.308 OCW test 178amax over varget analysis help

[scott123456789]

Sight in verification was with factory federal gold medal 168gr.

Load Details
.308 Cal
178 Amax Bullet
CCI BR-2
New FL sized Win Brass
Varget Starting at 42gr +.3
COAL 2.835 right at max mag length
Rem LTR Stock

Sight in cold bore was the high shot then three lower

First Round Through all 10 loads. 1" stick ons

Ignore the bigger circles and shots was testing a second rifle at the same time

A whole bunch better then last time but now what?

 

[Huckleberry75]

Re: .308 OCW test 178amax over varget analysis help

6,7,8 looks pretty decent. FWIW, my rifle love teh 43.9gn of Varget and 178 Amax.

 

[Tripwire]

Re: .308 OCW test 178amax over varget analysis help

Look at 3, 4, 5, and 10....do you see a relationship?

VERY similar points of impact, AND nearly perfect triangular "grouping"......

Those places in your test are somewhere within the two nodes for that range of powder weights. 3,4,5 being in the low node, and 10 being in the high node. Typical of what I find in an OCW. Note though, that I said "in" the node, not "the" node...at this point you can't tell exactly where they are in relation to the center of the nodes. You need to prove that out with smaller increments of barrel speed, later.

What I would do next is shoot the exact same test the exact same way and see if things repeat....afterall the very principle of OCW is gaining a predictable and repeatable load.

My guess is you haven't found pressure yet with #10, and there's still a little room at the top with your rifle. So, once you've re-shot THIS test for repeatability, then move on to testing the upper end, the node around #10, for pressure. That is, of course, if you are ultimately looking for the fastest accuracy node for this power/bullet in your rifle. Approach the pressure limit with caution, and with powder increments no bigger that .2 grains.

Once you find that UPPER LIMIT, then you can test say 44.5, 44.6, 44.7, 44.8, 44.9, etc, up to just shy of the pressure limit you found. The first sign of pressure is usually, IME, well within a scatter node, so there's no point in actually testing that pressure limit again....just stay shy of it enough to find and document the beginning of the upper end scatter node that contains your pressure limit, if only to tell yourself that is the end of your upper accuracy node.

Trust me, testing in .1 grain increments at that point will show you the exact beginnings and the exact ends of the nodes, and thus a more defined center of that node. That is, if you can shoot, and if that level of OCW precision is what you're after.

From there, you take the exact center of the upper accuracy node as your OCW with this combination of components and if the groups don't quite suit you, then you test SMALL incremental changes in seating depth to adjust the exit timing of the bullet to better put the exit at the optimal time in the cycle of the shock wave.

 

[X-fan]

Re: .308 OCW test 178amax over varget analysis help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tripwire</div><div class="ubbcode-body">Look at 3, 4, 5, and 10....do you see a relationship?

VERY similar points of impact, AND nearly perfect triangular "grouping"......

Those places in your test are somewhere within the two nodes for that range of powder weights. 3,4,5 being in the low node, and 10 being in the high node. Typical of what I find in an OCW. Note though, that I said "in" the node, not "the" node...at this point you can't tell exactly where they are in relation to the center of the nodes. You need to prove that out with smaller increments of barrel speed, later.

What I would do next is shoot the exact same test the exact same way and see if things repeat....afterall the very principle of OCW is gaining a predictable and repeatable load.

My guess is you haven't found pressure yet with #10, and there's still a little room at the top with your rifle. So, once you've re-shot THIS test for repeatability, then move on to testing the upper end, the node around #10, for pressure. That is, of course, if you are ultimately looking for the fastest accuracy node for this power/bullet in your rifle. Approach the pressure limit with caution, and with powder increments no bigger that .2 grains.

Once you find that UPPER LIMIT, then you can test say 44.5, 44.6, 44.7, 44.8, 44.9, etc, up to just shy of the pressure limit you found. The first sign of pressure is usually, IME, well within a scatter node, so there's no point in actually testing that pressure limit again....just stay shy of it enough to find and document the beginning of the upper end scatter node that contains your pressure limit, if only to tell yourself that is the end of your upper accuracy node.

Trust me, testing in .1 grain increments at that point will show you the exact beginnings and the exact ends of the nodes, and thus a more defined center of that node. That is, if you can shoot, and if that level of OCW precision is what you're after.

From there, you take the exact center of the upper accuracy node as your OCW with this combination of components and if the groups don't quite suit you, then you test SMALL incremental changes in seating depth to adjust the exit timing of the bullet to better put the exit at the optimal time in the cycle of the shock wave. </div></div>


All money right there.

 

[scott123456789]

Re: .308 OCW test 178amax over varget analysis help

Thanks a bunch for the advice.

Would it be a terrible idea to shoot the groups in order? With testing the other rifle and walking back and forth there was at least 30 minutes between rounds fired if not a little more. The wind and temperature changed a few times during the test as well.

 

[Tripwire]

Re: .308 OCW test 178amax over varget analysis help

I personally don't like wind, or hot, for testing....thus I test in the early morning or late evening when the wind is laid down, and in the shade during hot weather.

Can't recall ever wanting to test more than one rifle at once....keeps me focused on the task at hand.

 

[scott123456789]

Re: .308 OCW test 178amax over varget analysis help

Only get out to shoot once a week and thought it was a great opportunity to shoot groups while the other cools.


Now that I've done the round robin is shooting in strings ok or stay round robin?

 

[Jackalope33B]

Re: .308 OCW test 178amax over varget analysis help

Scott- I just loaded up some 178 Amax for my 308, and Im using Win brass and Varget as well. When I started my load at 43gr, I noticed that the rounds were some what compressing the powder. I loaded all the way up to 44.5gr and there was deff some powder compression. Did you have the same effect when you loaded your ammo?

