Need Help W/ 5.56 Lake City Brass Lengths & OAL

riverwalker76 · April 18, 2010, 09:58 PM

To start off .... I'm reloading a lot of Lake City once fired brass to military specs. The problem I have run in to is that a lot of the Lake City Brass length is 1.770.

Out of habit I trim all of the once fired brass I get down to 1.760, but here lies my problem .....

When I load to spec the OAL should be 2.260 and that puts cannelure .01 above the case mouth.

Should I leave all of my once fired at 1.770 and set the bullet to an OAL of 2.260?

Standard .223 should be set at 2.250, but I guess Lake City loads their 5.56 ammo .01" longer.

Would it hurt anything to leave my 5.56 brass at 1.770?

kraigwy · April 18, 2010, 11:37 PM

Forget the cannelure, set the OAL to the best accuracy that fits in the mag.

Just trim the brass to listed specs.

steve4102 · April 19, 2010, 07:12 AM

SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH “COL”
It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must
be seen as a guideline only.
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as 1) magazine length (space), 2) freebore-lead dimensions of
the barrel, 3) ogive or profile of the projectile and 4) position of cannelure or crimp groove.

Quote:

Would it hurt anything to leave my 5.56 brass at 1.770?

Duno, get one of these, you can check your chamber length and know for sure.
http://www.sinclairintl.com/product/...eadspace-Tools

riverwalker76 · April 19, 2010, 10:09 AM

OK. That's good to know, because I'm loading PRVI SS109 clones right now, and they are a little longer than your standard bullet. I measured a 'Green Tip' Lake City M855 and they measure 2.260, and the brass IS trimmed to 1.770. I guess that's a military standard.

The Lake City M855 loaded rounds gave me 1/2" groups at 50 yds., and when I tested reloads that were trimmed to 1.760 and an OAL of 2.250 I was shooting groups at .75" to 1.15". Maybe the longer case / seating depth makes the difference. I'll try it out.

**Unclenick** · April 19, 2010, 10:58 AM

Seems like some misinformation is creating itself. There is no difference in the case dimensions for SAAMI and Military. The .223 Remington was developed for the AR starting with the .222 Remington and evolving through the .222 Remington magnum and then finally to the .223 Remington. The 5.56×45 is the NATO standardized copy of it, but the external dimensions were not changed for that. NATO chambers are slightly bigger, especially in the freebore length, for smooth full auto operation, but the new cartridge cases are identical. This is why new Lake City or IMI or WCC brass fits in a commercial chamber just fine.

The correct case length specification is 1.740" to 1.760". Trim length is normally given as the midpoint in that range, 1.750". SAAMI specifies all case dimensions as a maximum with a minus tolerance, and all chamber dimensions as a minimum with a plus tolerance. So, SAAMI specs the case length as 1.760" -0.020". That is why most manuals show 1.760" on their drawing. They just don't usually include the tolerance. But read the trim length, and it will be given as 1.750".

I don't know why you got 1.770" cases? The once-fired processor either failed to trim them or did it before sizing (always trim after sizing because sizing draws the case out longer) or just didn't get the numbers right when he set up his gear. Most chambers have about 0.020" extra length as a safety margin, but starting with a case that uses up half of it is not a good plan, since chambering can sometimes increase length a bit. Overlong cases present a pressure hazard because if a neck is long enough, the end of the case mouth can jam into the end of the neck portion of the chamber. It then can't let go of the bullet normally, which raises pressure. Trim them to 1.750".

As to your cannelures, COL is just about feed compatibility for all SAAMI and NATO compliant magazines. You can't get an overlong cartridge into a magazine, but a short one usually feeds fine. So, look at 2.260" as a maximum for all makes of magazines. It is not a must-meet number, though. Figure that if you are seating 2 mm deeper to get to a cannelure using H335 (WC844 canister version) you should reduce the charge about half a grain to keep pressure constant.

As Kraig said, you don't need to crimp. Match bullets don't even have cannelures. Crimping is only needed for ammunition that will be dropped or otherwise handled roughly, or when the powder is having a hard time igniting well, in which case it helps build start pressure. A few loads have accuracy improvements from crimping for that reason, but you can usually tune them in without that.

riverwalker76 · April 19, 2010, 04:39 PM

Quote:

I don't know why you got 1.770" cases? The once-fired processor either failed to trim them or did it before sizing (always trim after sizing because sizing draws the case out longer) or just didn't get the numbers right when he set up his gear.

I must have confused you.

The Lake City SS109 Green Tip that I am firing is NEW Lake City M855 Green Tip. It has never been reloaded.

That would mean that out of the lots produced that day .... some 100k or more brass were left at 1.770 length.

**Unclenick** · April 22, 2010, 04:56 PM

I checked lot of WCC 92 I have and it was right about 1.760" on the nose, with a few running a couple thousandths over. However, after inspecting them I also realized that the heads were slightly concave, presumably from the primer crimping process. The necks themselves were no longer than my Federal loaded rounds which measured 1.752" on average. So, the extra length was due to the head deformation. It is the length of the neck coming off the shoulder that actually sets how close the lands get to the throat ogive, so these were safe from that standpoint, even when their total length went slightly over SAAMI max.

azredhawk44 · April 22, 2010, 05:11 PM

Quote:

The correct case length specification is 1.740" to 1.760". Trim length is normally given as the midpoint in that range, 1.750". SAAMI specifies all case dimensions as a maximum with a minus tolerance, and all chamber dimensions as a minimum with a plus tolerance. So, SAAMI specs the case length as 1.760" -0.020". That is why most manuals show 1.760" on their drawing. They just don't usually include the tolerance. But read the trim length, and it will be given as 1.750".

