SAAMI specs drawing for .22LR

Mike38 · July 31, 2016, 08:30 PM

If I'm reading this drawing from the SAAMI web site correctly, the rim thickness of a .22LR cartridge should be 0.043, plus 0.000 minus 0.007, and the head space relief in the breech face or bolt should be 0.043 to 0.051.

Am I reading this correctly?

Reason I ask is because I've had an email exchange with someone at Winchester inquiring as to what the rim thickness is on their XT22 target ammo. Their reply was that their ammo rim thickness meets SAAMI specs of 0.043 to 0.051. I went a bit deeper into the next email I sent, basically telling them they were wrong, and maybe that is the reason my target pistol is slam firing with there ammo, they are making the rims too thick. They stopped replying after I said that.

So who is correct, Winchester or me?

Drawing by SAAMI here >>>>> http://www.saami.org/PubResources/CC...20Sporting.pdf

NoSecondBest · July 31, 2016, 09:46 PM

First of all, what is your rim thickness? I wouldn't accuse them of causing a slam fire unless you knew your ammo was too thick. Second, you need to understand max material thickness. I think their answer would trump yours.

**Aguila Blanca** · July 31, 2016, 10:56 PM

Possibly you and the person at SAAMI were referring to different specs. You are correct that the drawing for the cartridge case calls for a rim thickness of .043" - .007" (.036 to .043"). However, the SAAMI drawing for the chamber uses the dimensions cited by the person from Winchester: .043" to .051".

My guess is that their response was intended to mean that their ammo is manufactured to function correctly in a chamber that's within SAAMI specs.

If you think their ammo is too thick, and you obviously have some -- what's the rim thickness? And are you certain that your pistol is within spec?

Mike38 · August 1, 2016, 06:42 AM

The Winchester XT22 ammo that I had measures on average 0.044 with one or two per box as high as 0.046.

The headspace relief cut in the bolt of my target pistol measures 0.0425 which would be a bit undersized, but does not slam fire with ammo of 0.044 or less.

Ammo such as RWS, Eley etc. measures around 0.041, which works great, but is a bit costly for a lot of practice.

Must have been a communication break down between myself and the person at Winchester. I bet you're correct, they meant to say their ammo would function safely in any chamber of 0.043 to 0.051

**Aguila Blanca** · August 1, 2016, 10:04 AM

Quote:

Originally Posted by Mike38

The Winchester XT22 ammo that I had measures on average 0.044 with one or two per box as high as 0.046.

The headspace relief cut in the bolt of my target pistol measures 0.0425 which would be a bit undersized, but does not slam fire with ammo of 0.044 or less.

Ammo such as RWS, Eley etc. measures around 0.041, which works great, but is a bit costly for a lot of practice.

Great. So your pistol is out of spec, AND the Winchester ammo is out of spec. Other than having your pistol machined for a headspace of .046" or .0465", I guess the only thing I can suggest is to not use that Winchester ammo.

Mike38 · August 1, 2016, 04:49 PM

Quote:

I guess the only thing I can suggest is to not use that Winchester ammo.

Yep, that's pretty much what I have to do. Federal is even worse on the slam fires.

Besides RWS and Eley, CCI Std Velocity works great, but I'm having a difficult time finding it.

Thanks for the replies!

SHR970 · August 1, 2016, 05:19 PM

What are you measuring your relief cut with and what is its stated accuracy? (Stated is NOT what the readout shows.. it is the documented inaccuracy of the instrument). If your instrument accuracy is only valid to +/- .001 reading to the fourth place is irrelevant. If for example you are using a Starrett that shows +/- .0001" I would believe the numbers as plausible. If you are using Harbor Freight Digitals....the number is HIGHLY suspect.

SHR970 · August 3, 2016, 09:22 PM

So Mike38.. no info on what you used to measure the rounds and bolt relief with? It is VERY relevant to figuring out what is going on here.

You might be right.. you might be misdirected.

If you wish to sort out why you have a slam fire situation all relevant information is needed.

Edited for: methodology is also important but we can get to that later.

Mike38 · August 3, 2016, 09:37 PM

Calipers, not Harbor Freight cheap-o's, but not a set a tool and die marker would own either. I used to work at a place that makes M4s for the military, and they passed there, but I don't think specs are super tight there. I think it would be safe to claim 0.0005 plus or minus.

My main point is clarifying SAAMIs drawing, which I think I've done. There was a mis interpretation in the email exchange, be it my fault or Winchester's, but someone messed up.

The pistol does not slam fire using high end target ammo such as Eley or RWS, which averages a rim thickness of 0.041. But when I try ammo with rim thickness of 0.043 - 0.044 I run into problems. I tried a box of Aguila sub sonic at $3.95 per box of 50. Ran flawlessly. Might just stick with that for inexpensive practice ammo.

SHR970 · August 3, 2016, 10:07 PM

I have a Brown & Sharpe Caliper (high quality and have been calbrated by a ANSI Z540.3 / ISO 17025 facilty). They are good to +/- .001". Your answer tells me that your measurements are suspect where tolerance is concerned. Your fourth place of precision is null and void. Had you used a Starrett Depth Guage (good to +/- .0005" we might have reasonable numbers to work with).

