178 Amax OCW Results

[he lives]

Prompted by Dan Newberry's post on the FGMM components earlier this week, I shot an OCW test this weekend with 178 amax's and IMR4064 from my 20" 308. I loaded 3 rounds each in 0.3 grain increments from 41.8 to 43.0. Then also loaded 43.5, 44.0, 44.5, 45.0, and 45.5 to test loads up to max listed charge weight. I noticed light pressure signs at 45.0 so I did not shoot groups at 45 or 45.5.

It was pouring rain the entire time, so the target is a mess. These groups were shot at 200 yards.

I want to pick the most promising charge weight, and shoot 5 shot groups at that weight plus 5 shot groups at +/- 0.3 grains to confirm.

The guy next to me at the range was shooting an 300 win mag with comp. We shot at about the same time and it caused me to pull a shot at 42.7. If not for the called flier, I think 42.7 looks like a good weight.

Where do you guys think the best charge weight is?

Thanks

 

[he lives]

I'd also be curious to see if anyone has had any issues with this bullet out of a 1-12 20" barrel?

 

[he lives]

Got back out today and shot another set of groups at 200 yards. Building on my results from last week, I shot these groups at 42.4, 42.7, and 43.0.

I am going to be shooting in a practical rifle get together next weekend. Targets will vary out to about 600 yards. Do you think I should load up 100 rounds at 42.7 grains? Or do you think there is more to be had with seating depth and primer selection?

Thanks

 

[gasdoc09]

This relevant to my interests. I'm working up a 178 amax load with 4064 right now also. I've always had better luck with 168 amax bullets in this gun (20" AR10, 1x11.25 twist) but am giving the 178s another go. Remington brass and 9 1/2 primers.

42.8 was my best. I loaded up 30 more at that weight and hope to get out to the range on Monday to see how they do at distance.

 

[he lives]

Thanks for the reply gasdoc. I'm curious, when you say you've had better luck with the 168's, in what way?

I haven't had this 308 very long. It wouldnt be too late to make the switch to the 168's if they had an advantage.

 

[gasdoc09]

The 168 amax just grouped better than the 178 amax out of my gun, with Varget. Both were sub MOA but the 168s could get to 1/2 - 2/3 if I was having a good day. I shot through a couple hundred of the 178s trying load workups and never could get the 178s below about 3/4 and they were more often close to 1. Tried different brass (Lapua, Federal, Remington, Prvi) and different primers (Rem 9 1/2 and CCI BR2) and they just didn't do as well as the 168s.

Recently I bought 16 pounds of 4064 because I couldn't find any Varget and I thought I'd try the 178s again. I think 42.8 will be consistently sub MOA, but I need to go shoot some 10 shot groups to really see if it'll be better than the 168s. Hopefully Monday, if I can sneak out of work early enough.

 

[pell1203]

He lives, I agree 42.7 to 42.8 is a good OCW to start with. Next time perhaps try some depth variation... that may help a bit but I don't think switching primers will make that much of a difference. Good luck!

 

[Macmathews]

At what yardage are you checking groups ?

Kyle

 

[gasdoc09]

At what yardage are you checking groups ?

100 yards for workups.


Made it to the range today, nice day for shooting, 78 degrees and still sunny late afternoon. Shot two 10 round groups at 100, both measuring just over 1". Took the remaining 10 rounds to the steel range and confirmed drop from 200 - 900 yards. The 178 amax with 42.8 of 4064 had chrono'd at just over 2800 fps but I don't believe that for a second, especially out of a 20" AR10 barrel. Real-world drop corresponded to a muzzle velocity of 2625 fps on my ballistic computer, which is a lot more believable. I think my chronograph is FOS.


Anyway, finished off by shooting 5 each of the 168s (43.0 Varget in Prvi cases) and 178s (42.8 4064 in Rem cases) at 600 yards. 4 at the 36" gong, then the last round at the 12" gong for grins, after adjusting the turrets a couple clicks. The 168s did about as well as I can ever shoot at 600, just under a 6" group and hit the 12" gong right in the middle. The 178s weren't so great, about 12" on the big gong and I missed the little gong. I don't know WTF was up with that one really low hit ... didn't call it.

I've still got a couple hundred of the 178s so I'll load them and shoot them but I think once again my gun is telling me to just buy the 168s.

 

[he lives]

I made it out to the range again too. Just a short trip to try a couple different seating depths before I loaded up for the weekend. Probably a waste of time though...the depth I was at seems to be best.

 

[he lives]

I've still got a couple hundred of the 178s so I'll load them and shoot them but I think once again my gun is telling me to just buy the 168s.

