Chasing the high accuracy node - worth it?

ZLBubba

ZLBubba

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Jan 15, 2009
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#1
The best load I've found for 175 SMKs in my 18" 308 is 44.4gr of Varget in Lapua brass, COAL at 2.853". This is a pretty accurate recipe, giving me excellent results out to 600 yards (the farthest I've been able to shoot).

I've read a number of different people that found another accuracy node around 45.7 gr of Varget, on the verge of crossing dangerous pressure thresholds. I've been contemplating setting my 44.4 load aside and doing more load development, but I'm wondering if squeezing just a little bit more speed is worth it. I'm fairly conservative in my reloading because I don't want to blow up my gun, or myself, but I wondering if I'm being paranoid about going after the really hot loads.

I haven't seen any pressure signs yet, but frankly I don't have the best eye for it since I've loaded so conservatively up to this point. Everyone always talks about sticky bolt throws, but my M2008's got a pretty stout bolt throw anyway so it's hard to tell if there's pressure signs that way.

What are your thoughts? Is chasing the higher node worth it? Thanks for the help.
 
#2
Re: Chasing the high accuracy node - worth it?

yes and no.
first you have to ask yourself. what are you shooting.
competition, recreation, hunting.....
If you are competeing then have you gotten everything out of your rifle that you could. Sports players that win don't stop training, they keep training to win again. Take your rifle and compare it with factory loads, maybe your rifle has peeked.

recreation shooting, then as long as you are happy then you have your load.
Hunting what are you shooting and how far. You don't want ammo that gives you big groups an chance only woundingyour prey.
 
#3
Re: Chasing the high accuracy node - worth it?

Bubba,
44.4 Varget in Lapua brass pushing 175s is fairly stout. If its getting the accuracy that you want, the extra 1.3 grains of powder is not going to get you that much more velocity but it will get you a lot more pressure. Its not a linear relationship between powder charge and velocity.
 
#4
Re: Chasing the high accuracy node - worth it?

If you're getting enough speed to stay above Mach 1.2 @ 1000yds when its freezing then I would stick with what you've got. It's easy on brass, safe for you, and it's not like a 175SMK is going to be massively better against the wind going an extra 150fps faster.

If, however, your MV isn't high enough to keep you above Mach 1.2 @ 1000yds on cold days then it might be worth looking into developing a faster load or switching to a 155gr Palma bullet should you ever show up at a match longer than 600yds.

Regarding pressure signs, use a precision mic or instant indicator to measure how much your shoulder grows from a full length resizing after 1 firing. Safe loads should only expand a couple thou. Heavy loads may be as much as 7-9 thou larger. Also you'll notice shiny rubs or circular bulges on the headstamp where the brass got pushed back into the ejector hole. That is bad. When you load primers if you notice the pockets feel loose (seat with almost no effort, when using a handheld seater it feels very different than normal) then you've overloaded the brass. Finally you might find that the case has expanded such that it doesn't want to fit easily into your shell holder any more. All of these indicate you stretched a case beyond it's ability to spring back properly.
 
#5
Re: Chasing the high accuracy node - worth it?

Thanks for the responses. I think I'm going to stick with my current load until I can test it extensively at 1k. If it performs ok at distance, I really can ask much more out of it.
 
#6
Re: Chasing the high accuracy node - worth it?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ZLBubba</div><div class="ubbcode-body">Thanks for the responses. I think I'm going to stick with my current load until I can test it extensively at 1k. If it performs ok at distance, I really can ask much more out of it. </div></div>

What velocity are you getting from your current load?
 
#7
Re: Chasing the high accuracy node - worth it?

Bubba what are your ES/SD like, single digits, then your GTG, if you have a 30fps ES but shoot bug holes at 100 then refine your loading routine and or load to get single digits while still stack them in the same hole
 
#9
Re: Chasing the high accuracy node - worth it?

Depends on how you're shooting. I ran into a similar situation with my 7-08. Because I use it quite a bit for matches, I went with the slower load. My upper load had great speed and numbers, but some of the matches I shoot require extended strings of fire. After about 3 rounds, my bolt would get hard to open using the hotter load. I only notice a slight reduction in ballistics, but the overall performance far outweighs that negative.
You may want to experiment though just to identify your limit and take care of your curiosity...
 
