Approach to Practical Wildcatting.
By Fred The Re-Loader.
1. 243 Win, 2. 7.62UKM, 3. 280AI, 4. 7mm08, 5. 7mmSSAI, 6. 243AI, 7. 6x47FM
In response to some of the many questions ask; I like to tell you about my experiences regarding the conversion from a standard cartridge case to an improved version and the development of save wild cat loads with basic tools and equipment readily available to the hand loader.
At the outset I like to dispel the notion that wild cats only gain higher velocities with high-pressure loads meaning above accepted standards. The wild cat or improved cartridge gains higher velocities by having greater case capacities and consequent lesser expansion ratios. However little or greater that may be is not the issue here. With the same pressure as the standard or unmodified case the wild cat will reach higher velocities. A reckless or unknowledgeable hand loaders can as easily produce unsafe high-pressure loads in a standard loading as well as a wild cat. More case volume produces more velocity in general. With exceedingly large cases, small bores and some types of powders, this is not always the case.
Also I will not cover the actual brass conversions, conversion may entail the necking up or down to different calibers. Or one type of brass case completely revamped to another. Nothing that I am writing here is new, and very few if any conversions are the best there ever were, most of them have been done before in one way or another, but some of them are totally new and exotic.
The most beneficial reasons of improving a standard cartridge is the ease of handloading the much better designed case. Effecting more efficient burning of powder charges, which can result in higher velocities and longer lasting brass. Most improved cartridges don't always produce velocities as high as being claimed. Some of them improve considerable compared to the standard case.
The 243 Ackley Improved is one of them and all the others based on the 308. The 250-3000, 22-250, 257 Roberts, 6mm Rem and many others. These small cases are excellent candidates for wildcatting and a pleasure to shoot and reload. Why some of them do improve more than others is not too well understood. Combustion energy is a very complex science. More powder will push bullets faster but not always more accurately.
In the improved case powder combustion is enhanced because of the shape of the powder chamber and more powder is burned inside the case due to the steep shoulder and minimal case wall taper. The improved shoulder I believe acts as a deflector, and gases first collide inside the neck at the point of convergence before being allowed traveling down the barrel. Perhaps this increased shoulder impediment is what I believe gives us more gas mileage from the same amount of powder?
A look at the 30-06 will tell you, too reach 3000 ft/sec with a 150 gr bullet will use 15% more powder then the same bullet in a 308. This is not a fair comparison because the 308's operate at a higher chamber pressure. Just the same you can do nearly as much with less. When you put a 40 degree shoulder on the 308 and straighten the case wall, you are right there with the 06 using comparable pressure with nearly the same velocity with considerable less powder, and of course using a short action for a handier rifle. Less powder also means less recoil. Wildcatting or improving in general has similar parameters, when using a sharp shoulder and minimum body taper.
The 30-06 type family, like the 280 Rem AI, 270 Win AI, 6.5-06 AI, and the 25-06 Ackley improved and the Gibbs designs are hand loading favorites. The 280 Rem case is the largest of them with generous long neck. It will provide the largest powder volume, especially if the shoulder is moved forward. A 0.300" long neck is long enough for any 300 caliber and under. Two other favorites are the 338 AI and the 35 Whealen AI either can be made from the 280 Rem case or the 06 case. The 280 case with its longer neck and a little more capacity would be better for these two calibers. Also the necks need annealing before necking up that much.
And then there are the magnum wild cats with endless possibilities, almost impossible to cover them. These big and smaller numbers produce power and velocities with modern powders that were unheard of when the magnum cases came into being. Wild cats of the big magnum sort are specialty guns, and as such have limited appeal to the general shooting public, except the long range target shooters. Besides these big powder burners need a seasoned rifleman and enough weight to tame recoil some? Also the many standard magnum cartridges have nearly eliminated the need for wild cats in that category.
Most of the Ackley Imp are designed to shoot the parent factory cartridge, for fire forming cases. I never use bullets to fire form cases; as a matter of fact non-of my wild cats can fire a factory loads. I simply don't see any reason to accommodate a factory load. The idea of replacing your custom loads"you lost" with factory stuff is laughable. And god knows where the factory loads will shoot if you did manage to find some in the woods.
