does brass make a difference?

[rtc111]

I know that different brand of brass will make a difference, and so will different weights.. but how much does brass really matter?

I shot Remington brass, sort them by weight and they have all been shot the same amount of times? i always clean them, do i need to do anything else? Or "should" i do something else?

I know that case neck wall thickness can create run off but at the end of my reloading session i always put them and fix them in my hornady concentricity gauge, so i shouldn't loose accuracy there right?

How can I get my bullets to travel exactly the same FPS, and also should i anneal my cases?

[Munk]

How can I get my bullets to travel exactly the same FPS

Volume-check your cases if you really want them to be as consistent as possible. The theory goes that cases with smaller volumes using the same mass of powder will have higher pressure spikes.

Don't forget to check your bullet mass and sort them for inconsistency.

Unfortunately, 100% consistency is nearly impossible due to gunpowder. You can come close by using a scale to check the mass of every charge you load. Unfortunately, no matter the manufacturing technique, there will be variance in the size of the granules of gunpowder in any given load. This leads to differences in surface area which affects burnrates ever so slightly.

Then there's barrel temp and dirtiness. Metal changes density as it gets hotter. This affects chamber size and bore diameter in some miniscule amounts, but as the day progresses, either your shooting will change the barrel temp, or exposure to sun, or just the changing ambient temperature as the day goes on. Add to this the residue of rounds and primers fired and you have more variance.

Then there's air-pressure which will change during the day. Did you know that at higher altitudes, where there's much lower air-pressure, bullets retain far more velocity at range than at the higher pressures in low-altitude?

With match-grade shooting, you're aiming to minimize variance as much as possible. Same bullet mass, same charge mass and batch, same batch of primers, same case-volume and mass (or as close as you can possibly come). Minimize the shoulder setback from your resizing, you want your headspace to have as little gap at the front and at the back as you can possibly attain. Seat bullets as consistently as you possibly can (this means no "double-tapping" the seater unless you're doing that on every hit. Metals are elastic, so there's a bit of flex when you first hit it, and the subsequent hit will seat it slightly deeper). If you're not mag-fed, don't crimp at all. Fire at least one shot through your barrel prior to your real testing so that it's "pre-fouled" with whatever residues your powder and primer will leave behind, so that all subsequent shots will have a similar amount of hindrance. Don't expect a gun that you zeroed in the cold of the morning to shoot at the same level as the heat of the afternoon. Air pressure has changed, which affects bullet drop due to speed loss (or lack thereof). When transporting your ammo to the range, don't put it in boxes that will allow the bullet to be knocked around, it may get seated slightly deeper, use a box or case or bandoleer that they slip or clip into.

That's as much advice as I can give on minimizing variance in loading and how to treat your ammo for match-grade consistency. The rest is on you and your gun; that's technique territory, and I'll have no part in that.

[lpspinner]

Brass is just one part of the equation. Beside case volume, powder position....you also have bullet weights. Like a powder charge, it also has variances which affects velocity.

So people also measure case volume by how many drops of water it'll hold.

Also, you may want to find a way to read you powder measure beyond tenths for better consistency.

[freonr22]

http://www.ar15barrels.com/data/223weights.xls