Load development ladder test

[Bob S.]

Let me start out with the background.
243 AI, Pacnor super match blued fluted barrel, accurized ruger mod 77 mark II action, bedded in a thumbhole laminate stock. Barrel broken in while fireforming 100 rounds of mid load 4831 and a host of leftover bullets. fireforming was definately sub moa using virgin lapua brass.
Ladder test with IMR 4350 starting at listed max (41.5) for 243 win in nosler book pushing 95 gr ballistic tips. 20 rounds loaded in .2 gr increments and seated 20 thousands off the lands. I had access to a chrony but it went away when my buddy shot it and its not back in business yet.

5 foulers fired from a clean cold barrel and zero set for 300 yds. All remaining shots fired about 3 min apart and 10 min cooldown time between every 5 shots. Barrel never hot to touch.
Next 6 shots marched right up the paper from dead zero to about 3 inches high and 2 inches right.
shots 7 through 19 were all within a 3"x3" block that was very difficult to mark towards the end. There was no deffinate stringing or grouping other than within moa.
shot 18 had sticky bolt lift and 19 left extractor mark so I stopped and did not fire # 20 which was loaded with 45.3 gr powder.
I could not get a definate node so I took shots 7 through 17 and figured about 3/4 way would be #14. loaded up 50 of those babys cause I'm going hunting this week and zeroed for 100 yds.
100 yd target revealed .25" 3 shot groups when I'm doin it right so I guess I'm in business for now.
I'll let you know how I do.
Anyone got a suggestion or comment on how I should have done this test other than use a chrony as confirmation for the load I picked?

 

[Jimm]

Hey Cowboy !

Where the heck you been ? /ubbthreads/images/graemlins/laugh.gif And just what in the world is someone going to tell someone thats shooting 2tenths or so at 100 /ubbthreads/images/graemlins/laugh.gif IU have a load that is shooting bugholes as well and so far has shot 1 " at 300. It is 41.6 grs. H4350 under a 107 smk jumping 25 thou.

the thing is that a chrony would be great for being able to range find with a laser then dial in the moa for whatever distance . I recently got a Swarovski 1500 and that along with a palm pilot with exbal has killed a lot of far away rocks on the first shot /ubbthreads/images/graemlins/cool.gif

What is your twist ? The 107smks are fantastic if you can stabilize them ( 8 twist or better I think )

Anyway , good to hear from you,

In his service, Jim

 

[ss7mm]

jimm:

I had been wondering if you got your Swarovski and how it was working for you. Sounds like it's doing o.k. Are you happy with the purchase and it's performance?

 

[Bob S.]

I've been real busy lately. I think I have shod every horse in the county except mine for opening day of gen rifle season. I'nm leaving tomorrow evening(opening day) for 4 days of hunting in gods country.
My twist is 1 in 10 so the 107's are to big I think but the 95's seem to work and I know 70's would be smokin. for now I'll stick with the 95 BT's unless I can get my hands on some mk's about the same weight.
Sorry I didn't get any pics of the ladder test target or the zero target. My wife's camera is out of town and I'm getting ready to be out of town. /ubbthreads/images/graemlins/grin.gif

 

[Jimm]

Hey guy ,

So far so great /ubbthreads/images/graemlins/laugh.gif Going on a pd shoot this coming week so will get to wring it out more . Realistically though there is nothing I can imagine that I would have a problem with.
Having said that I need to tell that if you wear glasses your eye to lens relationship is more critical than other lrf 's might be. not a big deal once you learn to adjust for it .

Jim

 

[lynn]

Cowboy
In working the ladder test i use the 1% rule on the powder increments.In your case i would use 0.4 grain increments instead of the 0.2 you used and this will keep your target from getting so cluttered up.It sounds like you had around a dozen shots in a cluster and at 0.2 grains that would be roughly 2.5 grains wide.That is about 0.5 grains more than my first guess would have been but it looks pretty good to me.If you had a working chronograph you could now go near the top end of your load and shoot 3-5 shot clusters while watching the extreme spreads.Lower is better in my opinion but if they start to drop then go back up again without ever getting low enough use te powder charge at te lowest point and try different primers.
Lynn

 

[CPorter]

The ladder test doesn't always produce a vertical string with visible nodes. Barrels (with residual stress left in them from manufacturing?) will string both horizontally and vertically and the resulting groups form an elipse. When I did my ladder tests I found I had to fire three shot groups at each load to get a meaningful test result. I looked for the groups that had their centers close to each other on the elipse and also had a shrinking group size.
Have you heard about the optimal barrel timing method of loading? <font color="black"> </font>

