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Author Topic: Handloading Accu-Loading Part 4: Powder & Ladder Test  (Read 394 times)

Offline TalkHunting Mag

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  • Join Date: Mar 2013
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Handloading Accu-Loading Part 4: Powder & Ladder Test
« on: April 03, 2013, 05:47:00 AM »
We got our brass about as perfect as we can & primed, our bullets are in perfect little sorted piles and their noses are clean. We got a great overall length to start with. The last big step has finally arrived; powder selection and setting up the Incremental Load Ladder Table.

But before we get going here let me reiterate a SERIOUSLY IMPORTANT safety note. One of the things we are going to do as upper level hand loaders is to use the book as a guide, but we’re going to decide what the max load is by slowly progressing up the charge weight ladder until one of two things happen: 1, we attain the desired accuracy and repeatability being sort, 2, we see signs of excessive chamber pressure.  I’m making the assumption that anyone loading at this level knows the pressure warning signs and is constantly checking for them. Just because we are outside the box with load charges, doesn’t mean we want to be inside the box tickling dandelion roots.

And in doing so it is imperative you understand this. In the case prep part we learned how to come up with a great starting point in overall length. We have already determined the OAL where the bullet was just kissing the rifling, and we extend the length an additional .010”. So in experimenting with powders and the following instructions we are going to do so WITH EVERY ROUND .010” JAMMED into the rifling. IF YOU DO NOT FULLY UNDERSTAND WHAT IS BEING SAID HERE & WHY! DO NOT LOAD (near) BOOK MAX, MUCH LESS OVER! If the load starts with the bullet jammed into the rifling with all other things being even you WILL GET significant more pressure levels. So it’s okay to find ACTUAL max (possibly beyond book max) WITH THE BULLET JAMMED. Because when we later experiment with final overall length, we may end up with the bullet seated out of the rifling, or the bullet jumping from the case into the rifling. “Jump” does not give a pressure spike like being jammed. So we can go from JAMMED (A pressure spike situation) TO JUMP because our chamber pressure will DROP.

But if a person were to experiment with max ++ loads with the bullet NOT engaging the rifling, they would ERRONEOUSLY think they found this particular rifles safe max load. Then if they decided to jam it in search for a better shooting load, with the associated pressure spike from being JAMMED and that MAX or MAX PLUS load; he’ll likely lose his eyeballs, some fingers, his hearing a good portion of his face and potentially his life. Got it? START JAMMED and Work TOWARDS JUMP! DO NOT GO THE OTHER WAY! Got it? No? DO NOT PROCEED! Review what has been written to this point! If you are still confused talk to someone to get it clear in your mind.

Before we get to the fun stuff of building the ammo I’d like to explain how to set up your loads for a incremental velocity ladder test. Since I first used the method of load development in my opinion is the best way to work up a Accu-Load. It typically saves times, components and barrel life. How’s that? Because we are only going to shoot one round at a given powder charge! Each single round is a rung of the ladder. There’s only one hang up for the ladder test it really needs to be done at a decent distance. You’ll need to have a place to shoot at least 300(+) yards. From my experience 300 is minimum, 400 is better and 600 is best, but it's easy for the wind to blow your hits off paper which knocks the test in the head. When you shoot your ladder try to pick a day when the wind is calm.

The first thing we need to do is decide on one or a few powders to experiment with. This is done by talking to successful shooters familiar with your cartridge, reloading manuals, and powder and bullet manufacture load data information available online.
Setting up a ladder test: Let's say Reloader 15 is the hypothetical powder for a .308 load. The Sierra manual states 35.9 is a start load and 41.3 is max. Now make a list of the loads you would load to have a single round from start, to max plus in .3 grain jumps. Write them down, or better yet use a spread sheet on your computer. Include a load number, Case Overall Length, primer, case (brass) history & type, powder type & grains also indicate Max and Max plus loads in RED font. This information will be of great help later.

1) 35.9 g ] 2) 36.2 g ] 3) 36.5 g ] 4) 36.8 g ] 5) 37.1 g ] 6) 37.4 g ] 7) 37.7 g ] 8) 38.0 g ] 9) 38.3 g ] 10) 38.6 g
11) 38.9 g ] 12) 39.2 g ] 13) 39.5 g ] 14) 39.8 g ] 15) 40.1 g ] 16) 40.4 ] 17) 40.7 g ] 18) 41.0 g ]
19) 41.3 g {BOOK MAX} ] 20) 41.6 g {MAX +} ]
For max and max plus loads; colour the neck of these cases RED with a sharpie. Don’t skip this.
So now you have a mere twenty rounds to shoot and you will obtain VOLUMES of info.
MORE SAFTEY ADVICE:
For shots #19,and #20 on proceed with caution, looking for and documenting any signs of excessive pressure. STOP shooting when you detect the least sign of pressure: cratered primer, shiny marks on case head, extractor marks, sticky bolt lift etc.
WRITE DOWN the actual max load for this powder, this bullet, for this particular rifle in your loading manual and several other places. Having max and max plus loads will let you know what the actual MAX load is for your particular rifle. ANY loads deemed too hot to be safe to shoot should be pulled apart unloaded right then and there at the range for safety.

