223 trimmed case length

Lilswede1 · November 6, 2017, 04:48 PM

I am using the "worlds fastest trimmer" which fits on a drill.
Very fast but no matter how much I tinker with it I get a variation of 1.748" to 1.751" with the majority trimming to 1.750".
The trim is measured from the shoulder not from the base. When I measure a number of the fired cases with the Hornady Case Guage prior to trimming they all come out at 1.450" to 1.451". Very consistent.
Anyone else have the same problem?
I get kinda annal when reloading, consistency creates accuracy, is what I have read in here and I believe it.

Nick_C_S · November 6, 2017, 05:02 PM

Quote:

Anyone else have the same problem?

What's the problem?

I use the same trimmer for my .223. I have "set" it to 1.750" - or as close as I can get it. My final trim length is typically 1.749 to 1.753-ish. Four thousandths variation is plenty good for what we're doing here.

Time to move on and tackle the next problem.

condor bravo · November 6, 2017, 05:59 PM

Re Nick C S,
Likewise, trying to trim '06 brass to 2.484 with a Forster trimmer will drive you up the wall if you're thinking about getting that trim length every time. No problem if you are getting plus or minus .001 or so from the desired length. Don't measure every one after trimming in order to maintain your sanity.

Metal god · November 6, 2017, 07:49 PM

So .002 from head to datum and the trimmer .003 . ? You're only really seeing a variance of .001 that's pretty good and that difference is likely because the trimmer is indexing on a different point on the shoulder then the Hornady gauge . As Nick said time to move on to bigger and more important things

**Unclenick** · November 6, 2017, 10:20 PM

Lilswede1,

The shoulder is what the case headspaces on to stop the neck going forward. You want to measure from the head to the shoulder and then from the head to the ogive of your seated bullets and see how consistent the difference between those two numbers is. This will tell you how consistently your bullets will be spaced from the throat. Measuring from the head is done because it is easy, but it's not the best measurement.

hdwhit · November 7, 2017, 01:06 PM

I use a Forster case trimmer. I set it to trim 223 brass to 1.753.

The non-standard trim length is due to the fact that I know how much (on average) my loading stretches my brass and I know how many loadings I can count on before my brass is "lost in the weeds" and I know that if I trim to 1.753, the brass will be lost before it needs to be trimmed again and trimming to 1.753 rather than 1.750 saves a lot of turns on the old Forster crank.

My caliper reads to the nearest 1/1000 and has a fifth digit that reads "5" or gives no indication. Once the trimmer is set up, I only sample the trimmed cases to make sure of the adjustment (like condor bravo suggests) and my trimmed brass reads 1.753 with that extraneous "5" occasionally appearing, so I assume I'm within my target +/- 1/1000 inch.

My rule is that if the bullet has a cannelure, crimp into it. If it doesn't, then don't crimp. With no crimp any length between 1.750 and 1.760 is fine.

But keep in mind that if a crimp is not being used, the only thing holding the bullet in place is the friction between the bullet and the neck, so trimming below 1.750 starts to reduce how tightly the bullet is held - not much for each 1/1000, but it adds up - so if you are routinely ending up shorter than 1.750, it might be advisable to set the target length a little longer so that the bottom end of the range is still at or above minimum.

ShootistPRS · November 7, 2017, 08:05 PM

I have an old Lyman trimmer that I made a set of bushings for. I never have to make any adjustments. I just put the correct bushing on the shaft and start trimming. It trims off the base so all my cases are the same length. I use it to check the length of the cases too because it takes less time than reading a caliper after getting a good bite. I run all my cases through the trimmer whether they need trimming or not. The ones that trim needed it and the ones that don't trim I know are in spec. One of these days I will take a picture of my setup.

Mobuck · November 7, 2017, 08:31 PM

0.001 +/- in length isn't an issue as long as it's under the max case length.

cw308 · November 8, 2017, 11:07 AM

Lilswede1
Are you neck or full sizing your cases ?

Lilswede1 · November 8, 2017, 11:16 AM

Thank everyone for their responses. I sorted the finished brass and out of 500, 380 measured 1.750" and the rest (120) were within .002" below that. I will keep them separate when reloading and see if there is any difference at the shooting range in my guns. Just like the peace of mind that consistency gives me.

Chainsaw. · November 8, 2017, 01:19 PM

I use the same trimmer and get the same results in 223, but Im loading for volume. In the three guns I run this ammo in the accuracy is perfectly acceptable. But then Im not sitting at a bench trying to get itty bitty groups.

