Superformance Powder and SOOTY Brass?!

[GF271]

Howdy!

I am a long time shooter, first time handloader. I'm starting with working up loads for my most basic rifle using the following components:

Make/Model: Remington 700 SPS Tactical AAC
Caliber: .308 Winchester
Barrel: 20", 1:10" twist

Brass: Federal, once fired
Bullets: SMK 168gn
Primer: Federal 210, Large Rifle
Powder: Varget

While waiting for Varget on backorder, I have Hodgdon Superformance I would like to experiment with. I am aware this may not be and ideal powder. However, I can find little info on it and I would like to carefully work up a load to understand it's viability. I loaded and chronographed (3) 3-shot groups:

41gn @ 1975fps
42gn @ 2020fps
43gn @ 2100fps

I expected the fps may be low as I was starting at that point for safety. integrity of all the spent cases was good. However, they were quite sooty on the outside and my barrel was filthy.

1) Why are the cases so sooty?

2) Is it a condition of too little powder?

3) Would a magnum rifle primer help this by encouraging a complete burn?

3) COAL is 2.935" as I am trying to make up for a ton of free bore in the factory barrel (The round is touching the lands at a COAL of 2.64"). Is shallow bullet seating a cause of the soot?

Thanks for any input!

 

[243winxb]

Use the Superformance for something with data.

Superformance has a burn rate near H4831. Both powders are to slow burning for 308. Look up data for IMR 4831, its also to slow, but it fills the case with a compressed load. http://castpics.net/dpl/index.php/reloaders-reference/powder-company-manuals/14-imr-reloading-manuals/40-imr2001 Full diameter of the bullet shank/base should be at the neck shoulder junction of the case.

 

[Gtscotty]

Way too slow for .308, you're probably not getting enough pressure fast enough for the case to seal the chamber before some gasses blow back around, hence the soot. If you can't get Varget yet, you'd be much better served by IMR4064 which seems to be in good supply everywhere I've been. Try feeding your .308 some 4064 and you might decide you don't have much need for varget.

 

[GF271]

Thank you, both. Each are helpful pieces of info.

 

[macgrumpy]

Wrong powder, you'd have to use upwards of 52 grains before you got to a reasonable speed and pressure and then the load would be compressed by quite a bit. An awful lot of people seem to think that reloading manuals aren't of any real value but this is why they don't list this powder for a 168gr .308 load.

 

[TwoEyedJack]

I'll second the vote for IMR4064. It seems to be the most accurate powder I have used in .308, with Reloader 15 a close second. Even my M1 .30-06 and my .22-250 love 4064. Very versatile.

 

[GF271]

Thanks, Guys. I appreciate it. As I said, I'm aware it's not ideal but I'm all for seeing through a process that I know has an induced failure (as long as it's safe), for the sake of my own training and experience. It's one thing to know something won't work. It's another to be able to explain "why" with first hand accounts.

Looks like I'll be searching for some 4064 with my down time.

 

[Gtscotty]

No prob, shooting those pricey match bullets, you might as well use a powder that can give you peak performance. FYI, obviously work up to it, but I see best accuracy with 168 hpbt's at around 43.5 grs 4064. Every rifle will have its preference, but a lot of .308's seem to do very well right around there.

 

[joneb]

For 168's I've had very good results with BL-C2 in a 22" 1:12, for 150 gr Varget has been very good to me.
I have some IMR XBR 8208 I'm looking to try with 125gr Nos BT.

 

[macgrumpy]

Heavy soot along the entire case proves that the case didn't expand in to the chamber wall (obturate) indicating that the powder burn didn't produce enough pressure.

Not enough pressure can be caused by several things but the most common cause for a novice would be the wrong powder or not enough powder. Simply adding more powder is possible and if done slowly could result in finding a powder charge that will work but that will waste a lot of resources (powder, primers, bullets, etc) or could damage you and/or the gun. It's possible to research these questions before you experiment with your guns and your body and that's probably something you need to learn how to do but for me I've settled on using computer software to estimate pressures and velocities. With the right tools you can save a lot of time, money and pain.