Now we are ready to pack up and head to the range. When you first start out I’d suggest using a large piece of paper. Pick up a roll of brown paper painters paper. It’s about 36”wide and many feet come on a roll. “Armed” with this large target area you can start the ladder test right away after you foul your barrel. All you need to do is put a “dot” near the top of the paper as a reference aiming point. The ladder will be best defined at longer ranges so use the longest range you are comfortable with.
We are going to shoot the start load first, and the MAX PLUS load last, all at the SAME AIMING POINT on the paper. So we are going to get a TALL vertical string. So no skimping on paper. From a good solid bench and shooting rest shoot each load at THE SAME AIMING POINT. And for once in your life in long range shooting you can ignore cross winds.

You are going to mark (chart) each bullet hole by its shot number after its shot because you will have overlapping holes. There are several ways of doing this whether it be shoot one and walk down and mark it, to really strong spotting and a target chart, DIY target cams, or colouring coding shots by colouring the bullet with a red, green & blue markers accordingly and shooting at white paper.

So what's happening on paper? You will get a vertical string of hits. (don't worry if they shift left and right with the wind, that is irrelevant right now, trust me.) First thought is that it's increasing velocity that makes the hits climb up the target, and that is true to a point. What is also happening for the most part is the bullets are leaving the barrel in a different state of barrel flex, or vibration. You need to understand this. When you fire your rifle, your barrel flexes in a sine wave pattern. What you’re getting in the ladder test is the bullet is exiting the muzzle shot to shot, with the barrel flexed more and more up. BUT, ahah! We got some groups anyway! You will get a few shots that cluster, or actually make a decent group on your target, despite their each one having a(get this) differing powder charge!

ENTER THE "NODE." The node is the very top of the wave and very bottom. For ultimate accuracy, you want your bullet exiting the muzzle precisely when it has flexed all the way up, STOPPED [for a nano second] before it begins it journey flexing back down. This is why you had a decent group or two during the ladder test, despite differing powder charges. So now you’re looking at the ladder test target. You got shots all over the place vertically, but some formed nice clusters, or groups. Note each powder charge that grouped. Let's say for this test, shot holes 2, 3, 4 formed a group, and 7, 8, 9 formed a group.

In a mere 11 or so shots, we learned at what powder charges the bullets actually leaves the barrel when the muzzle is not moving(vibrating) around wildly. So now we go home sip a beverage and study and DOCUMENT our findings. We see 36.5, 37 & 37.5grains shoot in the node of the barrel.

We now take these and do a refined but closer ladder test. (We do this for the other clustered shots too! Don't neglect to further ladder test any loads that formed a cluster/group.)

So now we are going to load rounds for another ladder test.

Let's jump in finer, .3grn increments now, we are refining things now. Let's go a little outside* this accuracy window (our shots that grouped), powder charge-wise though just for good measure;

1\36.3*
2\36.6
3\36.9
4\37.2
5\37.5
6\37.8*grains

So now we have a good lot of charges with overlap a little each way from the accuracy cluster of the first ladder test. We only loaded one of each charge again. Now go repeat the ladder test/target, and again in a mere 6 shots you will have volumes MORE information. [Don't forget to do this second ladder test for every accuracy cluster/group that showed up on the first test]For each ladder, it is optimal to back up -at least- another hundred yards from the last distance.

You will get another accuracy cluster, all the more dead-on the barrel's node. Let's say shots 2,3,4 again formed a group.

Now you go back and load 5 SHOT GROUPS for each of these:
5@ 36.6 grains
5@ 36.9 grns
5@ 37.2 g.

One of these will prove overall best. Now you got your powder charge! And it is the LEAST sensitive to shot to shot velocity variations due to being at the node.

Now go back with this same powder charge in every round but play with bullet seating depth. You’re at .010” jammed right now. Try a 5 shot group @ - .010 JUMP (not touching the lands) Keep trying groups as you move your OAL .010”. You’ll see the rifle perk up and shoot one of these lengths best. Now you got your load.

If you want to try to tighten your groups even more, play around again the powder selection and charge, rerun the ILD test and see if things get even better still yet. It may or may not. Then if you want to be super anal, and can get out the chrony and run primer brand testing too! You might get even more uniform muzzle velocity. I told you when we started it is addicting, this absolute accuracy mission.

If there are no more questions in your mind then we can get into cartridge assembly.

Dutch-Hunter

 

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