"Worlds fastest" and most accurate aren't exactly mutual. But you knew that. Guess the guestion is how accurate are you trying to be?

mikld · November 8, 2017, 01:37 PM

Your range is .003"? Do you know how small that is? +/- .0015" variation. This much variation can take place bu just the way you hold the case or how much pressure is applied or even how you hold your tongue while trimming...

T. O'Heir · November 8, 2017, 04:08 PM

"...from head to datum...The trim is measured from the shoulder..." NO!. Case lengths are measured from the case mouth to the end of the case.
The Hornady Case Gauge doesn't measure anything. It's a Go/No-Go gauge.

Stats Shooter · November 8, 2017, 04:26 PM

Im sure you probably won't believe me, but +/- .0015 variation in .223, especially being fired from an AR is negligible, and wont make any measurable difference. The other thing is, are you checking before or after you chamfer and deburr? Because burrs can mess up your measurements.

I use an RCBS 3 way cutter head on a trim pro 2 chucked up into a drill which cuts, chamfers, and deburrs all at once. With a 1.749" target I get 1.748-1.750" cut across 3500 rounds. If I use a standard head, I have to chamfer and deburr before measuring, otherwise there is much more variability.

Chainsaw. · November 10, 2017, 11:25 AM

T.O'heir. He's saying with that particular trimmer it works by putting the case in the trimmer, the trimmer stop on the shoulder of the case and the neck is trimmed from there.

RC20 · November 10, 2017, 11:46 AM

What you are getting is within the limits of the device and its more than good enough.

Try that on a RCBS trimmer with the clamp setup, far worse and inconsistent.

cw308 · November 10, 2017, 03:07 PM

I'm with T O'Heir . I have been using the RCBS Trim Pro , the older model with the shell plate , its giving me very accurate trimmed cases . Probably because I trim every firing , very little is shaved off with no resistance . I'm not in a rush I just want accurate measurements , never skip a step in peeping. Once the case is sized to the same dimension the case is trimmed . Measurement is from the head ( base of the case) to the end of the case neck . datum is for case headspace , base to datum . Once that is the same then you can trim to the exact case length. I set my trim length in the middle between the minimum & maximum ,works well for me.

**Unclenick** · November 11, 2017, 04:49 PM

Incidentally, the current SAAMI standard (2015) for .223 has changed since the previous on (1992 standard). In the older standard, the case length was 1.760" -0.020", so a case could be anywhere from 1.740"-1.760", and the middle value was 1.750", the middle value being what most folks use for trim-to length. The 2015 standard changed that to 1.760"-0.030", so 1.730"-1.760" is the current range and the new middle value is 1.745", which should, by tradition, be the new trim-too length. However, I don't see any load manuals jumping to change this, and I certainly am not going to both to change what I do with it.

cw308 · November 11, 2017, 09:19 PM

Unclenick
Thank you , I wasn't aware of the change. I thought it was 1.750 - 60 what do you think the reasoning is for a .030 of trim range in stead of .020

RC20 · November 12, 2017, 11:13 AM

Doesn't matter. As long as you trim to a consistent minimum you are good. 1.750 is as good as 1.745 - if its .003 off one way or the other its zero issue.

There is nothing magic about it, as long as the leading edge of the case does not get into the throat on the long end.

F. Guffey · November 12, 2017, 12:45 PM

Trimmers? I have trimmers, when I want accuracy I use the form/trim die, it is designed to be used with the man tool, the hack saw and finished with a file.

F. Guffey

cw308 · November 12, 2017, 09:06 PM

Mr.G
You sure have a tendency to make me stare aimlessly at a wall.

**Unclenick** · November 13, 2017, 10:07 AM

cw308,

I have no certain knowledge of what prompted the change. Other cartridges have not. I can speculate that so many cases are manufactured on contract overseas where they may use different numbers, that there may have been cost problems with tooling changes needed to keep the tighter old tolerance. If you look at the CIP drawing for the case, they have tolerances (about -0.008") for the positions of the two ends of the shoulder (junctures with the body and neck¹), but they give no tolerance for case length except in cartridges that headspace on the case mouth (rimless pistol cartridges). So, it may be understood under their standard that the case length given is a maximum, as it is here, and the manufacturers have some leeway on how much shorter it may be. For that reason, some .223 Rem manufactured in CIP countries could be shorter than the old SAAMI standard allowed. If a U.S. maker then goes to one of these manufacturers for a contract purchase, the headstamp die will be changed to the customer's spec, but it is likely cost prohibitive to require changing the cutting and length inspection system for the .223 Rem they already make just to comply with the last 0.010" of length.