A good smith that understands what it is all about should build your wild cat. It is after all a custom gun in all respects. Forget about the factory ammo and concentrate on neck length, twist, neck diameter, overall chamber length and performance. Fire forming without bullets is simple and saves the barrel for real shooting. Fire forming without bullets should always be done with a lubricated case, to allow the case to slide back against the bolt face. When the primer goes off it will drive the case forward a bit before the pressure increases. An unlubricated case sticks to the chamber wall and may produce undesirable headspace?
Chamber length is important since fire forming will shorten your case-necks from 10 to 18 thousands depending on case and caliber. By fire forming with cream of wheat the chamber neck can be made shorter by the amount the neck will shorten. Further more the shoulder can be moved forward if wanted. Cases are not trimmed before fire forming. They are forced into the throat by the amount the cases shorten. They are then trimmed for 0.005" chamber clearance. The slight crimp created by forcing the case into the throat is straightened with a tapered expander. Since I have never made cases by necking up, I can't say what happen to the neck length?
Note: Some bench rest shooters using the PPC cartridge and others fire form in three stages for extended brass life and uniformity. My fire forming method with cream of wheat could be used for this special process, I think?
A custom wild cat chamber is one that allows almost no brass stretching. A fitted steep shouldered case prevents the brass from flowing into the neck. Case life is long if the elastic limit of the brass is not exceeded. What that means is, don't try to get every last foot of velocity. It also means that the maximum safe pressure ring expansion on the case must be carefully established.
Wild cats work best with good dimensional consistent cases that are made with quality tempered brass. With the amount of work that goes into these cases it only makes sense to buy the best. It is no coincident that some are more costly than others are. Using second hand cases for wild cats could cause trouble I never use them. They are out of shape before you use them.
When a cartridge is fired the chamber expands and should not exceed the safe pressure limit of 60000 psi. The brass follows that expansion. The spring back of the brass due to its greater elasticity is more than the steel barrel. When the barrel is stressed above the brass spring back limit, the relaxing barrel compresses the brass. You then have a sticky case, a stuck case or worse, a damaged rifle. Cases should always come out of the chamber easy.
The wild catter must make himself familiar with the reading of pressure ring indications. Also I must point out that these expansion readings can be misleading in some tough extra strong brass, like the Winchester 300 H&H and 375 H&H brass. Other pressure signs such as sticky bolts, gas leaks around primers, flattened and gratered primers, loose primers, and hard to extract cases must be looked at with concern. This is where the chronograph comes in to warn you of high-pressure velocity spikes.
The Varmint Hunter Magazine July 99 issue #31 has a very interesting article by Don Miler for pressure estimation using the chronograph and formulas for the Powley method. This is a very fine article. Some times this winter I will put together an Excel spreadsheet to simplify this procedure. Actually the calculation can be done with a hand calculator. The Wild- catter should also be familiar with the use of the Powley computer for establishing starting loads; the Powley computer is available on the web.
For obvious safety reasons very little official wild cat data with modern powders is available and I don't think that will ever change. The hand loader must be capable of producing safe hand loads without loading data. In this respect the hand loader should possess the necessary knowledge to do so. Any published load for any wild cat cartridge should always be approached with caution. Your own cartridge water volume behind the bullet should guide you with the loading density this published load produces in your cartridge case. Do not assume any thing what so ever. You don't know the chamber size where this cartridge was being fired in.
Another good guideline for a starting load density is 85% with an appropriate powder. And never build any reduced loads with slow burning powder. The best loads are with powders that nearly fill the case. (LD= PC/WV.) LD = loading density, PC= Powder charge in grains, WV= Water volume behind the bullet in grains.
It is save to say here that any listed standard load in loading manuals for the parent standard cartridge is a save starting load for the improved cartridge. Such as a max load of a 243 Winchester will be a good starting load for the 243 Win Ackley Improved. A 6mm-06AI and the 6mm-284 can use starting loads designed for the 240 Wheatherby. The key here is to find the water case-volume in grains, to the underside of a seated bullet and compare them. If the wild cat is smaller than the parent is, reduce starting charges it by the percentage point less 15%.
