Armory Sponsor
Posted: 7/10/2011 10:03:03 AM EDT
|
This is gonna be a little wordy, bear with me.
So I tried an incremental loading technique for my AR yesterday with weird results. This is the first time I have tried this. The gun is a stock Spike's 16" midlegth with Geissele trigger and Swift 3-6x40 scope shot off my tailgate with sandbags at 100 yards. I let the gun cool down 5 minutes between shots. The test loads were 55gr Hornady FMJBT loaded to 2.250 OAL. I started wtih 24.7gr Tac and ended with 26.3gr, at increments of 0.2gr for a total of 9 rounds. All unmentioned variables are the same. The 9 rounds made a trapezoid shape approximately 3x3", with rounds 6 and 8 on the left, and 3 and 2 on the right. Rounds 1,7, and 5 were the closest at about 1" in the middle of the trapezoid. I was under the impression this technique would make a string of shots with the most accurate concentrated together. Obviously that did not happen(or did it?). What gives? Thanks for any input. For the record, I am a decent shot and an experienced reloader. |
|
Let me see if I have this right - you took one shot of each load printing on the same target?
One shot of each load does not allow for any of the normal shot to shot variations so it tells you very little as it will be just one data point in a range with a more or less normal distribution. A single 10 shot group or two 5 shot groups with each load will give you a better idea how each load performs as you can start to make some inferences about how widely scattered the distribution will be for each load. Another issue is that it is not uncommon for a rifle to shoot to a slightly different horizontal and vertical point of aim with different loads at different velocities due to barrel harmonics. Consequently when shooting 5 or 10 round groups with different powder charges you may find the mean point of impact varies horizontally as well as vertically - which all by itself is one reason your approach may not work. |
|
Couple of suggestions. One is that this technique only works well for rifles and shooter (disregard if you are a decent shooter) that is capable of shooting MOA spread. The reason is of course if one or both can only result in groups that are 2-4” in diameter, then you can see that the noise due to the rifle/shooter is going to obscure any pattern that you can make sense out of. So the recommendation here would be to shoot at least 10 FPGMM rounds out of your gun (if you have not yet done this) and see what you get. If you are sub-MOA, you are probably GTG for the ladder method. The other thing is if you know what you are going to use the rounds for, you might be better off shooting a number of 5 round groups. What I mean is say for example if you are just going to do something that does not require high MV i.e. punching paper at 100 yards, you could concentrate on the lower powder range. On the other hand, if you are going for longer distance varmint shooting, you are going to need the MV to flatten out your ballistics and buck the wind, I would concentrate on the high range. There are usually nodes/sweet spots on both the upper and lower end. So in your case, if you need higher MV, then shoot 5 shot groups at 25.5, 25.7, 25.9, 26.1, and 26.3 gr of TAC which only requires 25 rounds and you get a better idea of what groups well. Once you do this, you can come back and confirm with a 10-round group. |
|
100 yards is too close. Most people recommend 200 yards min. But this time after each shot you need to look either through a spotting scope and on another identical target you have at the bench or walk to the target with an identical clean target and mark where that round struck and mark it with its chronological number. It really helps to chrono each one as well. I use this method all the time and it does work. Eventually you'll see at least one 3 shot group appear. They WILL be in chronological order and this is called a node. If you cross reference the group to thier respective recorded velocities you will see they too, should be really close, even though they were different charges. Thats a node you experiment with later by adjusting seating length and the like.
