[Im2Tall2Play2!]

HI,
I have what might be a really stupid question. Is it true that the largest SAAMI cartridge will always fit in the smallest SAAMI chamber?
I was/am prepping some brass I bought. I was full length sizing to make sure all the brass would fit in all my guns. I have opened the SAAMI specs before and thought to myself, "well, what better a reference than the horse's mouth, SAAMI?" So, using my printed out copy of the .223 Remington and my brand new Hornady clip on the calipers head space checking device, I set the FL die to size .002" shorter than the max length for head space of the cartridge.
For reference, you can go to this link,
https://saami.wpengine.com/wp-conte...99.4-CFR-Approved-2015-12-14-Posting-Copy.pdf
Then page down to page 80 of the PDF file, or page 68 of the printed on the page numbers.
So, I set the headspace dimension to 1.464 (Actually .0026” less that max allowable cartridge dimension). Feeling all smug with myself, double checking my references, feeling quite self-assured that keeping to slightly less than the maximum dimensions on the print would completely assure me that said resized brass would fit in all my chambers.
A few thousand less sizing strokes later, I thought, “Hey, maybe just to be sure, I should try a few of these in one or more of my rifles chambers.” Uh Oh, closing the bolt on the first gun, the bold didn’t close well, in fact it just barely engaged the lugs, and on applying pressure felt as if it was resizing the brass. Not good.
Back to the specs. Head space is determined from the cartridge head or the bolt face to a BASIC (no tolerance) diameter of the shoulder, the .330 Basic diameter. For the cartridge, the length is shown as 1.4666” -.0070”. For the chamber, it is shown as 1.4636”/1.4736”. At maximum cartridge and minimum chamber this allows a .0030” crush of the cartridge. That doesn’t look right. I have always heard that the maximum cartridge should ALWAYS fit in a minimum chamber.
So, to double check, I dropped down to page 107 of the PDF, page 95 of the printed copy, the other of my favored cartridges, the .30-06. There the maximum cartridge is 2.0526”, the minimum chamber is” 2.0487”. An interference fit of .0039”. Ah HA! This doesn’t fit my preconceived notion either! The loosest fit would be 2.0587-(2.0526-.007) = .0131”. Humm… that seems a bit large but OK.
SO, is the takeaway here that at minimum chamber and maximum cartridge there is ALWAYS a crush or interference fit? That really doesn’t fit with what I thought was true/always thought I had heard! What should I aim for when I resize cases? Are the gas guns going to squish the cartridges enough to not fire out of battery? ARGH! This is giving me a head ache!
DAZED & CONFUSED IN GA!

 

[375Carp]

I have been reloading for 31 years. I never looked at SAAMI specs until year 29 or 30. I think the information that you will find in several reloading books and manual is much more applicable to reloading for specific rifles than SAAMI specs. Those specs are really designed manufacturers in my opinion.

 

[shooter444]

SAAMI who?

 

[JBelk]

Forget the suggestions by SAAMI. Deal with YOUR rifle.

First off, you don't know what's keeping the bolt from closing. HS is only one dimension. You have a die and you have a guage (chamber) you need nothing else to fit one to the other.

 

[ribbonstone]

Have the right idea of how it is suppose to work...max. to min. is supose to work and it generally does in commercally produced rifles/chambers/ammo.

But it doesn't always....SAAMI doesn't have the force of law.

Some chambers are cut to minimum. Reamers wear smaller with use. Ammo starts out small,but case forming dies wear larger with use. Keep them in use a bit too long,and can get miss-matches.

"Tight neck" chambers were (maybe still are) popular in some circles...headspace usually gets ther blame,but basically it's not enough neck expasnion with standard cases to give the bullet a clean release.

Some really bad match ups in militarty rifles.

 

[Im2Tall2Play2!]

Rifle I checked the three cases in is a Howa. Straight off the production line. I don't have a .223 GO gauge yet to check any of the rifles (on back order now 2 months). They all check OK with the NO_GO gauge. Yes Jack, I read your posts on GO gauges with tape is all that is needed. I would agree with your post above if I was planning to use the cases in one rifle. Perfect plan. However, this is more of a production line case prep session(s) intending to feed multiple rifles. And thousands of cases.

