Homemade gas checks. The “Freechex” system.

Haven’t loading components gotten expensive? I recall when I began in the early 90’s paying $35.00 for 1/2 kg of powder and the same for 1000 primers. We are rapidly approaching double those prices now. In fairness we are all quick to reminisce about the prices we used to pay but no so quick to remember how much more we earn now. That is to say that whilst prices have gone up I will wager that so have the average handloaders annual earnings. Still, the playing field has changed for me personally and those care free days of the single, unattached man spending his weekends and cash on rabbit shooting are gone and now I have a family to factor into the equation. I surely don’t want me hobby being a burden on the family budget and this in mind I am continually looking for ways to make my shooting dollar go just a bit further.

Gas checks are the mainstay of a lot of cast shooting. For those not familiar with them a gas check is a tiny gliding metal cup that is slipped onto a corresponding shank on the base of a and serves to add a degree of strength and rigidity to the bullet base. In real terms a gas check protects the base of a bullet from heat and pressure and provides a stronger gas seal than is possible with lead alloy alone. Commercial gas checks from Hornady are manufactured in such a manner than when a cast bullet is run through an appropriate sizing die the check crimps onto the bullet in a very positive fashion. The older style gas checks from the Lyman company are strictly ‘slip on’ and do not crimp in place when sized. Both work as they should and are fine, quality products however the last box of 1000 Hornady .30cal gas checks I bought were $55.00 and that was quite some time ago. Since that time the cost of all metals has gone sky high and this is having a roll on effect on all facets of life including our shooting sport. So what is the solution? How about making your own?

Freechex™ for the USA.

I have been experimenting with a pair gas check making devices for .303 and .224 calibres. Charles (Charlie) Darnall from Camarillo, California supplies a gas check kit that he makes and sells exclusively on Ebay. “Freechex™” is his trademarked brand name and a search on www.ebay.com will locate his auctions. The gas check making kits consist of three components; a punch for cutting discs of check material, a forming anvil and a mandrel inserted into the anvil. A very simple and easy to use system built to fine tolerances and capable of producing perfect checks. It all sounds too easy and good to be true but from first hand knowledge I can attest to the effectiveness of this gadget. Here is how is all works.

Each kit is supplied with a hollow punch to cut discs of the chosen gas check material. In the case of .30cal (.303) Charlie reams his kits to suit a 3/8 inch (9.5mm) wad punch. Disc of 3/8 inch form .30cal gas checks of the correct dimensions to fit most, if not all, .30-.31cal moulds. Using the punch supplied and a piece of end grain timber or a slab of lead to cut on, the material is punched out and discs collected. The discs are then inserted into the forming ‘anvil’ where they slide to the bottom of the die and stop at the shoulder where the die tapers to the end diameter of the check. Next the forming mandrel is inserted into the ‘anvil’ and with a couple of gentle taps with a soft face hammer on the mandrel, a gas check is formed and pushed from the bottom of the ‘anvil’. It’s that simple. I have found it is best to use at least two gentle strikes of the hammer. The first blow begins the forming and the second completes. When using one solid strike only lop sided checks are frequently formed which is not desirable as they potentially generate an out of balance bullet with an imbalance of weight.

Recently Charlie has been refining his design and added a nice little innovation. Freechex™ II has a fine cut is made horizontally through the forming die/anvil in such a way that a strip of check material can be inserted. A hollow cutting punch is then put into the die/anvil and tapped with a hammer to cut the material. The freshly cut disc slides to the bottom of the die with the hole punch through which is inserted the forming mandrel and with a couple of taps a gas check is formed. This new system is much faster to use and due to the tighter tolerances of the cutting punch and forming mandrel makes a better quality product also.

Charlie will taylor Freechex™ and Freechex™ II sets to the buyer’s requirements for bullet shank fit (dictated by the forming mandrel) and end gas check outside diameter (anvil exit size). Both anvil and mandrel are expertly hardened however I was able to hone my anvil out from the supplied .311 to .315 with the aid of some 600 grit wet and dry paper and a piece of 7mm brass rod. This process did take some time which is testimony to how hard the components are. The additional honing I performed created a very smooth finish that can be felt when forming the gas checks as the material slides through the anvil with a great deal more ease. Gas check materials.

Traditional gas check material is gilding metal; the same alloy used in bullet jackets and this is certainly the case with Hornady commercial gas checks. Gilding metal is an nominal alloy of copper (Cu) (90-95%) and (Zn) (5-10%) and is technically a form of brass. Lyman gas checks appear to be traditional brass as they have a bright gold colour instead of the copper appearance of their gilding cousins.

