Why 10% less powder for IVI/LC military brass???

[Brianma65]

After just reading a thread on if you should load LC military brass ,same as .223 commercial brass, I did some testing.
Most people said to load at 10% less for the LC military brass.

I tested 5 types of brass, trimmed at 1.750.

R-P : 30.3 g Benchmark ( case capacity)
95.5 g weight.

L.C : 30.3 g benchmark (case capacity)
95.6 g weight.

IVI : 30.1 g benchmark ( case capacity)
102.4 g weight.

Barnes :30.2 g benchmark (case capacity)
93.1g weight.

Nosler 30.2 g benchmark (case capacity).
95.2 g weight
So as you can see, the LC ,R-P,Nosler and Barnes are almost identical,but the IVI is heavier.

So , my question is, why do we need to load the military brass at 10% less if it has the same case capacity as
.223 commercial brass?

 

[Lefty Dick]

Cuz the cases are thicker and have a reduced internal capacity.
FWIW this is covered in most reloading manuals, I suggest you go buy a couple manuals.

 

[thepolinator]

But OP'S test showed that the internal capacity was the same...

 

[B]

Cuz the cases are thicker and have a reduced internal capacity.
FWIW this is covered in most reloading manuals, I suggest you go buy a couple manuals.

Go ahead and comprehend what you read before posting.

As for the OP that is interesting, I always just assumed the capacity is lower. Do you have any other brands to compare? LC should be mil brass too maybe RP is just made to the same spec?

 

[tjhaile]

That doesn't apply to .223/5.56. Case capacities between military and commercial cases are normally very similar, as can be seen in the table here:

http://www.m4carbine.net/showthread.php?55149-5-56mm-NATO-versus-223-Remington-Chamber-Differences

Other types of military brass can have thicker walls and lower capacity. The Lyman reloading manual recommends reducing maximum powder charge by 1-2 grains for .308 reloads using military cases.

 

[Brianma65]

Go ahead and comprehend what you read before posting.

As for the OP that is interesting, I always just assumed the capacity is lower. Do you have any other brands to compare? LC should be mil brass too maybe RP is just made to the same spec?

The LC and IVI both have crimped PP, so I’m guessing they’re Mil brass.
The IVI is a bit thicker but has almost identical case capacity.

The .2 g of powder in the IVI brass is not hardly close to 10%.

I do have some Win, FC brass I can check as well.

 

[Easy 9mm]

Interesting info. Try measuring case capacity with water. It would be a more accurate method of volume measurement than powder.

 

[Brianma65]

Interesting info. Try measuring case capacity with water. It would be a more reliable method of volume measurement than powder.

I thought about that, but I took each case and tapped it on the bench, so as to get as much as possible.
I can’t see .2 of a grain making much diff.

 

[dirtybarry]

After just reading a thread on if you should load LC military brass ,same as .223 commercial brass, I did some testing.
Most people said to load at 10% less for the LC military brass.

I tested 3 types of brass, trimmed at 1.750.

R-P : 30.3 g Benchmark ( case capacity)

L.C : 30.3 g benchmark (case capacity)
95.6 g weight.

IVI : 30.1 g benchmark ( case capacity)
102.4 g weight.

So as you can see, the LC and R-P are almost identical,but the IVI is heavier.

So , my question is, why do we need to load the military brass at 10% less if it has the same case capacity as
.223 commercial brass?

Western Powders (RamShot) is the only company that I've found that even publishes data for 5.56 military level loads and they make no distinction for brass, only bullet. Extrapolating from that, I loaded brass from Norinco, PMC, Federal AE and Lake City to maximum levels for a 55gr bullet. They were then all fired in 5.56 rated guns....and nothing. No drama, no failures, no damage at all. No pressure signs,no extraction problems, no primers blown out and every piece of brass has been reloaded and used multiple times since. This was done precisely because of the often contradictory "expert" opinions out there. As a result, I have zero worries about using any manufacturers .223 data in any otherwise serviceable brass be it military or commercial.

 

[Brianma65]

Updated with two more brands of brass added.

 

[Easy 9mm]

All full-length sized brass I'm guessing since they're all trimmed to the same length?

I have seen similar results in accuracy with my 223 using Federal, Rem and Norc brass with the same charge weight in the loads I have used for 69gr match kings. No difference in pressure observable in the fired brass or primer that I saw. This has got me curious about these brands as well.

