How wide is the accuracy node??? pic added

[BK7saum]

I shot a ladder test yesterday with my 7 SAUM, 180 JLK and Retumbo. Range was 300 yds off bipod and small rear bag. Started at 62 grains and worked up to 66. Velocity topped out right over <span style="text-decoration: line-through">3000</span> ~2950 with no signs of excessive pressure.

Question? how wide is the accuracy node. Starting at 62 up to 65.2 all shot into a 2" group. Velocities from about <span style="text-decoration: line-through">2800</span> 2749 to <span style="text-decoration: line-through">2950</span> 2911. The two higher charges of 65.6 and 66 shot about 2 to 3" high and right of the other charges.

I was really surprise not to see any stringing of bullets up the paper. Usually I have about 3-4 consecutive charge weights that group together. But this time there were about 10 charge weights encompassing 3 grains of powder grouping about .6 or so MOA.

Is this odd? I was hoping to narrow down a range and shoot for an OCW next weekend. I need to re-shoot this to confirm what I saw yesterday, but all shots felt good except for one that I know I pulled that ended up left of the group about 1".

WHen I shot a ladder test with H1000, I got stringing all the way up the paper with only a narrow grouping of a couple of shots to identify a node. Yesterday was a completely different outcome. It didn't end up a ladder at all, just a decent 300 yard group minus the two high charge weights.

This was the first time in a while the wind was calm enough to get a few accurate shots downrange. Oklahoma in the spring isn't too shooter-friendly.

BLK7

 

[vman]

Re: How wide is the accuracy node???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BLK7</div><div class="ubbcode-body">It didn't end up a ladder at all, just a decent 300 yard group minus the two high charge weights.

This was the first time in a while the wind was calm enough to get a few accurate shots downrange. Oklahoma in the spring isn't too shooter-friendly.

BLK7 </div></div>

I have had the same thing happen to me once... I put it down to a bad day at the range and my error.

If it happens again maybe your rifle is just being very forgiving. The best way to run a ladder is over a chrony, as provided its setup correctly, the FPS figures will get you a better idea of a node.

Answering your thread title, I think an accuracy node can be very subjective especially to the shooter and what he/she considers a tight verticle. Clearly if your looking for single digit ES/SD then you want to be right in the middle of that node... generally these loads shoot tiny groups even at long ranges.

I think you can easily see good grouping +/-0.5grain from the middle of the node, but you will see fantastic grouping right in the middle.

 

[BK7saum]

Re: How wide is the accuracy node???

vman,

I did shoot the ladder over a chrono. I was going off memory as to what the approximate velocities were. since i didnt shoot 2 at each charge, is there any other information I can obtain from single point velocities?

THanks, BLK7

 

[WTW]

Re: How wide is the accuracy node???

From your posting I take it that you only shot 1 shot of each charge weight? To me this doenst sound like it is repeatable or would give you what you are looking for. You really have no way of seeing what the different groupings are doing.
Each time I have done a ladder test I have fired at least a 3 shot group per charge weight. This makes a huge differecne as you can see what each charge weight it doing.

 

[BK7saum]

Re: How wide is the accuracy node???

Shooting one round of each charge, I was trying to narrow down where a possible node might be, then go out later and shoot 3-5 rounds at selected charges in this area.

When doing load development for my 6x47, I was easily able to distinguish the possible nodes with one round per load, which was verified again at a later date. I could see rounds string up the paper, then 2-3 would group together, then string up the paper, then 2-3 group together. In this manner, I was able to identify two different nodes.


I agree that shooing 3 shots per charge weight might give me the information I want the first time around, since I would have some basic ES and SD information from the first time. This was an attempt to save on cost of components and barrel.
I will give it a try next time with 3 rounds at each charge. Thanks.

 

[hugo121175]

Re: How wide is the accuracy node???

I had a bit of the same problem with my 270WSM. I ended up having to retest at 500+ yards. If the groups are to small to notice what you are actually looking at, shooting farther will reveal more as the groups start to open up.....

JM2C

Hugo

 

[BOLTRIPPER]

Re: How wide is the accuracy node???

and use a chrono, otherwise....how do you know what exactly you are doing?

 

[Fuzzball]

Re: How wide is the accuracy node???

"..How wide is the accuracy node??? "

I know mine but I dunno yours. You'll have to test it and let us know. ??

 

[WTW]

Re: How wide is the accuracy node???

I know what you mean trying to save barrel life. Im not really sure if you need to shoot 3 shots at each node but I felt it would give me the information I needed.

 

[BK7saum]

Re: How wide is the accuracy node???

I will have to reevaluate the chrono readings and see what I can figure out.

 

[BK7saum]

Re: How wide is the accuracy node???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">"..How wide is the accuracy node??? "

I know mine but I dunno yours. You'll have to test it and let us know. ?? </div></div>

That's exactly my question. At first glance, the accuracy node appears to be at least 3.2 grains wide and ranges from about 2800-2950 fps. All 9 rounds (62.0 to 65.2 grains) landed landed in about 1.75 inches at 300 yards (except for a called flier).

