556 ammo question

[hammie]

@alanwk: I apologize for my reply. I dashed it off in haste and it was rude and snarky. At one time I had an older copy of a Lee Reloading manual, and it was just reloading data copied and regurgitated from other sources. I did not consider that Lee manual to be definitive or comprehensive. Maybe that has changed with the newer ones.

I believe the major bullet makers do their own testing and load development and the book shelf in my reloading room contains the latest editions of the Lyman, Sierra, Speer, Nosler, and Hornady manuals. If you reload for many cartridges or for not so common cartridges, Ken Waters' "Pet Loads" is nice to have. I indicated in my first post the manuals which have dual data to the .223 Remington and the 5.56 NATO. I hope you found the answers you needed.

Again, please forgive me. I'll try to frame my answers better in the future.

 

[44 AMP]

First point, I've heard for many years that Lee does no do the pressure testing or load development for the data they publish. They print data from other sources (not Lee) and I don't think they generally credit the source where its easily seen. Don't know for certain its true, or not, guess you'd have to ask LEE.

Next point, what I've heard is that the differences in rifling leade and angle were so the 556 guns would accommodate a specific NATO tracer bullet not the standard ball. Again I can't say from personal experience, but its something to consider,

Next point, ALL the rifles both 223 and 556 survive proof test pressures. These are considerably higher than the working pressure, and it seems to me that if they take proof pressure, they aren't likely to blow up from a pressure that is less than that, even if it is above the listed working pressure.

Personally, I think the entire issue is another case of excess caution inflating a molehill into a virtual mountain, but that's just me.

 

[Don P]

At my former employer test rounds for our carrier group are 75,000

 

[alanwk]

I'm not sure if the original poster's question wasn't rhetorical and meant to be a criticism of the Lee manual, but I'll assume it was meant as a legitimate question. "Ike Clanton" came close to the answer, but I'll try to be more direct. The answer to "why would a manual not have info for the 556 round?" is: most of them do. The Hornady 11th edition, the Speer 15th edition, and the Sierra 6th edition all have separate sections for reloading data for the .223 remington and for the 5.56 NATO / or AR15 rifle.

Now for the advice to the original poster: get yourself a real reloading manual.

This is the response I got from Lee: There is not much load data for 5.56 NATO as it is not quite as accurate as 223 rem as well as the pressure concerns. The rounds are dimensionally the same in most regards, the main difference has to do with the chambers and pressures. From the data I have seen, the 5.56 looks to have a higher pressure as well as a slightly more spacious chamber. The other primary difference has to do with bullet profiles as a variety of types are used, the green tipped m855, tracer rounds, armor piercing, etc. There is some data for 5.56 nato, but you would need to dig a bit to find it and I've been looking for a decent 5.56 nato load for my own reloading. Keep in mind that we do not generate any load data and only republish information directly from the powder companies.

 

[Unclenick]

CAUTION: The following post (or a page linked to) includes or discusses loading data not covered by currently published sources of tested data for this cartridge (QuickLOAD or Gordon's Reloading Tool data is not professionally tested). USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assumes any liability for any damage or injury resulting from the use of this information.

The 7" twist in the NATO barrels is specifically to stabilize the M856 tracer. If you follow the link, you can see how long the bullet is, and as bullet length increases, so does the required spin rate for its stability.

The reason for the dearth of 5.56 NATO load data is that a cartridge can only really be called 5.56 NATO after thousands of samples have passed an exhaustive set of qualification tests. Recipes in a manual can't reproduce a passing score reliably. The normal canister powder ±3% burn rate tolerance, for example, is enough to cause more velocity variation than the 4±40 fps the NATO specs allow.

What handloaders can do is load 223 Remington or 5.56×45 NATO cases with military-type bullets to try to match the performance of 5.56 NATO as measured by firing samples of the qualified stuff in their own guns and matching its performance under whatever conditions they are interested in, all the while carefully watching for pressure signs. You have to choose a powder you know will work in the military ammo, such as H335, which is canister-grade WC844 and is a military powder for M193 and M855. With that powder, according to QuickLOAD, an increase in charge weight of 2% will achieve the 6-7% pressure increase with those bullets. It will be about 0.4 grains of additional powder. Not a lot.

One thing to keep in mind is that NATO EPVAT doesn't target achieving a particular chamber pressure, so simply adding that extra powder isn't going to turn it the load into a performance match. What they target first is the velocity and the chamber pressure. If a lot of powder produces those things simulataneously without exceeding the average pressure limit, then they are done, even if the peak chamber pressure is below what is allowed. Your test for gas port pressure will just be that your gun functions. So if you can reach the velocity that actual military ammo does in your gun and the gun is functioning and this is true at your targeted shooting conditions, for your purposes, you have matched military ammo.

 

[Metal god]

I found this if anyone in interested . It shows the dimensional differences between all the 5.56 rounds . It's interesting if accurate

https://www.inetres.com/gp/military/infantry/rifle/556mm_ammo.html

 

[Unclenick]

It's the same thing I linked to in post 18. Just a different host. It's copied from military tech manuals. Their information is not always reliable, though I don't have a reason to doubt that particular information.

 

[hdwhit]

223 Loading

I get good results in 223/5.56 with IMR-4198 in my 181- and 182-Series Mini-14s. It helps that maximum load is under 20 grains with 60 grain projectiles, so more rounds per pound.

My most consistent results are with IMR-3031.

 

[603Country]

Use 223 load data. Work up your loads for accuracy while looking for pressure signs. When you find your best load, load a bunch and go shoot. I use H335 behind Sierra 65 gr GK, and Lapua brass, and didn’t get that close to max loads, due to pressure signs. Same thing with LC brass.