RC20 is correct that this is in no way a critical dimension. When the M14/M1A platforms ruled the roost in service rifle matches, it was common knowledge the hard Lake City brass was only good for about 4 reloadings in those weapons before the threat of head separation became serious enough that the brass had to be scrapped. Knowing it grew an average of about 0.010" per loading cycle, many competitors would trim their once-fired brass down 0.040" below maximum trim length so they would only have to fuss with trimming once in the life of each case. Instead of the nominal trim length of 2.005" for that cartridge, they would go for 1.975". Most serious competitors reloading volume back then used the Gracey power trimmer to get the heavy trimming over with. And these were match shooters, so if the extra trimming impacted accuracy very much, they would not have been doing it.

¹ The CIP standard doesn't use a shoulder datum for a basic dimension, as the SAAMI standard does. Rather, they have a basic dimension value, S, from head to shoulder angle origin (apex) that SAAMI does not use.

F. Guffey · November 13, 2017, 10:42 AM

Quote:

Mr.G
You sure have a tendency to make me stare aimlessly at a wall.

For the short response "Thank you", and then there is the long response "Thank you very much".

I have forming die, forming dies are also listed as trim dies with the same stock number. My forming dies can be verified, I can measure the length of the forming die and then add .125" to the length of the die from top to bottom to get the correct trim to length of the case.

If I am forming cases for long chambers I can adjust the forming die off of the shell holder with a feeler gage when I want to add to the length of the case from the datum/shoulder to the case head.

After that it gets real complicated when I use a short forming die. I have adjusted my 308 W short forming die ..388"" off the shell holder when forming cases I do not have a forming die for.

F. Guffey

cw308 · November 13, 2017, 04:19 PM

Unclenick
Thank you for answering my question , I trim every firing , its no big deal for me I shoot 30 rounds of 308 each range trip . My trim length is .005 shorter them max. Every little is shaved off each time.

Mr G
I always like reading your posts , Your background in technical stuff is deeper then most , for a middle of the roader like me , its a little over the top , no disrespect. I always like hearing from you..

November 6, 2017, 04:48 PM	#1
Lilswede1 Senior Member Join Date: September 8, 2008 Location: NW Wash State Posts: 216	223 trimmed case length I am using the "worlds fastest trimmer" which fits on a drill. Very fast but no matter how much I tinker with it I get a variation of 1.748" to 1.751" with the majority trimming to 1.750". The trim is measured from the shoulder not from the base. When I measure a number of the fired cases with the Hornady Case Guage prior to trimming they all come out at 1.450" to 1.451". Very consistent. Anyone else have the same problem? I get kinda annal when reloading, consistency creates accuracy, is what I have read in here and I believe it.

November 6, 2017, 05:59 PM	#3
condor bravo Senior Member Join Date: August 23, 2014 Location: Nevada/Ariz/CA Posts: 1,753	Re Nick C S, Likewise, trying to trim '06 brass to 2.484 with a Forster trimmer will drive you up the wall if you're thinking about getting that trim length every time. No problem if you are getting plus or minus .001 or so from the desired length. Don't measure every one after trimming in order to maintain your sanity. __________________ Ouch, the dreaded "M-1 thumb", you just know it will happen eventually, so why not do it now and get it over with??

November 6, 2017, 07:49 PM	#4
Metal god Senior Member Join Date: April 10, 2012 Location: San Diego CA Posts: 6,876	So .002 from head to datum and the trimmer .003 . ? You're only really seeing a variance of .001 that's pretty good and that difference is likely because the trimmer is indexing on a different point on the shoulder then the Hornady gauge . As Nick said time to move on to bigger and more important things __________________ If Jesus had a gun , he'd probably still be alive ! I almost always write my posts regardless of content in a jovial manor and intent . If that's not how you took it , please try again .

November 6, 2017, 10:20 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Lilswede1, The shoulder is what the case headspaces on to stop the neck going forward. You want to measure from the head to the shoulder and then from the head to the ogive of your seated bullets and see how consistent the difference between those two numbers is. This will tell you how consistently your bullets will be spaced from the throat. Measuring from the head is done because it is easy, but it's not the best measurement. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

November 8, 2017, 01:19 PM	#11
Chainsaw. Senior Member Join Date: September 12, 2015 Location: Issaquah WA. Its a dry rain. Posts: 1,774	I use the same trimmer and get the same results in 223, but Im loading for volume. In the three guns I run this ammo in the accuracy is perfectly acceptable. But then Im not sitting at a bench trying to get itty bitty groups. "Worlds fastest" and most accurate aren't exactly mutual. But you knew that. Guess the guestion is how accurate are you trying to be? __________________ Just shoot the damn thing.

