165 gr. bonded premium bullet at 3050 fps.
My foremost recommendation is to use premium bonded strongly constructed bullets designed for controlled expansion for max or near max hunting loads.
Even with good quality jacketed soft points (not flat points) from Speer, Hornady, Sierra, etc, standard jacketed .30 cal soft points are designed to expand and penetrate well in the velocity range produced by .308 Win & .30-06 at ranges from 25yd. to 300 yd. A near max .300 Win load will exceed the ideal recommended velocity range of these bullets by 300 fps or so. You are likely (especially at ranges less than 150 yd) to experience excess expansion, poor penetration, excessive meat damage, or bullet break up (possibly jacket & core separation) if you load these standard bullets at velocities which are greater than the max velocities listed for the .30-06 for that bullet weight.
A good plan is to find a premium and a standard bullet of the same weight, bullet style, and ball. coeff. from the same manufacturer. (I use Hornady SST, 165 or 180 gr for my standard practice bullet, and Hornady 165 gr or 180 gr. Interbond as my Premium hunting bullet.)
These two bullets have identical shapes, ball. coeff., boat tails, and plastic tips. The SST has a cannelure and Interlock construction for standard velocity cartridges. The Interbond is bonded, with a thick tapered, inner grooved jacket; it is designed to penetrate and expand well at velocities that are 300 fps greater than the recommended velocity envelope of the SST. Both bullets are designed for accurate long range shooting, good retained velocity, and controlled expansion. Both shoot under 1" average 5 shot groups at the same point of impact in my rifle. Once they are loaded into the case, it difficult to tell them apart. I add an additional mark near the bullet tip to ID the Interbonds.
Work up your load with the SST bullet and sight in. Use loads with the SST bullets for practice, predator shooting, antelope, etc. When elk and mule deer season arrives, double check your zero with the Interbonds. For my rifle, the zero is always exactly the same or within .5".
When you think you have a perfect zero with the Interbonds, let your barrel cool. Fire a 5 shot group allowing several minutes cooling time after each shot. While firing this group, hold the fore end of the stock in your hand in the same way you would in a field position with the hand supported by the sand bags. The butt of the stock should be unsupported except by your shoulder. This will give you a good idea of where your first shot from a cold barrel will go. Do NOT clean or oil the bore after firing this last 5 shot group.
The Hornady Interbond is one of the least expensive high quality premium bonded bullets available. By using SST's for practice and initial sighting and Interbonds for hunting, you will typically use fewer than 20 Interbonds (or other premium bullets) per season. This is a fairly economical and very practical plan.
Do not use standard JSP boat tails at or near max velocities in your .300 Win unless they are bonded or have some special construction features to lock the core into the jacket. It is very common for standard boat tail JSP to separate core from jacket when impacting game at muzzle velocities greater than 3000 fps.
The 165 gr Interbond should give great performance on elk and mule deer at any range out to 400 yd. I no longer use 150 gr because the 165 gr shoots just as flat or flatter and retains velocity better. You can move up to 180 gr for elk if you want, but with premium bonded bullets, you will get good penetration and expansion with 165 gr.
I have also used the Speer Grand Slam at maximum veocity. It penetrates and expands well, but doesn't have as high of a ball. coeff. as the Hornady Interbond. The newer "Deep Curl" from Speer is a bonded bullet designed for good expansion and penetration from standard velocity cartridges. I have no experience with it, but according to Speer, it's performance at magnum velocities should be between that of their standard "Hot Core" bullets and their "Grand Slam" premium bullets.
Best kept secret for loading the .300 Win: you seldom need (or will get any real benefit from) the maximum attainable velocity with any weight bullet. As long as you use high quality premium bonded controlled expansion bullets, you will not need to use a hunting bullet heavier than 180 gr. in the lower 48. (Although a 200 gr. bullet might be useful for moose or bear at ranges less than 200 yd.)
The most efficient powders (not necessarily highest velocities) for good accuracy and near max velocity: IMR 4350 and IMR 4831
Best all around hunting load: Use the START load ( or 1 grain more) with IMR 4350 from the current Speer manual. The start load from the Speer manual chronographed at 3050 fps from my 24" barrel. And, as a special bonus, I could load 100 cartridges with 1 lb. of powder. It's possible to get another 150 fps or so by going all the way to max. But why? This load will probably give you good accuracy, good economy, a flat trajectory, a tad less recoil, and a little longer barrel life.
This load will equal the velocity you will get from some factory loaded 165 gr. JSP. If you start feeling you need the maximum velocity attainable, buy a box or two of Hornady Super Performance ammo with Interbond bullets. After fine tuning your zero, one box of 20 will last you two or three seasons.