Thoughts on 338 Lapua Versus 338 RUM

I have had numerous requests for either rifles built in 338 Lapua or actions for the 338 Lapua. Currently, I do not make my standard actions (Timberline, Timberline Magnum or Rimrock LSR) to accept the 338 Lapua case. I have two primary concerns about making the actions at their current dimensions to accept the 338 Lapua round. The first concern is that the bolt nose edges on a .7000 diameter bolt will be very thin and fragile with a 338 Lapua Boltface (.595) and the lug shear area even though it is greater than a Rem 700 seems marginal to me for the 338 Lapua and its bolt thrust. The second area of concern is the thread tenon diameter. The actions have a 1 1/16×18 thread and the barrel would be threaded the same. The root diameter of a 1 1/16×18 thread is about .990 inch. With a chamber diameter of .595, this leaves a wall thickness of .1975. Using a simple of model of the tenon alone and Chamber pressures of 65,000 psi results in a hoop tensile stress in the barrel tenon of 94,000 psi. The yield strength of 416R Stainless steel at 26 Rc is about 107,000 psi. So the SF (Safety Factor) for this application is only 1.1 which is well below what is recommended minimum of 1.5.


So, it would seem that unless a stout action is used, that someone wanting to use a 338 in a hunting weight rifle would be at a disadvantage. However, a closer analysis of the 338 Lapua versus the 338 RUM shows that this is not the case. The following table shows a 338 RUM versus a 338 Lapua for bullet weights from 210 Grains up through 300 Grains. The table shows that the 338 RUM delivers equal velocities with less powder and less recoil up through the 250 Grain bullets. Therefore, the only time a 338 RUM would be at a disadvantage over a 338 Lapua is for the 300 Grain bullet. The 338 RUM can be safely built in a rifle that uses standard profile actions, barrels and stocks and a 6 ¾ pound rifle (less scope) can be easily built that will deliver sub ½ moa accuracy while at the same time delivering significant muzzle energy for longer range shooting.

So the question for me would be: “Why would anyone want to use a 338 Lapua for a hunting rifle when a 338 Rum can be built in a much easier to carry rifle that will deliver equal velocity at less recoil?”

8 thoughts on “Thoughts on 338 Lapua Versus 338 RUM

  1. Your powder charges aren’t correct. The Lapua charges are ten grains over what it takes to safely achieve the velocities you show. For example: The 250 grains need around 85 grains of powder to exceed … 2840 fps in a 27 inch barrel. This is just one example. You are trying to show that the RUM is superior.

    I like the RUM, it is easier to build and is extremely efficient, at times more than the Lapua in terms of powder usage but not by what you show at all !! I think the RUM is better balanced, as accurate and with some loads even faster than the Lapua. It is too bad it isn’t doing too well these days. I shoot a Lapua but would not hesitate one minute to take a RUM to the field for long hunting shots. Both are great rounds. The RUM will fit one more round in magazines than the Lapua which can be an advantage in many hunting situations. There is no fly on the RUM, it just is competing with many other good .338 rounds. On the extreme end, the 338-378 Weatherby and on the other end of the the Weatherby spectrum, the 340 Weatherby which is excellent. If one is to strictly use a .338 for a general rifle, then the 338 Win. Mag is outstanding. If one is after long shots, then the RUM, Lapua and the king of them all, the 338-378 Weatherby. There is plenty of choice. Of all of them, if I only had one choice, it may well be the RUM. It will do anything the others will do with less fuss. My Lapua is a tack driver and it’s what I have…I like it a lot. As mentioned earlier there is plenty of good choice, but I do reiterate that your loads favor the RUM at the expense of the Lapua.

    • These may very well be but if one looks at the various reloading manual, the loads on the table in your example require on average 10 more grains than the ones in the loading manuals. They disfavor the Lapua and aren’t representative of what one can achieve with far less powder. Ten grains of powder at these speeds for these bullets add approximately 4 to 6 pounds of recoil. The Lapua can be operated at the speeds listed with much less powder and with superb accuracy. The RUM is an excellent, well balanced cartridge. The Lapua has more flexibility when it comes to heavy bullets but is nearly identical in regular loads. The length of the Lapua allows it to be chambered in standard long actions. The length of the RUM exceeds it by a little and requires a slightly longer action.

      • Paul

        The RUM cartridges fit in our actions that are same length as Rem 700 long –they just use and extended magazine system from wyatt. Once again the loads listed are ones from manuals and our experience making rifles here and is based on velocities attained with those charges over chronograph based on STATISTICALLY Based testing……..

        • Glad I visited this page again. I chronograph my loads and own three different chronographs. I am quite particular about posting my views. Please revisit the Barnes manual if you wish to only visit one. Powder charges can be heavier in either cartridge, however there is always an efficient powder that achieves high speeds with accuracy without resorting to 100 + grains in the Lapua. There are six or more reloading manuals and hundreds of loads for each cartridge. It’s easy to omit lower charges that are quite efficient.

    • The 338 Edge is built on the 300 Rem Ultra Mag case and present no concerns for you Timberline Magnum action. The article addresses the issue of using the larger diameter 338 Lapua chambering in 1 1/16 thread tenon actions……

  2. So you are saying that the pressure created by the edge are compairable to the lapuas but being that the mearurements being the same as the 300 rum. that it is safe to run those pressures?

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