The FL die is a Redding, with carbide expander ball. It has done an OK job before when screwed down to the shell holder. I thought I would get trickier with this batch, try to do a better job of getting brass to fit everything.

OK, did a bit more checking tonight. The 3 cases I checked right out of the Redding Die measure 1.4640 to 1.4655, in spec., right at the target I intended, picked at random from the bucket of sized cases. The 3 cases I ran thru to Howa measure 1.4600 to 1.4605, they were sized down .004+ in the chamber. The PTG NO_GO gauges (I have 2) measure 1.4615 & 1.4635, that seems like a lot for gauge variance & actually measures less length than the cases in question measure. Did I push the cases farther into the chamber with the extractor? I'll check that tomorrow. I did note the cases I cycled were pulled out of the chamber by the extractor and ejected like I expected.

On a further note, I looked at the CIP drawing, which DOES have the force of law in Europe. They agree with the SAAMI drawings within a few hundred thousanths of a MM. Designed in crush of max case/min chamber.

All this leads me to believe that a max production case MIGHT have to be resized a few thousandths of a inch when first fired in a small production chamber. I'm not convinced that is great in a gas gun. Is that one of the reasons they added the forward assist to the M16?

I would be very interested in hearing on this from UncleNick and his ilk.

 

[tex ohfive]

I have been a handloader for almost 50 years ( since my mid teens ). Have never consulted SAAMI specs for reloading purposes in my life. I size rifle cases the absolute minimum amount to load reliably in my rifles. Don't know or care what SAAMI has to say about dimensions.

 

[MikeG]

Read what Jack wrote. At this point you don't know WHERE in the chamber things are hanging up. 'Paint' a case with a dry-erase marker, ease it in, then tap it out, and SEE.

Might well be 'squooshing' the sides of the case out when resizing. Brass has to go somewhere. Turn the sizing die down in VERY tiny increments, till problem solved.

If a bolt gun is 'sticky' on closing, then there's not much chance a forward assist on an AR will help. It has practically no leverage whatsoever, compared to the lever on a bolt.

 

[gwpercle]

Always use your guns chamber as the gauge .

Size them untill they will chamber.

It doesn't matter what you measure or what the book say the numbers should be.

They must chamber in your firearm .

People put too much faith in book numbers and measuring devices and are surprised when the numbers are wrong .

50+ years reloading have taught me ...don't trust chamber gauges or numbers ...see if they will chamber in your gun .

Gary

 

[recoil junky]

Yep, same here.

I have four *.223's FOUR OF THEM ! all bolt guns, all set up for ground dwelling rodents, each with its own load, brass and bullet seating depth.

Build your brass and load to your rifle, pay little or no attention to measurements. Well, maybe except "trim to" length, that's always good, or powder charge, but the rest is just for a comparison, not an absolute.

RJ

*not 556's, .223 Remingtons, two 788's, a 700VLS and an M 85 Sako. Four different rifles, four different chambers.

 

[gwpercle]

Yep, same here.

I have four *.223's FOUR OF THEM ! all bolt guns, all set up for ground dwelling rodents, each with its own load, brass and bullet seating depth.

Build your brass and load to your rifle, pay little or no attention to measurements. Well, maybe except "trim to" length, that's always good, or powder charge, but the rest is just for a comparison, not an absolute.

RJ

*not 556's, .223 Remingtons, two 788's, a 700VLS and an M 85 Sako. Four different rifles, four different chambers.

LIKE LIKE LIKE ....one like wasn't enough , you deserve three .
Well said !!!
Gary

 

[noylj]

SAAMI chamber dimension exceed SAAMI cartridge dimensions.
Sizing dies should take the case down to original dimensions and, in most cases, a bit below to cover cases with thin walls.
For all your chamber and cartridge dimension questions, go to:

Cartridge & Chamber Drawings – SAAMI

saami.org

 

[unclenick]

...Is it true that the largest SAAMI cartridge will always fit in the smallest SAAMI chamber?...

...So, to double check, I dropped down to page 107 of the PDF, page 95 of the printed copy, the other of my favored cartridges, the .30-06. There the maximum cartridge is 2.0526”, the minimum chamber is” 2.0487”. An interference fit of .0039”...

