I wonder if trapshooters who reload their target loads realize how important a role their selected primer plays in regards to both interior ballistics; namely velocity and pressure, plus exterior ballistics effecting patterns. Many shooters who reload their own shotshells and want to save a buck buy whatever primer happens to be on sale at that time. Not realizing or knowing about the pitfalls that may arise from their indiscriminate selection. To show the reloader just what can happen with various primer substitutions the following primer comparison tests were carried out at my test facility, Ballistic Research. Under controlled conditions the following reload was selected:

First let us look at the velocities obtained from the highest to the lowest regarding the above recipe. (See Table 1) The Federal 209A registered the highest velocity at 1251 FPS with a variation of only 14 FPS on the ten shot test. At the other end of the chart is the Cheddite 209 with the lowest velocity averaging 1217 FPS with a variation of just 20 FPS. It can be seen that the maximum velocity difference between the various primers was 34 FPS. Maximum primer variation between lots was 48 FPS. This velocity change due to primer substitution could for example change your target load from a light to a heavy velocity designation, or vice versa depending on the strength of the primer selected, much depending on all the other reloading components selected.

Next let's look at what our primer substitutions did to pressure. Say we had selected the Remington 209 Premier due to its low pressure at 8810 PSI. This would be a soft shooting mild recoil loading. Let's say we ran out of the Remington 209 Premier primers and needed shells for tomorrow night’s league shoot. So we run down to our local sporting goods store finding out they are sold out of the Remington primers. Not too worried as the sales clerk says I have loaded thousands of shotgun shells with the Federal 209A primer with excellent results. As luck would be they are on sale so you feel confident buying them. The next night at the league shoot your mild 16-yard loads seem like they now have a little more punch and you wonder why. Well for one, your velocity increased by 23 FPS, but more importantly the pressure increased by 2050 PSI from a mild to a robust 10860 PSI. Your mild load is now rubbing the upper SAAMI limits of 12 GA 2-3/4 shotshell pressure of 11500 PSI. This is a very substantial pressure gain for a simple primer substitution.

TABLE I

Shotshell Primer Comparison
Winchester 12-Ga. 2-3/4" AA Hull
17.0 Grains IMR 700-X Powder
Greenduster GT 9210-12 Wad
One Ounce No. 8 Lead Shot

Comment: This listing is in the order of highest to lowest velocity. Maximum velocity variation between primer brands was 34 fps, while the maximum pressure variation between primer brands was 2,640psi.

The ballistics shown represent average performance for ten rounds with each loading using a 30 inch SAAMI test barrel with a 3 inch chamber and a 0.726 bore with skeet choke. Velocities were measured at 4 feet from the muzzle using an Oehler Model 33 chronograph in conjunction with the Skyscreen III system.

Pressures were recorded in pounds per square inch (psi) using a PCB 167A02 piezo­electric transducer in conjunction with a PCB Model 462B52 ballistics charge amplifier and a Model 451A07 digital peak meter. All powder and shot charges were loaded by scale weight using a Denver Instruments Accurate Load III electronic scale.

Copyright © 2000 - Tom Armbrust / BALLISTIC RESEARCH

Now if you really want your eyes opened concerning this next primer substitution test series let's take a look at Table 2. First, I would like to thank my old friend Wallace Labisky from DAK-TECH Ballistics (1324 Fourth Avenue SE, Aberdeen, SD 57401, phone 605-225-7906) for sharing this important reloading test information with me as follows:

Again the Remington 209 Premier primer shows both the lowest velocity of 1218 FPS and lowest pressure of 7040 LUP. Velocity variation is on the high side at 135 FPS. Yes, I realize in the chart, the CCI-209 Trap and Skeet primer showed the lowest velocity and pressure but it is no longer available to the reloader. If you want one hell bender load, let's try the Federal 209A primer. Velocity increased to a whopping 1331 FPS or an increase of 121 FPS over the CCI-209 Trap and Skeet offering. Pressure also very much increased by 3280 LUP versus the Remington 209 Premier primer. Wow, to say the least! A velocity level of 1331 FPS seems a little brisk for 16-yard clays exceeding the ATA 3 dram velocity limit of 1200 FPS, not to mention the very much increased felt recoil.

