advise about new. 18cal project

[rich]

Hi, I was looking for a little advice on a project I'm starting involving a new cartridge.
Actual bullet diameter is 4. 7mm, so it's not too far from a. 17.
However the energies are very high for a micro cal... 1100ft lbs compared to 900 for the 17 rem. Case is a custom design and capacity is near the 223, or slightly less.

My first question was fouling, because 4. 7 is close to. 17cal, and the 17s are notorious for fouling. Given that my bullets would be far heavier and slower than the 17, (about 3100fps with a 53grain).... do you think this would solve fouling issues?

Second question was stability. I hear the rem had terrible results with the 37grain Bergers. Partly because it needed a 1-6 twist

. I'm pushing for 53grain, with ultra long bullets, which again could create the same problems. Do you think the 37grain issues were down to poor bullet design.
I know that many of the microcaliber trials of the 60s-70s used 54grains...(rounds like the 4. 73 caseless).
Would it be best to approach with a short bearing surface (VLD shape), or a long rod-like bullet with large bearing surface?

Finally the length will be completely maxed out... about 27mm. The project is intentionally an experiment about B.C. and so this feature is essential. Do you think the length /diameter ratio would have implications for any stability difficulties? Again, the 4. 85 experimental had this length of bullet with no issues

thanks for any advice

[Bill K]

Why not just go with a 19 caliber in the 223 case, that James Calhoon has out. Dies, brass and bullets are all available, it would be easy to work with, from the get go. ??

[rich]

Hi like I said the project is an experimentation in B.C. and much of my prior research has centred on the 4. 7 so I'd rather stick with that.

[Bill K]

Nothing wrong with that, we all have our various wildcats.
I played with the 17 VHA, which is that 4.7x30 case necked down to 17 cal and year or so back, fun round, but went to the 17 FB, 17 HH & 17 HMR now instead.
Have fun and keep us posted on your results. Bill K

[RareBear]

When the issue is copper barrel fouling, the generalization is mostly a barrel quality issue (tooling marks and rifling surface finnish) more than any other factor regardless of caliber.

[L.Sherm]

Can you get an 18 cal barrel?

[17tbs]

Let's see one of those projectiles.

[GLWenzl]

I ran across some 18 caliber (actually 4.6) bullets.

http://www.saubier.com/forum/showthread.php?t=2686

[ray h]

Gary I thought Doug told us those bullets were left over from a private contract with someone like H&K. Doesn't Lilja make or did make a barrel for this cal? I thought I asked Dan once where I could get bullets that fit his barrels. He said claimed he didn't know.???? Why make the barrels???

[Bill K]

Might be pulled bullets, but then again someone makes a 18Cal bullet, as the 4.6x30 submachine gun is 18 cal and a lot of them are used by the secret service, right here in the US, from what I understand.

Remember a few being seen when Reagan was shot ??