Custom 300 wm build: dummy rounds, col, jump?

[Slowshot18]

I’ve finally gathered the parts to have my first custom build assembled. The rifle will be chambered in 300 wm. Parts consist of Stiller Predator, Bartlien 5R .30 1:10, McMillan adj Game Warden, and a Wyatt’s MBE-02 box.

Objective of this gun: hunting, steel, and to throw the lead downrange as fast as possible.
Bullet of choice: 212 eldx, sitting in ADG brass.

Having the ability to use factory ammo if I ever got in a bind would be nice. 99.9% of the time I will be using my handloads.

My smith asked for me to bring dummy rounds so he can base the chamber off of the rounds. Factory C.O.L is 3.34”; the Wyatt’s box has 3.82” of space inside the mag.

What C.O.L should I load the dummy rounds too? I know I’m going to need some room to chase the lands as erosion occurs but, if I ever got into a bind, could I use factory ammo safely (not extremely accurately) if my chamber was based off of a let’s say, 3.6” C.O.L?

Thanks

 

[Vargmat]

While I am by no means an expert, this is my experience from dicking around with the 300 WM for the last three years:

First, I bought a Remington 700 Police in .300WM. I never really measured the throat of it but in regular Remington fashion it was on the long side. It shot factory fodder horrible, it never really like handloads with 190 grain SMK neither. But that barrel REALLY liked the Hornady ELD-X 212 grain loaded with a COL of 3.5" with a MV of 2755fps. That load regularly shot .5 MOA at 100 meters and it gave me a first round hit on a 12"x12" plate at 1090 meters. Needless to say I was super happy with it.

Then, while my barrel was not really shot out (1080 rounds with no apparent loss of velocity or precision), but I had a custom barrel waiting for me at a gun smith so I just could not help myself. I sent it in to have it blueprinted and rebarreled. My smith wanted dummies so I sent him one with the 212 ELD-X. While I dont really know why, he throated it a bit longer than he needed so I can use a COL of 3.65". Its not really something I requested but that is another story. What sucks is that the new barrel with a long throat does not like the ELD-X at all. I have tried different powders and seating depths and nothing works. So I started to load develop with the Lapua Scenar L 220 grain and right at 2820fps it absolutely hammers with them. So while there are the aspect of barrels beeing individuals and all that. Maybe, just maybe the Hornady ELD-X is not too happy about long throats. I dont know, but I know that it shoots horrible with the new barrel at 100 meters (like 3,5", 5 shot groups). Oh, and just to have it stated, the new barrel shoots just as terrible with factory loads as the original barrel did.

So I would keep the throat set to use ammo with a COL at around 3.5".
I am pretty sure that factory rounds will never be longer than CIP standard at 3,34".

 

[Slowshot18]

Thanks for the information. I'm thinking about venturing off to a little bit longer throat since I have the Wyatts to handle the extended COL. If the 212 eldx does not work out, there are always other options out there!

 

[Vargmat]

Yes, there are no shortage of different high BC bullets to try in .308 caliber.