To all,

I am thinking of building an extreme range rifle. THe round it will be chambered in will be either the factory 338-378 Wby(prefer not), the 338-378 Kahn(35 degree conventional shoulder, better) or the 338-416 Imp(conventional shoulder, no belt, better yet).

TO get my performance goals of the 300 gr Sierra Matchking to a velocity of 3000-3100 fps at comfortable velocities, I will be using either a Pac-Nor or Lilja barrel of 1.350" diameter with a muzzle diameter in the .900-1.000" range.

Barrel length will be 32-34" to get these velocites. Also because of the extreme weight of the barrel, I will be using a barrel block or V-Block bedding system which will allow the action and forward section of barrel to be free floating and a non stress componant of the rifle.

I have seen several and shot a few Rem M700's that had been chambered for the Wby/Rigby class rounds for extreme range shooting and converted to single shot.

My question is, with a diameter of .695-.705", would you yourself open up a M700 bolt face to accept the .580" rim of the Wby or the .590" rim of the Rigby.

Another option would be to use the 338-300 RUM and accept 100 fps less in performance, nothing at long range for sure, just liked the idea of the 338-416 Imp to tell you the trueth.

Very interested in your opinion of such a conversion. Obviously a Sako extrator would be fitted to the bolt.

Thanks for your time!

50

Have you thought of the .338 Lapua? Long range sniper round - more info avail on snipershide.com

How far you gonna shoot?

Andrew

Teal325,

I did look into the Lapua and have developed loads for customers using the round in the Sako rifle. It is a great round, but basically the the 338-300 RUM is ballistically identical and actually has about a grain more capacity then the Lapua 338.

Most will not believe this but I have measured the case volume in the Lapua and Norma brass I got from customers and compared it to the 300 RUM cases I use from Remington. Filled to the mouth, the 338 Lapua held 116 gr of water to 117 for the RUM.

Also, if I'm going to spend the money on expansive brass, I would just as soon have the 200 fps advantage of the 338-378 or 338-416 Imp.

If I go with the 338 Lapua performance, I will just use the 338-300 RUM and get brass for 1/4 the price. Lapua brass may come from the factory in match grade shape, but a few hours on the loading bench with my prep tools will turn out match quality RUM cases as well.

I am building this rifle for a 1500 yard rifle, target and varmint/coyote. I have a fast twist 6mm-284 and 6.5-06 Ack Imp that are flat out deadly at 1000 yards but the big 6mm is lacking alot of everything for varmints the size of chucks and coyotes. The 6.5-06 Imp is a bit better but not a by much.

Add another 500 yards to the equation and both are pretty much useless except for paper punching and I want to hammer chucks and yotes with this rifle without the fear of loosing them.

The 300 gr .338 Matchking starting out at +3000 fps will certainly hit very hard and with a B.C. of roughly .800, will basically match my 50 BMG in long range trajectory and wind drift with alot less fuss.

Basically, I want the recoil of the 6mm-284 with the ranging ability and hitting power of the 50 BMG. It will be a compromise between the two with a bit more recoil from the 25 lb rifle and hitting a little(quite a bit) softer then the 50 BMG.

Thanks for the reply!

Good Shooting!!!

50

Sounds like you got your work cut out for you!!

I guess I would just go with the 338-300 RUM if it was me, given the arguments you made.

The .338-416 Rigby Imp. is an impressive ctg. I just built one for a friend but used a Geske instead of a Rem. Some friends have them built on Rem 700s but Lilja, Tooley, Borden and others say that it is not a good idea. Most predict that you will see lug setback, eventually.
I'd use an 06 boltface so that all of the original extractor cutout would disappear when opened up to the Rigby case. A Sako style extractor for this ctg. is available from Brownells, BTW.
The 300 gr. MK is used successfully by a lot of elk hunters.
If you ever find a source for RWS made 416 Rigby brass, I'll take a hundred or two. I've been told that it lasts forever.

The RUM is a good choice. I think that opening the bolt face is not a good idea although it has been done before. You might consider an alternative custom action or a Sako TRG which is available in 338 Lapua out of the box and has an adjustable stock.

My .02