TABLE II

Primer/Powder Compatibility Comparison

12-Gauge 2-3/4" Handload:
Fiocchi VIP plastic target hull (red, high basewad), once fired
Various primers
21.5 grains INTERNATIONAL CLAYS (Lot 2703L1592C)
HAWK wad (short crush section) 50 Ibs. seating force
1 oz. No. 8 West Coast Magnum lead shot (437.5 grs.)
8-pt. fold crimp
Crimp space: 1/2"

Comment: Test sample consisted of 10 rounds with each primer fired through a 30-inch pressure barrel with a 3-inch chamber and a bore diameter of .725 inch and no choke. The velocities shown are instrumental at 4.5 feet from the muzzle and were measured using an Oehler M-35 Proof chronograph with the Skyscreen III system. Ambient temperature was 75° F. All powder and shot charges were loaded by weight, (not volume).

ES = Extreme Spread

COPYRIGHT © 2000Wallace Labisky

You may ask, why did this second test series show such a larger increase in velocity and pressure levels, as a difference of 121 FPS and 3320 LUP is nothing to disregard to say the least. Hodgdon's International Clays powder has a somewhat slower burn rate, with a more elongated time pressure curve vs. IMR 700-X, all other components being the same. When a more mild force primer is employed behind the slower burn rate propellant, it is changed from a solid into a gas state in a slightly longer time frame then when a more forceful primer is used. This results in higher velocity and pressure due to its quickened and steeper time pressure curve.

You will also notice a trend towards more extreme velocity and pressure variations, when using the mild primers behind the slower burn rate propellant. To help relieve this problem of excessive variation, a heavier shot charge payload could be brought into play, namely 1-1/8 oz of shot creating more resistance to the expanding powder gases. In turn, elevating velocity and pressure and shortening the duration of time on the time pressure curve. A competitive AA trapshooter would not want excessive velocity and or pressure variation in his target loads if it can be helped. Keep this in mind the next time you select your combination of reloading components. As both uniform ballistics and pattern results can be adversely affected by indiscriminate component selections. Not to mention the possibility of unsafe pressure levels.

Crimps will also affect ballistics. Many active shooters like to apply light, shallow crimps because they believe such closures prolong case life. Other handloaders go to an opposite extreme and crunch crimps deeply, assuming that a heavy crimp will hold more effectively against ignition and early combustion pressures to promote a more complete powder burn. Unfortunately, those extremes tend to be predicted on logic rather than scientific evidence. The real results are more complex.

To show what happens with various crimp depths, another test was run in the Hodgdon Ballistic Laboratory using one control reload and different crimp depths. Unless otherwise listed, the data in this text was created using a standard depth of 0.055, which is a bit short of 1/16. However, some manufacturing variations exist in which case handloaders are urged to use a factory equivalent crimp depth for that particular shotshell. The test reload was checked for pressure and velocity at 0.020 increments. The test reload was assembled like this:

The resulting ballistic data was as follows:

The importance of crimp depth, then, should be obvious: crimp depths to either the high or low side of normal will directly impact pressure/velocity results.

I would like to thank Ron Reiber of Hodgdon Powder Company (PO Box 2932, Shawnee Mission, KS 66201, phone 800-622-4366) for letting me use this following article and reloading data by "The Master", Don Zutz, from Hodgdon's excellent shotshell data manual pages 30-33.

The following charts were created in the Hodgdon ballistics laboratory under controlled conditions. Winchester cases and Winchester wads were used for both the 1-1/8 oz and the 7/8 oz test. Cases were crimped deeper than normal to create the highest pressure possible for a given load. The only component changed for each test was the primer. Powder charges were the same throughout each test.

Review the statistics for these two tests, and note the large difference in pressure from the hottest load to the coolest load. This dramatically shows why a reloader should not switch primers without consulting his loading guide. Just changing the quantity of shot, changes the way primers perform. The hottest primer in the 1-1/8 oz test was not the hottest primer in the 7/8 oz test. Imagine changing cases, wads, and even gauges. The combinations are seemingly endless, as are the results.

ALWAYS CONSULT YOUR RELOADING GUIDE BEFORE SWITCHING COMPONENTS!

1 1/8 oz. TEST

7/8 oz. TEST

Thanks to Downrange Manufacturing LLC (4170 North Gun Powder Circle, Hastings, NE, phone Kevin 402-463-3415, fax 3452) for reintroducing their excellent Versalite wads in both 12 GA and 20 GA offerings after a long absence. Plus their extensive lineup of XL wads, Windjammer replacement wads, pattern control wads, and their DRA direct replacement Winchester wads. This lineup covers trap, skeet, sporting clays and hunting from 7/8 oz to 1-1/4 oz shot charges. High quality virgin plastic, with its very slippery texture, is employed to reduce barrel fouling and to enhance target breaking ability at a competitive price. These wads have shown minimum velocity and pressure variation in tests at my outfit, Ballistic Research, plus high quality pattern results. Their hot colors are sure to catch your eye.

