Heavy Brass, How much adjustment to powder charge?

[clearwater]

Bought some 308 NT brass. It weighs about 183 grains. It holds 49.3 grains of IMR 4895 to the top.

My Winchester brass weighs 159 grains. It holds 52.5 grains of the IMR 4895.

I am looking at 150 grain AccuBond bullets and the Hodgdon site calls for a compressed charge at max for WW cases.

What kind of reduction in charge should I expect when using the NT brass?
What sort of things should I consider in developing a load? I will be using a Chrony.

 

[mjcmichigan]

Lots of good questions.

What to expect...

1) tighter cases will hit max pressure at lower loads.. and generally..you’ll achieve similar velocities..but not the same.

2) there will be variability in the Winchester brass, especially lot to lot..so don’t agonize this NT lot being tighter than the WW lot you have.

3) I don’t pick up range brass for calibers I am picky about for accuracy reasons. Too much bother to grade an sort all the cases. If I’m really picky (my 300 WM). I bought 400 Norma cases and divided them by volume after firing. 223 and 308, I will pick up.

Ask some one for a Quickload.

Include barrel length, primer, powder, brass brand and volume,
You’ll get a report that tells you what to expect for an average lot of powder. If you velocities don’t match, read down further in the report, they will give you hotter and colder reference points, you can then recalibrate for observed velocities.

There are fast and slow barrels...

So keep your mind open and consider well any warning signs like, heavy bolt lift, flattened primers, damaged brass.


Sent from my iPad using Tapatalk

 

[mjcmichigan]

Lots of good questions.

What to expect...

1) tighter cases will hit max pressure at lower loads.. and generally..you’ll achieve similar velocities..but not the same.

2) there will be variability in the Winchester brass, especially lot to lot..so don’t agonize this NT lot being tighter than the WW lot you have.

3) I don’t pick up range brass for calibers I am picky about for accuracy reasons. Too much bother to grade an sort all the cases. If I’m really picky (my 300 WM). I bought 400 Norma cases and divided them by volume after firing. 223 and 308, I will pick up.

Ask some one for a Quickload.

Include barrel length, primer, powder, brass brand and volume,
You’ll get a report that tells you what to expect for an average lot of powder. If you velocities don’t match, read down further in the report, they will give you hotter and colder reference points, you can then recalibrate for observed velocities.

There are fast and slow barrels...

So keep your mind open and consider well any warning signs like, heavy bolt lift, flattened primers, damaged brass.


Sent from my iPad using Tapatalk

 

[1Shot]

As with heaver/thicker "military" 7.62/308 standard practice is one full grain less that commercial cases.
With that being said Winchester cases on average are thinner and will hold more powder than most any other in my experience.
Here is the reason that loading manuals have STARTING LOADS and then list a "possible" max load. NO TWO RIFLES ARE THE SAME.
Example of wide range of "max" loads listed for IMR 4895 from manuals for 150 gr bullets in the 308 Win:
Sierra 4th edition 44.0 grs Remington case.
Sierra 5th edition 43.7 grs Federal case.
Hornady 7th edition 46.4 grs Hornady Frontier case.
Lyman 48th 45 grs Remington case.
Hodgdon 2011 edition 47.3C Winchester case.

I have been handloading going on 41 years and have loaded for many 308 Win rifles and depending on the rifle it self usually 43 to 44 grs of IMR 4895 with 150 gr bullets is the most accurate. Depending on your barrel length will effect velocity. 22" usually will average between 2600 and 2700 fps and going up to 26" will get you another 100 fps usually.
PLEASE BE AWARE OF THIS: Bullets are different even though they weigh the same. In my experience with the AccuBond bullet with it's thicker jacket base and bonded core you will reach pressure quicker than with a thinner jacket standard cup and core bullet like a Sierra. You will usually get the same velocity but with less powder. So I strongly suggest that you at least start at the starting load and do a ladder test with one round each going up .3 grs at a time shooting over your chronograph watching the velocity closely and inspecting each case for any pressure signs. Don't try to make a 308 Win into a 300 Win mag. If you get 2700ish fps with 150s with good accuracy call it done. Good luck. P.S. Nosler has an on line load data manual on this site so I suggest you go to it and see if they list IMR 4895 for the 150 AB and follow that data.
I went to the Nosler data and 44.5 gr IMR 4895 is the listed max but they lump all their 150 gr bullets together. With the AccuBond I would approach that max with great caution.

 

[clearwater]

Thanks for the advice.

New rifle, Kimber Hunter, New Brass NT, New Scope.

I have a Rem 600 carbine in 308. The brass fired in it won't chamber in the Kimber. So new brass of different brand for the new Rifle for hunting loads. I did buy a small base die and converted some of the other brass for use with cast bullet loads. Also got a case length/headspace gauge, don't want cartridges getting stuck when I have buck fever.

Will try the ladder technique.