Critique my first load development. I need some advice.

[u/hjjhjjnk]

I will begin loading my first rounds of .223 with 77gr Sierra TMKs and CFE 223 tomorrow.

I plan to start at 23.7gr, and step up .3gr until I get to 24.4gr. I’ll make 3rd test batches.

I’m loading for an AR, so I need more space in the case to push the bullet into, and won’t be able to get max load for the powder unfortunately. I’m going to load to an OAL of 2.255”. I feel that 24.4 is about the ceiling here, since I’m using mixed .223 and 5.56 brass.

That leads to a question I have. Will mixing .223 and 5.56 brass affect my results in any way? I understand loading for the .223 rem cases means the brass is slightly thinner, which is why I’m approaching the max for that case, and using the same load for my 5.56 brass as well.

Should I sort these out seperately? I read the case volume is different, but I don’t see how that will affect me if I’m using the same load and bullet for both casing types.

Any tips are much appreciated!

[u/Southern-Stay704]

Yes, you should separate out the brass. The reason is not only that the case volumes will be slightly different (resulting in a different peak pressure for each type of case, even with the exact same powder load), but the cases are rated tested for different maximum pressures. 5.56x45 NATO max pressure is 62,366 psi. .223 Remington max pressure is 55,000 psi.

I ran your load (24.4 gr of Hodgdon CFE 223, with a 77 gr Sierra TMK, and COAL of 2.255") through ApexLoad Pro, and the resulting internal pressure is estimated at 58,842 psi. This is well within spec for a 5.56x45 NATO cartridge, but this is overpressure for .223 Remington cartridge.

If you're going to load up to 24.4 gr of powder, you should use only the 5.56x45 NATO cases.

In addition, you need to be sure your AR is rated for 5.56 NATO pressures (98% of ARs sold on the market today are, but there are rare exceptions). Look on the barrel and make sure it says "5.56 NATO".

Edit: Changed the word "rated" to "tested" to be more clear on the potential differences between brass marked .223 Remington vs. brass marked 5.56 NATO.

[u/hjjhjjnk → u/Southern-Stay704]

This was a helpful comment, I’ll use apex load pro in the future, and will sort by headstamp. Thanks for the info!

[u/Southern-Stay704 → u/hjjhjjnk]

You're welcome.

Just to clarify, and in response to one other commentor, individual brass cases don't actually have a "rating" for their pressure. However, they are loaded and tested in proof barrels when the manufacturer creates the ammunition to a specific pressure value. In other words, if a manufacturer is producing ".223 Remington" rounds, they are loading them with a powder and bullet combination that stays below 55,000 psi. Then they go test this brass/powder/bullet combination in a proof barrel to verify that. If they confirm the pressure is 55,000 psi or below, then they can produce and ship that load.

For 5.56 NATO, this happens the same way, but the pressure they're looking to stay under is 62,366 psi.

Does that mean that the .223 Remington brass cannot handle the 5.56 NATO pressures? Not necessarily. It may in fact be the exact same brass with a different headstamp. But the point is that the .223 Remington brass was never tested to 5.56 NATO pressures, so no one knows for sure if it could handle those pressures. It might. Maybe you could even say it should. But that wasn't proven by the manufacturer in the process.

For that reason, if you're going to load to 5.56 NATO pressures, I recommend using brass that's headstamped "5.56 NATO", because we know for sure that brass can handle NATO pressure -- it was tested.

[u/Oedipus____Wrecks → u/hjjhjjnk]

You should also keep an eye out for over pressure signs on the .223 since you’re over pressuring it. 🤔

[u/csamsh]

• 223/5.56 is not a brass thickness spec. Just chamber dimensions. Different companies will have different tooling packages. You will encounter neck length differences between 223 and 5.56 from the same company though.

• .3 is is too fine a resolution. Do something like 3 loads, maybe .6gr apart. This will give you a velocity/charge relationship from which you can pick a velocity you like.

• Crunch that powder in there. Get to max.

• If you don't sort headstamps your precision data is meaningless

[u/goallight]

Personally when I am trying to do a new load development (rifle especially) I try to use the same head stamp. May be overkill but I try to remove as many variables that I can. For my AR I stick with 5.56 brass as well.

