Is a ZERO extreme spread possible? Yes. Lou Murdica proved that, with AMP-annealed cases, and advanced reloading methods, you can achieve the exact same muzzle velocity — 2924 FPS for two shots in a row. Oh, and the accuracy wasn’t too bad either. Shooting in a tunnel with an F-Open rig on the bench, Lou put two rounds within 0.1 inch. Note, the rounds were fired with the wood-stocked F-Open/Benchrest rifle on the left, not the Rail Gun on the right. The full annealing and reloading process is shown in the video below:
See Complete Testing and Reloading Process in 3-minute Video!
We highly recommend you watch this video ALL the way through, and then watch it again. You will see one of the best shooters in the world loading precision ammo. Lou is a world-class short-range benchrest, long-range benchrest, and F-Class shooter. In this video you can see Lou load a cartridge start to finish, beginning with annealing using a computer-controlled AMP induction annealing machine.
After firing, the 6.5 Creedmoor case was annealed with the AMP induction annealer.
Here is Lou Murdica’s Reloading Procedure Used in this Test:
1. Anneal 6.5 Creedmoor cartridge in AMP Mk II Annealer.
2. Lubricate case with Imperial Case Wax.
3. Full-length size case with Redding FL bushing die in single-stage RCBS Big Max Press.
4. Apply Moly dry lube to inside of case-neck with brush.
After FL Sizing, and before bullet seating, Murdica applies dry Moly lube inside the case-neck.
5. Seat Primer with Bald Eagle Precision Primer Press.
6. Throw charge to within 1 kernel with Auto-Trickler System and Force Restoration Lab Scale.
7. Drop charge in case with precision funnel.
8. Seat bullet with hand die and Sinclair Arbor Press.
Two Rounds, Same Case, Both with Exact Same Velocity — 2924 FPS
If you watch the video, you can see that, for the second 6.5 Creedmoor round, the velocity is 2924 FPS. That is exactly the same velocity as shot number 1. So the two-shot Extreme Spread (ES) is Zero. The second shot was 0.1″ from shot number one — pretty close to one hole. Lou was using Vihtavuori powder and Berger AR bullets. On the screen, Oehler Ballistic Instrumentation software displays bullet velocities and impact locations using inputs from chronograph and acoustic target sensors.
Credit Boyd Allen for identifying Oehler System and RCBS Big Max Press.
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The way you drop powder in the case will affect your max powder volume and the load density. Look at the photo above. These photos show the SAME 30.6 grains of powder using four different fill methods. If you are working with a powder that is below max safe pressure at your current “full case” (with room left for the bullet), and you want to get more velocity with that powder, consider a different case-filling technique.
Most of us assume that if we weigh our powder carefully (down to the tenth of a grain or less) we can achieve a uniform powder fill from case to case in our handloads. Weighing does ensure that the weight of the propellant in each case is the same, but is the column of powder the same by volume each time? “Not necessarily” is the answer. An interesting experiment by our friend Boyd Allen demonstrates that the manner in which you place kernels in the case can make a significant difference in the height of the powder column within the brass case.
Using a Gempro 250 scale, Boyd measured exactly 30.6 grains of Vihtavuori N-133 powder. He then inserted this powder in the same cartridge case multiple times. (The case has a fired primer in place.) But here is the key — Boyd used various filling techniques. He did a slow fill, and a fast fill, and he also experimented with tapping and drop tubes. What Boyd discovered was that you can start with the exact same weight of powder (in fact the very same set of kernels), yet end up with vary different fill heights, depending on how you drop the kernels into the case. Look at the photos. Despite variations in lighting, the photos show the same 30.6 grains of powder, placed in the same cartridge, with four different methods.
Using funnels with long drop tubes packs kernels more tightly, creating a shorter powder column. That allows you to get more propellant (by weight) into the case.
Boyd Explains the Procedure Used for his Experiment.
EDITOR’s NOTE: So there is no misunderstanding, Boyd started with a weighed 30.6 grain charge. This identical charge was used for ALL four fills. After a fill the powder was dumped from the case into a pan which was then used for the next fill technique to be tried. So, the powder weight was constant. Indeed the exact same kernels (of constant weight and number) were used for each fill.
