Pics-Weight sorted LC brass

[remaction]

If anyone is interested, I was working on some Lake City 5.56 brass today and had just finished sizing, trimming, cleaning, etc. when I wondered how consistent the weights were. I had a batch of 179 ea with 2009 headstamp and 105 ea with 2003 - 2008 headstamps (about 50 of the 105 were 07).

Results:
90% were between 91-92.5 grains (1.6% weight variation)
-94% of the 09 brass was in this weight range
-82% of the 03-08 brass was in this weight range
61% were between 91.6-92.4 grains (0.9% weight variation)
-68% of the 09 brass was in this weight range
-50% of the 03-08 brass was in this weight range
30% was between 92.1 and 92.4 grains (0.4% weight variation)

 

[Mag 300]

Re: Pics-Weight sorted LC brass

amazing I would have thought they would be closer , what was your range that you would use ?
Say 1 grain differance??
Bill

 

[goose_boy]

Re: Pics-Weight sorted LC brass

Remaction, glad to see someone else is curious about this too. I checked a bunch of LC I had as well as several bullets. I think mine was similar but didnt have quite the extremes as your test batch. Did you uniform primer pockets and deburr flash holes? Wonder if that would make a difference.

 

[remaction]

Re: Pics-Weight sorted LC brass

After going through the bother of weighing them, I think I'll work up a load with the heavier brass. Once I have a load, average velocity and S.D. established I'll then try the lightest casings and see what the effects are on 2 gr. lighter brass.

This is for my RRA varmint AR so the results may not be as true as if I were using a bolt gun, but as long as I went through the weighing effort I may as well experiment. There may be other factors at play, such as loading from the mag and the chambering effect so I'll probably put one in the mag and chamber it, put another in the mag and chamber it, etc. I read in Sierra's manual that the chambering process of an AR with factory ammo affected their OAL by .003 to .007", so this would be a better experiment in a bolt gun for the true effect. I'm at about .002" tension so I may find that I need to go to a bit more neck tension. I'll have to measure a few before and after chambering to see if I need a bit more tension.

I need the weather to improve here in WI first...

 

[Hookturnr]

Re: Pics-Weight sorted LC brass

I have found this to be a pretty common range with several different brass manufacturers. I recently sorted 150pcs of Norma 300RUM brass and found very similar results. My Remington brass shows a little flatter curve but similar weight range as well. Winchester was an even flatter curve yet but still holds the majority in a 1.5gr. range For my big guns, it's been nosler or norma lately for consistency. For the others, Rem, Win, Fed, LC..

 

[remaction]

Re: Pics-Weight sorted LC brass

I did uniform the primer pockets and de-burr the flash holes first, and trimmed them all to 1.750. Actually, I was surprised that for the most part, the brass was free of any major "ears" when I did the flash hole de-burring.

Note that the 9 ea lightest brass were from the 03-08 lots (90.4 - 90.8 gr). For the most part, the 07 brass ran about the same weights as the 09, but I had a much smaller sample of the 07 brass (only 55 ea as compared to 179 ea of the 09 lot).

The weight spread of the 09 lot of brass was 90.9 - 92.7 gr., or 1.8 gr total variance for this limited test.