 

[zingdingo]

Cowboy,

In the ladder tests I have done, I always use multiple aiming points (sometimes on the same sheet of paper, sometimes different, depends on what I expect the accuracy of the gun to be) and make sure that the area where the bullets will impact has some markings or a grid in order to easily compare the targets. I'll often mark my targets A,B,C, and D. Shots 1-5 go into A, 6-10 into B and so on. The only time you have to look at two of the targets at once is when you are comparing shots 5 and 6, or 10 and 11, or... It has worked pretty well for me. If I was at home I would post pics of my last two from my 30-06 ladder tests using 168 BT's and 165 Interbonds. They used 4 aiming points each, and show nice distinct nodes at similar powder levels.


Carl Porter,

Interesting idea using the three shot group to improve the reliability of the test. My only comment is, I thought that the point of the test was so that you didn't have to shoot groups at all the different powder levels, that you could narrow down the range of powder levels to look for good groups at? By the way, my tests (all factory barrels) certainly don't string just vertically either, more scattered or elliptical.

Also, what is this optimal barrel timing method you speak of?

 

[BountyHunter]

Ladder test with chrony does one very important thing and that is it allows you do find the middle of a node based on MV. You will need that, not only will the bullets cluster but the MV will also.

I always go for the middle of the MV node instead of the top end. you might be on the ragged edge and a rise in temp or humidity set you over on another day. Whereas if you go in the middle it stays in "tune" much better.

Finally, in order for you gun to show a cluster producing a cluster, ie it must be capable of at least .5 MOA, otherwise you do not know what is the cluster or what is just the aberation of the accuracy level of the rifle.

BH

 

[CPorter]

zingdingo,

You are right, the point of the ladder test is to reduce the number of rounds necessary. Unfortunately not all guns will throw a nice vertical string in a ladder test. These guns require more rounds per load to get anything from the test.

Optimal barrel timing is based on traveling shock waves in the barrel. In the cartoons when a gun is fired the barrel balloons out and the balloon travels down the barrel to the muzzle and spits out a bullet. In reality the balloon isn't that bad but it does travel down the barrel and back 3 or more times before the bullet leaves the muzzle. It's been shown that when the traveling wave reaches the muzzle the bore opens up slightly and this degrades accuracy. Best accuracy is when the bore is at it's minimum diameter. Optimal barrel timing takes this into account. So far in my experiments ladder testing has shown two or three nodes and the optimum barrel timing predicts them fairly close.



Optimal barrel timing

 

[Mikecr]

Ladder testing has been a tough one for me.
My max bench available range is 280. Last week, I shot a ladder with a T2K in 6xc. But was not able to see a best load.
32shts in .1gr increments. 105 bergers fully into lands. My 32shot group ended up being about 4", so even with a 32x NF scope, I wasn't able to follow and map each impact. There were 2 distinct velocity shelves with with an ES of about 2-4(I use an Oehler w/12ft screen spacing). Definitely not linear. So I threw together 10rnds centered in each low ES area, and really hoped I would be grouping well in one of them. But groups turned out poor there. This is where I dialed in the BOSS on my last rifle/load developement.

So I have to take pause and reapproach this.
#1 I have to setup somewhere shooting alot further.
#2 I need to explore different components to test.
#3 I need to find a wireless camera/monitor system.
#4 Next rifle gets a tuner

 

[sewwhat89]

If they are all shooting that close, shot multiple targets with a reference point. That way, shoot say five to ten rounds at each target then you can overlay them and see your total grouping. If you wanted to get super fancy, photocopy the individual groups onto clear laminates so you can use a transparency and enlarge your target from a 4x6" target to 6-8'. Then you can see then nodes better maybe.

Just an idea!

 

[BountyHunter]

couple points

1. shoot with .2 or maybe .3 increments
2. you really need 300 and better 400 yards.
3. movement will never be linear, often at angle left and right, but it will show clusters on both grouping and MV
4. walk/drive down,mark each shot and plot on sep piece of paper so you can track.
5. Record MV of each shot so you will see the cluster there too.

good luck

BH

 

[Bob S.]

Thanks for the replies guys. Sorry it took so long to read them but I was hunting. I am going to leave it alone for the time being (its hunting season). I think I can do a little better and may try a different powder and a chrony. I will also go bigger increments and then step down when I get close. I think I will also start doing less shots at the same target to avoid the confusion of everything being in the same group.