Hypothetical Wildcatting - Bring on the cold water

**Desperatezulu** · 11-12-2024, 17:44

With my bucket of cold water sloshing....

The lower(er) pressure of rimmed cartridges pertains to the ability of the case design and thus brass to survive multiple firings. Simply using a stronger action and running at higher pressures will result in shorter case life. Case head separation on a rimmed cartridge in a falling block action sounds like fun....

To doodle with such a project for sentimental reasons is all good and well but to double-down and expect performance (velocity and accuracy) with your base materials is optimistic to the point of delusion. Silk purses from sow's ears and all that.

If you're going to go to the considerable hassle of custom reamers, not to mention custom dies, why not play with something that has a better chance of making you happy. Maybe something around the 250 Savage case - necked down to 243 (or more practically, a 22-250 necked up to 243) where components shouldn't be a mission and you can realistically create the varminter you're seeking. Have a chat to Ralph Badenhorst and see what he can do for you re reamers, dies etc.

**Heath Robinson** · 11-12-2024, 20:06

Thanks for your responze Zulu, but you're going to have to explain your concerns either in much more detail or in much simpler words.

Why would a rimmed case be less resistant to pressure than a rimless one? Seems to me it should be the other way around as it has less un-supported area (because except for the case head itself, it's really the barrel that is taking the load as the case is far too weak and there is no extractor groove in a rimless case).

Just for clarity, the reloaring process would be controlled just as for a rimless bottleneck case, IE the sizing die would be set up to give minimal shoulder bump if at all.

Secondly, why do you feel that case head seperation is either more dangerous or more likely in a falling block? Again, it seems the opposite to me as firstly the action is much stiffer than a rear-locking bolt action and secondly the shooter's face is much better protected, as are his hands since the gas would mostly be vented out the top.

And thirdly, why do you feel such a combination would be less accurate?

**Heath Robinson** · 12-12-2024, 08:03

For interest's sake, I sectioned a PMP .303 case and a Federal .308 (should have been PMP but I don't have any) this morning.

Case head thickness (measured from the base of the case to the lowest area next to the flash-hole) is 4.84mm on the .308 and 4.81mm on the .303.
Case wall thickness just where the radius ends on the .308 is 1.04-1.06mm, on the .303 it's 0.97-1.11mm. Thus the Federal is much more concentric which is probably not surprising, but the average is probably very similar.
15mm forward of the base of the case, the .308 is 0.78-0.80mm, the .303 is 0.78-0.98mm.

Thus I very much doubt there is any difference in strength between the two, and by inference thus between a 6mm Musgrave case and a .243 case. And by further inference then I don't see any reason why the same pressures can't be handled in any given action.

However, I guess the inconsistency in the PMP case might explain some of the accuracy issues. And since only PMP ever made 6mm Musgrave cases...
So then I went looking to see if any of the premium-quality manufacturers still make .303 cases, and found exactly nothing.

However another rabbit-hole then presented itself: Lapua makes 7.62 x 53R cases, and that has a larger base diameter. That would then allow either even greater case capacity or a shorter powder column for the same case capacity...

So let's define the goals a bit better: I do want high velocities but I don't want to break any records and I am happy to use relatively light bullets. Let's say 3700-3800ft/s with 70grainers and say 3300ft/s with 90grainers. Both the above appear to be achievable with .243 Ackley, so any increase in capacity above that of .243 Ackley would just be used for lowering pressures (I don't much like pressure really).

As for accuracy, I don't think I need anything too extreme although 2MOA would be somewhat of a disappointment. I think I would be OK with 1.25MOA although clearly when it comes to accuracy less is never more.

**oafpatroll** · 12-12-2024, 08:27

Those dimensions are so close that it seems unlikely its coincidental. Re the inconsistency with PMP, that absolutely mirrors my experience on checking case volumes across batches of 270 Win. I measured thirty or so across a few batches and they were significantly less consistent than the US and European samples I had on hand.

**TStone** · 12-12-2024, 10:30

Originally Posted by Heath Robinson

So let's define the goals a bit better: I do want high velocities but I don't want to break any records and I am happy to use relatively light bullets. Let's say 3700-3800ft/s with 70grainers and say 3300ft/s with 90grainers. Both the above appear to be achievable with .243 Ackley, so any increase in capacity above that of .243 Ackley would just be used for lowering pressures (I don't much like pressure really).

One big advantage of most single shot actions is that the actions are very short. As an example, a Ruger no. 1 action with a 26" barrel is ± the same overall length as a bolt action with a 22" barrel. You can put a 26" or even a 28" barrel on a no. 1 action and still have a rifle that does not handle like a fence post. Those extra inches will make it easier to reach your target velocities.

**Messor** · 12-12-2024, 10:48

Originally Posted by TStone

One big advantage of most single shot actions is that the actions are very short. As an example, a Ruger no. 1 action with a 26" barrel is ± the same overall length as a bolt action with a 22" barrel. You can put a 26" or even a 28" barrel on a no. 1 action and still have a rifle that does not handle like a fence post. Those extra inches will make it easier to reach your target velocities.

I would just not want one (single shot) for the stated purpose of said rifle.
You want to stay on target as much as possible, the design in question make that kind of troublesome.

**TStone** · 12-12-2024, 11:32

Originally Posted by Messor

I would just not want one (single shot) for the stated purpose of said rifle.
You want to stay on target as much as possible, the design in question make that kind of troublesome.

True. However, the OP's choice seems to be based on desire for a single shot rifle rather than practicality.

**Heath Robinson** · 12-12-2024, 12:04

Originally Posted by TStone

True. However, the OP's choice seems to be based on desire for a single shot rifle rather than practicality.

That and the barrel length/rifle length advantage you mentioned earlier.

Primary purpose will be Springbuck (where quick follow-up shots should not be necessary). Jackal is a distant secondary purpose. I am not a night person. Virtually all my rifles are single-shots with under-levers, the only exception being a lever repeater. Thus handling would be similar to what I am used to.