.22 LR Case Dimensions

MCR,

.22 LR Case Dimensions:

0 Bullet Diameter: .223"
0 Neck Diameter: .224" [bullet in 'heel seated']
0 Base Diameter: .225"
0 Rim Diameter: .275"
0 Rim Thickness: .041" +/- 0.002" *
0 Case Length: .595" [includes rim thickness]
0 Cartridge Length: .975"
[ * Note: Rim Thickness added 1/7/03 ]

.22LR Chamber Dimensions

Type______Length__Mouth Dia._Throat Dia._Taper @ Throat
Sporting____0.7751"____0.2307"____0.2270"
Bentz______0.6900"____0.2270"____0.2255"_____1.5° Taper
Match _____0.6876"____0.2267"____0.2248"
Win 52-D___0.5800"____0.2278"____0.2248"_____2.0° Taper

The "Ruger" 10/22 factory chamber is the "Sporting" chamber above.
The "Bentz" chamber is the 'match' chamber for semi-autos.
The "Match" chamber is for bolt actions.
The "Win M52-D" is a bolt action target rifle.

.22 Long Rifle Headspace: .0425" GO // .045" NO-GO

There you go..............! !

.

 

You da Man Big Mike!
That's exactly what I needed. Thanks!
You wouldn't happen to have the rim thickness handy would you?


Mark

 

MCR, since this is a rimmed cartridge, the headspace is the rim thickness. The extreme allowable rim thickness variations are noted by Big Mike's "Go/No-Go" specifications.

 

Thank You MikeP

~

I thought that was obvious, so I didn't not note it in the table...! !

I guess the "obvious" to some isn't quite so obvious to others...

 

22 LR dimensions

Looking at the SAAMI prints, the case length for the 22 Long Rifle is given as a maximum of 0.613" (Sporting and Match). The chamber length given above includes the leade. Without the leade, the chamber length for a Sporting is 0.818" and 0.643" for the Match (both maximums). Rims are includes in these dimensions.

I keep wondering how anything chambers in the Winchester 52 given the chamber dimension listed.

Guy Neill
CCI-Speer Technical Services

 

.22 LR Case Dimensions

Guy Neill,

Well, many years ago I put about 200,000 + rounds of Remington Standard Velocity [#6122] through a M52C, and I never had a chambering problem...! !

Same with the Remington Rifle Match ammunition...! !

Yes, the M52C had a "tight" chamber....! !

Regarding the M52D length, in comparison with the other "match" chamber length, I am now wondering if the .5800" was a typo on the Site where I got the dimensions [Copy & Paste]...? ?
[ "Win 52-D___0.5800" " ] [ .6800" would be more realistic...! ! ]

Unfortunately, I did not annotate the source of the data...! !

Yes, the rifling did engrave on the major diameter of the bullet, if you were to extract and eject and unfired round, and this was apparent on any "alibi" rounds during a match. I never noticed any marks on the fired cases, indicating the brass was not hitting the end of the chamber...! !

 

"I thought that was obvious, so I didn't not note it in the table...! !

I guess the "obvious" to some isn't quite so obvious to others... "


Please forgive my unforgiveable ignorance.
Perhaps I failed to ask the question properly and to give enough backround as to why I asked.
Here's the thing, while measuring a number of different manufacturer's cases for (a) a CAD drawing I was doing and (b) for general future reference (nearly all measurements I took were within a .002" of eachother) I thought that it would be better to see if I could find the industry specs (the idealized dimensions).
Though I did take note of the headspace tolerances given by Big Mike, they don't really match any measurments I've taken of actual .22 LR cases. What I've measured varied between 0.040" and .0425 (aprox). None have exceeded this last number so far. Added to this was my assumption that an auto loading rifle bolt with headspace of .0425 (as with CPC) and a round with a case thickness much greater than that dimension would pose an unacceptable risk of slam fire.

So my question remains, is the SAAMI spec for a .22 case rim really from (>) .0425" to (<) .045" and what would the "ideal" thickness, if such exists, be?

BigMike, MikeP, I really DO appreciate the help but please don't mark me off as irreparably brain damaged just yet!

Mark

 

It was my suspicion that it might be 0.6800" instead of 0.5800", but I have no reference to confirm it. That would put it a bit tighter than the Match chamber (including the leade).

Guy Neill
CCI-Speer Technical Services
866-286-7436

 

More Data on .22LR

Hey Gents,
As I "think" I mentioned earlier I've been taking measurements from various .22 LR cases.
The information provided by BigMike is golden but the question I had about rim thickness still bothered me.
So, I've collected data from 40 different rounds of .22 LR in my collection (8 brands, 5 rounds each) and came up with the following information:

Winchester Dynapoint
High: 0.038"
Low: 0.037"
Av: 0.0378"

Dybamit Nobel R50
High:0.039
Low: 0.038
Av: 0.0383

Eley Subsonic HP
High/Low: 0.038
Av:0.038

Lapua Score Max
High:0.042
Low: 0.0385
Av: 0.0399

Wolf Match Target
High/Low: 0.038
Av: 0.038

Aguila Colibri
High:0.039
Low:0.038
Av: 0.0388

Federal Lightning
High:0.040
Low: 0.039
Av: 0.0395

CCI Velocitor
High:0.041
Low:0.040
Av: 0.0404

Aggregate Av: ~0.0388"

As can be seen by these numbers none of the measurements meet even the lower of the Head Space dimensions supplied to us by BigMike.
It IS possible that I mis-measured some of these case rims (all were unfired BTW) but I doubt if any given data point could be off by more than 0.001" which wouldn't throw off the conclusion.
What I infer from this is that the Head Space data is just that; which is to say information on proper Bolt dimensioning not case rim thickness.
Is there something I'm missing here?

Mark

 

.22 LR Cartridge Case Rim Thickness

MCR,

.22 Long Rifle Headspace: .0425" GO // .045" NO-GO

The 'operative' word here is space, not rim thickness. The "headspace" must provide space for the thickest [+ 3 sigma] .22 LR cartridge case rim that is allowed by the SAAMI standards...! !

This is the standard applied to the firearms industry by the SAAMI to assure that all .22 LR ammunition will safely chamber in all the rifles made to this standard. There is also a similar SAAMI standard for the .22 LR cartridge, which is dimensionally less, to assure that a + 3 sigma .22 LR round will safely chamber in the minimum headspaced chamber [.0425"]. Therefore, one may reasonably conclude that the maximum + 3 sigma .22 LR cartridge case rim thickness must be less than .0425", and that the mean .22 LR cartridge case rim thickness will be less than that by several thousandths, probably in the range of ~ .039 to .040"...! !

If one were so inclined, one could do a statistical calculation to determine what that number would be with a certain 'confidence limit' based upon the data you have taken; with a sample of only 40 rounds, the 'confidence limit' on the number obtained would be very, very low...! ! My 'guestimate', based upon some 30+ years in Quality Control in a precision manufacturing industry as an engineer, advanced engineer, and manager, is probably closer than you could calculate...! !

To obtain the exact SAAMI .22 LR cartridge case rim thickness dimensions [nominal, min., and max.], you would have to contact the SAAMI directly and request the information. Note: it may not be provided to you, as the SAAMI is a membership type organization.

SAAMI < < Link

Hope this helps...! !

.

 

Mark, I assume that all rimfire cartridges should have rims that measure a bit less, and certainly not more, than the minimum headspace dimensions called for in the specifications for manufacturers' tolerance ranges. Otherwise, a bolt action may not close on the cartridge, and an automatic may slam-fire upon trying to close, or not fire at all.

I would assume that, all things else being equal, it is better to have a cartridge's rim dimensions close to a particular gun's headspace for best accuracy. On average, target-grade ammo will be more consistent than other types in all aspects, including rim dimensions, from round to round. Competition shooters search very hard to find the most accurate cartridge for their guns, and I would assume one of the determining factors is how compatible a gun's headspace is compared with the cartridge's rim dimension. Some shooters are constantly looking for the most accurate ammo for their guns, even searching for the most accurate production-run lots of their most accurate ammo. Some have their guns' headspace adjusted if it is on the larger size of the allowable specifications in the quest for maximum accuracy.

Best of luck with your project.

 

MikeP, BigMike, many thanks!

BigMike, your reply actually confirmed an assumption I made concerning the headspace numbers i.e: that the rim thickness needed to be less than the minimum headspace (my second question being about rim thickness) .
Excellent reply! BTW, your mention of statistical analysis for the rim thickness had me and my wife giggling. Sitting next to my lap top as I type here is the "Handbook of Satistical Analysis" used in one of my earlier jobs. The night before last we were trying to figure out how many samples I needed to come up with a reasonably accurate average rim thickness! You seeem to have read my mind (yeah, its an open book! )

Again thanks guys!

Mark

 

Excellent Reference

Suggestion: Post the dimensions and headspace data as a 'Stickey' so it's avilable without using the search feature.
Useful....... Thanks for posting

 

Is A Sticky

Ziplok,

It is already in a STICKY at the top of this Forum, entitled:
".22 Ammunition Reference Section"......! !

 

last post on this one

Hey Jents,
I just got an email back from Coy Getman at CCI.
According to his drawings the rim thickness for a .22 LR case is:

0.041" +/- 0.002"

So, theoretically at least case rims can run anywhere from 0.039" to 0.043". Interestingly enough, this still runs somewhat thicker on average than what I'm measuring (now up to 75 cases on the way to 100). My average is still running at 0.0389" with a high of 0.0415" and the low of 0.037"

Again, thanks for all the help!

Mark