Your bolt relief may be on the tight side of conforming and the ammo in question may be on the wide side of conforming. The additive error could be the cause. And that is before we take into account methodolgy of measurement.

I'll bet your bolt is tight.; they will bet the ammo is "comforming".

You might want to talk to a machinist that is versed in doing spec work in the .0001" range. He might even true your bolt relief for you for a marginal cost.

**Aguila Blanca** · August 4, 2016, 07:00 AM

Quote:

Originally Posted by SHR970

I have a Brown & Sharpe Caliper (high quality and have been calbrated by a ANSI Z540.3 / ISO 17025 facilty). They are good to +/- .001". Your answer tells me that your measurements are suspect where tolerance is concerned. Your fourth place of precision is null and void. Had you used a Starrett Depth Guage (good to +/- .0005" we might have reasonable numbers to work with).

???

The SAAMI dimensions are given to three decimal places, and the OP's measurements are to three decimal places. What's this about a fourth decimal place? The ammo is clearly out of spec -- if the spec is a maximum rim thickness of .043 and his ammo measures ,044 to .046 -- even if his caliper is off by .001 the ammo is still out of spec.

SHR970 · August 4, 2016, 07:02 AM

Aguila: reread post 4. he clearly goes to 4 places.

**Aguila Blanca** · August 4, 2016, 04:48 PM

^^^ You're right. But he goes to four decimal places only for that one dimension, all others are to three places.

SHR970 · August 4, 2016, 05:42 PM

He also did not specify the stated accuracy of HIS instrument (see below). Is his a dial caliper or electronic? If dial, did he zero it? Is his caliper actually in tolerance? Goofing up the reading .001 to .002 is easy to do if you don't do it right. I'm not saying he did it wrong but he could have. His calipers may also be off...he didn't state the brand either. If they are made in China they are suspect. You can use a caliper as a depth gauge.. but a REAL depth gauge is more accurate; especially if you take readings in several places instead of just one.

Giving us a reading in 4 places even for that one measurement suggests he might be doing one or more things wrong in addition to that faulty significant figures measurement.

Quote:

I think it would be safe to claim 0.0005 plus or minus.

That means he doesn't know. Browns are QUALITY instruments and they are +/- .001 and mine have a pedigree with a certified calibration facility. If he has Starrett they would also be +/- .001. I am seeing enough that I can understand why Winchester is not entertaining the conversation.

Mike38 · August 5, 2016, 09:41 AM

I really didn't seek out a debate on the accuracy of my calipers, or the lack thereof. What I was looking for, and believe I've found, is whether or not I was reading the SAAMI drawing correctly.

All I know is, the relief cut of the bolt face for the headspace on my .22LR target pistol measures 0.0425 using my calipers. I also know that when using the same calipers, ammo that measures a rim thickness up to 0.043 does not slam fire in this pistol. Ammo that measures a rim thickness of 0.044 to 0.045 will occasionally slam fire. Ammo that measures a rim thickness of 0.046 will definitely slam fire.

Using the SAAMI drawing as a reference to how thick a .22LR rim should be, I believe my calipers are close enough to come to the conclusion that Winchester and Federal are making out of spec ammo. CCI, Agulia, Eley, and RWS make ammo with in specs. Thanks everyone for the replies.

July 31, 2016, 08:30 PM	#1
Mike38 Senior Member Join Date: December 28, 2009 Location: North Central Illinois Posts: 2,710	SAAMI specs drawing for .22LR If I'm reading this drawing from the SAAMI web site correctly, the rim thickness of a .22LR cartridge should be 0.043, plus 0.000 minus 0.007, and the head space relief in the breech face or bolt should be 0.043 to 0.051. Am I reading this correctly? Reason I ask is because I've had an email exchange with someone at Winchester inquiring as to what the rim thickness is on their XT22 target ammo. Their reply was that their ammo rim thickness meets SAAMI specs of 0.043 to 0.051. I went a bit deeper into the next email I sent, basically telling them they were wrong, and maybe that is the reason my target pistol is slam firing with there ammo, they are making the rims too thick. They stopped replying after I said that. So who is correct, Winchester or me? Drawing by SAAMI here >>>>> http://www.saami.org/PubResources/CC...20Sporting.pdf

July 31, 2016, 09:46 PM	#2
NoSecondBest Senior Member Join Date: December 7, 2009 Location: Western New York Posts: 2,736	First of all, what is your rim thickness? I wouldn't accuse them of causing a slam fire unless you knew your ammo was too thick. Second, you need to understand max material thickness. I think their answer would trump yours.

