Range Report Ladder test 1 shot each load or 3?

[Mag 300]

I have read the web pages for ladder testing and have an opportunity to do them next week at 300 yards.
there are two methods one has you keep same point of aim and shoot one each of the rounds for the loads spaced .3 gr apart.
the other has you shoot 3 rounds of each . to find the node of the barrel wich would be a more accurate method?
thanks for the opinions?
Bill

 

[doc76251]

Re: Ladder test 1 shot each load or 3?

Hi Bill,

IMHO, shoot at a different target for each load in a "Round Robin" type of format. If you have 5 loads set a target with 5 aiming points and separated impact points. If it helps to keep them separated label the targets 1 - 5 and the loads A - B.

Shoot A#1 into target 1
Shoot B#1 into target 2
Shoot C#1 into target 3 and so on until you are shooting E#5 into target 5.

This will give you 5 distinct groups and conceptually will remove (or at least spread them evenly) the variables associated with shooting a single load into the target and then shooting the next.

Important Part: Once you fire the first "record" shot DO NOT ADJUST THE SCOPE. The impact areas will move around all by themselves, that's what you want!

Important part #2: Do not shoot at the aiming point! Dial down 2 MOA or so. If you hit the aiming point the appearance of it will change and you will center/quarter it differently and your group will start to string giving false readings.

Cheers,

Doc

 

[Mag 300]

Re: Ladder test 1 shot each load or 3?

Doc,
Thanks that is just the advise I was looking for
Greatly appreciated
Bill

 

[akxx]

Re: Ladder test 1 shot each load or 3?

The 2nd method is the Optimal Charge Weight development method, and I have switched over to it from the ladder method.

You're looking for a "scatter node" that should be obvious, and the next 1-2 load increments above the scatter node will often yield the accuracy node. Look for where the POI (beyond the scatter node) shifts the least for the 3-round groups. This will be the robust node that is not as sensitive to slight powder charge variations.

 

[DaveV]

Re: Ladder test 1 shot each load or 3?

http://optimalchargeweight.embarqspace.com/#/ocw-vs-ladder/4529811360

 

[Greg Langelius *]

Re: Ladder test 1 shot each load or 3?

I use up to six rounds per charge weight.

I fire at separate aimpoints for each charge weight.

I fire in 'Round Robin' order.

The trouble with using a single aimpoint for ladder testing is that bullet deviation seldom follows a logical or predictable path, in addition to which, sorting out all those impacts in a close vicinity can get pretty confusing.

As long as one keeps the sight adjustment the same for all shots, the different aimpoints can help sort out the specific effects of charge weight variations on POI variations and dispersions.

I do my load development shooting in two stages.

The first uses charge variations of 1/2% of the whole charge, extended from min to max published charge weights. For a 25gr average charge, I'll do variations of .3gr, and for a 45gr average charge, I'll vary by .5gr.

The second narrows in on specific charge weights which show a better consistency of impact points, and I'll vary them by .1gr, going from just above the next lower increment to just below the next larger increment.

Generally, this will allow me to narrow in on a better charge weight in just two sessions, while shooting up to six rounds per charge weight makes the statistical probability of success much greater. By using larger increments in the first stage, a lot of redundancy is eliminated, allowing more shots to be used at the various increments, allowing better statistical chances of success.

In the very rare instances where first stage testing shows no clear preferences, I will repeat the first stage with smaller increments, and if that doesn't work, I'll try a different powder.

Greg

 

[Onemoretime]

Re: Ladder test 1 shot each load or 3?

I'm no expert but I use 5 rounds per charge in .2 grain increments.

I tried 3 once but felt more data was better so went back to doing 5 rounds.

 

[crm08]

Re: Ladder test 1 shot each load or 3?

Awhile back I tried the ladder test to work up a varmint load for my .260, I used 95 gr vmax's 3 shots per charge at .3 gr increments. Looking at the deviation in velocities/charge, I couldn't spot any groups that were significantly tighter than the others. I'm pretty new to reloading but I felt like I was pretty consistent in my load development and that the velocities accurately represented the charge amount. There were however 2 charges that grouped really well on paper, so I convinced myself that the avg. vel. for these two groups were the "sweet spots" for my barrel. After spending all that time loading the rounds for the test and walking away at the end of the day a little unsure if I had accomplished anything, I will definitely be taking the time to load at least 5 or 6 shots per charge when I work up this year's deer load.