#10
Re: Chasing the high accuracy node - worth it?

I developed this load with OCW and need to get a chrono to see how it meters. Then I need to find a few better places in MD to shoot because the county I live in sucks. Seems like from the above advice though that if I've got small ES/SD with this load, then I've got my winner.
 
#11
Re: Chasing the high accuracy node - worth it?

I rather doubt it.

My view is that once one develops a load that combines accuracy with some lenience to the bore, seeking a higher node is likely counterproductive.

Think about it.

The likeliest scenario where the added accuracy and velocity would be more desirable involves additionally extended distances. So any accuracy increase would likely be at least somewhat negated by the uncertainties that a longer time of flight can introduce.

Now some would say that the added accuracy would mitigate in favor of improved accuracy, maybe reduced inaccuracy. My response is no, it really doesn't work that way in reality. The added distance simply introduces a higher degree of uncertainty, whatever the underlying degree of accuracy. Unleashing added mayhem inside the bore is not a strategy for extending accuracy, but rather for decreasing bore life.

If you want to shoot well at a longer distance, start by combining a known accuracy resource with improved wind skills. One finds new data by changing one variable at a time, and not several.

Greg
 
#12
Re: Chasing the high accuracy node - worth it?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">My view is that once one develops a load that combines accuracy with some lenience to the bore, seeking a higher node is likely counterproductive.

Thinks about it.

The likeliest scenario where the added accuracy and velocity would be more desirable involves additionally extended distances. So any accuracy increase would likely be at least somewhat negated by the uncertainties that a longer time of flight can introduce.

Now some would say that the added accuracy would mitigate in favor of improved accuracy, maybe reduced inaccuracy. My response is no, it really doesn't work that way in reality. The added distance simply introduces a higher degree of uncertainty, whatever the underlying degree of accuracy. Unleashing added mayhem inside the bore is not a strategy for extending accuracy, but rather for decreasing bore life.

If you want to shoot well at a longer distance, start by combining a known accuracy resource with improved wind skills. One finds new data by changing one variable at a time, and not several.

Greg</div></div>

All that's true, but it also hinges on not going transonic @ 750yds. I've got a great load using Varget and 155 AMAXs. Shoots bug holes and gentle on the bore. But it's only a 750yd load and I know that. Beyond 750yds it's a recipe for frustration because the load is no longer accurate or predicable. The bullet's BC combined with the MV simply aren't enough to keep it supersonic any further than that.
 
#13
Re: Chasing the high accuracy node - worth it?

Yes, of course, transonic transition can lead to instability/inaccuracy.

Essentially, my view reflects a policy of "if it ain't broke, don't fix it"; and transonic transitions are outside the scope of my argument.

Honestly, I think that numeric juju like single digit ES/SD's are wishful thinking and/or mythology being accepted as fact.

Whenever I look to the chrono as an arbiter of good shooting, I am reminded that the chronos come packed with directions that clearly state all reported values to have an accuracy standard of no better than +/-1% of the velocity displayed.

Compare, yes; depend, no.

This spread can be as little as 20fps and as much as several times that. How one acquits claims of single digit values from data which has an expected error rate of several times any possible claim, I honestly don't understand.

Greg
 
#15
Re: Chasing the high accuracy node - worth it?

Alas, since I relocated to Maryland, I haven't been able to do any of John's new courses and matches. Kind of sucks. The good news is that once work slows down in the June time frame, there's a strong possibility that I'll be moving the family out to Colorado for law school.

I appreciate the offer, Ratbert. I never realized how good I had it in North Carolina for shooting. I shot no less than 3 times a week, with IDPA matches every other weekend. Now I can't hardly find a pistol range that will let me shoot reloaded ammo that doesn't have a 2 hour wait. If I want to shoot LR, it takes me driving at least 90 minutes if I can find a group going to Ft Meade, and that happens maybe once a month.
 
#16
Re: Chasing the high accuracy node - worth it?