Commercial brass and copper are materials very suitable for making home made gas checks however I want to use these as a last resort due to the price of each metal. Available as ‘shim stock’ both materials work as they are expected to however they are not the only materials that will make quality gas checks cost not withstanding.

Aluminium (Al.) has long been touted by backyard gas check makers as a suitable material and most often the source of this metal is quoted as beverage (soda) cans. The major benefits in using Al. are 1) it is soft and easy to cut/work and 2) beverage can material is FREE. All that glitters is not gold however and the one drawback I have found with beverage cans is the mainstream varieties (Coke, beer) have wall thicknesses of only 0.0042 inch or just shy of 0.11mm. This is very thin indeed especially when you consider that Hornady .30cal gas checks are made from 0.017 inch/0.43mm material. Four layers of beverage can Al. is required to make a check of equivalent gauge. Our cousins in the USA have it a little better as their beverage cans appear to be 0.006 inch in the side walls giving them a 50% advantage. That said this scrap metal still has its place and can be of use. Al. in heavier gauges than beverage cans is most suitable though. One good source of heavier gauge Al. plate is lithograph printing plates used wild in the printing industry. I have been able to locate such plate measuring 0.30mm/0.0118 inch and this is very suitable material. Bullet mould gas check shank variations.

Bullet gas check shanks generally taper slightly from bottom to top to aid in the application of the gas check. The taper is as little as 0.004 inch. The major variation to be aware of is the shank dimensions from one manufacturer to another. Lyman .30cal moulds bare shanks of 0.280-0.285 however Jim Alison of Cast Bullet Engineering (CBE) in Australia tailors his mould shanks to best suit the intended use. Jim has a huge range of for the .303 British and due to the wide variations in groove measurements in the good old ‘three oh three’ he cuts some gas check shanks larger than the norm. I find Hornady commercial gas checks must be flared slightly prior to fitting to a CBE shank but by cutting shanks 0.286/0.290 Jim helps ‘bump’ the gas check out in diameter to better fill ‘stout’ barrels. This is a good feature and promotes nice parallel driving bands and straight bullets especially beneficial during the seating process.

Bullet designation Shank base Shank top

CBE 316 175 0.286 0.290

CBE 316 240 0.286 0.290

CBE 313 215 0.284 0.289

CBE 313 220 0.284 0.289

Lyman 311466 0.282 0.285

Lyman 311316 0.280 0.285

Lyman 225415 0.214 0.214

Lyman 225462 0.210 0.213

The exception to the taper design I discovered was my Lyman 225415 flat nose bullet; a proven accurate and effective small game bullet. Its shank is a parallel 0.214 but both Lyman and Hornady .22 checks fit it with ease.

DIY gas checks – trials and tribulations.

I have been testing the materials I have gathered in varying combinations to ascertain the most suitable thickness/gauge and metal for making my own checks. Combinations of materials were used in order to duplicate material of different gauges and for the .303 British these have been:

a) ‘Coke’ can 0.0042, 3 ply 0.0126 b) Lithography alum plate 0.0118, single ply 0.0118 c) Litho alum 0.0118/’Coke’ can 0.0042 , 2 ply 0.0160 ** d) Copper shim 0.0105, single ply 0.0105 e) Copper shim 0.0105/’Coke’ can 0.0042, 2 ply 0.0147 ** f) Copper shim 0.005/Litho 0.0118, 2 ply 0.0163 g) Brass shim 0.0150 0.0150

** very good fit and accuracy.

The above combinations were formed on mandrels with outside diameters of 0.284 and 0.290 and in anvil honed to 0.315 inch. Inside diameter 0.284 checks were deemed a ‘snug’ fit (seated with some pressure) and 0.290 considered loose (barely stays on). Combinations exceeding 0.013 extruded somewhat when formed on a 0.290 mandrel in the 0.315 anvil, took some more forceful forming and tended to spring back 1-2 thousandths of an inch when exiting the anvil.

In the experiments I have conducted the major successes have been with gas checks the material of which completely fills the void between bullet gas check shank and barrel groove diameter. Completely. I prefer to have a fitted gas check that is at least the same diameter as the final bullet sizing or larger. See the following:

Example 1: .303 British – sizing 0.314, forming mandrel 0.284

0.314 - .0284 = 0.030 / 2 = 0.015; material should be at least 0.015 inch.

