Powder work-ups

[KMW1954]

Have the new 28" Shilen barrel on and have been working up loads. Have 6 different powders to work with. A2460, BL-C2, Benchmark, TAC, VARGET, LEVERevolution. All shot with Lapua 105gr Scenar.

The A2460, BL-C2 and Lever have all been loaded twice. The BL-C2 first was loaded at .5gr intervals just to shoot and sight the scope to the new barrel. But it shot so well I had to try it again.

The A2460 and Lever had been shot before thru the old barrel and were the hands down best in that barrel. So the A2460 I did ladder in .3gr and then in .2gr.. The .2gr were loaded for the old barrel and had to be pulled apart because they would not close in this new chamber. Too long by.005".

The Lever twice because it just shot so well and because of the reputation it is developing and the velocities it generates. Using the Hornady Bolt data at .3gr intervals I came up with 10 different load levels so I did the first 5 loads and then the second 5 loads.

The disappointing part of this test is that they all shot exceptionally well. So well in fact I cannot pick one as the best powder. Though I still feel the A2460 and Lever were the most consistent over the ranges of loads.

[Rickhem]

If you have a bunch that shoot well, try shooting those in different temperature conditions. See if one is less subject to change due to temperature fluctuations. Another factor is powder availability and cost. A load that is #2 by a small margin is preferable to a great load with a powder that you can't get or that is $100/pound.

When you say it was too long for the new chamber by .005", was that at the shoulder (headspace), or the COAL? If it was COAL, why not just reseat the bullet a little deeper?

I'm guessing that a 28" barrel is going to be a target rifle, so maybe temp variations won't be too extreme, but target shooting is a little more demanding of the precision aspect, so a quarter MOA matters.

[KMW1954]

Yes this is a target rifle and the temps we shoot our league at are SE Wis., January thu March.

These are all powders I have shot with in the past with the exception of the Lever. So I know the TAC fluctuates the most and the Benchmark isn't giving me the speeds I am looking for.

The length was headspace. The old barrel sat at max with my comparator at 1.900" while the new barrel is at 1.845" but I can still close the bolt on 1.855".. The loads I just shot measured 1.850" with my Hornady comparator.

[grayfox]

One thing you might want to keep in mind, is that with such a relatively small "boiler room" (case capacity) in the 6 Arc, all the powders including Lever (which I think is the slowest but I might be wrong) reach 100% combustion at a very short barrel length, Lever at ~16" by my estimates. Of course you can still get some acceleration beyond that but it will be a law of diminishing returns.
I have a 107 smk bolt action load using lever, and the powder curve says 99.9% burned at 16" length, 17+ are all 100% burn. So consistent gas generation, and as much as possible b/c not all powders generate the same quantity of gas, will be a consideration.

[KMW1954]

Thanks for that grayfox. The length was more for the weight than for additional speed.

[grayfox]

No worries, this model also shows powder pressure at exit, I have a 107 smk bolt load with Lever, and if extrapolated out to 28" it does still show pressure at 7500 psi give or take, so the gas is still expanding... was not trying to knock the length at all.
I have the smk's b/c of my 6 Creed, so thought it would be nice to try in the Arc.

[KMW1954]

No worries, this model also shows powder pressure at exit, I have a 107 smk bolt load with Lever, and if extrapolated out to 28" it does still show pressure at 7500 psi give or take, so the gas is still expanding... was not trying to knock the length at all.
I have the smk's b/c of my 6 Creed, so thought it would be nice to try in the Arc.

All is good, I enjoy the conversation. For me the ARC is a poor mans 6BR. Especially since we are only shooting out to 300yds. This is one of the many proprietary targets we shoot. This is a 100yd Cold Bore Target. First 2 shots must be taken at the top left sub-target. The circle in just under 1".

   

[grayfox]

cool.
Out to 300 yd... hmm.
String of thoughts here.
1. First things, which you've probably already covered, but to be sure. Barrel (check), optics, trigger.
2. For out to 300 yds, whatever bullet shoots best (what your barrel likes) would be fine. No particular order. 103 eldx, 105 hdy/bthp, your scenar, 107 smk, tipped version 107 tmk, (I don't particularly like - 108 eldm), bergers Vldh or others... And, since you're going for <0.5 moa... stability/adjustability of your rest.
The pics above suggest that the rifle is a good shooter and your load is probably pretty good, but;
3. Now I'm just an average guy, no expert here, but when I see a more or less consistent "flyer" cropping up I think it's something shooter, or position, or eye-blink, momentary loss of focus, body/finger twitch, those things.
The rifle is a mechanical system, so other things being equal, it should behave like a mechanical system, with some statistical pattern of the group. Now for my theory: To check group size for an OAL tweak I need 4, maybe 5 shots -- that way I can see either a normal pattern (mechanical system behaving, no other issues), or (don't know what to call it) an "affected" pattern. Statistically, a mechanical system should produce a rounded pattern of some diameter "x" due to its random variations, smaller the better but you get the point. An "affected" pattern will show some kind of pattern-outlier: the two most-often I see are 3 in a small triangle and 1 flyer far enough out to qualify as a flyer, or a "2 and 2" group. These tell me I did something, can't blame the bullet or load.
Is your MV on or near a mechanical node? If not then load tweaking is the first thing to do. As I look at MV, OALs, and exit timing, a powder delta of 0.1 gr is a larger effect than an oal delta of 0.010". So settle on the gross measure first (powder), then adjust the length, then proof test over a few sessions.

Row "#3" - does this indicate a better and better attempt at zero left to right? (ie, shooter)
Row "#4" First 2 groups show me a "flyer" but as an "affected" pattern (there really needs to be a better term for this!). By the 3rd group you're settled in.

Anyway, these seem to be more of shooter-oriented issues, which btw is often the case with me!

---

Edit to add: much of the fine tuning is a process of trouble shooting, correct the biggest error-effects first, then the ever smaller ones. By trying to correct a more minor effect leaving the bigger one untouched, you won't see any solid progress, any small correction will be masked by the larger effect still looming over your target results.

[KMW1954]

Correction first. The picture is a target from last year when I was still shooting the 223.

I have to agree 100% with your three points. At 100 and 200yds I was able to keep up with the other shooters and their bigger calibers but at 300yds it was a struggle. Hence the move up to the 6mm. Also after that target was shot I switched scopes and went from a 8-34X56 FFP MRAD to a 10-40X56 SFP MOA with 1/8th adjustments.

Point #2. At this point I was just working to establish a familiarity with the cartridge and the powders. Then using up these Scenar that I obtained on the cheap (.20c ea.) from a fellow league member. I got about 600 of them. Once I get settled a bit more I will start with using more of a Match bullet.

#3. I too am just an amateur and still have a number of bad habits. Though I am getting to were I can call many of the misses.

[grayfox]

There are at least a couple really good shooters on here, maybe they will also chime in with some advice... be a help to us both, lol

[BD1]

I am not anyones idea of a "expert" but I have been at this awhile, and I shot NRA High Power when I was younger, (pre-bifocals, I'm wearing trifocals these days).
I have been going through this process myself this year, using Varget, LVR and CFE.  Bullets I've worked with include Lapua 105 Scenars, The Berger 105 and 109s, 107 and 110 SMKs.  The Lapua Scenars, Berger 105s and 107 SMKs are all tangent ogive, while the Berger 109s and 110 SMKs are secant ogive, and seem much fussier to get tuned in to me.  I'm shooting an AR with a 22" Craddock RTR barrel, The local match I compete in is 440 yards off the bench. While LVR and CFE give better velocities, the Varget is giving me better accuracy, and better consistency across the seasonal temp variations, (May to October in northern Maine; 40F to 90F).    My mags will allow me to load out to 2.290, and I've tried single loading the 110 SMKs out to 2.33, but my most consistent results have been with 107 SMKs at 2.260 which puts them about .015 off the lands.  I may do some more work with the 110 SMKs to see if I can find an OAL inside of 2.290 that will work, but for now the 107's are staying under 1/2 MOA at 200 and keep up with the 6.5s and .308s in the wind so I'm happy with them so far.
It took me a while to come to the realization that 100 fps does not make much difference at a 1/4 mile, and is certainly not worth giving up any precision.  The local match is 5 spotters followed by three ten round strings from the bench, using the NRA 100 yard military target, (3-1/4" 10 ring, 1-1/4" X ring) primarily because the club has a big pile of them. They are scored after each string allowing for sight corrections. I managed to win for the first time  this year last Saturday with a 289-6X.  I had won a couple times last year using an AR in .223, but on the windier days the bigger bores would beat me every time, so I built this 6 ARC.  My work up process is: powder charge ladder in 2 grain increments at .010 to .020 of the lands. Then, using the best result, COAL variation ladder at .002 increments from .02 under the starting COAL to touching the lands, (depending on how close to max charge I am). Follow by a barrel tuning ladder, (if that rifle has a tunable brake).  I generally have a usable load at that point, which I may, or may not mess with further depending on the precision I've gotten.  I shoot all my ladders at 200 yards using 5 shot groups. If  I wind up with a couple that are very close, I'll do a "Shoot off" using 10 shot groups at 400 yards on a dead calm day, (pretty rare day around here).  At this point the rifle is capable of more precision than I am, so I'm more interested in additional barrel time than I am in additional load tuning. However, I think I may spend a little time this winter sorting brass and bullets by weight.

[KMW1954]

Just posted a picture of the ladder target I shot today in my other thread If interested in taking a look. I believe it's coming along very nicely.