Shot Talk

Shooting Sportsman readers call, write and e-mail me a lot. I like that. I enjoy helping whenever I can with technical shotgun and ammunition questions.

To this end, following is an assortment of the hundreds of technical queries I have received during the past several months. I believe the questions and answers are of interest to many readers, as they are the ones that pop up the most.

Square Loads

I’ve read your Buffered Lead and Bismuth Shotshell Reloading Manual and Shotgun Barrel Alteration Manual. They were extremely helpful and interesting.

Somewhere I heard or read the idea that a shot load should not be any higher than the diameter of the bore in order to be most efficient. A fellow trap shooter calls it a “square load.” Does this ring a bell with you? Bob Brister, in Shotgunning: The Art and the Science, came close to the idea on pages 116 and 291.

As it relates to your thought that most reloading manuals are generalized and none of the listed loads are tested, have you come up with a good 12-gauge non-buffered load for the various clay target games?

The idea of a “square” shot-charge load is a very old one. It has relevance only for soft shot types such as lead, the idea being that the squarish configuration minimizes pellet deformation by minimizing the percentage of pellets in the outside of the shot charge that might suffer bore-scrub deformation. Additionally, a square shot charge provides lots of room for cushioning of the shot from a long wad column.

Actually, a shot charge even shorter than a square one relative to the bore diameter would deform even less shot, as an even smaller percentage of such a load’s pellets would be in contact with the bore and there would be even more room for wad-column cushioning.

The square-charge concept was much more valid before the development of plastic shot protection devices and the recent arrival of hard shot types such as steel, HEVI-Shot and so on. In fact, it has no value whatsoever for the hard shot types, as they simply will not deform from the same forces inside the barrel and shotshell that deform lead and other soft pellet types.

There are myriad non-buffered lead loads suitable for the various clay target games, so, no, I don’t have a pet one. In my opinion such a load with lead shot would not exceed 1,250 fps (with 1,200 fps being better), except for extreme-range targets where the distance exceeds 40 yards. At these distances an instrumental velocity of 1,300 fps helps many shooters with their perceived leads. Such a load should contain the hardest- and roundest-possible lead shot in size No. 7-1/2. It does not need to exceed 1-1/8 oz in weight. For most shots in most American clay target games, nothing more than 1 oz (and some would say 7/8 oz) of lead shot is needed.

Proof Testing

I recently purchased an 1898 Damascus-barreled Dickson 12-gauge from Holt’s auction house and British agent Diggory Hadoke of Vintage Guns. The gun has barrel walls of no less than 0.025" at any point.

As is required by British law, the gun is “in proof,” and both Holt’s and Vintage Guns say this means the gun is perfectly safe for use with low-pressure loads of appropriate length (2-1/2"). They have suggested the low-pressure 7/8- or 1-oz Pure Gold loads sold by Gamebore. I notice that Polywad also sells a Vintager 7/8-oz load with 21/4 drams of powder (much lower than I use in my modern 20-gauge).

In your opinion, does all this make sense? I followed with great interest the various “to failure” tests of Damascus barrels that appeared some years ago in The Double Gun Journal but don’t want to be foolish.

Congratulations on acquiring your Damascus-barreled Dickson. Now you need to find out from the proof house in England what the maximum working chamber pressure is that is safe to shoot in the gun. (Contact Proof Master, Birmingham Gun Barrel Proof House, Banbury St., Birmingham, B5 5RH, England; www.gunproof.com). You need the exact maximum allowable chamber pressure in psi. Once you have that figure, you can make intelligent and safe choices of modern 12-gauge loads to fire in the gun.

I would recommend you not exceed the 2-1/2" length of cartridges for which the gun is chambered. If your sources have stated that your gun can shoot low-pressure 7/8- or 1-oz 2-1/2" Gamebore loads and you trust these sources, then that is what you should shoot. I also would find out what your sources’ definition is of “low pressure.” Low pressure can mean different things to different people in the shotgunning world.