 

[Tripwire]

Re: .308 OCW test 178amax over varget analysis help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: scott123456789</div><div class="ubbcode-body">Only get out to shoot once a week and thought it was a great opportunity to shoot groups while the other cools.


Now that I've done the round robin is shooting in strings ok or stay round robin? </div></div>

Understood....

I'd stay with round robbin because it spreads other influences like you, barrel heat, etc., over the entire test...instead of possibly skewing one certain area. That's why Dan suggests round robbin in his guidelines, it makes it a little more of a scientifically reliable test.

And, if you are hitting compressed loads like Jackalope eludes to, then you're on your own....I don't do compressed loads, ever.

I'll move on to a little faster powder to get away from them......

 

[X-fan]

Re: .308 OCW test 178amax over varget analysis help

What are your thoughts on compression Trip?

 

[Tripwire]

Re: .308 OCW test 178amax over varget analysis help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: X-fan</div><div class="ubbcode-body">What are your thoughts on compression Trip?
</div></div>

It's just not for me.....

I like a 90 to 98 percent load density with any given bullet, and thus search out a powder that yeilds that with the upper end accuracy node. My concern is the physical alteration of the powder kernals, especially on the highly compressed loads with a stick powder. Powders are formatted on purpose by the manufacturer to achieve a specific burn rate....which includes it's shape and the coating. If that is compromised by crunching them, and possibly breaking them, it alters the burn rate to an unpredictable amount in each charge.

Of course compression varies from slight to severe depending on the circumstances, and some compression might not show any difference because nothing was actually damaged. I simply choose to not compress a load and consider that to be insurance that I get the full intended benefit of the designed burn rate....THAT is the only way I can guarantee myself accurate consistancy from shot to shot.

 

[Jackalope33B]

Re: .308 OCW test 178amax over varget analysis help

Do you suggest that I take these round apart, and start at a smaller grain per bullet? From what I have read on here, people are using Varget W/ 178 Amax with 44 +/- grains. Didnt think I would be compressing them

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tripwire</div><div class="ubbcode-body">

</div></div>


And, if you are hitting compressed loads like Jackalope eludes to, then you're on your own.... [/quote]

 

[scott123456789]

Re: .308 OCW test 178amax over varget analysis help

Seating them as long as they did it was what I would call just barely compressed. So if I test the next .1 of a grain or so it would be a bit more.

My ultimate goal is at least throwing rounds out to 1k so the extra speed would be good, but living in texas I need as stable a powder as possible so varget fits that bill. Also I plan to hunt with this load and it can be down to the teens so I would prefer to stick it out with varget.

With no shooting skills doesn't the idea of taking a shot every 30 minutes resetting getting up walking to the target, readjusting have a worse influence? Especially since I am very close to knowing where I want to be with the load.

 

[Gene Poole]

Re: .308 OCW test 178amax over varget analysis help

I respect Tripwire a lot and he has some great advise overall, but I disagree with the compressed load thing. There's nothing wrong, in my humble opinion, with a compressed load, and, in fact, the max loads for .308 in Hogdon's manual for Varget have a "(C)" which doesn't mean "Copyright", but "compressed!" Lots of the larger diameter stick powders show perfectly acceptable loads that are compressed and I personally would rather have a consistent compressed load where the powder doesn't move at all, than having a space where the powder can creep around during chambering, etc. leaving a gap in inconsistent locations throughout the cartridge depending on gravity and inertia.

 

[Tripwire]

Re: .308 OCW test 178amax over varget analysis help

I fully expected someone to disagree with me about compressed loads.....this is, afterall, the internet.

Do note that I was asked my opinion, and I gave it, and I gave my personal justification for my opinion....which included the concession that some compression is probably just fine.

I'm not here to argue you, or anyone, out of compressed loads....it's just that, once again, they're not for me. I'm never not able to aquire perfectly acceptable results without crunching kernals.

 

[X-fan]

Re: .308 OCW test 178amax over varget analysis help

Interesting thoughts Tripwire.

Taken to the extreme powder compression can cause issues..It is fairly common to hear of issues with specific cartridges such as the 458Winchester...Then again we are talking massive compression and can usually add significant heat to that equation.
I have also heard of ignition problems with heavy compression.

I have found heavily compressed loads to be somewhat inconsistent at distance...Not to mention increasing velocity variation.
As far as mild compression I can see no difference.

 

[Break Bad]

Re: .308 OCW test 178amax over varget analysis help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: X-fan</div><div class="ubbcode-body">...I have found heavily compressed loads to be somewhat inconsistent at distance...Not to mention increasing velocity variation.
As far as mild compression I can see no difference.
</div></div>

Its good to hear this coming from experience. My recent test, 155 scenars 44 - 47gr varget in .5 increments, showed nodes at 44 and 47 (both half minute groups at 200). Wanting a flatter trajectory, I'm tempted to work up another test around the 47 node. But, this is a new rifle and I have a match (my first) in two weeks, will likely just settle on 47 for now and try to get it zero'd and dope'd.

Beyond that, it would be interested to see how the maybe the 44gr compares with a 47+gr out thar

 

[X-fan]

Re: .308 OCW test 178amax over varget analysis help

To be honest I am not much of a 308 guy...There are so many better choices (DOH!

)

I see a lot of guys running fairly heavily compressed loads in that round with good accuracy, but I wouldn't know if it works consistently or or not. I suspect consistency will be reduced if you get too carried away.

One more thing of note that reinforces Trip's thinking.
If you pull apart a load that has been heavily compressed and left in the sun for a while the powder gets stuck together in one lump...Sort of like it fuses together...It can be broken apart with a pick, but that can't be good for ignition right?
Not all powders do that, but I thought I would mention it.