Post by windchill on Dec 15, 2012 7:25:11 GMT -6
The Myth: Military 5.56mm/223 brass is thicker and its internal capacity is less than its commercial 223 Remington twin.
Where does this belief come from? I believe we can go back to the reloading of LC cases in 308/7.62 as a good example. Indeed it is true that 308/7.62mm brass is heavier with thicker case head web area and wall thickness making the internal case capacity less than most Commercial 308 Winchester cases. Is this always the case (pun intended) no. There are reports of IMI military brass having the same internal capacity as some Remington/Winchester brass. But for the most part Lake City in 7.62 is thicker and has less internal capacity.
So if the 308/7.62mm Lake City cases are thicker and have less internal capacity.... it HAS to be the same for the little brother 223/5.56mm right? Not so much. Why does this keep getting passed around? I have seen this very topic being passed around on the internet and more importantly by Gun article writers in major magazines. You know the guy who does evaluations on the side from his Law Enforcement job. Receives a new product from a vendor and makes every excuse in the book on why it didn't shoot or function while shooting off hand onto a steel plate for the accuracy testing! Ha! But yet it's always the best bang for the buck! Hmmmm? It's THAT guy who heard it from the guy before him and from the guy before thatc.. And hence the myth all based off of the 308/7.62 issue. Even the 30'06 can be traced to some of the same issues so this dates way way back.
OK let's do some testing and debunk the myth setting the record straight. Most precision rifle shooters and reloaders measure internal case capacity using volume of water. This is the standard excepted method for better or worse. The case is weighed empty and recorded. The case is then filled to the mouth so that it is even and then reweighed making note of the difference between the two weights gives you the internal volume in grains of water.
There are a couple things to do to make this a valid comparison. Taking once fired brass and running it through the same FL sizing die and trimming the OAL to the same length. Also using a large enough lot of brass to take the middle or average empty case weight to minimize the variation from inside a brand name lot. For example. If I take 50 pcs of LC09 and weigh them all, I want to take 5 of those from the middle average of that weight for my internal capacity test.
I have done my own test but this one I stole from another web site as its nice neat and tidy with more cases than I tested personally. Result was exactly the same as below.
* Average case weight of sized, deprimed, once fired brass (except new Lapua lot). Weight is average of sample lot.
** Case capacity of three sample cases that weighed closest to the average weight of that brand. All cases were full-length sized and trimmed to 1.750. A spent primer was inserted in the primer pocket, the case weighed. Then the cases filled with distilled water to the top of the case mouth and weighed again.
.223 Rem Case Weight vs. Capacity
Case Manufacturer Case Weight* H20 Capacity**
Lake City 06.....................92.0..............30.6
WCC99............................95.5..............30.5
Sellier & Belloit..................92.4..............30.5
Remington.......................92.4...............30.4
PMC.................................93.5..............30.4
Hirtenberger.....................93.7...............30.4
Lake City 04.....................93.0...............30.4
Federal............................96.3...............30.2
Hornady...........................93.9...............30.1
IMG (Guatemalan).............95.4...............30.1
Lapua (new lot)................93.4...............30.1
Winchester......................93.9................30.1
Olympic...........................97.4...............30.0
Radway Arsenal................96.1...............30.0
PMP...............................104.5...............29.9
FNM 93-1.........................97.3...............29.8
Lapua (old lot)................104.0...............28.0
Where does this belief come from? I believe we can go back to the reloading of LC cases in 308/7.62 as a good example. Indeed it is true that 308/7.62mm brass is heavier with thicker case head web area and wall thickness making the internal case capacity less than most Commercial 308 Winchester cases. Is this always the case (pun intended) no. There are reports of IMI military brass having the same internal capacity as some Remington/Winchester brass. But for the most part Lake City in 7.62 is thicker and has less internal capacity.
So if the 308/7.62mm Lake City cases are thicker and have less internal capacity.... it HAS to be the same for the little brother 223/5.56mm right? Not so much. Why does this keep getting passed around? I have seen this very topic being passed around on the internet and more importantly by Gun article writers in major magazines. You know the guy who does evaluations on the side from his Law Enforcement job. Receives a new product from a vendor and makes every excuse in the book on why it didn't shoot or function while shooting off hand onto a steel plate for the accuracy testing! Ha! But yet it's always the best bang for the buck! Hmmmm? It's THAT guy who heard it from the guy before him and from the guy before thatc.. And hence the myth all based off of the 308/7.62 issue. Even the 30'06 can be traced to some of the same issues so this dates way way back.
OK let's do some testing and debunk the myth setting the record straight. Most precision rifle shooters and reloaders measure internal case capacity using volume of water. This is the standard excepted method for better or worse. The case is weighed empty and recorded. The case is then filled to the mouth so that it is even and then reweighed making note of the difference between the two weights gives you the internal volume in grains of water.
There are a couple things to do to make this a valid comparison. Taking once fired brass and running it through the same FL sizing die and trimming the OAL to the same length. Also using a large enough lot of brass to take the middle or average empty case weight to minimize the variation from inside a brand name lot. For example. If I take 50 pcs of LC09 and weigh them all, I want to take 5 of those from the middle average of that weight for my internal capacity test.
I have done my own test but this one I stole from another web site as its nice neat and tidy with more cases than I tested personally. Result was exactly the same as below.
* Average case weight of sized, deprimed, once fired brass (except new Lapua lot). Weight is average of sample lot.
** Case capacity of three sample cases that weighed closest to the average weight of that brand. All cases were full-length sized and trimmed to 1.750. A spent primer was inserted in the primer pocket, the case weighed. Then the cases filled with distilled water to the top of the case mouth and weighed again.
.223 Rem Case Weight vs. Capacity
Case Manufacturer Case Weight* H20 Capacity**
Lake City 06.....................92.0..............30.6
WCC99............................95.5..............30.5
Sellier & Belloit..................92.4..............30.5
Remington.......................92.4...............30.4
PMC.................................93.5..............30.4
Hirtenberger.....................93.7...............30.4
Lake City 04.....................93.0...............30.4
Federal............................96.3...............30.2
Hornady...........................93.9...............30.1
IMG (Guatemalan).............95.4...............30.1
Lapua (new lot)................93.4...............30.1
Winchester......................93.9................30.1
Olympic...........................97.4...............30.0
Radway Arsenal................96.1...............30.0
PMP...............................104.5...............29.9
FNM 93-1.........................97.3...............29.8
Lapua (old lot)................104.0...............28.0