That said, before moving to the low-pressure loads available from Polywad, RST and other companies, I would contact the ammunition manufacturers to determine that the pressures developed by their loads do not exceed the pressures of the Gamebore loads and/or the maximum pressure level determined by the proof house.

(Editor’s Note: For more information on proof, see Guncraft, p. 106.)

Dram Equivalent/Recoil

I was intrigued by your article in May/June 2008 on calculating actual recoil. My question: Is there a template for conversion of dram equivalent to velocity? Some ammo makers list just the dram equivalent and not the velocity on the box. I shoot sporting clays for fun. I have been shooting 1-oz 2-3/4-dram-equivalent loads in a 7-3/4-pound gun, and these loads feel comfortable for 100 rounds. Are grains of powder and wad columns always 18.0 and 33.0 respectively? I just want to run the numbers on how much recoil is in different loads.

There is no formula for converting dram equivalent to velocity in US ammunition. Dram equivalent is an antiquated, arbitrary, nonsense system of indicating velocity. There is a list, however, in the SAAMI Voluntary Standards that shows dram equivalent versus velocity versus gauge and load weight for many but not all lead loads. In the case of the 1-oz 23/4-dram load you mention—and assuming it is a 2-3/4" 12-gauge lead load—the instrumental velocity of the load would be 1,180 fps.

According to my recoil calculations, in your 7-3/4-pound gun this load should generate less than 20 foot-pounds of free recoil.

If you want to use the recoil formula given in my May/June column with the exact weight of the powder charge and wad column in any given load, you’ll need to cut apart three shells of that load and weigh and average the powder charges and wad columns. For this you will need a reloading scale that measures in grains. Powder-charge weight and wad column weight vary by load.

Pattern Fall-Off

I have been patterning steel-shot loads and can’t get any of the high-velocity stuff to pattern worth a damn.

Yesterday I checked a couple of loads in my son’s 20-gauge. One was Federal No. 4 steel (7/8 oz) at 1,300 fps. It produced a beautiful 80-percent pattern at 40 yards out of a Modified choke. I then tried a Winchester Drylok No. 4 steel load (3/4 oz) at 1,425 fps. Ugh! It produced a 46-percent pattern at 40 yards out of the same Modified choke.

In the limited patterning I’ve done, once I’ve hit velocities of about 1,350 fps, no matter what the guns, loads or shot types, patterns have deteriorated and often the points of impact have changed. There also has been an increase in recoil (to elephant-gun levels in 12 gauge). There just seems to be something about crossing that 1,350-fps threshold.

Anyway, I’d like your take on this. It’s getting tough to find factory steel loads with modest velocities. Am I missing something—or perhaps I’m set up wrong? Or is the high-velocity craze crazy?

I never have recorded as big a pattern drop-off as you did from your Federal No. 4 steel load at 1,300 fps to your Winchester No. 4 load at 1,425 fps. But, yes, in the many tens of thousands of patterns I have fired, the general trend I have measured through most chokes with most loads regardless of shot type is that as velocity levels increase, pattern densities decrease. With soft shot types like lead, bismuth and the various tungsten/plastic composite pellets, this is understandable because ever-higher launch velocities result in more pellet deformation. But with the essentially non-deformable hard shot types like steel or HEVI-Shot, the trend makes less sense because the pellets cannot be substantially deformed inside the barrel.

Additionally, as velocities of any given load increase, recoil levels certainly increase—often to very uncomfortable levels for many shooters.

In my testing I have found that the best range of velocities in terms of pattern performance and lethality while still maintaining comfortable recoil levels is about 1,100 to 1,250 fps for lead, bismuth and the various high-density tungsten composite pellets; and about 1,275 to 1,400 fps for steel.

To correspond with Tom Roster or to order his third-edition reloading manual on buffered lead and bismuth shotshells, his new HEVI-Shot reloading manual, his 75-page manual on shotgun-barrel modifications or his instructional shooting videos, contact Tom Roster, 1190 Lynnewood Blvd., Klamath Falls, OR 97601; 541-884-2974; tomroster@charter.net.