To illustrate the pattern variations possible with changes in components, a control reload was selected for use in a Beretta 686 Essential Over and Under with 28 inch barrels. The Beretta modified choke tube was used, and I arbitrarily selected a test range of 35 yards because that's where, in my opinion, modified choke is at its best. The control reload was:

Performance wise, a 5 pattern string with the above reload placed an average of 158 pellets in the outer 5-inch ring and 249 in the 20-inch diameter core ring for a total of 407 pellets, again, on the average.

But what happens when a subsystem is changed? Will the core density thicken, remain the same, or weaken? Will the outer ring receive more or less pellets, or will it retain the same basic count? And what about the overall density? Would it change as some components were switched?

These are important questions, because experts in the field observe changes in downrange effectiveness as total pattern and ring/core densities vary. Patterns with high core counts still have some range effectiveness remaining, since it is the core density that eventually becomes the ring density as air resistance forces the pellets outward. Conversely, patterns with weak cores have already shed much energy into the outer ring and fringe and have therefore reached or passed their point of maximum effectiveness. Thus, while a high outer ring count promises added effective hitting area, it also indicates the end of the line for positive, energy-laden, multiple-hit potential from that particular pattern.

The first experiments focused on primer substitutions. This should not be construed as a recommendation for indiscriminate primer switching! It was done here to illustrate how patterns can vary as components change, because handloaders frequently practice primer switching without concern for reload performance. Primer switching can cause chamber pressure to rise beyond industry standard and is, therefore, a safely hazard as well as a cause of potential pattern modification. Moreover, it was done with the control reload because its chamber pressure was quite low. Had the published pressure been closer to the industry's suggested maximum average working pressure of 11,000 LUP or 11,500 PSI, such indiscriminate primer switching would not have been tried.

The amassed data from 5 shot tests over 35 yards is compiled in the accompanying chart. Test No. 1 was based solely on primer switching with all reloads holding hard, high-antimony No 8's. Shooting proved that the reload, as published by Hodgdon, was actually the best of the lot; subsystem alternating didn't produce a better performer on an overall basis. It gave an efficiency of 88 percent, on average, and had the heaviest outer ring density. The next best averages, at 82 percent, came from the Remington 209P and CCI 209 standard-force primers, but those two primers had relatively weak outer rings while their core densities were quite heavy. Only the CCI 209 Magnum primer came close to matching the outer ring performance of the Winchester 209 primed test loads, but the CCI 209M also suffered a low-density core.

Subsystems Variation Performance Chart

Test No. 1: primer substitutions with hard lead No 8 shot

Test No. 2: primer and chilled shot substitution

(All values based on average of five patterns per load).

As the chart shows, changes in primers produced a wide range of efficiencies and distributions. The efficiencies ran from 88 percent with the W209s to 78 percent by the Fiocchi 615s, a span of ten percentage points. That may not seem significant to a reader, but remember that ten percentage points in shotgunning is equal to about one degree of choke!

The same basic primer substitution test was then run with low-antimony chilled shot. Prone to deform, chilled shot almost invariably delivers lower percentages than hard shot. The results are again listed in the appended table as Test No 2. When analyzed, the data clearly shows a density loss for each reload. For example, the control loading with Winchester 209's fell from 88 to 80 percent with only a change in pellet hardness. In general, most of the patterns showed more significant losses in core density than they did in outer ring density. This was probably caused by pellet deformation, because out-of-round shot will spin or flare from the main mass as air resistance is encountered, whereas spherical pellets will remain in the core. Thus, the lower number of pellets remaining spherical account for the lighter core densities, while the outer ring continues to pick up errant, mildly deformed members.

An obvious example of this appears when Federal 209As were used with softer chilled shot. This load's outer ring count actually improved as compared to its hard-shot results; however, its core density dropped markedly by an average of 56 pellets as opposed to its performance with hard, high antimony shot.

Handloaders who switch indiscriminately, therefore, are given notice that such substitutions can impact patterns as well as chamber pressures and velocities. Both densities and distributions can, and do, change. Luckily, most patterns still contain enough core pellets to produce a hit when the shooter places his 20-inch diameter core properly, but it's a different matter when the outer ring comes into play. Be wise. Check the patterns scientifically.