Twist rate and caliber for subsonic 50MBG payloads??

[jope]

d-mon thanks for the tips:

How is the case volyme in caliber 50/50/70? Does it use the same barrel diameter as 50BMG? Lothar Watlther has just a wee little too much carbon and cromium for welding. That extra makes the barrel stronger but practically impossible to weld without getting a brittle heat affected zone.

tp555:

How is the case volyme in the phantom compared to 510 whisper and suitability for shooting heavy (750gr and up) subsonic loads? Phantom has the .50BMG barrel diameter, right?

Whats the thicknes at the thickest point in those cases? .510 Whisper is quite straight which is good because then there will still be some material left around the chamber. Especially if I end up building this on my thin Encore barrel.


Anybody know mathematical formulas for the strength calculations?

- Jope

[tp555]

Can't help you on this. I made the brass from jeffreys (machined the head and cut down to size).The phantom stamped brass is original samples.All have been shipped out already. regards.

[d-mon]

Hello Jope,

The 50/70/750 would be the case with the smallest wall diametre I believe. The 510 whisper being based on the 338 lapua, might have a diametre a bit bigger.

Remember, the encore works best with rim cartridge.

If you look into the old Handloaders, you will find an article about that calibre and the contendre barrel that goes with it. (at least 4 or 5 years ago).

For strenght calculation, ask Dr. Kolbe about it, he is a Dr in Physics and know a lot about these things.

I assume that if a contender barrel could be chambered in that calibre, then the outside diametre of that barrel would give you a good Idea of what can be achieved.

ND

[jope]

D-mon:

Can the old handloaders articles be read anywhere on the internet?

And it uses the .50BMG projectiles right???

I wrote border barrels last weekend to ask about the twist for 510 whiper and awailability of suitable barrel blank but no reply so far...

I had ordered .300Whisper reamer from pasific tool and gauge but when I received ot yesterday, 300 hush was written on it. I wrote dave kiff confused to ask about this, but no reply form there either. I hope they just call the whisper hush and its the right reamer and there hasnt happened any misundestangind.

- jope

[d-mon]

Hello Jope,

Regarding Border,
Maybe, You would have been better asking for a quote for a barrel of x dimensin, y profile...etc ,in .50 cal and then asking for their advice in term of twist for stabilising an a-max bullet.

I have somewhere a program to calculate the twist, if you have an a-max close to your hand with a caliper , I should be able to help you. (i will ask you for certain dimensions of the bullet later on).

Regarding the handloader, it is June 1995, page 18. Yes it shoots .50 cal projectiles and the a-max.

I got a reamer from Pacific tool and gage in 30/221 which is what I wanted. I have built one rifle, that I did not have the chance to try yet. (I am in New Zealand and the rifle in Europe). I used a Border Barrel.
They call it Hush because they cant use the "Whisper" name that belongs to SSK I believe.

ND

[jope]

Got a reply from PTG and its the same reamer.

Still no reply form border barrels.

I attached some measure pictures of the 750gr amax. It would be a great help if you d-mon could help me and count the neccesary twist. Shooting subsonic up to 300meters from a 16-20" barrel.

How is the legistlation in the UK. Do you need a license or any paper to buy a barrel blank??

Border barrels exporting license sounds like a big paper mess. In Finland you dont need any license or permit for a rifled barrel as long as it is un chambered. I'm thinking visiting the UK anyway and then I could just pick up the barrel and save all the paper mess. If it goes the same way as here...? Anybody know?

- Jope

[d-mon]

Hello Jope,

No, getting a barrel shipped to Finland must not be a problem. i am sure that if you provide a paper from your police or custom services stating that you do not require a licence for import, Border will do his bit on its side and you should get your barrel quickly.
Delays are at least a month, sometime up to 3 depending of their production.So the paperwork is done meanwhile.

Yes, a barrel unchambered is not subject to any license in the UK as well. But I would not risk a trip just to see that you barrel is not finished yet. And they are in a very very remote and private place...
Thank you for your pictures.
I will work on the programme and give give you an answer in 2 days.

Good night.
ND

PS: I am in NZ now.

[jope]

Hello!

Have you had success calculating the twist?

Is there something bad if a choose a twist too tight? Im thinking the 1 in 7.5 from border barrels.

- Jope

[d-mon]

hello jope,
yes I have been struggling calculating the twist. something wrong with the program with such a big bullet maybe? I will investigate that.

I don't think you can go wrong with 1 in 8.
The risk with overstabilising the bullet, is that at long range you might have it planning and arriving sideways or even bottom first in your target,specialy with subsonic, where the departure angle is further up to compensate for the banana trajectory.

Again, I think that if you write a letter to border regarding your project, they will defenitly answer to you and help you with what you are looking for.

regards.
ND
PS: I will probably be visiting them in june, i can for more info if you want.

[jope]

It would be great if you could find out what they know off about the twist needed for stabilizing the heavy subsonic 50bmg projectiles.

Anybody know what the minimum barrel thickness should be for .510Whisper? I wouldn't like the barrel to blow up on my face. Encore barrels outer diameter is one inch. I could bore through an old encore barrel and put the new .510barrel in it. Then the new 510Whisper barrel couldnt be thicker than aproximately 20mm/0.79 inch.

For reference, does anybody know the outer diameter in the 50 Beowulf barrels used for AR? I belive .510 whisper wouldnt have to be any thicker...?

- Jope