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300 Win Mag Spec asks for Case length not exceeding 2.620"
However, my once fired brass was cleaned and primed and I assume that no need for trimming. However, when I checked case length, I was seeing 2.628"-2.636" That is 0.008" to 0.016" over.
Is that okay or should I de-prime and size then prime again?

Unless you are trying to achieve "Match Grade" I would not worry about it.

If shooting out of a bolt gun, the case will fire form to the chamber. Most semi-auto chamber are a little looser by design anyway.

Just my opinion.

I am trying to load:
Re-used case: Hurter's Select Hunting rds, once fired.
Primer: Win LR Mag
Powder: Alliant Power Pro 4000-MR (Similar to RL-22?) 70 grs.
Bullet: Hornady .30 Cal 208 gr A-max.

Rifle: Steyr SSG-04 with factory certificate of 0.6 MOA
Purpose: to get 5 rds all touching at 100yrds.

This is a bolt gun?

Was the brass you are using shot from your chamber? If not, I would fire a few rounds through it to fire form the brass. Then Neck-Size the brass and trim. Fire forming the brass shapes it to the exact form of your chamber then the brass will have no room to move in the chamber. It will headspace perfectly.

Are you using bench rest quality primers?

Seat the projectile as close to the rifling as you can and weigh your powder charges very closely.

Then you can go for 0.6 MOA.

Since I started fire forming brass for my Rem 700, I'm hitting a 10" plate at 400 yards every shot. Not quite 0.6 MOA, but it works for me.

Yes, it is a bolt action.

Here is the steps I am doing right now.
1) Lube the case with LEE lube
2) De-prime and size (factory die at this time, I may switch to neck-size)
3) Sonic clean the brass for like 25-30 min
4) Trim the case to factory spec
5) Weigh the powder with Hornady auto-dispenser
6) load the charge using a funnel.
7) Seat the bullet to 3.340" (factory spec) or 3.350" for deeper seated bullet into the chamber
9) Lee Factory crimp (optional)

Go shoot group of 5rds.
First 10 rds at 3.340" OAL.
First 10 rds at 3.350" OAL.

ddstuder wrote:This is a bolt gun?

Was the brass you are using shot from your chamber? If not, I would fire a few rounds through it to fire form the brass. Then Neck-Size the brass and trim. Fire forming the brass shapes it to the exact form of your chamber then the brass will have no room to move in the chamber. It will headspace perfectly.

THIS!!!!

The books can only tell you what the SAMMI spec is. If you want accurate handloads, you MUST "listen" to your rifle. It will tell you the right case length (with once-fired casings from it) as well as proper cartridge length to the lands.

Read the article by Brian Litz on cartridge length here (http://www.bergerbullets.com/effects-of ... to-part-1/" onclick="window.open(this.href);return false;). You should fine-tune your jump distance to what works best, and RECORD EVERYTHING.

Have fun!

Beiruty wrote:Yes, it is a bolt action.

Here is the steps I am doing right now.
1) Lube the case with LEE lube
2) De-prime and size (factory die at this time, I may switch to neck-size)
3) Sonic clean the brass for like 25-30 min
4) Trim the case to factory spec
5) Weigh the powder with Hornady auto-dispenser
6) load the charge using a funnel.
7) Seat the bullet to 3.340" (factory spec) or 3.350" for deeper seated bullet into the chamber
9) Lee Factory crimp (optional)

Go shoot group of 5rds.
First 10 rds at 3.340" OAL.
First 10 rds at 3.350" OAL.

Load a few and shoot through the rifle. Then switch to neck size directly after. This will require a neck sizeing die. Different than what you have. After a couple firings don't for get to anneal the brass. It will make it last longer. 300 mag is not a chunk of brass people leave on the ground. Take care of your brass and customize it to your rifle.

You'll be glad you did.

I actually have 62 pcs of once fired if your interested