Whether something is worth it depends on what it cost. Here, that would be mostly time and money, less of the former if you take your stuff to the range with you. Running back and forth from your bench to the range will wear your ass out. That might not be worth it.

Also whether seeking the higher node is worth it depends on the application for which you endeavor to use your rig. Do you need the higher velocity? Do you want the higher velocity? Finally, why not experiment anyway?

I have more fun when I let myself screw around carefully and try something different within reasonable boundaries than when repeating loads others have worn out. Load a bullet backwards if it pleases you.
 
#17
Re: Chasing the high accuracy node - worth it?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ZLBubba</div><div class="ubbcode-body">I developed this load with OCW and need to get a chrono to see how it meters. Then I need to find a few better places in MD to shoot because the county I live in sucks. Seems like from the above advice though that if I've got small ES/SD with this load, then I've got my winner. </div></div>

If you don't know the velocity of your current load, how do you know you're not already getting the velocity you need? No sense in chasing a higher node if you're already there......
 
#18
Re: Chasing the high accuracy node - worth it?

Which is kind of why its a really really really good idea to have a chrony with you when you develop a load
smile.gif
 
#19
Re: Chasing the high accuracy node - worth it?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">Whenever I look to the chrono as an arbiter of good shooting, I am reminded that the chronos come packed with directions that clearly state all reported values to have an accuracy standard of no better than +/-1% of the velocity displayed.

Compare, yes; depend, no.

This spread can be as little as 20fps and as much as several times that. How one acquits claims of single digit values from data which has an expected error rate of several times any possible claim, I honestly don't understand.

Greg </div></div>

LOL. Yeah Greg, I was reading about the accuracy devience in chronys a while back and thought the same thing, it gave me a chuckle thinking about some of the posts I've read. Made me not near as confident about some of the numbers I've seen on my chrony.
wink.gif


Bubba, your current load is NOT conservative.

okie
 
#21
Re: Chasing the high accuracy node - worth it?

Hell yes, Look for a faster load with the Accuracy you desire. Work up slow and see what happens. You have a load that works if you don't find another... but the next may be Much better.
 
#22
Re: Chasing the high accuracy node - worth it?

My velocity goal is set to the standard that the bullet needs to be doing at least 1200-1250fps at the target distance.

If it won't, my first remedy is to find a longer barrel. If that doesn't work, I'm trying to make a silk purse out of a sow's ear, and need to find a more capable chambering.

New handloaders think they can achieve magic at the reloading bench. Not so.

The barrel is like a candle. Burnt at both ends, it gives a lovely light, but lasts so much less.

Greg
 
#23
Re: Chasing the high accuracy node - worth it?

It can't hurt to see if you can do better but, get a chrono out with you so you can see your velocity, Like many have already said.

I'm debating the same thing myself... I have a 300wm load shooting well with 208gr amax and, my velocity is only about 2800fps.... it shoots bug holes in my rifle.... I could probably bump that 150fps and add some yardage to the load but, it isn't like I'm going to have trouble making 1000yds ( or even 1500yds ) with this load so, I'm wondering if I should chase that upper node knowing that I'm just going to go through brass ( and barrel )twice as fast when I'm done and for little return.
 
#24
Re: Chasing the high accuracy node - worth it?

I agree that retained velocity is the key. That's why I switched awhile ago to the Berger 185 BTLR's for my 1000 yard shooting. They launch about 100 fps slower than the 175 SMK, but retain approx 100 fps more than the 175 at 1000. The 175's are pretty weak at 1000 yards in my opinion, but are excellent at 600 yards.
 
#25
Re: Chasing the high accuracy node - worth it?

I remember an engineer talking about chronies. The distance between most sky screens is 12". As Greg points out they generally have a 20-30 fps variance if they work to +/-1%.

Too many variables in the short chronies to read much into a string. I have a good 600 yard load. A 25 fps spread is roughly 2" at that distance off my base velocity of 2800fps.

Hard to tell if that is really happening. I dont know if anyone can tell. I dont think even a woohoo chrony is accurate enough to be a holy grail to ballistics if its on a 12" base.

Extreme spreads on short based chronies might make a good discussion for benchrest shooters or rainy days on the internet.

Its not raining today.
 
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