 

[Brianma65]

I get that loading to 5.56 specs and using in your .223 chamber, MAY cause excessive pressure.
But isn’t that due to increased powder charges? Not because mil cases are 10 % smaller, due to brass thickness.

 

[Brianma65]

The IVI brass are thicker though, which means they should be better ? Right?

I’ve got about 2000 and will be loading as normal.

 

[tiriaq]

I get that loading to 5.56 specs and using in your .223 chamber, MAY cause excessive pressure.
But isn’t that due to increased powder charges? Not because mil cases are 10 % smaller, due to brass thickness.

The difference is in the throating and leade dimensions. 5.56 may experience a fit issue in a .223 chamber, and that is why SAAMI states that 5.56 should not be fired in SAAMI spec .223 chambers.

 

[Brianma65]

The difference is in the throating and leade dimensions. 5.56 may experience a fit issue in a .223 chamber, and that is why SAAMI states that 5.56 should not be fired in SAAMI spec .223 chambers.

Ya, I got that part.
But people has been advising to load the military brass,at 10 % less.
Stating that mil brass is thicker and has less case capacity.

Which is not so.
Well not 10% less anyways

 

[tiriaq]

More of an issue with 7.62X51 and .308.
Your research was worthwhile.
In the other thread, Ganderite commented on the 5.56/.223 case issue. He knows more about ammunition than anyone else I've met.

 

[Brianma65]

More of an issue with 7.62X51 and .308.
Your research was worthwhile.
In the other thread, Ganderite commented on the 5.56/.223 case issue. He knows more about ammunition than anyone else I've met.

Yes, Ganderite basicly said the exact same thing.
He knows his stuff and because of his posts, I’ve learned a lot.

 

[bigedp51]

American Lake City 5.56 cases are made of harder brass to increase its strength. You can not make 5.56 cases thicker because they would loose too much case capacity.

Lake City 7.62 cases are made thicker in the base to increase its strength and the thumb rule was they had 2 grains less of H2O capacity.

At AccurateShooter.com there has been postings showing case weight does not correspond with H2O capacity.

The only way to find out is to check the 7.62 cases for H2O capacity. Most 7.62 ammunition is fired in machine guns with larger diameter chambers "BUT" some 7.62 ammunition is made for sniper rifles and the cases may be made of thinner harder brass.

I just checked some weight sorted Lake City 7.62 2009 dated cases I have loaded and the cases weigh approximately 179.1 to 179.5. I did not check case capacity and these 25 cases are a workup load with H4895.

Below shows the thicker flash hole web of a Lake City 5.56 vs a Federal .223 case, "BUT" the Lake City weighs 3 grains less than the Federal case with 0.1 more case capacity.

Cartridge Case Capacities
http://kwk.us/cases.html

.308 Reloading data only (read Dan Newberry's posting)
http://www.sniperforums.com/forum/reloading/43364-308-reloading-data-only.html

Old School .308 Winchester Match Loads
http://www.provenreloads-handloads.com/articles/2016/9/18/old-school-308-winchester-match-loads

Service Rifle Loadings
http://www.bearblain.com/Service%20Rifle%20Loadings.html

Bottom line, you need to check the case capacity of military 7.62 cases "AND" make a work up load checking for signs of excess pressure. Just remember the majority of 7.62 military cases are thicker in the base and flash hole web to add strength. And this is because machine gun chambers can be .002 to .004 larger in diameter. And if you have ever resized any machine gun brass you will understand.

NOTE, case capacity for "your" rifle means checking the capacity of a case fired in your rifle. If the cases have not been fired in your rifle then full length resize them to make them uniform and then check the capacity.

 

[jethunter]

After just reading a thread on if you should load LC military brass ,same as .223 commercial brass, I did some testing.
Most people said to load at 10% less for the LC military brass.

I tested 5 types of brass, trimmed at 1.750.

R-P : 30.3 g Benchmark ( case capacity)
95.5 g weight.

L.C : 30.3 g benchmark (case capacity)
95.6 g weight.

IVI : 30.1 g benchmark ( case capacity)
102.4 g weight.

Barnes :30.2 g benchmark (case capacity)
93.1g weight.

Nosler 30.2 g benchmark (case capacity).
95.2 g weight
So as you can see, the LC ,R-P,Nosler and Barnes are almost identical,but the IVI is heavier.

So , my question is, why do we need to load the military brass at 10% less if it has the same case capacity as
.223 commercial brass?

Is that 1f brass, or new brass?

 

[Brianma65]

Is that 1f brass, or new brass?

1F brass