+1.

I trim all my 5.56 / .223 to 1.745".

I hate trimming but don't want to over-do it, so I figure I'll lose or wear out the brass before it makes it to 1.760+ again.

I'm in the middle of processing several thousand pieces of .223 / 5.56, and I notice that the shortest once-fired stuff tends to either be WCC or RORG/RG headstamps. LC seems to peel a lot of metal off my trimmer lathe.

I guess ATK/Federal is running the LC brass towards the longer end of the spectrum these days. Most of my brass is stamped 04 to 09.

April 18, 2010, 09:58 PM	#1
riverwalker76 Senior Member Join Date: February 13, 2010 Location: Kentucky Posts: 993	Need Help W/ 5.56 Lake City Brass Lengths & OAL To start off .... I'm reloading a lot of Lake City once fired brass to military specs. The problem I have run in to is that a lot of the Lake City Brass length is 1.770. Out of habit I trim all of the once fired brass I get down to 1.760, but here lies my problem ..... When I load to spec the OAL should be 2.260 and that puts cannelure .01 above the case mouth. Should I leave all of my once fired at 1.770 and set the bullet to an OAL of 2.260? Standard .223 should be set at 2.250, but I guess Lake City loads their 5.56 ammo .01" longer. Would it hurt anything to leave my 5.56 brass at 1.770? __________________ *Admiral Isoroku Yamamoto* - “You cannot invade the mainland United States. There would be a rifle behind each blade of grass.”

April 18, 2010, 11:37 PM	#2
kraigwy Senior Member Join Date: June 16, 2008 Location: Wyoming Posts: 11,061	Forget the cannelure, set the OAL to the best accuracy that fits in the mag. Just trim the brass to listed specs. __________________ Kraig Stuart CPT USAR Ret USAMU Sniper School Distinguished Rifle Badge 1071

April 19, 2010, 10:09 AM	#4
riverwalker76 Senior Member Join Date: February 13, 2010 Location: Kentucky Posts: 993	OK. That's good to know, because I'm loading PRVI SS109 clones right now, and they are a little longer than your standard bullet. I measured a 'Green Tip' Lake City M855 and they measure 2.260, and the brass IS trimmed to 1.770. I guess that's a military standard. The Lake City M855 loaded rounds gave me 1/2" groups at 50 yds., and when I tested reloads that were trimmed to 1.760 and an OAL of 2.250 I was shooting groups at .75" to 1.15". Maybe the longer case / seating depth makes the difference. I'll try it out. __________________ *Admiral Isoroku Yamamoto* - “You cannot invade the mainland United States. There would be a rifle behind each blade of grass.”

April 19, 2010, 10:58 AM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,084	Seems like some misinformation is creating itself. There is no difference in the case dimensions for SAAMI and Military. The .223 Remington was developed for the AR starting with the .222 Remington and evolving through the .222 Remington magnum and then finally to the .223 Remington. The 5.56×45 is the NATO standardized copy of it, but the external dimensions were not changed for that. NATO chambers are slightly bigger, especially in the freebore length, for smooth full auto operation, but the new cartridge cases are identical. This is why new Lake City or IMI or WCC brass fits in a commercial chamber just fine. The correct case length specification is 1.740" to 1.760". Trim length is normally given as the midpoint in that range, 1.750". SAAMI specifies all case dimensions as a maximum with a minus tolerance, and all chamber dimensions as a minimum with a plus tolerance. So, SAAMI specs the case length as 1.760" -0.020". That is why most manuals show 1.760" on their drawing. They just don't usually include the tolerance. But read the trim length, and it will be given as 1.750". I don't know why you got 1.770" cases? The once-fired processor either failed to trim them or did it before sizing (always trim after sizing because sizing draws the case out longer) or just didn't get the numbers right when he set up his gear. Most chambers have about 0.020" extra length as a safety margin, but starting with a case that uses up half of it is not a good plan, since chambering can sometimes increase length a bit. Overlong cases present a pressure hazard because if a neck is long enough, the end of the case mouth can jam into the end of the neck portion of the chamber. It then can't let go of the bullet normally, which raises pressure. Trim them to 1.750". As to your cannelures, COL is just about feed compatibility for all SAAMI and NATO compliant magazines. You can't get an overlong cartridge into a magazine, but a short one usually feeds fine. So, look at 2.260" as a maximum for all makes of magazines. It is not a must-meet number, though. Figure that if you are seating 2 mm deeper to get to a cannelure using H335 (WC844 canister version) you should reduce the charge about half a grain to keep pressure constant. As Kraig said, you don't need to crimp. Match bullets don't even have cannelures. Crimping is only needed for ammunition that will be dropped or otherwise handled roughly, or when the powder is having a hard time igniting well, in which case it helps build start pressure. A few loads have accuracy improvements from crimping for that reason, but you can usually tune them in without that. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

April 22, 2010, 04:56 PM	#7
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,084	I checked lot of WCC 92 I have and it was right about 1.760" on the nose, with a few running a couple thousandths over. However, after inspecting them I also realized that the heads were slightly concave, presumably from the primer crimping process. The necks themselves were no longer than my Federal loaded rounds which measured 1.752" on average. So, the extra length was due to the head deformation. It is the length of the neck coming off the shoulder that actually sets how close the lands get to the throat ogive, so these were safe from that standpoint, even when their total length went slightly over SAAMI max. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle