finding the best hand load for 223 rem

[rebs]

I loaded 20 rounds of 223 with 55 gr fbhp and 23.4 gr of H335, I also loaded 20 rounds of the same bullet with 24.0 gr of H335. I shot 8 groups of 5 shots each and the groups are so much the same that I cannot tell which is the better load. I have also loaded 20 more of the same rounds and varied the OAL from 2.200 to 2.230 again all groups are too close to distinguish which is a better load.
Which direction should I go from here ? I forgot to say all groups are under 1" @ 100 yds. How can such variances produce the same results ? This is bench rest shooting with a bipod on the front and a sand bag under the stock.

[Unclenick]

It just means the things you were varying were less significant than other sources of error in the shooting system. I don't know whose bullet you used, but that would be a first choice thing to look at for me. I don't know what rifling twist rate you have, so I can't tell if you are overstabilizing that bullet, which can cause wobble that prevents groups getting smaller than a certain value. Are you using a CCI magnum primer? They are formulated specifically to better ignite the now roughly half-century old Western Cannon series of powders (H355 is canister grade WC852) which have stubborn-to-light deterrent coatings.

Most people think that if you take a source of error that produces 3/4 inch groups and add a source of error that produces 1/4 inch, you will now have a 1" group. It's not true. For that to happen the same to bullets in each group would have to be simultaneously subjected to maximum error influenced in the same direction from center by both sources of error. That happens, but not all that often. Instead the influences add as their standard deviations do, as the square root of the sum of the squares of the individual influences. Thus, when you add a three quarter inch error source to a quarter inch error source you get:

√(0.75² + 0.25²) = √(0.5625 + 0.0625 = √0.625 = 0.79 inch group

So you can see that even if you were making improvements that would take a 1/4 inch group down to zero, with a 3/4 inch error source still in place, you would only see a 0.04 inch improvement.

So you need to rid yourself of the main source of error before you'll necessarily be able to detect the effects of small changes in powder charge or in bullet seating depth.

As I said, I would look at the quality of the bullets (good match accuracy reputation like Sierra or Berger?). I would also look at regularity of ignition of the H335. CCI actually changed their magnum priming mix formulation in 1989 just to cover problems with irregular ignition in the WC powders. Some of the more modern developments, like the Ramshot line, are not as hard to light up and respond well to standard primers.

Irregular ignition doesn't mean failures to fire, but rather tends to manifest itself as irregular ignition delays. These are only in the milliseconds, which is too short for the shooter to tell, but it has the same effect as varying the lock time of the gun, allowing any small disturbances, from the act of pulling the trigger to the slam of the firing pin, to have different amounts of time to move the muzzle small amounts. It's enough to open groups up.

Usually, you can tell if you have a chronograph, because irregular ignition is usually accompanied by irregular muzzle velocity. So if you make an improvement you can tell by the velocity becoming more regular.

Back in the mid-1990's I experiment with Accurate 2520 (a spherical propellant) in my M1A because the maker was advertising it as "Camp Perry Powder", claiming a great following among match shooters. At the time I was unaware of slamfire concerns with sensitive primers in floating firing pin guns like the service rifles, and was using Federal 210M primers, figuring a match primer is just going be the best in a non-magnum case. With those primers, that gun could be tuned to group 0.7 moa with IMR4895, Brigadier 3032, IMR4064. Basically, it would do that with any appropriate burn rate stick powder I tried. But the 2520 grouped 1.25 moa and just would not get smaller (these were all 10-shot groups).

Then, on a lark, one day I decided to deburr the flasholes of the cases. I'd just bought a deburring tool and wanted to give it a try just because I could, but didn't expect to see it make any difference in a service type rifle. But to my surprise it caused the 2520 groups to shrink to 0.7 moa, just as good as the rifle got with stick powder. All excited, I then tried deburring cases for the stick powders to see if they would get even better. They didn't. They were still at 0.7 moa.

So, what happened was the stick powders in a case with flash hole burrs already ignited as well as it could take advantage of. It lights up so easily, ignition perfection was a much less significant help with them. But the 2520 was harder to light, partly because of heavier surface deterrent coatings and partly because it didn't fill the case as well as the stick powder charges, so it needed the primer spark more uniformly applied to get start pressure to build uniformly,

Back then I didn't know CCI had adjusted their magnum priming mix for heavy deterrent spherical propellants. If I had tried CCI 250's, the 2520 groups might have improved as much as deburring improved them, but without the extra step of flash hole deburring.

