Loading 208gr AMAX in .308

[Younggun]

Well, I found the max load for my use.

Think I might have a good area to work also, but I'll have to check the brass better before I know for sure.

FYI, pressure spikes quickly from 41.6 to 41.8gr.

 

[dee]

I would imagine your safe max will be close to 41 even then.

 

[Younggun]

The cluster consists of shots 1, 3, 4, 5, and 6.

Shot #4 was 41gr so that would be ok. Still, primer pocket stretched on #8 so I'll need to check the others.

 

[dee]

The main concern I would have is if the spike seemed to happen fast in mild temps it will be much worse in the middle of summer.

 

[Younggun]

Very true.

 

[Younggun]

Looks like the sweet spot gave me a .46moa group. I'd say the rifle likes the bullets just fine, just a matter of whether or not they will play nice with the caliber.

If not, I'll really be considering giving the 178s a try.

 

[orbitup]

I've been using the 178s but I haven't been pushing them hard.

Sent from.... RIGHT BEHIND YOU!

 

[Younggun]

Just cleaned a few of the cases by hand so I could check primer pockets and such compared against the loads.

40.8 and 41 still had an ok feel to the pockets. Didn't think to measure them.

40.6 was .2095"
41.2 was .209"
41.6 was .212" and primer had little resistance seating
41.8 was .220" and primers can be dropped in and out.

Pocket from brass that has not been used for testing these rounds was .208".

Resized cases had grown .005" which has been pretty common for most of my loads using Federal brass.

 

[Younggun]

I could probably resolve some of the issues with the pockets by switching to Lapua brass and maybe a harder primer than the Fed GMM.

I'm not entirely sure the .001 increase in pocket size was caused by these loads alone either. I had 20pieces of brass that were my favorites based on weight sorting that I liked for load testing. (I know, need to measure case capacity, but they made me feel warm and fuzzy)

May do 5 rounds at 41gr through the cases at the lower end of the scale and see how they group and if the pockets stretch anymore. I don't really care to invest in Lapua brass for this project just to see if it works.

 

[dee]

Lapua will lower the internal case capacity.

 

[Younggun]

I've been doing some reading on that.

I'm pretty torn on this. It looks like it could be a damn accurate load, and 41gr is the listed max for a shorter AOL.

I'm going to check the case capacities of the Federal brass against some Winchester I have and see if I can get a bit of cushion in the load aside from the OAL. The load upper test loads were compressed and I have no doubt that contributed to the rapid increase in pressure.

My big fear is August and ammo getting left in the sun. Something to be avoided with any load, but it happens.

On the other hand, I could probably use a different bullet and work up something much more forgiving. These just seem to cluster really well, at 100 yards anyways. .46moa with .6gr powder variation seems to be pretty good in my limited experience.


I do appreciate your input on this dee. It's been very helpful.

 

[Younggun]

Anybody tried the Hornady 178gr HPBT match?

 

[KiloKilo]

subscribed

 

[dee]

I know Lapua has a lower case capacity due to being thicker all the way through. I don't have much experience with Federal brass as it has given me problems in the past. I use Winchester for most everything I can, it's fairly cheap and consistent. Lapua makes small primer pocket brass but I don't know if it's worth the price.

 

[Younggun]

Checked a few cases just for a general idea.

Filled case with water, emptied water in to tray on electronic scale. All weight in grains.

4 Federal cases

54.2
54.2
54.3
53.1

6 Winchester cases

55.4
55
55.8
55.2
55.4
55.2


I want to check the case that pressure spiked on but I don't know if it would still be accurate to what it was before fired. I could see ha wing a capacity similar to the 4th fed case measure (over a grain under average) causing pressure to rise quickly.

 

[Governors20]

The heaviest I would use in the 308 is 175gr. You can go heavier, but it i would only go to 180 for a specific hunting round. The Army went to 220 grain for the 300 win mag, and ended up burning up barrels in 1500 rounds. Using the 190 grain more than doubled barrel life, so they went back to the 190gr. The same could hold true for the 308 shooting heavy 208gr. The 208 is more of a handicap in my opinion. You cant get the velocity up high enough to take advantage of the high BC, so you have more recoil and no long range benefit. I havent read the whole thread, but if you are shooting under 300 yards, a 155 gr AMAX will work just as well if not better.

I was shooting M118LR out to 800 yards over the weekend. I can tell you that 800 yards with 175 gr loads out a 20 inch barrel is close to the limit.

 

[dee]

The heaviest I would use in the 308 is 175gr. You can go heavier, but it i would only go to 180 for a specific hunting round. The Army went to 220 grain for the 300 win mag, and ended up burning up barrels in 1500 rounds. Using the 190 grain more than doubled barrel life, so they went back to the 190gr. The same could hold true for the 308 shooting heavy 208gr. The 208 is more of a handicap in my opinion. You cant get the velocity up high enough to take advantage of the high BC, so you have more recoil and no long range benefit. I havent read the whole thread, but if you are shooting under 300 yards, a 155 gr AMAX will work just as well if not better.

I was shooting M118LR out to 800 yards over the weekend. I can tell you that 800 yards with 175 gr loads out a 20 inch barrel is close to the limit.

If he can stay over the 2350fps the 208 has a large gain in wind deflection over the 175gr bullets by far. Now if using the 185gr juggernaut there is no difference besides less recoil with the lighter bullets as the higher bc and higher velocity win out.

 

[Younggun]

So I switched over to the Winchester brass for the case capacity. Knew it would drop my velocity a little bit stuck with the 41gr load that fit in the low end of the accuracy node using federal brass. Loaded 13 rounds intending it to be 3 to check grouping and zero, 5 shot group at 100, and 5 shot group at 200. When I went out to shoot all that went out the window.

The first group started out really well so I decided to not break it. Had a couple where the velocity fell in to the high 23s and they went their own way.

These are the 4 rounds that stayed in the low end of the accuracy node.

Decided to take the last 7 rounds and go back to 200 yards. Seemed fairly obvious which rounds were hitting the mark and which weren't velocity wise.

Did something stupid at this point. Adjusted up 2.75 moa to keep the rounds just under the bull, then decided to adjust for the windage and cranked the knob left instead of right shot 3 rounds before it clicked on my head. Went back 2moa right and shot the last 4. Had one fly high which wasn't unexpected. The other three grouped up nicely.

Lots of potential there. Another .2-.3gr would put me back in that ~2430fps velocity range and should get rid on the flyers, but I don't think it would be safe to push it that far. I'm running at max load right now and it seems like a recipe for disaster when summer sets in and temps start hitting 100. Only other option would be to try another powder like RL17 (or 15, can't remember) and see if it could get the velocity with a lower pressure spike.

 

[dee]

RL15 is in tge same burn rate area as varget and 4895. RL17 is in the 4350's burn rate. I've played around with RL17 and it gave great velocity but I have not gotten to test temp stability yet.

 

[rushthezeppelin]

You could always opt to simply just use them in 300blk. Don't you have a blackout? They are one of the most accurate subsonic bullets out there in that platform (although you don't want to hunt with them unless you are earholing piggies).