Many years ago I had a .22RF Martini action rifle converted to centrefire and rebarreled to .32-20 (click here for the article). In short, the reason for the build was to create a small game rifle shooting subsonic ammo through a suppressor that would still have generous knock down power on the very large European hares we have in NZ. My load was a Lyman 311008 plain base, flat nose bullet of a nominal 115gr over 4.3gr of Unique for 1030fps producing 271 ft/lb of muzzle energy or twice that of a 37gr HVHP .22RF round. Twice as much may sound impressive but 271 ft/lb is pretty tame when you consider a .22WMRF produces 324 ft/lb and a 7.62X39 1527 ft/lb. Energy however is not always a true indication of how well a hunting load will perform. Projectile nose profile, expansion or lack of said and momentum (velocity x mass) also play a significant role and those who shoot round balls from muzzleloading firearms will confirm this. A large, blunt, lumbering projectile will drop an animal as convincingly as a super light screamer.

A good, practical demonstration of this comes from an experiment I conducted a few years back. Sourcing some discarded 25lb blocks of bakery margarine/shortening as a test medium I decided to compare the ‘wound’ channels created by .22RF hunting ammo and my .32-20 subsonic small game load. The blocks were placed end on at 50 yards one round of each load was shot length ways into the shortening. A thin mixture of plaster was then poured into each cavity and allowed to set prior to the blocks being cut open to reveal the end result. these are as follows. The top cast is the .32-20 and it should be noted the very end of the plaster broke off so the cast does not reflect the full 15 inches of penetration.

I like to brew up batches of lead alloy for my bullet casting sufficiently large that I can rely on a decent degree of consistency in my projectiles over a reasonable run of casting. Ideally a batch would be 100-200lb at the time but like with so many other aspects of the hobby I am limited by the equipment available. My basic smelting/batching set up is a former domestic cooking vessel able to hold a maximum of about 60lb of lead with a source of heat being supplied by an ancient kerosene camp stove formally owned by the late Robert Ernest Brown; my father.

Dad’s old kerosene (paraffin) stove is a Veritas Mk 1 and proudly stamped “Made in England” as was everything worthwhile in Dad’s day (though he did concede that some decent stuff came out of the US also). I guess he would have bought it in the late 40’s or early 50’s as that appears the correct period for the brand and style and he told me about various bicycle tours he and his friends ventured forth on in his years of early manhood. Such a stove would have been the primary source of cooking heat. Father was and great proponent of kerosene for heating our old rustic holiday home, providing lighting in said abode and obviously for cooking out of doors. To this day I can still smell the burning petroleum distillate as it flamed up at the top of the wicks of dad’s menagerie of appliances. I have to remind my self that this was a time before propane canisters.

Back to the Veritas Mk 1; this weekend just gone I was smelting up a batch of 40-1 alloy that was to be cleaned and poured into ingots in order to later cast some projectiles for my .32-20, .310 Cadet and .30-30 WCF. The old stove was not co-operating and suitable heat was intermittent; a particularly poor outcome for alloying lead. The stove is a pressure feed model and relies on an initial warm up of the head unit by burning alcohol in a catchment immediately below the fuel feeding tubes. Once the cooking head is hot the fuel reservoir is then pressurised by pumping a horizontal plunger at which time the fuel is forced through a tiny orifice or ‘jet’, mists/vapourizes then ignites with a bright, blue and exceedingly hot flame. Here in lay my problem. The business end of the plunger has a cup shaped leather piston and over time these leather devices wear out. I can’t be sure but I suspect this was the original. Without a good seal it was impossible to pressurise the fuel chamber.

Excerpt from Fouling Shot 267


By Larry Gibson

In the past I have posted this explanation of why I drill out flash holes for use with low end reduced loads:

"I shoot many thousands of squib loads in various calibers but mostly in .30s. Many of these are rimless cartridges; 30-06, .308, .308 CBC, 7.65, 7.62x39 etc. The squib loads I shoot most often is a Lee 314-90-SWC-TL over 2. 7 to 3. 2 grains of Bullseye depending on the cartridge. Velocity is around 800 - 875 fps. I found a long time ago the shoulders do in fact get set back with light loads such as those. With many cast loads that use normal weight bullets in the 1600 to 2000 fps range there was little setback. It basically is a matter of the psi the load generates. It takes roughly 7,000 psi (depends on thickness and hardness of the brass along with how much the case needs to reach the chamber walls.)

Measurements of shoulder set back or increase are easily taken with a Stoney Point tool. There have been basically the two theories regarding the cause; the firing pin blow theory and the primer theory. I ran the same tests with a fire formed case and inert primers; headspace was not changed. I then used the same fire formed case with live primers. In as little as two firings there was a measurable decrease in headspace. After five live primers the fired primer was noticeably backed out after firing. NOTE: this increase in headspace was with case taking LR primers. I never experience the problem with the . 222 Rem or the 5.56 NATO.

Using number size drills I gradually increased the flash hole diameter with a progressively larger drill. Using a different fire formed case with each larger drill and firing 5 primers I then measured the headspace before firing and after. As the size of the flash hole increased the head space decrease lessoned. With a # 29 drill I no longer got any decrease in head space. I dedicated five . 308 cases and five 30-06 cases that were well fire formed to their respective rifles chambers and drilled the flash holes with the #29 drill. Over the next few days I fired 50 shots with each case. There was an indoor 50" range where I was stationed so it wasn't all that bad. After the 50 firings there was negligible change in headspace with any of the five cases of each cartridge. The results of my test firmly demonstrated to me that it was the force of the primer explosion that drove the case forward and set back the shoulder. The squib load does not have the pressure to expand the case out to fit the chamber. By drilling out the flash hole the force of the explosion mostly went directly into the case as there is little rim left to contain it. Two other side benefits that were unforeseen; the extreme spread and standard deviations of the velocity readings improved and the case position sensitivity of the small charge was greatly reduced.

As a result of the above tests I dedicated fire formed cases for squib loads for each rifle in rimless cases and drill out the flash holes. I have fired them many, many times now with no further change in headspace. Besides the squib load mentioned I also use 313631 (the 118 grains GC 32-20 bullet) with Unique in the above cartridges loaded to 1400 fps or so for a little more powerful small game load. The flash hole drilled cases work just fine for those. I now use the flash hole drilled cases for all my rimless cartridges with squib and really light loads.

Further pressure testing in the .308W the last few years indicated that loads with a psi above 12,000 will obdurate sufficiently to prevent the primer from driving the case forward thus setting the shoulder back."

Since then seems like every time the subject comes up we get admonitions not to do so because it is very "dangerous" should the cases with such drilled out flash holes be used for a "regular" load. Having previously tested such cases with "regular cast bullets loads creating 28- 30,000 psi (measured via an Oehler M43 PBL) I have endeavored to ascertain the danger of loading such to the psi of "regular" loads at 55,000 +/- psi.

I had enough cases LC 92 7.62 NATO (308W) cases I was going drill out the flash holes to run a series of 10 tests using five 9 shot tests and five 8 shot tests. I would run a test with the flash holes as they were (.061") and then increase them in size incrementally to .140". That is the maximum size to enlarge the flash hole while still retaining enough of a shelf for the primer anvil legs to rest on. I used numbered (#) drills alternately from #44 up through #28 to enlarge the flash holes.