Posting the question for a computer illiterate friend.

What would be the ideal neck wall thickness for a 7mm STW. The rifle is a custom chamber and the original brass is turned down with a hand lathe.

Current dimension is .013 and hold the bullet loosely.

Well it sounds to me like the necks were turned down to fit a custom "tight neck" chamber then resized using factory dies. Unless they were simply turned to far you have to live with the neck as it is or have the neck recut on your chamber.

With the thinner brass "smaller OD"in a normal die you don't get a small enough ID in the neck to hold your bullet. Get a collet die or have a custom resizer made to fit you neck.

Maximum loaded round neck diameter is .315" or .317" depending on what internet measurement is correct. .315" - bullet diameter of .284" gives .031" divided by 2 = .0155" maximum wall thickness. Most factory brass will not be near the maximum neck thickness of a loaded round. If you have a tight neck chamber, your case wall thickness should be .001" smaller on each side. Or .002" smaller than your chambers neck diameter. If you just want the brass to hold the bullets, you will have to buy bushing dies like Redding sells. This will let you pick how much you size the neck and to what diameter when outside neck turning the brass. I hope my math is correct, someone double check it please.

What is the Dia. of a fired neck. With springback a fired case should come out of gun 0.002" smaller than the neck of the chamber. If you want a tight neck loaded round then the loaded round (sized case with loaded bullet) should be the same dia. as the dia. of a fired round. LOAD FROM A DISK shows the nick thickness of a 7STW as 0.0165" and the neck of a 8mmRem Mag as 0.0155". You can't get a thicked neck by necking down a 8mm Rem Mag to a7STW. I have a couple people that I know that neck down 243 Win cases to 22-250 then uses Lee collet necksizers to size the cases so they will have a thicker necks for factory chamber. Being a 7STW I hope you get a good load before it turnes into a 7MM shotgun.

quote:

Originally posted by Frostbit:
Posting the question for a computer illiterate friend.

What would be the ideal neck wall thickness for a 7mm STW. The rifle is a custom chamber and the original brass is turned down with a hand lathe.

Current dimension is .013 and hold the bullet loosely.

What kind of dies are you using? If your turn necks you should be using a bushing die so that you can adjust neck tension. .013+.013+.284 loaded should be .310" might need .309" or .308" bushing.

Redding sells a Type S FL Bushing sizer for the 7mm STW @ $61. plus shipping from Sinclair a steel bushing @13.95 each. Well good luck

I would try a .308 bushing to start as brass springback is outwards towards the bushing. You will end up buying about 3 bushings. Redding type S full length sizing bushing die would work well, as said above.

My friend says thank you for the detailed responses. On a side note I think he is realizing the wealth of knowledge on here and maybe that will spur him to register and learn to log on.

I forgot to add that Redding also make a Body die for sizing the 7mmSTW and they also make a type S neck die.

There an outfit call JLC
http://www.6mmbr.com/CarstensenJLC01.html

You might have your friend call him he might be able to convert the existing die over to a bushing and send him acouple fired cases and he set up right for that rifle.

Jim does a nice job.

Thanks to all of you and your response. Frostbite logged this on for me.
This rifle is a rem 700 action and Homer Strickland(Accuracy Arms)built it for me about the time the7STW came out.I have not played with it for about 6 years.
The case starts out as an 8MM mag and is necked down to 7mm then the neck is turned and the case is fireformed. I am using Neil Jones dies and I have bushings for .311,.310,.307.I am using 73 grains of R22 and a 185gr Berger.Occaisionally I will get a significant flattened primer.All loads a measured indiviually.The only thing that makes sense for the over pressure is that the bullet is jumping to the lands when the primer ignites and that is creating over pressure.Any other Ideas??

Sounds to me like you simply have high pressure and some cases show it more.

I used 8mm cases in my 7stw. However I found 73grs of rl22 was on the very high end for 120gr bullets in my rifle. Alliant calls max as 70grs for 175gr.

I've not seen higher pressure signs with a loose neck.