DAZED & CONFUSED IN GA!

The answer to your question is yes. The reason lies in what Jack said about headspace not being the only number. There are also critical diameters for which the maximum case is smaller than minimum chamber diameter. The diameter gap is critical as that allows the case to upset outward into the chamber when the bolt closing compresses it back 3.9 mils. You will feel that if you work the action slowly. But fast bolt work will get it done by inertia if the case is straight into the chamber. If it has to feed from a magazine, you may run into problems.

When you don't push a case fully into your resizing die, the sides may not get small enough, so your case head-to-shoulder datum may just make the upper limit with the sides still too wide. It depends on the die tolerances (usually about.0.002" on diameter) and how wide your chamber is, as that affects spring-back coming out of the die.

 

[dave_72]

.223 can sometimes be problematic for hand loaders. Cases stretch and need to be kept trimmed for length. If a case has been fired in one rifle on in a loose chamber machine gun(military brass) cases need to be full length resized. New cases need to be FL sized, and bullet depth measured carefully. .223 has a shorter throat than 5.56, so barrel makers use the wylde chamber to allow use of both types of ammo.

Don't overthink .223. Start with new cases for your particular rifle. FL size them, and load them. Firing them will fit them to your rifle chamber. You can either neck size them or FL size them, since they should fit your gun. Howa 1500s have good barrels with tight dimensions, so if your case necks are a bit thick, they might need turning. Winchester brass necks seem a bit thinner than some other brass, and Winchester brass is good quality too.

Start by FL sizing new cases and see what you've got.

 

[JDinFbg]

I agree with what most have suggested - load for YOUR rifle. And, that includes everything - case sizing, case length, bullet seating depth. It does not matter what SAAMI or the reloading manuals say. Your chamber is what you've got to fit, so work to that. For bolt rifles, the best way to determine how much to size brass is to strip the bolt so nothing hampers closing, then size the brass just to the point that the bolt will essentially drop closed when a case is chambered. You also need to determine your chamber length. You can buy tools to measure this or build your own fairly easily. This will tell you how long your cartridge can actually be. Case in point: I have a 94 Win in 30-30 and wondered if I really needed to trim cases when they exceeded the length specified in the reloading manuals. I built a tool to measure the actual chamber length and determined that my chamber would allow cases to be as long as 2.091". SAAMI says the max should be 2.039", and Lyman says to trim to 2.028". The result is that I will likely never need to trim brass for my rifle, and if I have to it will only be to just square up the end of the case mouth. The only caveat on total cartridge length is that you may find that the magazine/feeding mechanism may be more limiting on O.A.L. than what the chamber will allow based on allowing for a 0.020" bullet jump. But again, you have to load for YOUR rifle.

 

[unclenick]

...o, I set the headspace dimension to 1.464 (Actually .0026” less that max allowable cartridge dimension). Feeling all smug with myself, double checking my references, feeling quite self-assured that keeping to slightly less than the maximum dimensions on the print would completely assure me that said resized brass would fit in all my chambers...

I was typing on my tablet before, so I didn't provide a thorough explanation of the root of your problem, which is in how SAAMI dimensions things. While, as I said in the last post, a maximum cartridge can be chambered and fired, the fact remains it is a near thing. If you had taken a couple of boxes of different commercial ammo and measured the head-to-shoulder-datum on those new case, you would have found they mostly run around -0.002" to -0.003" below SAAMI's minimum chamber headspace, right about on the edge of their minimum tolerance. Going -0.002" below chamber headspace has been found to be acceptable for the full function and feeding of most any action when reloading, and with new cases with factory diameters, it is the manufacturer's way of preventing customer complaints.

So, what's the deal with SAAMI dimensions? SAAMI follows a standard engineering practice for handling critical dimensions. Most everyone is familiar with the common +/- tolerance used to get something within a size range. However, there are some situations where one end of the tolerance range is deemed critical. For example, if you made a shaft for a bearing that is out of tolerance on the small side of diameter, you make the machine it is part of run sloppily and the work won't last well. But if you make the shaft out of tolerance on the large side of diameter, you can't assemble the machine at all because it won't fit together, much less still run. So in that instance, the high diameter tolerance limit is considered critical as exceeding it completely prevents operation of the machine, while the low tolerance is important but not critical.

