A Safe Maximum?By Matthew Camerom
- 21st Jan, 2020 Jan 21, 2020, 11:55 AM
- 3 Comments
If the rules are followed, processing components into useful ammunition is not all that difficult. In columns like this, and in the reloading manuals, writers always exhort reloaders to be safe and sensible in how the processes are carried out.
Without fail the reloader is told NOT to exceed maximum loads. This is sensible advice because without pressure measuring equipment it is impossible to know exactly what pressures are being generated inside the cartridge case. It’s an inexact science and without reliable pressure testing equipment by the time signs of high pressure appear you may already be in dangerous territory.
Logic suggests that when pressures start to rise there should be multiple warning signs, but I believe you should stop immediately the first sign occurs. Modern manuals are full of good data, however this is revised regularly based on what is popular and what is not.
Older data is often dropped when it is regarded as out of date. This problem arises when reloaders are confronted with either an older cartridge that has faded into obscurity or a more modern wildcat. In either situation there’s a lack of credible loading data. In addition, for the older cartridges the data may have been developed with powders that are no longer available.
“For older or wildcat cartridges what you need is a safe starting load with a modern powder.”
Where do you start? What’s on the internet is uncontrolled and should be looked at with a jaundiced eye, but the fact remains that the amount of information available is staggering. The same applies to old shooting publications, including reloading manuals - they contain a wealth of information and can be a good starting point when you’re dealing with the unknown. For older or wildcat cartridges what you need is a safe starting load with a modern powder.
Research is everything and you cannot amass too much information. Almost certainly someone, somewhere has loaded a particular cartridge at some point. A common complaint by new reloaders is that different loading manuals specify different maximum loads for a particular powder.
This creates confusion until you consider why this is so. It is highly unlikely that any two manuals would use exactly the same components to test ammunition. Unless the ammunition is tested in exactly the same way variations will occur - barrels might be of a different make and so might the projectiles.
Projectiles of a given weight may look the same, but when we get accurate measuring tools out suddenly things are different. The bearing distance (the surface that actually touches the bore) will almost certainly differ between brands of projectiles. It might not sound much but there are also very small differences in projectile diameters, not all are exactly the correct size.
These factors contribute to exactly how much pressure is generated by “X” grains of “ABC” powder, and don’t forget that pressure is transferred into velocity.
How does the new reloader overcome these differences? My answer is that for any particular powder/cartridge combination you should average out the maximum loads given in the manuals.
This new averaged maximum MUST NOT BE EXCEEDED. Note that the powder may not be exactly the same but equivalents can be used. The following example covers the .270 Winchester cartridge and 130gr projectiles.
|ADI Manual 130gr Hornady SP||AR 2209||54.3gr|
|Nosler Manual 130gr projectiles||AR2209 = H414||54.5gr|
|Hornady Manual 130gr projectiles||AR2209 = H4350||55.3gr|
|AR2209 = IMR 4350||54.6gr|
|AR 2209 = W760||54.4gr|
|AR2209 = AA4310||54.0gr|
|Speer Manual 130gr projectiles||AR2209 = H414||54.0gr|
|AR2209 = IMR 4350||56.0gr|
|AR2209 = W760||54.0gr|
The average of these nine loads is 54.56gr (call it 54.6gr). This is the new maximum; DO NOT EXCEED THIS FIGURE! As a matter of interest I developed this load more than thirty years ago and in the intervening period the rifle has safely fired several thousand rounds using 54.0gr of AR2209 and several different types of 130gr projectiles.
This particular load was the most accurate; note also that there is not a huge variation in the powder range, from a low of 54gr to a maximum of 56gr. The above averaging technique is very straight forward and has worked in many other calibres over time. However, I ask again, how do you arrive at a safe maximum when loading information is skimpy or non-existent?
We faced some of these problems when we decided that the time had arrived for a new long range varmint rifle built to benchrest standards. Several months of research followed and the decision was made to chamber the rifle in .22-243 (Imp) firing a 65gr JLK low drag flat-based projectile using AR2209 powder.
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The logic was simple enough; powder and cases were freely available as were the projectiles from the USA. Letters of enquiry were sent out to a number of gunsmiths to see who was willing to build the rifle. Only one bothered to reply and he got the job, the only problem was that he did not have a .22-243 reamer!
THE .22-284 ARRIVES
Back to the drawing board, the ‘smith made several suggestions, one of which was the .22-284 (Imp) which we eventually went with. The rifle was designed to use JLK 80gr low drag projectiles in a barrel with a 1:8 twist. This took much more research.
Cases were prepared to benchrest standard and included turned necks. While there was some information about the cartridge available from the USA most of the powders used were unavailable to us. Ackley’s Handbook for Shooters & Reloaders was not of help, the projectiles mentioned did not exceed 63gr in weight.
Eventually I used the Load from a Disc program. The internal ballistics section suggested that IMR 7828 would be suitable for the 80gr projectile. It also suggested that the maximum load might be in the vicinity of 51.7gr with a possible velocity of 3210fps. This was well below the velocity being attained in the USA. Investigating further, it appeared that AR2214 might be suitable so we worked up at one grain intervals starting out at 49gr.
“Cases were prepared to benchrest standard and included turned necks. While there was some information about the cartridge available from the USA most of the powders used were unavailable to us.”
Shot number 16 using 58.0gr of powder produced hard case extraction, and load development ceased at that point. We decided that 57.5gr would be the maximum load. Interestingly enough the computer predicted 56.3gr as a maximum. Note that this load was developed in the summer months.
