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I like those numbers it's not a lot but would be a just enough extra
Why is the focus on improving cases always about speed?Going to likely ruffle a lot of feathers here but in my opinion it would not be worth the effort. That said, i also do not believe any improved version of the 308 family of cases or the 284 or any WSM cases are worth it either.
the very best improved designs out there will gain 100-125 fps over their parent cases WHEN LOADED TO SAME CHAMBER PRESSURES. Thats the rub. We often load our improved wildcats to higher pressures and as a result we get more performance. The improved wildcats on the 308 family of cases, 284 based cases and wsm based wildcats will get 75 fps max when loaded to the same pressures as the parent case.
now many times these wildcats are chambered in very well built, very strong full custom rifles which can easily handle the added pressure safely. That said, the parent cases in the same quality of fun loaded properly can also handle a bit more pressure for added performance and still be totally safe.
we often look at commercial advertised performance numbers which these days are pretty lawyer proof by necessity for sure.
figuring in the added cost of custom loading dies and mainly the time and effort needed to form brass which is often wear and tear on the barrel life. These rounds have just never made sense to me. Did a lot of testing over the years to find out just how much performance gains could be expected from many different types of wildcats.
my testing procedure was a bit crude but i feel accurate. The test receivers i used for these tests were one of my fully blueprinted rem 700s that i used for all long and short action rounds tested with the 0.470" head diameter. For the larger wildcats i had an nesika bay single shot receiver with a standard mag bolt and an extra bolt with a lapua class bolt face.
first test i ever did was with the 260 rem as i was hearing wild claims about the performance of the 260 Ack Imp which i simply could not understand.
so to start, fitted up an admittedly cheap A&B test barrel to the Rem 700 in 260 rem using my reamer i had jgs make to my specs so certainly not saami specs, much tighter. I ran two tests, one with the 120 gr ballistic tip if i remember correctly and the other with the 142 gr sierra mk. At the time, one of the best LR bullets on the market in 6.5mm.
I would load up a batch of ammo at a very mild starting load and fire the cases so that the actual testing would be done with mildly loaded once fired cases. The reason is to be fair to the improved case test results. i loaded the 260 up and shot over a chrono and increased powder charge by 1/2 grain until i got to the point where the case would show the very first hint of gas leakage around the primer with only a 1/2 grain powder charge increase. Admittedly, these loads were well over safe pressure but i could not think of a way to get an accurate point in the pressure curve to stop testing at. Used same lot and brand of brass for all testing. So with both bullets tested i knew the powder charge and velocity produced at this FAIL point. Thought about doing .2 gr increases but the results were not clear enough as one case would leak at one point, another would leak at 0.2 grains sooner or later so just went with 0.5 grain jumps.
with this data recorded i would then pull the barrel, rechamber to the ack imp version, again, i have all my reamers made to my specific specs so neck diameter, throat length and diameter and leade angle are all the same.
i would then repeat the test work up with the improved case. To make things as fair as possible again, the virgin cases were fireformed with a very mild fire forming load and then once fired, the test would be started. This was the best way i could fairly compare max case failure point between the two chamberings.
in nearly every round tested and i tested the 243, 260 and 7-08. Also tested the standard length 25-06, 270, 280 and 30-06. For magnum chamberings i tested the 270 wsm and 300 wsm and also tested the 7mm rum and 300 rum.
for the big boys at that time, i also tested the 30-378 and 338-378 against the 300 kahn and 338 kahn which are the same rounds but with a conventional 35 degree shoulder angle.
again, in my testing, i found that with the 308 class of rounds, the smaller the caliber showed the most velocity gains when loaded to the same max chamber pressure, or at least as close as i could get. The 243 showed an 80 fps improvement, the 260 rem showed just shy of 70 fps gains and the 7-08 was just over 60 fps gains……. This really did surprise me. Would have thought it to be more then this.
the tests run on the 06 class of cases showed more velocity increase. Likely simply because the larger cases use a bit slower burning powders and their case designs were transformed more dramatically and had larger powder capacity increases. The 25-06 which i feel is one of the best AI rounds out there added a solid 140 fps over the parent case. The 270 and 280 were both right at the 125-130 fps range and the 06 gained around 110 fps over the parent case.
onto the wsm rounds. 50-75 fps was the max increased with either of these.
the RUM cases showed more capacity gains then i was expecting which was due to their long length and large diameter cases. Reducing body taper on a case of this length and diameter increases volume significantly more then smaller rounds. Still the velocity gains were in the 100-125 fps range.
with the big weatherby cases, they were both within 25 fps of the parent case but to be fair, only the shoulder design is changed going from standard to the Kahn design. However this leads me to one of my points, the change in shoulder angle does very little to increase capacity. It can improve case stretching control but proper case sizing solves most of these issues already in most situations.
not to be fair in all these results, if one compared the resulting performance of the improved rounds against CONVENTIONALLY ACCEPTED max velocites of the parent cases, the velocity spreads would have been much higher. However my goal was to represent and show the actual gains that could be expected comparing max loaded parent case to max loaded improved case designs. All being as equal as possible.
i know this will irritate many with these findings as i have already had many heated debates with many people about these test results but when all is as fair as possible in these comparisions, the gains just are not that impressive.
i used these results in developing my wildcats at the start or at least choosing the parent cases for my wildcat families. Never bothered with the 308 class of cases. The 06 cases showed good improvements but they had all been done to death. The RUMs showed decent gains but when i decided to use the RUM cases for one of my wildcat families, they would be necked down to 257, 6.5mm and 270. I wanted much more in my 7mm, 300, 338 and 375 cal wildcats.
as such, for the 7mm and up i went with the lapua parent case which shows tremendous velocity gains in the properly improved design, because of its diameter however, you need more case body taper for proper extraction at full pressure level then a true ack imp design. Something i learned early on but thats a topic for another post sometime.
my wildcats based on the Lapua parent case will easily match the performance of the much larger capacity weatherby case and do it with 10-12 grains less powder. Yes, this is partially due to the extreme strength of the lapua class cases, at least those made by lapua and peterson.
so with the long winded explination why, i dont think the PRC would be a good choice for an improved round. This is what i would tell my customers and if they still wanted one, i would build it for them and it would be a great performing round and a very accurate rifle and all would be happy!! If you want one, that is the main reason to have one built!! Spice of life ya know!!
Thats why I had Lance do it! He is trusted and VERY unbiased and thorough!!
As others has noted, very little is gained in improving modern cartridges. Good luck!