July 31, 2016, 10:56 PM	#3
Aguila Blanca Staff Join Date: September 25, 2008 Location: CONUS Posts: 18,473	Possibly you and the person at SAAMI were referring to different specs. You are correct that the drawing for the cartridge case calls for a rim thickness of .043" - .007" (.036 to .043"). However, the SAAMI drawing for the chamber uses the dimensions cited by the person from Winchester: .043" to .051". My guess is that their response was intended to mean that their ammo is manufactured to function correctly in a chamber that's within SAAMI specs. If you think their ammo is too thick, and you obviously have some -- what's the rim thickness? And are you certain that your pistol is within spec?

August 1, 2016, 06:42 AM	#4
Mike38 Senior Member Join Date: December 28, 2009 Location: North Central Illinois Posts: 2,710	The Winchester XT22 ammo that I had measures on average 0.044 with one or two per box as high as 0.046. The headspace relief cut in the bolt of my target pistol measures 0.0425 which would be a bit undersized, but does not slam fire with ammo of 0.044 or less. Ammo such as RWS, Eley etc. measures around 0.041, which works great, but is a bit costly for a lot of practice. Must have been a communication break down between myself and the person at Winchester. I bet you're correct, they meant to say their ammo would function safely in any chamber of 0.043 to 0.051

August 1, 2016, 05:19 PM	#7
SHR970 Senior Member Join Date: January 24, 2011 Posts: 1,427	What are you measuring your relief cut with and what is its stated accuracy? (Stated is NOT what the readout shows.. it is the documented inaccuracy of the instrument). If your instrument accuracy is only valid to +/- .001 reading to the fourth place is irrelevant. If for example you are using a Starrett that shows +/- .0001" I would believe the numbers as plausible. If you are using Harbor Freight Digitals....the number is HIGHLY suspect.

August 3, 2016, 09:22 PM	#8
SHR970 Senior Member Join Date: January 24, 2011 Posts: 1,427	So Mike38.. no info on what you used to measure the rounds and bolt relief with? It is VERY relevant to figuring out what is going on here. You might be right.. you might be misdirected. If you wish to sort out why you have a slam fire situation all relevant information is needed. Edited for: methodology is also important but we can get to that later.

August 3, 2016, 09:37 PM	#9
Mike38 Senior Member Join Date: December 28, 2009 Location: North Central Illinois Posts: 2,710	Calipers, not Harbor Freight cheap-o's, but not a set a tool and die marker would own either. I used to work at a place that makes M4s for the military, and they passed there, but I don't think specs are super tight there. I think it would be safe to claim 0.0005 plus or minus. My main point is clarifying SAAMIs drawing, which I think I've done. There was a mis interpretation in the email exchange, be it my fault or Winchester's, but someone messed up. The pistol does not slam fire using high end target ammo such as Eley or RWS, which averages a rim thickness of 0.041. But when I try ammo with rim thickness of 0.043 - 0.044 I run into problems. I tried a box of Aguila sub sonic at $3.95 per box of 50. Ran flawlessly. Might just stick with that for inexpensive practice ammo.

August 3, 2016, 10:07 PM	#10
SHR970 Senior Member Join Date: January 24, 2011 Posts: 1,427	I have a Brown & Sharpe Caliper (high quality and have been calbrated by a ANSI Z540.3 / ISO 17025 facilty). They are good to +/- .001". Your answer tells me that your measurements are suspect where tolerance is concerned. Your fourth place of precision is null and void. Had you used a Starrett Depth Guage (good to +/- .0005" we might have reasonable numbers to work with). Your bolt relief may be on the tight side of conforming and the ammo in question may be on the wide side of conforming. The additive error could be the cause. And that is before we take into account methodolgy of measurement. I'll bet your bolt is tight.; they will bet the ammo is "comforming". You might want to talk to a machinist that is versed in doing spec work in the .0001" range. He might even true your bolt relief for you for a marginal cost.

August 4, 2016, 07:02 AM	#12
SHR970 Senior Member Join Date: January 24, 2011 Posts: 1,427	Aguila: reread post 4. he clearly goes to 4 places.

August 4, 2016, 04:48 PM	#13
Aguila Blanca Staff Join Date: September 25, 2008 Location: CONUS Posts: 18,473	^^^ You're right. But he goes to four decimal places only for that one dimension, all others are to three places.

August 5, 2016, 09:41 AM	#15
Mike38 Senior Member Join Date: December 28, 2009 Location: North Central Illinois Posts: 2,710	I really didn't seek out a debate on the accuracy of my calipers, or the lack thereof. What I was looking for, and believe I've found, is whether or not I was reading the SAAMI drawing correctly. All I know is, the relief cut of the bolt face for the headspace on my .22LR target pistol measures 0.0425 using my calipers. I also know that when using the same calipers, ammo that measures a rim thickness up to 0.043 does not slam fire in this pistol. Ammo that measures a rim thickness of 0.044 to 0.045 will occasionally slam fire. Ammo that measures a rim thickness of 0.046 will definitely slam fire. Using the SAAMI drawing as a reference to how thick a .22LR rim should be, I believe my calipers are close enough to come to the conclusion that Winchester and Federal are making out of spec ammo. CCI, Agulia, Eley, and RWS make ammo with in specs. Thanks everyone for the replies.