Eventually 57gr of AR 2214 ignited by CCI BR2 Benchrest primers produced a consistent load with accuracy averaging ½ inch for three shots at 100yds, and an average velocity of 3470fps. According to ADI the burn rate of AR2214 was about 10% below AR2213 and a few percent below IMR 7828. There are several lists on the internet relating to the relative burn rates of various powders.
Two of the lists indicate that AR2214 is very close to RE-25. A great deal of time was expended to ensure that we used the best powder available but eventually our stock of AR2214 was used up and the powder became obsolete - it was replaced by AR2217 and/or AR2225. Interestingly enough both powders produced the best accuracy at 55gr each and were within 10fps of one another.
For a cartridge that is supposed to be over bore perhaps it is actually more flexible than first thought, certainly it has performed flawlessly. Several years after the .22-284 (Imp) took up residence in the family gun safe the original gunsmith contacted me and advised that he now had a .22-243 (Imp) reamer, was I interested? Of course as the rifle was designed to switch barrels; the only addition was a set of straight line dies.
NOW FOR THE .22-243
This cartridge was designed with a 40 degree shoulder, the brainchild of Paul Middlestead, a California gunsmith in 1964. In practical terms it is simply the .243 Winchester case necked down to accept a .224 calibre projectile. This may well be the perfect case capacity for .224” projectiles.
The original rifle propelled a 76gr projectile at 3400fps. With its case capacity some 4/5 gr above the .220 Swift, the cartridge prefers somewhat slower powders. In some ways it is similar to the .22 Cheetah and the .220 Jaybird; thankfully we had kept the original research. Using the 65gr JLK low drag flat-based projectile with CCI BR2 primers and AR 2209 we worked up from a starting load of 36.5gr.
Eventually it became apparent that the most accurate load was 41.5gr of AR2209, which produced approx. 3550fps. This is now our standard load, which is very accurate and consistently produces ½ inch three-shot groups at 100yds. Although 42gr did not indicate any pressure problems the groups had started to open up. I am still not sure what the maximum load might be.
There was quite a bit of starting information available in terms of powder types and possible loads and from researching the various books and manuals it appears that our particular version of the .22-243 (Imp) may in fact be a .224 Durham Jet with a long neck.
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THE .243 ACKLEY
Recently we acquired a new .243 Ackley barrel. With a twist rate of 1:7 it was intended for the heavier 105gr and possibly 115gr projectiles for long range work. Previous work by others suggests that the starting load for the expanded Ackley case is the maximum load in the parent case. With the diameter of the case body increased and the shoulder blown out to a steeper angle the available powder increase is perhaps five grains.
ADI recommends a maximum of 37.5gr for 105gr projectiles and AR2209 for the parent .243 Winchester case. In the Ackley barrel the most accurate load was 41.5gr using a 103gr projectile with a different nose profile. At 42gr the accuracy was a neat inch but the bolt lift was tight, definitely a maximum. The most accurate load turned out to be exactly the same as the .22-243 (Imp) - co-incidence?
For the same 105gr projectile AR2217 had a starting load of 46.0gr according to ADI. We managed to get up to 49.0gr into the Ackley case via a drop tube but the accuracy was indifferent. The best accuracy was achieved at 47.0gr, with velocity just over 3000fps.
Once again, even though the capacity might be there, from an accuracy point of view it may not be useful. With the Ackley barrel there were no excess pressure marks on the head of the cartridge, merely the hard bolt lift. We thought a change of powder might be interesting. The Alliant RE-26 website showed a maximum load for 105gr projectiles in the .243 Winchester as 46.7gr which produced some 3056fps with the 103gr projectile.
The manual velocity was 3078fps with 47.7gr, but this produced a hard bolt lift and a progressive flattening of the primers. Thus even though 46.7gr was a starting load it was also the maximum. Reducing the load to 46.0gr produced 3096fps and much better accuracy. This just goes to prove you must always be on the alert when dealing with pressure. Overall the load averaged sub 0.50 MOA groups and 3080fps.
There is no information in the ADI manual for 115gr .243” projectiles but Berger had data that suggested 44.5gr of AR 2255 for a starting load in the Ackley case. Berger has an extensive range of projectiles for the .243 Win parent case. None of my other reloading manuals had any data above 107gr projectile weights.
The only other data was on the internet for 115gr DTAC projectiles. The short story is that 45gr of AR2225 was all we could cram into the case with a drop tube, which produced an average of 2815fps and three groups that averaged 0.62 inches, good enough for me!
“...just what should you do to be safe when you don’t know what the maximum load is? The key is extensive research.”
Back to the question - just what should you do to be safe when you don’t know what the maximum load is? The key is extensive research. There is of course a comparison of powder rates in the latest ADI reloading manual. As mentioned, there are other lists of powders on the internet which may only be a guide but they are better than nothing.
Quite often they include those no longer in production, the addresses are: t2ammo.com, and under technic-powder burning rates: stevespages.com/powderrates. Several older books about wildcats are an invaluable addition to the reloader’s library if you are interested.
Wolfe Publishing Co has printed some interesting volumes over the years; they also publish Handloader and Rifle magazines which have covered many different cartridges. Now out of print is Precision Shooting magazine that also covered a lot of “odd” cartridges.
Keep in mind that all information needs to be treated with a degree of suspicion unless it is backed up from another source. You can never have too much information!
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