November 7, 2017, 01:06 PM	#6
hdwhit Senior Member Join Date: June 22, 2017 Posts: 1,011	I use a Forster case trimmer. I set it to trim 223 brass to 1.753. The non-standard trim length is due to the fact that I know how much (on average) my loading stretches my brass and I know how many loadings I can count on before my brass is "lost in the weeds" and I know that if I trim to 1.753, the brass will be lost before it needs to be trimmed again and trimming to 1.753 rather than 1.750 saves a lot of turns on the old Forster crank. My caliper reads to the nearest 1/1000 and has a fifth digit that reads "5" or gives no indication. Once the trimmer is set up, I only sample the trimmed cases to make sure of the adjustment (like condor bravo suggests) and my trimmed brass reads 1.753 with that extraneous "5" occasionally appearing, so I assume I'm within my target +/- 1/1000 inch. My rule is that if the bullet has a cannelure, crimp into it. If it doesn't, then don't crimp. With no crimp any length between 1.750 and 1.760 is fine. But keep in mind that if a crimp is not being used, the only thing holding the bullet in place is the friction between the bullet and the neck, so trimming below 1.750 starts to reduce how tightly the bullet is held - not much for each 1/1000, but it adds up - so if you are routinely ending up shorter than 1.750, it might be advisable to set the target length a little longer so that the bottom end of the range is still at or above minimum.

November 7, 2017, 08:05 PM	#7
ShootistPRS Senior Member Join Date: January 3, 2017 Posts: 1,583	I have an old Lyman trimmer that I made a set of bushings for. I never have to make any adjustments. I just put the correct bushing on the shaft and start trimming. It trims off the base so all my cases are the same length. I use it to check the length of the cases too because it takes less time than reading a caliper after getting a good bite. I run all my cases through the trimmer whether they need trimming or not. The ones that trim needed it and the ones that don't trim I know are in spec. One of these days I will take a picture of my setup.

November 7, 2017, 08:31 PM	#8
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	0.001 +/- in length isn't an issue as long as it's under the max case length.

November 8, 2017, 11:07 AM	#9
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	Lilswede1 Are you neck or full sizing your cases ?

November 8, 2017, 11:16 AM	#10
Lilswede1 Senior Member Join Date: September 8, 2008 Location: NW Wash State Posts: 216	Thank everyone for their responses. I sorted the finished brass and out of 500, 380 measured 1.750" and the rest (120) were within .002" below that. I will keep them separate when reloading and see if there is any difference at the shooting range in my guns. Just like the peace of mind that consistency gives me.

November 8, 2017, 01:37 PM	#12
mikld Senior Member Join Date: February 7, 2009 Location: Southern Oregon! Posts: 2,891	Your range is .003"? Do you know how small that is? +/- .0015" variation. This much variation can take place bu just the way you hold the case or how much pressure is applied or even how you hold your tongue while trimming... __________________ My Anchor is holding fast! I've learned how to stand on my own two knees...

November 8, 2017, 04:08 PM	#13
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	"...from head to datum...The trim is measured from the shoulder..." NO!. Case lengths are measured from the case mouth to the end of the case. The Hornady Case Gauge doesn't measure anything. It's a Go/No-Go gauge. __________________ Spelling and grammar count!

November 8, 2017, 04:26 PM	#14
Stats Shooter Senior Member Join Date: August 26, 2016 Location: North Dakota Posts: 1,636	Im sure you probably won't believe me, but +/- .0015 variation in .223, especially being fired from an AR is negligible, and wont make any measurable difference. The other thing is, are you checking before or after you chamfer and deburr? Because burrs can mess up your measurements. I use an RCBS 3 way cutter head on a trim pro 2 chucked up into a drill which cuts, chamfers, and deburrs all at once. With a 1.749" target I get 1.748-1.750" cut across 3500 rounds. If I use a standard head, I have to chamfer and deburr before measuring, otherwise there is much more variability.

November 10, 2017, 11:25 AM	#15
Chainsaw. Senior Member Join Date: September 12, 2015 Location: Issaquah WA. Its a dry rain. Posts: 1,774	T.O'heir. He's saying with that particular trimmer it works by putting the case in the trimmer, the trimmer stop on the shoulder of the case and the neck is trimmed from there. __________________ Just shoot the damn thing.