Anyway, if you have or can beg, borrow, or steal a chronograph, it should tell you whether any particular step you take is improving ignition consistency. I would get the CCI primers, specifically (either CCI 250 or CCI #34), if you can, but 1989 is long enough ago that anyone's magnum primer may now do just fine. I haven't done a recent comparison.

Before you do that, you can try deburring flash holes. You can also try taking extra care in how you seat your primers. Seat them fairly hard and make sure they are about one typing paper thickness below level with the back of the case head.

Get some good match bullets if you're not already using them.

If you don't have a runout gauge, see if you can borrow one long enough to sort some very straight ammo from your reloads and see if they group better. Some chambers care more than others about bullet tilt. If it helps, then you need to embark on tooling up to make straighter ammo.

Also try a stick powder. At your bullet weight Reloader 10X should be a good choice. Even IMR 4198 can do very well for accuracy, though it won't get you quite as much velocity as its fast burn rate limits how much you can use in a charge without going over pressure. But its still a very good accuracy powder.

If you haven't read it yet, look at Dan Newberry's method of finding best loads. His round robin and target evaluation method can be used either with powder charge steps or with seating depth steps.

[rebs]

Unclenick, Thank you for all the information, I appreciate it and the time it took you to type it all.
I have 2 AR 15's, one is a Colt match target competition with a 20" 1 in 9 twist. The other is S&W with a 16" 1 in 8 twist barrel. They both shoot the same bullets with almost identical accuracy. Since powder and primers are so hard to get at this time a change in either would be hard to do. I have almost 6 lbs of H335 and around 2000 CCI # 400 primers. So for the time being I have to work with what I have. I will give the deburring the flash holes a try and also read Dan Newberry's article. I will also pay more attention to primer seating. I almost forgot to add I am shooting 55 gr Varmint x-treme fbhp bullets.
Is there anything else you recommend ?

[Unclenick]

You may want a heavier bullet. The 64 grain flat base Berger 22316 varmint bullets are a great choice, but not inexpensive. The 69 grain Sierra MatchKings are a time tested standard that should shoot in both barrel twist rates well. The 77 grain MatchKing should do well in the 8" twist barrel.

Deep primer seating is the main thing to accomplish. Cut a strip of typing about a quarter the width of the primer and lay it across the primer, then set a flat screwdriver to bridge the primer pocket over it sideways. The paper should be possible to slide out. If not, the primers weren't seated hard enough. You don't want to smash them, but just get them to pass the paper. With AR's, especially, you have floating firing pins so you never want to risk a high primer causing a slamfire or an Out of Battery firing event in them. Ideally you'd use one of the military hard primers for further insurance against those events. The ones currently made are:

CCI #41 (magnum strength)
TulAmmo KVB556M (magnum strength)
Federal GMM205MAR (standard strength)

But finding them is another story.

You can also experiment with crimping with a Lee Factory Crimp Die to see if it helps. Go lightly with it. It should increase the bullet pull, making it easier for the powder to build pressure, helping increase consistency of ignition time.

Good luck with the development work.

[Bart B.]

Cut a strip of typing (paper?) about a quarter the width of the primer and lay it across the primer, then set a flat screwdriver to bridge the primer pocket over it sideways. The paper should be possible to slide out.

Which means the primer cup flat's about .005" or more below flush with the case head when this happens.

None of my primers are seated that deep. They're typically .003" to .004" below flush. Accuracy's excellent. Just measured three types of standard 20-pound typing paper and they're all .004" to .005" thick. Industry specs for 20-lb bond varies from about 0.0038" to about 0.0045" thick.

The primer pocket depth makes a difference too; they're not all the same. Primer's need to be seated so their anvil pushes into the priming mix a little bit, but consistantly. Measure how thick your primers are from the cup flat to the anvil legs. Then measure how deep the primer cups are where the primer anvil legs contact. A little grade school math will tell you how much below case head the cup flat needs to be to attain that "crush fit" that's best for the primer. Persnickerty folks uniform primer pockets to exact depths across a lot of brass. Then set their priming tool to seat their primers such that the anvil gently compresses the priming compound.

All this aside, it's better to seat 'em too deep than too shallow.

[Unclenick]

Originally Posted by Bart B.

Which means the primer cup flat's about .005" or more below flush with the case head when this happens.

Shouldn't be quite that big. 16 lb Bond is nominally 3.2 thousandths thick, while 20 lb bond is nominally 3.8 thousandths thick (though I've mic'd it from 3.4 to 4.4 thousandths, so the tolerances aren't exact, and I suspect they vary with humidity). Note that I said it should be possible to pull the paper out and not that it should slip freely, so I'm assuming some drag. Yellow legal pads are mostly 16 lb paper that I've measured, and depending on your primer pocket depth, that may be a better choice.

That said, the fixed depth primer seating tool built into the Forster Co-ax press pushes the primer -0.005" below flush, and results in very reliable ammunition. The standard Olin and Remington and the Naval Ordnance Station at Indian Head gave in the past was consolidation of between 0.002" and 0.006", meaning that once the primer anvil feet touched the bottom of the primer pocket, compression should go that much farther to set the anvil/cup bottom priming compound bridge thickness. This information is included the last several pages for a number of firearm and non-firearm primer types listed in this 1970 report.

Primer pocket depths vary about ±0.001" if you don't uniform primer pocket depths with a cutter. Plus you get primer residue build-up if you don't clean the primer pockets pristinely. So for any kind of fixed primer seating value below flush for brass that you're not uniforming pockets in, you really want a range of consolidation to work with and to aim roughly at the center of it. You can use a depth mic to measure primer pocket depth in your brass and take the average, and then use an OD micrometer to do the same with your primer lot's total height. If you are going by the Remington/Olin/NOSIH standard for consolidation range, subtract 0.004" from the primer height average, then subtract the result from the average primer pocket depth. That gives you a target value for how far below flush the primer should be, and also for the paper thickness (less maybe half a thousandth for drag slip).

One possible exception to the above consolidation range that I'm aware of is the Federal primer line. In 1994 or 1995, Federal told Dick Wright they thought consolidation should be 0.002" for small primers and 0.003" for large. It's the only set of fixed numbers I've encountered, if, indeed, they are fixed and not merely minimums. That would be hard to hit consistently without the K&M Primer Gauge tool. It is the only priming tool made that I'm aware of that lets you actually measure consolidation. It zeros the gauge to the height of each individual primer against the depth of each individual primer pocket, then lets you measure how far past that zero (anvil kissing bottom of the pocket) you actually seat the primer. You can experiment with that, but the way it works, you have to mount the primer and case twice—once to zero and once to seat—so it's very slow going.

Wright commented that he had that tool, but was too impatient to use it, though Mrs. Wright used it. He also commented that Mrs. Wright had been beating him in matches.

Writing in the 1995 Precision Shooting Reloading Guide, Dan Hackett made this observation:

There is some debate about how deeply primers should be seated. I don’t pretend to have all the answers about this, but I have experimented with seating primers to different depths and seeing what happens on the chronograph and target paper, and so far I’ve obtained my best results seating them hard, pushing them in past the point where the anvil can be felt hitting the bottom of the pocket. Doing this, I can almost always get get velocity standard deviations of less than 10 feet per second, even with magnum cartridges and long-bodied standards on the ’06 case, and I haven’t been able to accomplish that seating primers to lesser depths.

Dan Hackett
Precision Shooting Reloading Guide, Precision Shooting Pub. (R.I.P.), Manchester, CT, 1995, p. 271.

That was the case in my own experiments, but they were almost twenty years ago and were inconclusive as to whether 0.003" or 0.004" or 0.005" or 0.006" really made a difference. They were done before I got the K&M Primer Gauge tool, instead depending on depth and OD micrometers and seating by feel, and then tweaking, and then sorting the result. It was less exact than the K&M tool, and it was just with the Federal 210M primer. I would like to find time to run a test matrix with more recent production primers, but using that tool. Alan Jones says primers and their formulations change more frequently than people realize and the changes are is seldom advertised, so old information may be obsolete on top of everything else.

The bottom line regarding what is useful is that testing velocity consistency is a good reflection of ignition consistency, and, proof being in the pudding, actual group size at enough distance to see vertical stringing is best of all. I find 300 yards about the minimum for this, though benchrest rigs can often shoot tightly enough that 200 yards will do.

This page includes a table of paper thicknesses (scroll down to the see the table).

[Bart B.]

The bottom line regarding what is useful is that testing velocity consistency is a good reflection of ignition consistency, and, proof being in the pudding, actual group size at enough distance to see vertical stringing is best of all.

My 1000 yard test with 1/2 to 5/8 MOA vertical stringing at 800 to 1000 yards with primers .003" to .004" below Winchester, Federal, Western Cartridge, Remington case heads on both 30 caliber magnum and .308 Win. must be about right.

Weak firing pin springs can cause more than 1 MOA vertical stringing at that range. So, when testing primers' performance at long range, a new, correct, firing pin spring may be needed.

As does insufficient firing pin protrusion from the bolt face. But head clearance has to be less than .004", too. Anything less than about .050" protrusion for large rifle primers can cause the same vertical stringing. .060" to .065" is about right.