I never shoot less than 15 different loads and usually end up with 2/3 shot groups. This method saves alot of headaches and money. |
|
100 yards is indeed not a good distance for a ladder, but I don’t think this is his problem since his 9 round groups ended up in a 3x3” box. The problem with shooting at 100 yards is that the rounds can almost go through the same holes which makes figuring out which round is which difficult, the longer range allows the grouping to open up. If you have to shoot at 100 yards, I find that the fool proof way to document which round is which is to actually set a video camera up close to the target and video tape the session. Obviously don’t shoot the camera….  What I don’t like about the ladder the way most people do it is they shoot the ladder with the complete range of powder weight i.e. low to max. The fact is if you are really only interested in either the low powder range (to save powder) or high powder range (need high MV), one of the ends of the ladder is a complete waste of time and components. This is why I suggest doing the 5 round groups within a limited range of powder weight. |
| But what if NONE of those groups shoots well?? I would waste the better part of a box of, not inexpensive bullets, testing with my old method. I still have the majority of a box when I'm done with a 15-20 round ladder and I know what is what with my ammo at the end. I don't believe I have ever had to shoot a ladder twice. I always have at least 2 groups to work off of. |
|
If none of the groups shoots well, then the same powder weight in the ladder will also not group, there is no way around this. Remember if you are only interesed in say the high MV product, finding a node in the low end does not help you. The fact is after shooting the 15-20 round ladder, you will still have to confirm what you think is a node. Here you have two choices, you can bet big and choose one and go for a 10 round group, but if you are wrong, you are back to doing another confirmation. Another way you can go is to choose a few weights and do 5 round groups. If you do the math, if you ran a 15 round ladder, did two five round groups, you will have used 25 rounds. With the method I mentioned which is to concentrate only on the powder weight end you are really only interested in, you again only use 25 rounds but it was done in a one range visit and your results are more reliable. |
| Thanks guys for all your input. After thinking about it, and jlow confirming it, I think the biggest problems is that my 16" AR is not a sub moa gun. Even so, the trapezoid shape of the rounds was not even close to what I expected. And for the record, I marked each round after the shot with a number corresponding to its place in the string. |
|
Not a problem and glad I am of help. FWIW, you are not the only one who has gone through this. The problem is that people who describes this great method always neglect to give that important caveat which is a shame. The method has its place but it is certainly not applicable in all situation. I think everyone who wants to do precision load development should start with their gun on a vice and a box of FPGMM so that they know what they are dealing with. That stuff may not be the best ammo in the world, but it does give you clues as to what is possible and not. I myself learn this the hard way. |
| I don't think I'm illistrating my point....I will scan my last ladder group in and post it....at 200 yards with a bolt gun the group starts midline and walks up and to the right. Shape of the group has absolutely nothing to do with this method. And for that matter neither does loading for velocity....the goal is the accurate load...always |
|
Quoted:
This is gonna be a little wordy, bear with me. So I tried an incremental loading technique for my AR yesterday with weird results. This is the first time I have tried this. The gun is a stock Spike's 16" midlegth with Geissele trigger and Swift 3-6x40 scope shot off my tailgate with sandbags at 100 yards. I let the gun cool down 5 minutes between shots. The test loads were 55gr Hornady FMJBT loaded to 2.250 OAL. I started with 24.7gr Tac and ended with 26.3gr, at increments of 0.2gr for a total of 9 rounds. All unmentioned variables are the same. The 9 rounds made a trapezoid shape approximately 3x3", with rounds 6 and 8 on the left, and 3 and 2 on the right. Rounds 1,7, and 5 were the closest at about 1" in the middle of the trapezoid. I was under the impression this technique would make a string of shots with the most accurate concentrated together. Obviously that did not happen(or did it?). What gives? Thanks for any input. For the record, I am a decent shot and an experienced reloader. For best results shooting groups, shoot of a bench. Shooting off the tailgate I believe is part of your problem. Is your forend a free float? The Hornady 55 gr FMJBT is the best of it's kind, but a FMJBT is not a target bullet. To test your rifle to see if it is capable of moa, try this target load; Win case trimmed and debured, Sierra 52 gr HP Matchking, 27.0 grs Re-15, Rem 7 1/2, OAL 2.250, no crimp. Good luck eta, Welcome to the Reloading Forum. 
|
Armory Sponsor