Gunsmithing 300 wm chambering ??

[ctharv117]

ok guys

putting together my 300 wm and was going to make a dummy round that fits in my Aics mags then send it to have a custom reamer made but

i am going to use 210gr vld burgers and i know they are fussy about there seeting depth so how do i know were to put the lands in relashion with the bullet

10 th of lands
5 th of lands
or what

any help would be great

 

[Hateca]

Re: 300 wm chambering ??

You don't, not two barrels or chambers are the same. And even if you did after a few hindered rounds the throat going erode to move anyway.

 

[DAVETOOLEY]

Re: 300 wm chambering ??

Seat the bullet so you have at least .040" left over in the magazine. You want the bullet touching at that length. .015" or so will erode rather quickly, like in a couple of hundred rounds then the throat erosion will slow down some. That "some" varies with powder type, quantity and rate of fire.

 

[Clark]

Re: 300 wm chambering ??

SAAMI spec:
.212" - .220" from breech to end of belt for cartridge
.220 - .227" .from breech to end of belt for chamber

If you just give this to a gunsmith, the chamber will be cut to ~ .221".


But most RP or Win brass will be between .213" and .215", meaning that you will typically be .006" or .008" of slop on the first shot.

I would suggest you use the biggest piece of brass you can find as the go-gauge for headspacing. In my belted magnums; 7mmRM, 300WM, and 338WM, I headspace at .215".

 

[ctharv117]

Re: 300 wm chambering ??

thanks guys i will see how it comes out

 

[BOLTRIPPER]

Re: 300 wm chambering ??

i should think one would consider from what magazine box these boolits will be working from.....

 

[LRI]

Re: 300 wm chambering ??

Using a piece of brass, small, large, or huge is generally looked upon as a bad idea. Its been done, its been successful, but depending on a cartridge as a qualifying gauge is never the prefered method.

IMHO a shoulder gauge is the way to tend to belted magums. This defeats any guesswork or questions about H/S and if/whether the ass of the case is in the right spot in relation to the shoulder. Use the same gauge to qualify the set up on your dies and you've killed lots of birds with one little rock.

As for throat lengths and whatnot. Decide up front if you want max performance or longevity. If performance is the goal set your bullet to seat just above the neck/shoulder junction with the bearing/boat tail intersection just above. This allows for good charge density and avoids any. "O" ring issues in the neck. If you want the ability to increase barrel life by pushing the throat out then seat them deeper. This reduces some case capacity and may cause some neck tension issues due to the "O" ring at the neck/shoulder junction. In either scenario you fiddle with your seating depth/charge weight to tune the gun. Bergers tend to be a little particular about where they sit. Try a healthy jump once. You might be surprised at what you find.

Hope this helped.

C.

 

[bignada]

Re: 300 wm chambering ??

Call Dave Kiff at PTG and tell him your goals w/regard to specific bullet you'll be shooting and he'll grind you a custom reamer.