Like RC said it only has to fit the bolt and like Guff said a shell holder...

These dang gauges folks get their hands on cause more problems than they solve... most of the time...

The only gauge that counts is your CHAMBER...

Jimmy K
 
a hole is a gage. I purchase them when I find them at gun shows (cheap) because no one knows what there are.
Click to expand...

Could you describe it more or post a picture? I'd hate to walk past a cheap tool at the next fun show...

Justin
 
Jim Kirk, "The only gage that counts is your CHAMBER..." I could not agree with you more But when I say I take one measurement from the chamber and transfer it to the press and back to the chamber no one has a clue, some forum members are so commercially oriented the only answer allowed is purchase another tool, the original poster said he found 10 percent of his case would not fit a Wilson case gage, the Wilson case gage is not a chamber gage, the Wilson case gage has a lot of room inside, it measures from the head of the case to the shoulder and from the shoulder forward to the mouth of the case, it is a case length gage. If the rim of the case will not fit the gage I believe it is important to find out why. The original poster wanted to know a quick way to trim the rim, he said he has a working knowledge of lathes and mills and had the ability to operate the equipment, and he said ideals were welcome, I make no excuses, I gave him a very good plan, wasted on the choir, but I was not talking to the chair, just trying to tolerate them. I did not waste his time telling him the he was wasting his time.

Again if the case head expands .003 with the first firing the brass is too SOFT or the load is too high.

Hole gages: I was at the Dallas Market Hall Gun Show when I found a box of miscellaneous tools, I said "DATUMS!!", one shopper said "WHERE!" another said "I don't see one" and the Vendor ask "What does one look like?" I make tools out of nothing or something that already exist but that is not what reloaders on forums do or appreciate.

F, Guffey
 
The beauty of the case gauge is it will catch rim defects. You can put the case in the gauge upside down a little ways & sometimes fix a small burr. The 2 defects I have found to be most common are something hit the rim making a wide spot on the rim or the rim is not flat due to some hard extraction. Either can happen from landing on cement. When using One Shot on .223 I would get cases the were almost sticking & rims would get bent. Switching to real case lube made world of difference.

You can also put the high spot/bur to the open spot of the shell holder.

Once in a while I got a .223 that just won't resize and fit a case gauge. Less than 1 per thousand for sure.
 
fguffy, wntfw and other positive thinkers... thanks.

Okay, a couple of things. Why bother? How about because in this batch of brass I saved 25 otherwise fine 30-06 NM cases by cleaning up their rims which were several ten-thousandths oversized. But krochus you're right, we shouldn't trim, swage, size or clean our brass, just throw it out and buy new.

Second, safety in reloading is paramount, multiple inspections and QC levels of rifle cases is imperative. I've had a rifle blow up in my face due to poor reloads, and I will do everything possible to ensure that will never happen again. If a sized case doesn't drop into a go/no go gauge I want to know why. If there is an inexpensive and quick way to facilitate case prep I want to know. If not, I'll make a tool that will help.

Third, consistency in M1 ammo is everything. M1s will digest about anything. That's what they're designed to do. But they get better results with better ammo.

This thread has given me some ideas for tools. Thanks.
 
Rim Diameter to Large

Large rims can cause feeding problems in autos as the head slides up the bolt face. I have had it happen in 45 acp, a low pressure round, after many firings. No idea on the best way to turn a lot of rims. :confused: Lathe maybe? BoltFace.jpg
 
...in this batch of brass I saved 25 otherwise fine 30-06 NM cases by cleaning up their rims which were several ten-thousandths oversized.
Click to expand...

Do you even have a micrometer or calipers that measure to ten thousands (.0001")? If so, don't sweat that your rims measure .4735" or whatever.

If a sized case doesn't drop into a go/no go gauge I want to know why.
Click to expand...

Uh, you don't measure case dimensions with go and no-go gages. Those gages are for measuring chambers.

Don
 
That's exactly what a Wilson case gauge is for. Either the case fits, or it doesn't.

Okay, I should rephrase that. A case guage ensures a cartridge is below nominal size in all important dimensions. If it doesn't fit, something is not right and should be made so.
 
Last edited:
The Wilson case gage can me used to measure the effect the chamber had on it when it was fired, there is a minimum and minimum step to be used when sizing cases for the perfect chamber, I use a set-up table and or a straight edge with feeler gages to determine the length of the case from the head of the case to it's shoulder, sometimes the case is shorter than maximum and or longer, the feeler gage when used with the straight edge determines how much and where.

A chamber with .010 thousands head space will results in a .005 thousands + reading when checked in the Wilson case gage.

Again I transfer the reading on the feeler gage to the press.

F. Guffey
 
Follow Up to Rim size "problems"...

Okay, I did a bunch of investigating and measuring. Turns out it's not a rim size problem at all. In fact, after measuring 100 cartridge rims I find the rims are exceedingly precise in size, but undersized at 0.469" as opposed to the spec'ed 0.473". There was almost no variation at all. The 15-20% of the cases that weren't seating in the Wilson case gage were because of a single, tiny, almost invisible burr raised on the perimeter of the rim! A quick application of a file to the burr and "voila" (a little French lingo) a perfect case.

Okay, that problem is solved and many cases saved from the brass bucket. Now the problem is to find out why some 15-20% of the cases are getting a burr upon extraction.
 
The 15-20% of the cases that weren't seating in the Wilson case gage were because of a single, tiny, almost invisible burr raised on the perimeter of the rim! A quick application of a file to the burr and "voila" (a little French lingo) a perfect case.
Click to expand...

And that, is my same experience with ~5% of my .223 range pickup and Wilson Gauge.

Glad you figured it out and fixed it!

Justin
 
Status
Not open for further replies.

Similar threads

1KPerDay
  • Locked
Stupid question of the day: .223 rims won't enter case gauge?
Replies
11
Views
926
Certaindeaf
C
C
  • Locked
Trim to chamber length?
Replies
10
Views
810
ctrout
C
Twmaster
  • Locked
Yet another how to make 7.62 x 25 Tokarev brass.
Replies
10
Views
3K
Twmaster
Twmaster
B
  • Locked
Rifle case prep center?
Replies
24
Views
1K
BunnMan
B
chamokaneman
  • Locked
Overseat primers?
2
Replies
26
Views
2K
gifbohane
gifbohane
Back
Top