Load question - brass

[AZRedhawk44]

I've got a load that I can shoot 1.25 MOA from prone:

Lake City '07 Brass
Nosler 77gr OTM
AA 2520 25.5gr
2.255" OAL
Lee FCD crimp
CCI #41 primer



Problem is, I only have about 200 or 250 pieces of Lake City '07 brass.

I have another 250-300 pieces of Lake City '11 brass.

And another 250-300 pieces of mixed year Lake City.

How much weight variation or design variation is there from one year to another in Lake City brass?

And, in comparison to other brass, how much likely is this load to deliver the same accuracy?  I know Winchester has the most internal case capacity and guys like using that for their 500/600 yard loads for that reason.  But what about LC various years, versus Prvi, or Federal, or Remington, or IMI?



ETA:  Warning.  The above load data is running at MAX load as published by Accurate Powders, and MAX load only for rifles certified to fire 5.56 (as opposed to .223) NATO spec ammunition.  Page 12 of the below PDF.  Use at your own risk.

http://www.accuratepowder.com/wp-content/uploads/2011/01/accurate_load_data_3.5.pdf

[RoadKingLarry]

One way to tell is by trying it out.
About the only way I know of to really ID case capacity is to measure it. CCs of water, I think is how it's done.
Other than that weight sorting may be a close 2nd.

[AJ Dual]

One way to tell is by trying it out.
About the only way I know of to really ID case capacity is to measure it. CCs of water, I think is how it's done.
Other than that weight sorting may be a close 2nd.

Yeah, weigh comparative samples. Measure water in CC's accurately, and take a few random samples and cut them in half and take a micrometer to the case web thicknesses etc.

[JonnyB]

I'm definitely not a precision shooter, so take this with some degree of skepticism...

If you're looking for only 1.25 MOA, is the brass that critical? If you were aiming for (no pun intended) sub-MOA - say .3 to.5 - it's probably a big deal.

Won't any old out-of-the-box ammo deliver that degree of precision? I load 5.56/.223 for prairie rats on a Dillon 550B. None of my brass is weighed, measured, trimmed, etc. I check a few with a gauge when getting started; if they're OK, I load a bunch. Check a few; load; repeat.

jb

[HankB]

Assuming you've done the usual prep like uniforming primer pockets and flash holes and sorting for capacity/weight, getting the best accuracy of out brass usually involves neck turning . . . the hardcore benchresters will neck turn their brass to get the thickness absolutely uniform (to the limits of their measurement capability, anyway) all the way around, but it can thin the brass to the point where they need a custom neck sizer and/or custom expander to get the right tension.

If you're using a gasgun, you may not want to do that - in which case the answer may be partial neck turning, where you adjust the tool so you're only actually cutting on about half the OD of the neck, in essence, taking down the "thick" side of the case neck just a bit.

You didn't give details on your gun, is it some sort of AR?  I'm asking because if I could shoot a service rifle from any position and consistently get 1.25 MOA with iron sights and my eyes, I'd be grinning from ear to ear.

[AZRedhawk44]

I'm definitely not a precision shooter, so take this with some degree of skepticism...

If you're looking for only 1.25 MOA, is the brass that critical? If you were aiming for (no pun intended) sub-MOA - say .3 to.5 - it's probably a big deal.

This very well may be a half minute load.  If I shot it from a bench.

You didn't give details on your gun, is it some sort of AR?  I'm asking because if I could shoot a service rifle from any position and consistently get 1.25 MOA with iron sights and my eyes, I'd be grinning from ear to ear.

White Oak Armory A2 upper AR-15 service rifle, iron sights.

I've not shot it from a bench... only slung in prone, with iron sights.  I don't think I'm a 1MOA prone shooter.  So having a load that shoots 1.25MOA prone is pretty exciting to me.  It's very likely a GOOD load.

Which is why I need to find out if I have other brass that will be compatible with the load and yield the same accuracy.

The group spread horizontally much more than it did vertically.  It had about a 1" spread vertically at 200 yards, and a little under 2.25" spread horizontally.  I'm going to write off the horizontal spread as my fault, rather than the load.  I shot the group "rapid fire" with 1 shot every 5 seconds.  I seem to have a tendency to crawl sideways on my rapid strings in matches.

[Gewehr98]

I wouldn't trust LC brass, either in 5.56mm NATO, 7.62mm NATO, or even .30-06 to be consistent in weight from year lot to year lot.

When forced to use the stuff, I've always weighed them and segregated them.  It's not that much work with a digital powder scale, and you're probably doing that with the bullets, anyway.

Now, my Lapua 7.62x51 headstamp brass, that's a different story.  The stuff is downright scary in how consistent it is.  Loaded with a Sierra 155gr Palma and launched from a Remington 700 PSS, it's boringly accurate, well inside 1/2 MOA.  I just wish I had snagged more back in the day...

 

[AZRedhawk44]

I didn't weigh bullets or brass for the load work-up in question.  I did uniform the flash holes and trimmed to length on my Giraud, but that's it.  Just grabbed 20 random LC 07 cases and loaded them in 0.5gr increments.  25.5 seemed to be the magic number.

When I work up the LC 11, maybe I'll do that.

[French G.]

I have no answer to your question but I will happily steal your load data. I kept nothing but LC for my personal eventual .223 loading, but I think all my years are prior to 07, that's after my serious brass whore days, else I'd offer you some. My one experiment with brass segregation was amazing, picked out one year of LC 9mm brass and loaded it up hot with XTPs. Most accurate 9mm I've ever shot.

[AZRedhawk44]

French G:  Be aware of my disclaimer I just added to the OP.  It's MAX load according to Accurate, and they make a further distinction between regular old .223 and rifles certified to shoot 5.56 NATO at higher pressures.  This is max for 5.56 data.

Shooting conditions were a cloudy AZ day around 55* F.

Come summer and 100* F temps, I'm betting I'll have to back this data back down half or even a full grain.


ETA:  It was interesting, coming up from 24.0 to 25.5.  I was thinking I was wasting time when the 24.0 group was 4", the 24.5 group was 6", the 25.0 group was 5".  That 25.5 group coming in at 2.5" was unexpected.  Is this common for double-base propellant to stabilize best at highest possible pressure?

[RoadKingLarry]

There's a little black magic mixed in with the rocket science when it come to reloading. Sometimes a given gun just "likes" a particular load. Things like barrel harmonics and even how YOU hold the rifle can come into play. Even 2 essentially identical rifles from the same lot may "like" a slightly different load.
That's why we work up a load for a given gun.
All part of the fun.

[Gewehr98]

Never forget that military brass is so much thicker than commercial that load data has to be modified accordingly.

A max load in Winchester brass may very well be over the top in Lake City brass. 

You really have to work up carefully, watching your pressure signs.

[French G.]

Yep, comparing case liquid volumes is never a bad idea. Max load noted, I skipped straight to max once in my loading career, now I cross check books and start conservatively. Although a 90gr .380 HP shoved in a 9mm is pretty cool when it must be opening in flight. 7 yard holes in cardboard target looked like 12ga slugs. Too bad the mag blew out. I felt like Clark for a day.

[Gewehr98]

OMG, I'd forgotten about our boy Clark!