Boyd writes: “I used the same powder for all fills, 30.6 gr. on a GemPro 250 checked more than once. All fills employed the same RCBS green transparent plastic funnel. The fast drop with the funnel only overflowed when it was removed from the case neck, and 15 granules of powder fell on the white paper that the case was sitting on. The fast-funnel-only drop with tapping, was done with the funnel in place and the case and funnel in one hand, while tapping the case body with the index finger hard, many times (about 20 fast double taps). My idea here was to “max out” the potential of this tapping technique.
The slow drop with the funnel and 10″-long .22 cal. Harrell’s Precision drop tube, was done by holding the scale pan over the funnel and tapping the spout of the pan repeatedly on the inside of the funnel about 1/3 down from the top, with the scale pan tilted just enough so that the powder will just flow. Many taps were involved, again, to max out the technique.
Again, to be clear, after each case filling, the powder was poured from the case back into the scale pan carefully. You may notice the similarity between the fast drop with the drop tube, and the funnel only with tapping. Although I did not photograph it, fast tube drop and tapping (combined) improved on tapping alone, but only to about half as far down the neck as the slow with drop tube. Due to the endless possible permutations, I picked four and left it at that.
I believe that I can make the rough judgment that the scale pan funnel and drop tube technique, which involved a longer drop period, and probably less velocity at the top of the tube, left more room in the top of the case neck than the slow drop from the measure with the same drop tube. You have both pictures, so you can make the comparison.” — Boyd
Does Powder Column Height Variance Make a Difference?
Boyd’s experiment proves pretty conclusively that the method of dropping a given weight of powder can affect the height of the powder column in the case and the degree of powder compression (when a bullet is seated). He showed this to be true even when the exact same set of kernels (of constant weight) was used in repetitive loadings. This raises some interesting questions:
If you shoot a .308 Win, or any cartridge that uses a Large Rifle (LR) primer, you should read an important new article by Laurie Holland in Target Shooter Magazine. Holland, a talented shooter from the UK, tested no less than sixteen (16) different large primer types using a custom F-TR target rifle shot from the bench. Laurie loaded .308 Win ammo* with 16 LR primer varieties and then tested for average velocity, ES/SD, and group size. This may be the most comprehensive and thorough LR primer test ever done. Here are the primer types tested:
CBC Magtech 9½
CCI 200 LR
CCI BR2 Match
CCI 250 Magnum
Federal 210
Federal 210M Match
Federal 215M Magnum Match
Fiocchi Large Rifle
Kynoch Large Rifle
Murom KVB-7 (PMC LR)
Norma Superflash LR
PMC LR Magnum
Remington 9½ LR
Remington 9½ M Magnum
Sellier & Bellot LR
Winchester WLR
Test Rig: Osprey Rifles-built F-TR rifle with Savage PTA action, 32″ Bartlein 1:12″-twist ‘Heavy Palma’ barrel, and Dolphin Gun Company modular stock with an F-Open/Benchrest fore-end.
Some of Laurie’s results may surprise you. For example, would you guess that Sellier & Bellot primers had the lowest ES, by a significant margin? And get this, among ALL the primers tested, Rem 9½M Magnum primers produced the lowest velocity, while Rem 9½ LR (non-magnum) primers yielded the highest velocity. (The total velocity spread for all primers was 35 fps). That’s counter-intuitive and it’s odd that Rems were at opposite ends of the speed spectrum among ALL primers tested.
“The rationale for doing side-by-side tests is to see what effect primer choice has on ballistics, i.e. average velocities and MV consistency. There are a great many views on the subject, a few based on tests (including primer flame photography) but most apparently hearsay.” — Laurie Holland
Every serious hand-loader should definitely read the full test results to understand Laurie’s methodology and get all the details. This is an important test, with significant findings. But if you can’t spare the time right now, here are some highlights below:
Primer with Lowest Velocity: Remington 9½ M Magnum (2780 fps)
Primer with Highest Velocity: Remington 9½ LR (2815 fps)
Primer with Lowest ES/SD: Sellier & Bellot LR (12/3.1 fps)
Primer with Highest ES/SD: Remington 9½ M Magnum (47/14.0 fps)
Primer with Smallest Group Size: Remington 9½ LR (0.43″ average, three 5-shot groups)
Primer with Biggest Group Size: CBC Magtech 9½ (0.7″ average, three 5-shot groups)
Editor’s Comment: Laurie shot three, 5-shot groups at 100 yards with each primer type. The average group size for the top six primers varied by only 0.10″ (0.43″ to 0.53″), so one can’t conclude that one type is much better than another. Total group size variance (from best to worst) was 0.27″.
