Thread: Attempting a new .224 wildcat

When I purchased my used Desert Tech rifle it came with a few barrels, one of which was a 24" Trueflite .22-243 with a 1-8" twist built by Robbie Tiffen.
It had clearly seen some use as the throat was completely burned out. The first 35mm or rifling is non existant, it is completely shiny and balled.
I removed the barrel extension nut to use on my new 6.5x47 Lapua barrel and this barrel has sat at the back of my work bench awaiting its fate.

Due to the way Robbie machined it to be a light weight barrel with an alloy sleeve for the rifles unique clamping section instead of the solid lump of s/steel of the OEM units, it was going to be a small mission to set back and re use for something else.

However, when boredom sets in I new Id have a crack at something.

So I got thinking, what .224 cartridge sharing the .308 bolt face should I put into this thing?

The first consideration was it is a 1-8" twist which means 65 to 90gr bullets are favorable.
I wanted something that will get used as much as my .223 and re chambering it in .22-243 was of no interest to me.
A combination of the long shoulder angle, large powder charge and extreme high velocity of this cartridge will destroy the throat in as little as 1000 rounds.

So a smaller cartridge shooting the lighter 69gr bullrts was my preferance.

I considered, .22BR, .22 dasher, .22x47 Lapua .22-250 Ackley improved and .22 Creedmoor.

After researching all of these I short listed
.22x47lap .22 Creedmoor and .22-250 Ackley.
All of these cartridges can also be hard on throats but not as bad with the 30 and 40 degree shoulders.

My next consideration was build cost, this was a very accurate barrel and deserved setting back but its not one Ill use often so I didnt want to spend a fortune on reamers brass and reloading dies etc.
This pretty much ruled out .22 creedmoor and .22x47Lapua as dies are custom jobbies or a case of buying 6mm creedmoor brass and using a .22 bushing die to neck them down then neck turn to remove donuts etc.

So I was left hovering over .22-250 Ackley improved.
The reamer and head space gauges I already had available to use so no additional cost there, just brass and dies needed.
The best brass available for fire forming is Lapua but it is only available in large rifle primed brass.
All my other 7 cals I load for are small rifle primer pocket brass and I really wanted to keep that universal.
So I was swinging back to the idea of .22x47 Lapua because I have about 500 pieces of brass in 6.5x47 Lapua already.

Now the .22x47Lap with a 30deg shoulder has a case volume that sits between .22-250rem and .22-250 Ackley but the brass is a lot stronger with its thicker walls and small primer pocket. It is reported to last 4 times longer than the 22-250/AI brass in its .22 role.
It was a no brainer for me.. I need to run this tough brass that I already have a ton of.
I compared the case drawings of 22-250AI and .22x47 Lapua and unfortunately it wasnt going to be as easy as just necking it down to .22 and fire forming to the
.22-250AI chamber.
The .22-250 Ackley brass is approx 55 thou longer than the 22x47 and possibly will get shorter again when fire forming the shoulder from 30 to 40 deg.
So what if I short ream the .22-250AI chamber to the max length of a fire formed 22x47Lap?
Another quick comparison of the cartridge drawings and a measure up of some brass says yes it can be done.

So I am creating a monster, a "5.5x47 Lapua 40 deg improved".
In theory it promises better efficiency and velocity than the 60 thou longer .22-250.
I intend to shorten some redding .22-250AI dies to form my brass so this so far was my only cost with this build. I found a Redding 2 die set available locally so its all go.

The first plan is to make up a test chamber in a bit of scrap .224 barrel and use that to wax fire form some brass for final dimensions.

I have short reamed a small section to use a a projectile seating gauge for setting up any new bullet jumps.
I also wanted to avoid neck turning after sizing the necks down so will ream the chambers neck to .257 for a no turn neck.





It will be a mish mash of about 4 or 5 different chamber, neck and throat reamers but a fun project regardless.