Can anybody inform me as to what the differences are between these three rounds? Which are harder hitting or flatter shooting etc.?

The .338 Lapua would definately be the hardest hitting. It is predominately a military cartridge, at least that is what it was desighned for. It has impressive reach, and accuracy potential. It would also be the most expensive of the three to shoot (by a long margin). The .338 Federal is a necked up .308. For my money, I would (and do) go with the .338WM, it is time tested (been around since 1958), and will take about any game animal you want to point it at. I am not a great fan of new cartridges, but that's just personal preference. I like to shoot calibers that will still be around ten years down the road.

The 338's I would consider are, .338 win mag, 338 Rem Ultramag, .340 wby, I own the latter.

There's also the .330 Dakota, and many others I'm sure, but the above 3 I think are the most popular/available/around.

I think the .338 Lapua is very close to the speeds of the .338 RUM and .340 wby, though I believe its usually loaded with lighter bullets like 180gr or 210gr, which the RUM I think is only loaded with 250gr and most 338 guys use 225 or 250, handloaders can load 275gr! So the lapua with a 180 or 210 will be faster than a 340wby or 338rum is with 225 or 250 but comparing those weights I think the RUM and Wby are faster.

Are you looking to get one, or just wondering the differences?

I am interested in getting one, but im not at the point where im comfortable with my knowledge of the intricacies and abilities of the approximate .338 sizedcartridges Basically, im trying to find out as much information as i can about thecartridge's perfromance abilitiesbefore i decide on one, but im not at the point where i feel that im knowledgable enough about the cartridges to make an accurate assesment of each one.

The 338-win mag & 338-Remington Ultra Mag are the two rounds you should look at the hardest.
One more 338-caliber round to consider is the 340-Weatherby. I own & hunt with a Sako rifle that is chambered in 340-Weatherby, I love this gun.
The 338-Lapua is a awesome round, but you will have a heck of of a time finding one light enough that you want to hunt with it.Sako used to chamber the 338-Lapua in asporter/hunting style rifle. I have never seen factory ammo for the 338-Lapua.

The 338-win mag will have the cheapest factory ammo. The 338-win mag riflemight be a few dollars less than the 338-Remington Ultra Mag & 340-Weatherby?
The 338-Lapua???
The 338-Federal, I am not sure why they even developed this round? I would steer clear of it because it might die off in a few years? Then ammo or brasswill be hard to find.

338 Federal-Baby Bear(teenager)
338 Win. Mag.-Mama Bear
338 Lapua-Papa Bear
340 Weatherby Mag.-Papa Bear's Brother. Tom.

btw, I never understood why the .338 win mag shouler was shorter than compared to the .300 win mag, don't both these rounds use the same case essentially? the .338 win mag is noticeably shorter in overall ht than the .300 win mag. I wonder if the shoulder was at or closer to the same point of the .300 win mag how much more velocity we would get out of it. I love the .338 as a big all around, but personally the only ones I considered were the .338 RUM and the .340wby, I already had a .300 win mag,though, so I wanted to put a bit more spacing between my .300 and my .338. Also when looking at a .338 the RUM's were still kinda being questioned and a gun nut I know said don't get a RUM and recently I saw an article talking about which rounds were successes and which were failers, the .375 RUM is dead or dying, I think the 7mm is as well, the .300 RUM is quite popular and should be around, I think they listed the .338 RUM as likely to survive and I kinda agree with this assesment, also the .340wby pushes the bullets a tad faster and with less kick, the .340 uses less powder than the .338 RUM. I do like that the case is beltless though.The .340 has been around for much longer. I've heard it dubbed the ultimate long range elk cartridge, course the .338 RUM would be in that category now as well. Surprising to me that the .340 wby isnt more popular than it is, compared to any round that comes out iwth the name, remington, winchester, ruger....I know cost of wby rifles is a step up, they now have the vanguards, but also you can get a mark V fibermark, for $1200 and a synthetic will be even cheaper than that. Doesn't seem like much of a stretch from a $800 remington to a $1000 weatherby.

It was made shorter to keep idiots from chambering a 300 Win mag cartridgeinto a .338 Win mag chamber and hurting themselves or others.

The RUM's are made the same way.

Of the 338's, ihave hunted with, and taken DG with the 338-06, 338 Win. Mag., and 340 WBY.

If i was you, i'd take the .338 Win. Mag. as it's plenty for anything in the USA including the biggest brown bears... Just use the proper bullet for the animial hunted..

It's much cheaper to shoot than the WBY, with less recoil, less muzzle blast, doesn't need a 26" bbl, and has more power than the .338-06 or Federal.. And the ammo is easier to find.

It's a easy decision for me...

DM

Is that really the reason they shortened the .338 win mag? seriously? so how much extra velocity would a .338 win mag get if it was full lengthy of the .300 win mag?

I think that's the stupidest reason I've ever heard on why a cartridge was made shorter.

I think we need a new wildcat....haha, full length .338 win mag.....let's call it the .338-300 win mag! haha. .338 ackley improved? might need to use .300 win mag to form it though! haha.