November 10, 2017, 11:46 AM	#16
RC20 Senior Member Join Date: April 10, 2008 Location: Alaska Posts: 7,014	What you are getting is within the limits of the device and its more than good enough. Try that on a RCBS trimmer with the clamp setup, far worse and inconsistent. __________________ Science and Facts are True whether you believe it or not

November 10, 2017, 03:07 PM	#17
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	I'm with T O'Heir . I have been using the RCBS Trim Pro , the older model with the shell plate , its giving me very accurate trimmed cases . Probably because I trim every firing , very little is shaved off with no resistance . I'm not in a rush I just want accurate measurements , never skip a step in peeping. Once the case is sized to the same dimension the case is trimmed . Measurement is from the head ( base of the case) to the end of the case neck . datum is for case headspace , base to datum . Once that is the same then you can trim to the exact case length. I set my trim length in the middle between the minimum & maximum ,works well for me.

November 11, 2017, 04:49 PM	#18
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Incidentally, the current SAAMI standard (2015) for .223 has changed since the previous on (1992 standard). In the older standard, the case length was 1.760" -0.020", so a case could be anywhere from 1.740"-1.760", and the middle value was 1.750", the middle value being what most folks use for trim-to length. The 2015 standard changed that to 1.760"-0.030", so 1.730"-1.760" is the current range and the new middle value is 1.745", which should, by tradition, be the new trim-too length. However, I don't see any load manuals jumping to change this, and I certainly am not going to both to change what I do with it. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

November 11, 2017, 09:19 PM	#19
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	Unclenick Thank you , I wasn't aware of the change. I thought it was 1.750 - 60 what do you think the reasoning is for a .030 of trim range in stead of .020

November 12, 2017, 11:13 AM	#20
RC20 Senior Member Join Date: April 10, 2008 Location: Alaska Posts: 7,014	Doesn't matter. As long as you trim to a consistent minimum you are good. 1.750 is as good as 1.745 - if its .003 off one way or the other its zero issue. There is nothing magic about it, as long as the leading edge of the case does not get into the throat on the long end. __________________ Science and Facts are True whether you believe it or not

November 12, 2017, 12:45 PM	#21
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	Trimmers? I have trimmers, when I want accuracy I use the form/trim die, it is designed to be used with the man tool, the hack saw and finished with a file. F. Guffey

November 12, 2017, 09:06 PM	#22
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	Mr.G You sure have a tendency to make me stare aimlessly at a wall.

November 13, 2017, 10:07 AM	#23
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	cw308, I have no certain knowledge of what prompted the change. Other cartridges have not. I can speculate that so many cases are manufactured on contract overseas where they may use different numbers, that there may have been cost problems with tooling changes needed to keep the tighter old tolerance. If you look at the CIP drawing for the case, they have tolerances (about -0.008") for the positions of the two ends of the shoulder (junctures with the body and neck¹), but they give no tolerance for case length except in cartridges that headspace on the case mouth (rimless pistol cartridges). So, it may be understood under their standard that the case length given is a maximum, as it is here, and the manufacturers have some leeway on how much shorter it may be. For that reason, some .223 Rem manufactured in CIP countries could be shorter than the old SAAMI standard allowed. If a U.S. maker then goes to one of these manufacturers for a contract purchase, the headstamp die will be changed to the customer's spec, but it is likely cost prohibitive to require changing the cutting and length inspection system for the .223 Rem they already make just to comply with the last 0.010" of length. RC20 is correct that this is in no way a critical dimension. When the M14/M1A platforms ruled the roost in service rifle matches, it was common knowledge the hard Lake City brass was only good for about 4 reloadings in those weapons before the threat of head separation became serious enough that the brass had to be scrapped. Knowing it grew an average of about 0.010" per loading cycle, many competitors would trim their once-fired brass down 0.040" below maximum trim length so they would only have to fuss with trimming once in the life of each case. Instead of the nominal trim length of 2.005" for that cartridge, they would go for 1.975". Most serious competitors reloading volume back then used the Gracey power trimmer to get the heavy trimming over with. And these were match shooters, so if the extra trimming impacted accuracy very much, they would not have been doing it. ¹ The CIP standard doesn't use a shoulder datum for a basic dimension, as the SAAMI standard does. Rather, they have a basic dimension value, S, from head to shoulder angle origin (apex) that SAAMI does not use. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

November 13, 2017, 04:19 PM	#25
cw308 Senior Member Join Date: September 2, 2010 Location: Plainview , Long Island NY Posts: 3,863	Unclenick Thank you for answering my question , I trim every firing , its no big deal for me I shoot 30 rounds of 308 each range trip . My trim length is .005 shorter them max. Every little is shaved off each time. Mr G I always like reading your posts , Your background in technical stuff is deeper then most , for a middle of the roader like me , its a little over the top , no disrespect. I always like hearing from you..