There is one thing about this test that I noticed once I got home and plotted the grain/velocity ratios. There were two times that day when I got a little impatient and shot two groups of 3 back to back without letting my barrel cool down. The average velocity slope had a noticeably higher rate of change at these two intervals. I would be interested to know if anyone a little more experience than me could take a look at these plots and let me know if the barrel temperature can actually start to affect the velocity this much after just 3 or 4 shots?...or should I take this as just a coincidence in my data.

Here is the link to Vel./Powder Amt. chart:

http://i234.photobucket.com/albums/ee54/codyag07/shotbyshotchart-1.jpg

This is the avg. vel. plot where the increased rate is more noticeable:

http://i234.photobucket.com/albums/ee54/codyag07/averagevelocitychart.jpg

 

[Greg Langelius *]

Re: Ladder test 1 shot each load or 3?

My .260/95V-Max load is 46.0gr of R/S Hunter.

 

[crm08]

Re: Ladder test 1 shot each load or 3?

Greg, I was using 4064 for that ladder test...I have stuck with the "group #7" shown in the graphs which has been really accurate for my model 700 (at least during the hot summer months in Texas, never tried the vmax in cold weather), that group consisted of 42.4 gr and averaged out at 3275 ft/sec. I'm sure my paper groups would squeeze back in again somewhere after 43 grains but I just haven't been reloading long enough to go above max and trust that I'll notice pressure signs. Not sure what model you have but I figure you might find the actual numerical results of the test somewhat interesting, you can find em here:

http://i234.photobucket.com/albums/ee54/codyag07/velocitychart-1.jpg

 

[GuinnessNM]

Re: Ladder test 1 shot each load or 3?

How many shots you must fire depends upon the size of the effect you want to measure. See these links:

http://www.snipershide.com/UserFiles/Image/articles/group_size_oct_27.pdf

http://www.snipershide.com/forum/ubbthre...rue#Post1312910

 

[okiefired]

Re: Ladder test 1 shot each load or 3?

........... OCW, be done with it.

okie

 

[Mag 300]

Re: Ladder test 1 shot each load or 3?

not going to be done till I id the best rounds for the rifles . what the hell is OCW!!!!!!!!!!!!!!!!!


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

........... OCW, be done with it.

okie </div></div>

 

[AQC440]

Re: Ladder test 1 shot each load or 3?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bill Stoffels</div><div class="ubbcode-body">not going to be done till I id the best rounds for the rifles . what the hell is OCW!!!!!!!!!!!!!!!!!


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

........... OCW, be done with it.

okie </div></div> </div></div>

Optimal Charge Weight

 

[Greg Langelius *]

Re: Ladder test 1 shot each load or 3?

CRM;

While IMR4064 can be a good powder for the .260, I deliberately chose to use a slower than ideal powder because it fills the case more completely, giving me a higher charge density percentage. I find this helps accuracy under match conditions, by making ignition characteristics less dependent on charge orientation within the case.

This is not really a very crucial issue, and the more telling reason is that I happen to have a moderate stock of R/S Hunter which is otherwise not being used. These days, I can't justify leaving perfectly useful powder languishing on the shelf.

When it's gone, I will redevelop with H414/W760.

Your numbers are interesting, but there are no group sizes I can spot. Of all the numbers I'd like to see, those are the ones which are most important to me. The other numbers can be squeaky clean admirable, but without correspondingly nice group sizes, they mean essentially nada to me.

OCW is an interesting concept, but for now, stick to shooting ladders and finding the tightest groups. Once you can do that, finer points like OCW may deliver further improvement.

Greg

 

[KYpatriot]

Re: Ladder test 1 shot each load or 3?

Bill read about OCW here:

Optimal Charge Weight

I just used this technique and it seems to work great. It is similar to a ladder shot round robin style, but jist of it is you are finding a charge weight that groups to a similar point of impact as the step above and below it, then adjusting the size of the group with seating depth. In theory this results in a load that is less sensitive to environmentals.

I was very lucky in that over a nine step charge range my most similar POIs were also my best groups so I could just quit right there...not likely always happen that way. I would post my target but it is 3 shot groups...the link will explain everything.

 

[DaveV]

Re: Ladder test 1 shot each load or 3?

I posted a link on 11-2 that would take you to info on OCW

 

[rc2125]

Re: Ladder test 1 shot each load or 3?

Ran an OCW deal with my rig this past saturday. OCW showed the load I was running was off and the rig is capable of really impressive groups. Amazed at the accuracy of the quickload node predictions/etc.