Example 2: .30-06 Springfield – sizing .309, forming mandrel 0.284

0.309 – 0.284 = 0.025 / 2 = 0.0125, material should be at least 0.0125 inch.

From these equations it is easy to see how the shooters of true .30cal have an easier life when sourcing check material. 3 layers of NZ beverage can side wall is spot on for a .30-06/.308/.30-30 however quite a few ‘thou’ short for the venerable old three-oh-three. Further the guys in the US have the luxury of 0.006 material so get by with only 2 layers. Likewise one layer of litho printing plate will sort your .30cal checks needs. Always locate the heavier gauge plate on the underside when forming so it becomes the outside of the gas check and affords a greater degree of strength.

For my .303 British rifles and .303 Pygmy the premier results were achieved using a 2 ply gas check formed with one outer layer of 0.0118 litho plate one inner layer of beverage can side wall at 0.0042 for a combined thickness of 0.016.

0.016 + 0.016 = 0.032 + 0.284 = 0.316

BINGO! Actually the situation is slightly better than it appears due to the outward taper of the gas check shanks. Once the checks are pressed onto the bullets the diameter is closer to .318 so perfect for my oversize .303 Pygmy with its .317 groove and only a small amount to size down to .314 requirement in .303 British. When using 2 sheets of material in the Freechex II system the heavier lithography plate is inserted into the cut in the anvil and precut discs of beverage can material are manually inserted in the top of the die. The reason for the manual application of the beverage can material is even with the very fine tolerances of Charlie’s machining the 0.0042 inch thick aluminium binds when cut in the anvil whereas the lithography plate, which is 3 times the thickness, shears perfectly. This is a factor of shear and tensile qualities Charlie explained to me over the phone. All very complicated in theory; much like why planes fly.

Critical to the process of forming the checks is working on a FLAT, HARD surface. In order to produce a gas check that has a flat base and crisp, clean edges the forming mandrel must be used on a suitable surface. I used either the anvil on the back of my 6 inch bench vice or a slab of 1 inch thick steel that a fellow shooter gifted me. In my initial experiments I developed a rig using a piece of timber mounted in the vice with a hole drilled through the middle. The forming mandrel sat in a recess over the hole and the formed gas checks dropped into a can underneath. The theory was great (how many times have we heard that!) as was the speed of manufacture but the major flaw was the checks never had the chance to form against a hard surface and consequently were a little irregular in profile. This did me no favours as they exited the muzzles of my rifles. Flyers galore.

You have to want it.

As with any DIY project you have to want to make it work. In the same way that handloading, especially cast bullet shooting, requires varying degrees of experimentation to find the best combination of components to achieve a good result so too does the Freechex™ system. Charlie makes a fantastic little gadget at a price point I consider that does not adequately reflect the work he puts into it however he can only do so much. The DIY gas checker must be prepared to do some of the hard yards to achieve the desired results. Charlie sets up his .30cal kits for forming 0.010 material to suit .30cal bullet moulds. In my tinkering the first thing I did was open the forming mandrel up to .315 from the original .311 to better suit the groove dimensions I would be using the checks in with my .303 British chamberings. He was initially a little scornful of my doctoring of his hard work (the statement “not to be monkeyed with” with used in one email) until he saw the results and logic. Charlie now makes a .30cal system and in addition a .303 Brit kit made to my specifications. Our American cousins are very well versed in shooting .30cal rifles but only discovering the idiosyncrasies of the empire’s old war horse . Of course once I had opened up my mandrel I had to also increase the gauge of the material I was using to match the difference between bullet shanks and barrel grooves. Like any experiments however once the tests have been conducted, results tabulated and conclusions drawn the trial work is complete and production/shooting does look back…………until the shooter changes something.

A final word on aluminium.

Aluminium oxide (corundum) is second only to diamond in hardness. A lot of discussion has been had and continues today about the use of Al. as a gas check material and the risk of lapping out barrels and shortening their life span. When using Al. as a gas check platform use only material that is coated. Beverage cans are coated both inside and out so no oxide forms. The same for the lithography plate I rely on. Be wary of plate you might find at the local hardware store as it is likely going to be carrying so oxide. I remain on the fence on the subject of Al2O3. Ask me again in 5000 rounds time.

So there you are. Need another hobby, more peripheral clutter and just one more project to go on with? Look up Freechex™.