I got a couple thousand rounds of 55gr brass ammo for a good price.  Only problem is, they're all mixed together in ammo cans.
- Wolf Gold 55gr
- PMC Bronze 55gr
- Perfecta 55gr
- PPU 55gr M193

Is it worth sorting them out?  Or is the trajectory or POI shift negligible enough that it doesn't matter?

I would just use it for plinking .
The difference in trajectory is probably minimal .

Unless you're shooting for precision with a scope, I wouldn't worry about it. 1/2 MOA here or there won't be noticeable with a red dot.

Try them at known distances.

Take notes.

I've had some shoot to wildly different POA's with an EOTech or ACOG with a somewhat fine aiming point.

I haven't noticed lot-to-lot shifts nearly as much with my 3MOA CompM.

It would be good for imprecise red dot blasting.

A lot of assumptions here because I don't own a chronograph:

A user on another forum chronographed Federal's 55gr. sister rounds from a single 16" gun and found:

Federal AE223
2793fps

Federal XM193
3140fps

I plotted this into a ballistic calculator with Federal's specified ballistic coefficients for each round (they list different coefficients for their .223 and 5.56) and found the following (not correcting for temperature, elevation, barometric pressure or wind):

NOTE: drops are in inches

223 55gr .269 G1 ballistic coefficient
100 +1.32
200 -.55
300 -9.98
400 -29.44
500 -62.41
600 -113.58

5.56 55gr .246 G1 ballistic coefficient
100 +1.58
200 +1.11
300 -5.48
400 -20.32
500 -46.49
600 -88.36

So inside of 400 yards, you may still hit the target.

Not an issue for SHTF or plinking.
Think about it.. Troops don’t check brand/lot of given ammo.

Don’t overthink it.

Many people seem to think that the difference in the points of impact between two different loads fired from a rifle with the same windage and elevation settings on the sights are due solely to the difference in the exterior ballistics (trajectory) of the two loads. This notion is false.  There isn’t a ballistic program on the planet that can predict these changes in the points of impact and trying to do so using the different muzzle velocities and different ballistic coefficients of the two different loads is a wild-goose chase.  

The difference in the points of impact between two different loads (with the same sight settings on the rifle) out to say 75-100 yards will be due in large part to matters of interior ballistics; barrel harmonics and recoil vectors for instance. These components may not be the same from rifle to rifle and are not predictable using ballistic software. The only way to know what the difference in the points of impact will be, is to shoot the different loads in your weapon.

To illustrate the above points with a specific example, the graph below shows that there is nearly no discernable difference in the trajectories of the Sierra 55 grain BlitzKing and the Hornady 70 grain GMX out to 100 yards.





Yet, when I actually fired the Hornady 70 grain GMX load from an AR-15 that had been zeroed for POA=POI at 100 yards with the 55 grain BlitzKings, the group of the 70 grain GMX impacted 2.9” LOW and 3.7” TO THE LEFT of the point of aim.





...

If you’re shooting a 10-12” steel plate at 300yds, you’ll probably notice.  Only one way to find out how bad it will be.

Sort it out, even for practice or plinking. If not you'll probably be frustrated for reasons outlined by Molon above.

Best practice is to pick on good load to zero with for all rifles of a given type or usage assuming they all shoot it well. Obviously given today's constraints that may not work if you didn't build a stash up before the craziness.

You did stock up, didn't you? If so, save this stuff for close range or as a last resort.

But wouldn't "troops" be issued and shoot the same ammo they zeroed their rifle with and with full 5.56 velocity? Seems to me the only change in POI would be very tiny lot-to-lot variation.

Thank you for coming back.  Excellent, as always!

Biggest thing for me would be the difference in felt recoil. Going from a hot XM193 round to a weak PMC bronze is going to feel odd.

Topic Moved

Didn’t we just have this discussion?

This.

I found out today .223 55 gr FMJ PMC Bronze only shot one inch lower than Federal 69 gr Gold Medal Match. Of course this was at 50 yards, but for today's plinking the difference was immaterial.

At close range, 50-100yds, you're not likely to find much difference. Generally, all full power ammo shoots within a couple inches at 100yds. Every once in a while, you'll find a lot or load that just does not agree with a barrel and goes wild. IME this is the exception, but I have had it happen. With high power rifles, trajectory differences are minimal and not terribly relevant, you're focused on offset due to barrel harmonics and black magic.

At 2-300, you may still hit steel, but it's questionable whether trajectory or offset is to blame for a miss.

You really need to shoot each load on paper, at least at 100yd if you have a chrono, or 100 and 2/300 without. The best you can do is verify that load B shoots Xup and Yleft, and either do the math based on drop and known BC (from firing at a further distance), or use the velocity from the chrono to plot trajectory.

These plots can then be compared fairly from the same assumed zero. Then the zero distance can be adjusted with each one to achieve Maximum Point Blank Range, or whatever else you may wish to do.

E.g. if you use two different bullets, you may find that A is best used with a 50/200 zero, but B is best with a 36/300. Since actually zeroing at 300 could be difficult due to wind or range restrictions, you can consult the tables and reference that with A @ 50/200, it will be 1" high at 100yds, and that B @ 36/300 is supposed to be 2.5" high at 100.  Now go fire and zero your rifle for A. It now hits 1" high at 100. Fire B. B actually hits 3" low. Now you know, that if you wish to use B, you need to come up 5.5" at 100, or 5½MOA.

To throw in a horizontal offset, do the same, but no real math is needed. Just fire a group of each in good conditions or a well measured wind (accounting for wind drift). You then know for later that with a zero for A, B needs however much offset.

I just sorted an ammo can full of lose 7.62X39 rounds that have been sitting around for 15 years. But I was specifically trying to find out which loads shoot better in my new AK and the differences were dramatic in group size and POA.

It's a great opportunity for the OP to find out which loads his particular gun prefers.