Faced with that situation, the standard engineering drawing practice is to give the diameter's critical maximum value as the diameter dimension, and the tolerance is then given as the range from that critical end to the minus direction. So if the critical value was 0.500" and the minimum value was 0.498", instead of a nominal dimension of 0.499"+/-0.001", the values are expressed as 0.500"-0.002". This is called a unilateral tolerance, as it has only one sign instead of both + and -, which run in both directions. This is exactly the type SAAMI cartridge dimensions are. If you make the case too large, the cartridge can't be chambered in a minimum chamber and made to shoot at all, whereas if it is a little too small, the gun will still load and shoot, albeit perhaps less reliably or less accurately.

So SAAMI is not expecting anyone would intentionally make a case with a maximum dimension. Indeed, as I described, to avoid chambering problems in dirty or worn or slightly out-of-spec guns, most manufacturers make their cases at the small end of the range.

SAAMI chamber dimensions have the same issue in reverse. There, if you make a dimension too small you prevent cartridge chambering and operation of the gun. So the critical dimensions for the chamber are the minimum dimensions. Thus, the chamber specs given are the critical minimums with unilateral + tolerances.

The bottom line here is that the given numbers are not the expected values in production, but warning flags to tell the manufacturer what they want to avoid getting too close to so none of their production runs over and becomes completely unusable.

 

[rojkoh]

SAAMI is an industry reference, not an enforced standard. Depending of rifle and chamber, they can be all over the place.

 

[unclenick]

Indeed, to take it further, no industry standards have legal enforceability unless government statutorily incorporates them into code or regulations. That has happened with a lot ANSI and ASTM building materials standards. The only exception I can think of is you can be prosecuted for making false or misleading claims if you say your product meets an industry standard that it does not.

From the OCST study, Voluntary Industry Standards and their Relationship to Government Programs:

"Specifically, development of a regulatory regime that integrates both regulations and voluntary standards is consistent with the underlying principles of Federal regulatory policy. Executive Order 12291 (February 17, 1981), for example, proscribes {forbids as harmful or unlawful} Federal standards covering private goods or services except where those are needlessly unsafe or product variations are wasteful, and private standards have failed to correct the problem."​

There are, of course, guns that don't meet SAAMI standards simply because the standards don't cover them, even if they once did. The reason is, meeting the pressure standards depends on using reference ammunition maintained by testing by multiple SAAMI member test facilities to find and track average results. Once a cartridge is dropped from the standard (the 357 Maximum, for example), reference loads are no longer maintained, without which there is no way to follow even the old SAAMI standard for it. New cartridges introduced by manufacturers but not yet submitted to SAAMI for standardization are another group that has no way to comply with a SAAMI standard.

 

[JBelk]

The first of the Civvy BARs showed American ammo makers they were getting sloppy on dimensions. I measured a BUNCH of new BARs that wouldn't chamber and shoot various domestic ammo. RCBS started selling Small Base dies as a result of the BAR (and some pumps and autos) Norma ammo headstamped Browning is smaller in body dimension than anything else around. By about 1972, FN had loosened up some or the ammo companies tightened up and the problem went away.
About the same time, a good friend had an FN/FAL that wrecked every case it fired and smoked like a steel mill from split case and leaked or pierced primers.
Dimensions matter, but MATCHING dimensions matters more.

 

[rojkoh]

The first of the Civvy BARs showed American ammo makers they were getting sloppy on dimensions. I measured a BUNCH of new BARs that wouldn't chamber and shoot various domestic ammo. RCBS started selling Small Base dies as a result of the BAR (and some pumps and autos) Norma ammo headstamped Browning is smaller in body dimension than anything else around. By about 1972, FN had loosened up some or the ammo companies tightened up and the problem went away.
About the same time, a good friend had an FN/FAL that wrecked every case it fired and smoked like a steel mill from split case and leaked or pierced primers.
Dimensions matter, but MATCHING dimensions matters more.

Small base dies over work the brass often leading to case separations.

SAAMI is reference, not an enforced standard. If you knew where to look, you'd find two different chamber reamers used in a company making multiple rifles in the same calibers.