If you want to get rid of those 178's shoot me a pm and we can figure something out...they seem to be working out well for me.

 

[Wildboarem]

I know Erik Cortina over on accurateshooter.com suggest testing seating depths at .003 intervals. I thought it was to little to make a difference but may try loading up some at .01-.02 in .003 increments. Maybe worth a try, it worked for me.

Sent from my KFTT using Tapatalk 2

 

[CharlieNC]

Using LC brass my node is at 41.2gr for 20" 10twist barrel; this agrees exactly with the optimum barrel time calculation as well. Going even a little heavier in charge, Quick Load pressures became high and the POI and group size became very erratic. Your charges seem a bit heavy to me; are you using Win brass?

 

[gasdoc09]

Using LC brass my node is at 41.2gr for 20" 10twist barrel; this agrees exactly with the optimum barrel time calculation as well. Going even a little heavier in charge, Quick Load pressures became high and the POI and group size became very erratic. Your charges seem a bit heavy to me; are you using Win brass?

IMR's load data lists 40.7 - 45.2C for 180 gr bullets, yielding 2445 - 2683 fps out of a 24" barrel. 42.8 doesn't seem to be unreasonable. I've been using Remington brass, worked up to 42.8 gr of 4064 with the 178 amax. No pressure signs on the brass. Estimated 2625 fps based on my calculator and observed drop out to 900 yards.

 

[briang7511]

I am using same bullet with excellent results, need to weigh them as they can vary and my gun likes to be .030 off the lands. using same powder 4064, and using varget and rl 15.

 

[he lives]

Using LC brass my node is at 41.2gr for 20" 10twist barrel; this agrees exactly with the optimum barrel time calculation as well. Going even a little heavier in charge, Quick Load pressures became high and the POI and group size became very erratic. Your charges seem a bit heavy to me; are you using Win brass?

I'm using WCC Nato Brass. I did notice pressure signs up around 45 grains, but nothing at all at the 42.8 load I'm at now.

 

[CharlieNC]

My barrel seems to be a bit pressure sensitive for some reason. In the past a load of 44.6 Varget gave a calculated pressure of 58.5K psi which led to sticking bolt and blown ejector spring when the temp warmed up with 175SMK. Well I just I recently cut my barrel back from 26" to 20", and switched to 4064 and 178Amax with LC brass at the same time! I use the Chris Long OBT chart with Quick Load and have validated excellent agreement many times, so I began to explore nodes in the 40-43gr range. I ran up to 42.5gr with no pressure signs at calculated 59.0Kpsi; but the groups really went to crap at that point. (Note - just days before I observed a similar issue with my 6BR when I was approaching a higher charge node; calculated pressure above max, but no apparent sign of pressure, but group went to crap.) Except for a couple of these high charge/high pressure node situations the OBT / Quick Load tool has worked perfectly, and it appears the failure is when the pressure shock wave becomes excessive. The low node is now at 41.2 grs with LC brass. For 20" barrel there is a node at about 43.2 but unfortunately my barrel will not let me work up to it due to pressure.

Also in terms of going by bullet weight alone, there are major calculated differences using Quick Load for different bullets. 178 Amax is around 600psi higher than the 175 SMK, so you need to be careful when pushing max loads and going by weight alone.

 

[Doc68]

I just loaded up 21 rds from 41.8 - 43.3 of imr4064. I have a 20in remington stock barrel COAL 2.810. Gonna shoot 3rd groupings. I'll have to post my findings. Oh and it's 178gr AMAX. With hornandy match brass trimmed down to 2.05 +/- .005. Don't ask how far off lands because I don't know.

 

[gasdoc09]

Well, I decided to start anew, from the beginning, to see one more time if I could get the 178s to shoot well.

Insanity is doing the same thing repeatedly and expecting a different result, so to change something, this time I went with Prvi brass. Once fired Prvi brass, Redding full length die with the 336 neck bushing, trimmed in Giraud. Remington 9 1/2 LRP, 4064 powder.

The 45.0 gr charge popped the primer, 44.6 put a bit of a cut into the case head, so I didn't fire the other two rounds loaded at those charges. 3-shot group sizes:

41.4 - 0.65"
41.8 - 0.34"
42.2 - 1.17"
42.6 - 0.95"
43.0 - 0.46"
43.4 - 0.63"
43.8 - 1.12"
44.2 - 1.44"
44.6 - quit after 1 shot
45.0 - quit after 1 shot

Cases from left to right, from 41.4 gr to 45.0 (I pulled the unfired rounds):

Rifle is a 20" AR10, 1x11.25" twist. Bipod and rear bag at 100 yards. The targets:

Think I'll load up and shoot some 10-shot groups around 43, to see if that area turns out to be the sweet spot it looks to be.