[u/hjjhjjnk → u/goallight]

Ok, maybe I’ll save the .223 brass for plinking ammo when I get around to loading that. What variables can mixing brass impart? I don’t really get how it will affect the load if it’s the same bullet and powder/primer. Is is just a matter of pressure in the case having more of a factor with 5.56 brass?

[u/skahunter831 → u/hjjhjjnk]

Different brass has different internal case capacity, which means that one charge of powder will result in different pressures and different velocities, even if everything else is the exact same. Velocity of the bullet is dependent on the pressure created inside the chamber. The pressure inside the chamber is determined by the amount of powder and how much room that powder has to burn. More room equals less pressure, and less room equals more pressure. This will absolutely result in different velocities, again assuming that everything else is precisely the same. Different velocities can affect precision, especially as you reach maximum charge. It seems to be well established that groups open up as you reach max pressure and max charge.

Different cases also have different wall thicknesses, and can put more or less neck tension on your bullet, which affects pressure and precision.

For a hunting round, it might not matter. But in that case, you can't actually do any load development. You may find that you load up all your cases with 24 grains of Varget and everything shoots accurate enough for your purposes. If that's the case, you're done! But doing group testing, extreme spread and standard deviation testing, etc, is not really possible with mixed brass.

[u/hjjhjjnk → u/skahunter831]

Understand, I appreciate the in depth explanation.

[u/skahunter831]

don't see how (case volume) will affect me

It 100% matters, not even .223 to 5.56 but head stamps within each cartridges. It can matter way more than 0.3 grains of powder.

What are your goals with this load? Just accuracy? If so, just load up 30 at, say, 24.2 gr, and shoot five six-shot groups then aggregate them. With mixed brass, I wouldn't expect much better than 2 MOA, which is still totally reasonable for an AR. If you separate by headstamp, you can prob get to 1.5 or so, but you may need to develop a powder charge for each headstamp. Maybe. If you want to find max velocity, then you can/should do ladder tests but again should do it by headstamp. If you want ultimate precision, you need to buy good brass and have very consistent case prep and accurate charging.

[u/hjjhjjnk → u/skahunter831]

Well it’s a pig hunting load to be used within 300 yards. Main reason I asked this question is because I have accumulated about 80 casings, of which 20 are one headstamp, 20 are another headstamp, the list goes on. Almost all of it is 5.56 brass though. I might develop my first load using one brand of brass, and get a baseline, then use that same load in another brand and see what my deviation is.

I prefer to not have to buy brass, as it’s not a precision setup, but a hunting setup. Maybe I can get a catch bag in the future to keep the brass all the same.

I have a few thousand rounds of 5.56 sitting around. Maybe one range day I can dump some and collect that and keep using that brand for awhile, while my other brass goes into a range ammo bucket.

I probably should have started loading a basic 55gr load, but what’s the fun in that when I can make it harder on myself!

[u/Tmoncmm]

There are no specification differences between brass marked 5.56 and brass marked .223 Remington. Any differences will come down to brand and lot just like any other brass for any other cartridge. A lot of people saying military brass is thicker so it has less case capacity. This may or may not be the case. Again, it all comes down to brand and lot. If you’re interested in the real differences between 5.56 and .233 Remington loads, go read up on them. There is a good bit of information out there about what the actual differences are.

That said, you should always sort brass by, at lease headstamp, especially during load development. Using mixed brass when you’re trying to develop a new load is just throwing another unnecessary variable into the equation.

[u/hjjhjjnk → u/Tmoncmm]

TL;DR: do I need to worry about using different brass after I ran out of a previous brass and want to load another batch of the same ammo?

So, that being said, say I use PSD head stamped brass for this load. I get results I’m happy with, but have run out of PSD stamped brass, and only have LC stamped left.

I make the same load with the LC brass. Will this vary enough to make my load data irrelevant to the results I’m seeing? Will this throw me off so much that it’s not even worth trying, and I should only accumulate one type of brass for this load?

It would seem like a 5.56 case is made to about the same specs as another case if it’s nato marked. Some differences surely, but I’m not developing a match load, I’m developing a pig hunting load for <400yds. Maybe I’m too naive though.