Waiting on a stamp for a SBR in 308 Win.  Have been working up loads in a 16" barrel with Varget while waiting until I can swap out to the 12.5" barrel.  Got to thinking that a faster powder may be more efficient out of hte shorter barrel and yield a higher velocity than a slower powder.  Bullet weight range of 125-180 grains.  Has anyone already done the work on this?

Tagged for interest.

I think the 125TMK out of a shorty .308 would be downright nasty, though.

use a 147-155 grain bullet and 41 grains of H 322 will work well.

I have a 12.5 inch 308 "pistol". Am using 8208 XBR with 168 A-Max and 150 FMJ. Pm me for load info if your interested. Got Both rounds real close @100 yards without changing optics position.

was going to reccomend this exactly except I don't own a 12.5. I played around with this concept with a 16" .308 with powders as fast as IMR4227 and as slow as 2000MR and bullets as light as 110gr to 178gr.

here where my results 4227 was SCARY! ran great one outing with no pressure signs, went out a few months later with 10-15 higher temps and almost blew up the gun!

H4895 worked well with all bullet weights 110,130,150,168,178

Varget wasn't any better than H4895 but seemed alot louder

2000MR was 100ft/sec faster with 168's at my accuracy node 1gr below max and slightly higher at max but es/sd and groups opened up. was about 75 ft/sec faster with the 178's but couldn't reach the next node in my rifle so my accuracy load velocity wasn't very impressive.

The 168 amax at 2600ft/sec (averaged 3/4moa)from my 16" LR308 using 2000MR was from my limited testing the best all around load. I was hitting 3MOA target at 800yds 4 out of 5 times consistantly and 5 out of 5 a few times using a 1.5-5 leupold MR/T.

8208 xbr is worth a try and is actually my favorite powder right now(I did not have this during my initial testing). I have found like many it seems to be most accurate near or just beyond max loads. but in my experience 2000MR will get the nod for velocity (I hear cfe223 is another good one to try for speed)

I built a savage with a 18.5" tube and so far the 168 amax 8208 combo is working great. velocity is only 2623avg but it shows great promise. I was able to drive 155TMK's 2825 with 8208 in my 18.5 but it was happier in the mid 2700's which if you crunch the #'s isn't a big enough gain to justify their greater cost (read brian Litz's response about TMK's BC very inflated with the 155's) they were loaded .020 off the lands which with this bullet is out there aways (want to say I was 2.860ish don't have my notes in front of me) I have some 175gr nosler RDF's inbound that I will try with 8208 and 2000MR.

If your willing to single feed for a long range load, the 208 hornadys are beast's! my 18.5 will drive them to 2525 loaded 3+" with 2000mr. makes a huge difference in the wind, and on the receiving end!(both the shoulder and target)

I picked 8208 due to a faster burning powder than most so most will burn in barrel and not waste it. 4064 wasted to much.

All of the powder will actually burn within the first 2-3 inches of barrel.  

Big thanks to you and Bearcat.  How does 8208 meter?  H4895?  Sounds like IMR 4227 is definitely out of the running.  Should have noted in initial post that it will be a SBR in a LR308 semi auto set up.  If it matters, it is a 2A Armament light weight build.  Entire 16" rifle is 6 pounds, under 7 with suppressor.

Meters pretty good. I use a hornady auto loader to get close, then trickle the rest in with a omega trickler on a gempro 250. Slow but accurate.

This topic is of great interest to me as well.

Ought to pick up my 12.5" AR10 in .308 in a week or so from being assembled.

Bearcat, PM sent for your data, if you don't mind sharing. Or you could post here, whichever you care to do.

Thanks much

Eric

8208 meters very well. I load my .223 blasting ammo on the progressive with no worries. in a dryflash syle modded redding 30br powder measure it's within .1gr with it but I now have a hornady autocharge that I use. H4895 isn't as bad as Varget (one of the worst!) but before I got the autocharge I have a stand I built for the 30br that has a spot for my rcbs trickler. I would drop a charge .3gr low and trickle up on my rcbs 505. you'll get a crunch here and there with H4895 but Varget almost always crunches.

If you decide to try 2000mr or cfe223 I'd strongly reccomend running a Slash heavy buffer, with a vltor a4 buffer tube (longer for  a full sized buffer) and a sprinco RED. (truth be told those mods would be a good idea regardless) made my rifle much smoother operating and didn't dent the brass on the deflector near as bad. A adjustable gas block would be a good idea with the suppressor

Couldn't agree more.

I load my 77gr .223 with 8208 on a Dillon and was planning to do my initial load dev for 150gr and 175gr projectiles for this rifle with 8208 as well so I can load on the progressive and avoid weighing individual charges of Varget.

My experience has been that faster powder usually won't work better in a shorter barrel than a slower powder, all other factors being equal.  Appropriate powder speed is more strongly associated with the ratio between case diameter and case capacity, from what I understand anyway.

It is usually true that whatever load will give you maximum velocity in a long barrel (20 to 24 inch) will also give you max velocity in an SBR (12.5 inch in your case) relative to other loads it's competing against.  In other words, even though the same load fired from a 12.5" barrel will be lower velocity than if it's fired from a 20", that load will still fall in the same pecking order of fastest to slowest.

It's somewhat rare for a fast powder load that already produced lower velocity than a slow powder load in a long barrel produce more velocity than the slow powder load in a short barrel.  On occasions where the fast powder does produce more velocity, it's usually because the velocities of both loads are extremely close to begin with, close enough that other factors could be affecting the result as well.

I would just wait until you have your SBR on hand before worrying about working up loads.  A different barrel could very well not like whatever load you work up in your current barrel anyway.  Don't be afraid to use slower burning powders in an SBR if they are called for by your loading data.

just snagged a 12.5" pistol as well so hoping Bearcat could post his data if at all possible.

You could also look for data for .308 handguns like the Encore. Most of these have 15 inch barrels though, and no gas system. Still, its a start. There should be plenty of information worked up by handgun hunters.

Here you go...

temp was 70 degrees
168 A-Max 8208XBR 42.0 grains 2365 fps avg 10 shots
150 Hornady FMJ 8208XBR 42.4 grains 2392 fps avg 10 shots
162 AP 8208XBR 42.2 grains 2326 fps avg 10 shots
for comparison I tried commercial ammo
Winchester 168 Match 2338 fps avg 10 shots

This is what I am set for shooting. Took a bit to get all three rounds to get close @100 yards. Works for me. enjoy. But I do suggest you still work up loads as each rifle is different.

While not .308, I recently worked up some loads for my 7.25" POF P415 pistol, and had the same thought about faster powder=more velocity. I found that the opposite was true. CFE223 consistently yielded 100-200 fps more than 8208 XBR in every load that I worked up. It may be different with .308, but I just wanted to share my experience because I just got done with testing these about a month ago.

I have a POF P308 with a 14.5" barrel, and 45gr of IMR 4064 with a 155gr Nosler CC gets me an average velocity of 2535 fps. A Nosler 150gr E Tip over 49gr of CFE223 averages just over 2700 fps. I have a lot of IMR 8208XBR, but have not tried it in any .308 loads yet. I've used it for .223 exclusively so far.