 

[mtang45]

I'm certainly not experienced enough on looking at an OCW test to give advice, but to me it looks like your node is 41.8. There is too much of a radical POI shift between 42.6 and 43.0 for the latter to be a node to work around..... Unless of course I'm looking at the target wrong

Might be a node between 43.0 and 43.4

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[YAOG]

Well, I decided to start anew, from the beginning, to see one more time if I could get the 178s to shoot well.

Insanity is doing the same thing repeatedly and expecting a different result, so to change something, this time I went with Prvi brass. Once fired Prvi brass, Redding full length die with the 336 neck bushing, trimmed in Giraud. Remington 9 1/2 LRP, 4064 powder.

The 45.0 gr charge popped the primer, 44.6 put a bit of a cut into the case head, so I didn't fire the other two rounds loaded at those charges. 3-shot group sizes:

41.4 - 0.65"
41.8 - 0.34"
42.2 - 1.17"
42.6 - 0.95"
43.0 - 0.46"
43.4 - 0.63"
43.8 - 1.12"
44.2 - 1.44"
44.6 - quit after 1 shot
45.0 - quit after 1 shot

Cases from left to right, from 41.4 gr to 45.0 (I pulled the unfired rounds):

Rifle is a 20" AR10, 1x11.25" twist. Bipod and rear bag at 100 yards. The targets:

Think I'll load up and shoot some 10-shot groups around 43, to see if that area turns out to be the sweet spot it looks to be.

Whoa! You may be loading those cases up way too hot! Looking at your spent case photo it looks like you may have ejector marks starting in the third row from the left which would tell me to back down the charge weight. I have about 600 Privi .308 cases and the dozen cases I sampled measured between 55.4-55.7 grains H2O. Using QuickLoad with IMR 4064 powder even using an imaginary 56g H2O case capacity you are looking compressed before 42g where you are 5% away from the danger zone. I'd back down on the load and go with a lower / slower node load at about 40.0g You are definitely going to hurt something or someone soon if you keep using the hotter loads in this weapon.

HTH!

 

[gasdoc09]

I have about 600 Privi .308 cases and the dozen cases I sampled measured between 55.4-55.7 grains H2O. Using QuickLoad with IMR 4064 powder even using an imaginary 56g H2O case capacity you are looking compressed before 42g where you are 5% away from the danger zone.

Hmm, interesting. I haven't used Quickload. This rifle leaves ejector marks with some factory ammo, so I wasn't real concerned that some of the mid loads in the test had some marks.

41.8 sounds a little better now ...

 

[jsthntn247]

You two nodes are 41.8 and 43.2. If 43.2 is not too hot I would do a seating depth test there.

 

[he lives]

Gasdoc -

It seems like you really want this bullet to work for you and are willing to put the time/funds into load development.

If it were me I'd want to shoot a test that left no doubt about the results. To be exhaustive, I'd shoot 5-shot groups with 0.2 grain increments from 41.4 - 42.2. I'd shoot these at at least 200-yards. That seems to be your most promising range of charge weights and shooting 5-shots at a little longer range should give you your answer.

Good Luck

 

[Smokerroller]

My lr 308 leaves very light ejector marks on just about all the brass. From factory loads to light hand loads at the bottom of the pressure ladder. I can't comment on whether or not you should be concerned. It looks like 41.8 is a good load and you could go with that one unless you want to push this load to distance you may be getting more fps from your 43 grain load, which is also great.

 

[JSTARSZ]

I have been working with the same powder, IMR 4064 and 175 Sierra BTHP, as they both have been available lately, for my 308.

Rifle - Accurate Ordnance 24" Bartlein Barrel...I loaded from 42 - 44.7 grains of IMR 4064 and a seating depth of 2.815" and conducted the tests at 100 yards looking for nodes. I ended up having two nodes at the lower end of 42.6-43.2 and in the 44.4 range. I didn't pop any primers and even the 44.7 didn't show any signs of pressure or extractor swipes in the casings. I also decided to chrony the loads to see where that came out.
42 - 2594 fps
42.3 - 2610
42.6 - 2635
42.9 - 2648
43.2 - 2673
43.5 - 2703
43.8 - 2709
44.1 - 2720
44.4 - 2742
44.7 - 2755

I decided to work at the 43.2 as it gave me a good node and also a decent speed of 2673 fps. This is my first time doing an OCW so it was interesting to see how it turned out as I saw some distinct differences with the varying loads and where a node showed up and went away. I am loaded up some 43.2 and am going to try them at 200 yards this coming weekend.