When developing a load I make three or four sets of 3 cases, each set is charged with powder in one-grain intervals. Each set of three is chronographed and recorded. Pressure ring measurements are also recorded. Each set is marked with indelible ink such as 1-1, 1-2, 1-3, 4-1, 4-2, 4-3, etc. All cases are measured prior to firing and again after firing. An index line is put on the case at the pressure ring and measuring is always done with the index line centered between the micrometer anvils. That way you measure at the same spot every time. The Idea is to establish a bench mark pressure reading.
Index lines and numbers are refreshed with repeated loading if needed. After multiple reloads you can measure and find out what is happening to the case, and allows you to pin point a loose primers and its cause. What this means is"Back off with the powder".
With the increase of powder in 1/2 or one-grain increments, you will see increases in velocity and measurements. With most new brass you need to take up the initial slack found in most cases. If you don't know your chamber size at the pressure ring, drive in a lead ball in your chamber with a wood dowel. Gently tab it back out and get a measurement. This will tell you how much initial clearance you have. I have seen cases as much as 0.006 undersize at the base.
However at gradual powder increases you will see when measurements will gradual increase by .0001" or .0002". Your increases in velocity will also be in fairly gradual steps. Perhaps 40 to 50 ft per grain of powder. Now the next grain of powder will show a 75 or 80 ft or more increase, and the measurement has increased by 0.0005" or more. This means you are in the high-pressure zone. Reduce the load by 1.0 gr or 1.5 gr (grains) of powder and compare the pressure ring dimension with the velocity. This measurement is your bench mark or near maximum load. This is not a very exacting way to get pressure values. Nevertheless, for lack of laboratory testing equipment it is the only save way for the home wildcatter.
Even with a piezometer type gage like the Oehler strain gage, the home wildcatter would have to calibrate the gage. This would require a similar exercise of working up a load until cases start to stick and the bolt is hard to open. This happens in the 70000-psi range and then back off 15% to 60000 psi. It is still a guessing game but a calculated one. Once you know what that reading is on the gage, you got it made.
One other key indicator is a loose primer. When I develop a load I always have a Lee hand press along. At the range I deprime an empty case after firing, and install a new primer with a Lee Priming tool. A primer that shows any looseness is aback off signal. Your records will tell you where that point is. Again this not cast in stone either because cases with below standard base dimensions will do that even with lower pressures. This can be detected with a velocity correlation. Don't use undersize brass! There are always some variations because of different alloy make up, used in brass case production.
Always record your brass weight. When you prepare a new batch of cases it is helpful to know the difference of weight. Brass is 8.6 times heavier than water. This allows you to adjust loading densities and charges without actual filling the case with water again. You should also know the bulk densities of the different powders you use. Bulk density is the amount of powder that occupies the volume as the water. Like a certain case will hold 100 gr of water to the top of the case mouth and say 94.0gr of a certain powder. Bulk density would be 0.94. A higher bulk density powder may provide better ballistics.
The reading of books on the subject and the use of conventional data to compare the standard loads with improved loads are definite priorities. A chronograph and good measuring tools are a"must have" when loading data is produced. For wild cats the production of the most accurate ammo possible is a forgone conclusion. Mass production of ammo does not bring out the best performance in wild cats.
If all this sounds involved, laborious and time consuming, it definitely is. On the other hand there are no shortcuts to safety. This is not a game of chance but a careful intelligent and investigative hobby. Only you can decide if wildcatting is worth your efforts. Wildcatting is at its best when an outlandish concocted wild cat cartridge wins consistently in major bench rest competition. Or perforates the "egg" at 500 yards. But I am quite happy using hunting wild cat rifles and hit a gopher now and then at 400 yards with a rifle of moderate weight."Play it safe and wear safety glasses!"
I like to hear from you and welcome your critique. Please direct your comments or questions to:
Fred the Re-Loader