“The biggest surprise to me … came from an elderly (at least 10 years) lot of Czech Sellier & Bellot standard caps with an ES of 12 and SD of 3.1 fps, way below those of the nearest competitor. By contrast to the Fiocchis, they were an almost slack fit in the cases and this may have contributed to their consistent performance.” — Laurie Holland
NOTE: Values in chart are based on 15-Shot strings. The ES/SD numbers will therefore be higher than is typical with five-shot strings.
Testing 16 primer types was a huge task — we commend Laurie for his hard work and thoroughness. This extensive test is an important contribution to the “knowledge base” of precision shooting. Laurie’s findings will doubtless influence many hand-loaders who hope to produce more consistent ammunition, or achieve better accuracy. Credit should also be given to Target Shooter Magazine for publishing the results. Well done gentlemen…
*Reloading method for Test Ammo: “Test batches consisted of 16 or 17 rounds for each primer, charges thrown by an RCBS ChargeMaster and checked on lab-quality electronic scales, adjusted if necessary to within ± 0.04gn, so any charge weight variation would be under 0.1 grain which equates here to 5 fps.”
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Conventional .308 Winchester brass has a large primer pocket with a large, 0.080″-diameter flash hole. Last year, Lapua began producing special edition .308 Win “Palma” brass that has a small primer pocket and a small flash hole, sized 1.5mm (.059″) in diameter. Tests by U.S. Palma Team members showed that the small-flash-hole .308 brass possibly delivers lower Extreme Spread (ES) and Standard Deviation (SD) with some bullet/powder/primer combinations. All things being equal, a lower ES should reduce vertical dispersion at long range.
Why Might a Small Flash Hole Work Better?
The performance of the small-flash-hole .308 brass caused some folks to speculate why ES/SD might be improved with a smaller flash hole. One theory (and it’s just a theory) is that the small flash hole creates more of a “jet” effect when the primer fires. Contributing Editor German Salazar sought to find out, experimentally, whether this theory is correct. German explained: “During one of the many internet forum discussions of these cases, Al Matson (AlinWA) opined that the small flash hole might cause the primer flash to be propagated forward more vigorously. In his words, it should be like shooting a volume of water through a smaller nozzle, resulting in a flash that reaches further up the case. Now that kind of comment really sparked my curiosity, so I decided to see what I could see.”
More Primer Testing by Salazar
You can read more about this test and other primer experiments on RiflemansJournal.com.
Large and Small Flash Hole .308 Cases — But Both with Small Primer Pockets
To isolate the effect of flash hole diameter alone, German set up a test with the two types of .308 case that have a small primer pocket: Remington BR brass with a 0.080″ flash hole and Lapua Palma brass with a 0.062″ flash hole. NOTE: German reamed the Lapua brass to 0.062″ with a Sinclair uniforming tool, so it was slightly larger than the 0.059″ factory spec. The Remington brass has a .22 BR headstamp as this brass was actually meant to be re-formed into .22 BR or 6 BR before there was factory brass available for those cartridges.
German set up his primer testing fixture, and took photos in low light so you can see the propagation of the primer “blast” easily. He first tested the Remington 7 1/2 primer, a primer known for giving a large flame front. German notes: “I thought that if there was a ‘nozzle effect’ from the small flash hole, this primer would show it best. As you can see from the photos, there might be a little bit of a flash reduction effect with this primer and the small flash hole, the opposite of what we expected, but it doesn’t appear to be of a significant order of magnitude.”
Next German tested the Wolf .223 primer, an unplated version of the Small Rifle Magnum that so many shooters use. German notes: “This is a reduced flame-front (low flash) primer which has proven itself to be very accurate and will likely see a lot of use in the Lapua cases. With this primer, I couldn’t detect any difference in the flash produced by the small flash hole versus the large flash hole”.
Remington BR case, 0.080″ Flash Hole, Wolf .223 Primer.
Palma case, 0.062″ Flash Hole, Wolf 223 Primer.
German tells us: “I fired five or six of each primer to get these images, and while there is always a bit of variance, these are an accurate representation of each primer type and case type. You can draw your own conclusions from all this, I’m just presenting the data for you. I don’t necessarily draw any conclusions as to how any combination will shoot based on the pictures.”
Results of Testing
Overall, looking at German’s results, one might say that the smaller diameter of the small flash hole does not seem to have significantly changed the length or size of the primer flame front. There is no discernible increased “jet effect”.
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