Either that is very wide and forgiving (and definitely not what I expected) or something else is going on. Just looking for a little more insight on how to narrow down the node(s).

Looking at possibly retesting at 600 yards to hopefully spread out the shots a little more. Any other suggestions......

Thanks, BLK7

 

[steve123]

Re: How wide is the accuracy node???

That's a tough problem to have.I feel sorry for you

How about bolt lift and primer flow ? All I can say is it seems like my rifles shoot best right below max.The bolt isn't sticky yet but almost.Primers getting flat but not flowing.Except my 6x47L of course,haha.It's hard not to get primer flow with that sucker even with CCI 450's because I need to get my bolt bushed still.

I bet you would get a better indication if the temps right now were warmer.I'd say to repeat the test one more time at 400Y.BTW since your gun is shooting that well you probably have already found your seating depth.

 

[BK7saum]

Re: How wide is the accuracy node???

Bolt lift is easy and primer flow is nill. I haven't reached max yet according to those indicators and don't feel the need to get over 3000. I hope to find a good load at 2900 to 2950 with low ES and good accuracy and stay there. 180s at 2900 is fast enough I think.

I did a previous ladder with H1000 and wasn't happy with the results. Couldn't get but about 2850 to 2900 without brass flow into the ejector.

I know what you mean about the primer flow in the 6x47L. I get primer flow with mild loads using 450s, BR4s?, and Rem 7 1/2s. I guess it is the nature of the beast. Haven't popped one yet, but they sure aren't pretty. It's on a Tac 30. The firing pin on mine is fluted. I don't know if that contributes to primer flow or not. Definitely less mass in the firing pin than a solid round factory style pin.

Seating depth is .015 into the lands (actually about .013 when I remeasured the length to ogive on remaining unfired rounds.

 

[Alan Griffith]

Re: How wide is the accuracy node???

Yes, it can happen! A ladder with hardly any vertical climb. I've seen it a few times.

Alan

And yet, here is the same rifle, same powder but different bullet.

 

[Alan Griffith]

Re: How wide is the accuracy node???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BLK7</div><div class="ubbcode-body">Bolt lift is easy and primer flow is nill. I haven't reached max yet according to those indicators and don't feel the need to get over 3000. I hope to find a good load at 2900 to 2950 with low ES and good accuracy and stay there. 180s at 2900 is fast enough I think.
</div></div>

Well, in your OP, you said you hit 2950 fps. You want 2900 to 2950. So go and take the powder charges that were in the velocity range and either start shooting groups or shoot a ladder at much longer range. IMHO, a barrel/load combo that does this is a large, forgiving node. Consider yourself lucky and run with it.

Alan

 

[BK7saum]

Re: How wide is the accuracy node???

Alan,

That's what I was wondering about, whether or not a ladder would not show any vertical. I put the caliper on the 62.0 to 65.2 "group" (minus called flier) and it measure 1.67 CTC (302 yards). With called flier, it measure a little over 2".

I was posting off of what I remembered and I was not accurate in the velocities in the OP. The lowest charges on the ladder 62.0 Retumbo at ~2750 and the highest 66.0 Retumbo at ~2960.

The group of the ladder except for the one to the left (called flier) was from 62.0 to 65.2 (velocities from 2749 to 2911, including total of 3 rounds at 62.0 to foul bore). The two impacts to the right and high were 65.6 and 66.0 (above the 2911fps). They both felt great when shot, so I feel that it probably wasn't me.

I sure hope I can find a good load somewhere in the middle at 2850 or so. I don't want to torch the throat, but there might be another node closer to 3000. If I can get great accuracy at 2850, I will probably stay right there and not push it.

Thanks to all for your input. I finally got the pic of the ladder up for you to see what I have been talking about.

 

[Fuzzball]

Re: How wide is the accuracy node???

How wide is the node? I suspect those who pay for a Promethus dispenser/scale would have us believe it's probably no wider than +/- .0001 gr!

 

[Big Dog Steel]

Re: How wide is the accuracy node??? pic added

There's not enough info here to get a clear result. When I do a ladder test I typically start with at least 10 rungs @ 1-2% rungs of highest powder charge. When I find the highest node I dial that one in with less than 1% rungs, typically between .2 & .4grains.

Someone suggested firing multiple shots per rung. That defeats the purpose of the test IMO. I warm the gun up a little by shooting a 5 shot group @ the lowest charge. Go down to the target an observe the group to get a feel for how I'm shooting. Fire lowest rung, go down to the target and mark it, fire next rung, mark it, repeat. Preferably wait until next day and shoot the same test again to make sure it is repeatable and good data.

If it matches find the middle of the node and use it.

This test was done with RL22 and 162gr amax's. The node is 7/8" vertical @ 300 yards. You can see them clearly climbing after.

This is important...if you are shooting and you shots are not grouping consistently, if they are not climbing, just jumping all over the place vertically, it is typically not a good test. Either you are not shooting good or you are out of the node.

Also should add to make sure you chrono your results, as that information will come in handy later. also make sure you have a good aiming point. I try and get something with a vertical and horizontal line so I can use them to align sights. Just using a 1" dot leaves to much wiggle room IMO.