The new Nosler data 338 WM 250 grain NP

rbTanzan · Dec 2, 2010

I've noticed a change in Nosler load data that is so large as to need discussion. The 250 grain NP had previously been listed at 2780fps with 71.5 grains of H4831. That was always considered a bit on the 'hot' side, since the 338 WM was originally factory loaded to 2700 fps with 250 grain bullets.

However, now the new load data on the Nosler site lists 69 grains of IMR 4831 for only 2533 fps.
Admittedly, IMR is slightly faster than Hodgdon, but 69 is only 2.5 grains below the Hodgdon load and is within a grain or so of what I would have expected as its 'max' (70). Yet here we are given a drop in velocity of over 200 fps. Something is/was not right. And now none of the 338WM loads reach 2700 for the 250 grain NP. It looks like the lab may have lowered the acceptable PSI by quite a bit without telling anyone.

SJB358 · Dec 3, 2010

Some of the Nosler data has been skewed for me also. Seems they are getting more speed with alot less powder than I need in most of my rifles. On the other hand, other loads are right on? I just run them over the chrono and watch the case and rifle to tell me when it is enough. Alot of variance out there. Scotty

rbTanzan · Dec 3, 2010

Agreed, sometimes a rifle needs more powder for nominal pressures and speeds. I've got one 338 WM with a chamber .002 fatter than the specs just ahead of the belt. (Fired cases measure .5163" in mild and hot loads.) In a sense it is a 'factory improved wildcat' that needs one or two grains of extra powder for equivalent loads with all bullets and powders. Shoots great and tight, .5"-1.0".

A chrono can help a lot in keeping things sane. I should have said that the Hodgdon 71.5 was a 'fast load' not a hot load. I wouldn't expect many rifles to duplicate that speed with that load, but I would expect something just over or around 2700fps. With a chrono a person can stop load development if they reach a cartridge's typical maximum energy output. A 338WM was rated around 3900-4100 ftlbs and 250 grains at 2700 is 4046 ft lbs. Some years ago the European equivalent of SAAMI lowered their max-specs for the 338 to 62000 PSI which may partially explain the downgrading of loads in this calibre. Some of the new calibres and rifles are set for 65000 PSI in the 'WSM-short magnum' series, though I suspect that those specs will drop after the cartridges establish their market niche.

chet · Dec 3, 2010

I believe that the variable that has caused the change is the test rifle. Maybe The test rifle that liked the 71.5g of H4831 had a larger bore/bigger chamber/ect ect ect...... maybe the barrel was shorter also????? it's really hard to say. Also the powder was from different lots, and the humidity/temperature was different between the two..... brass was likely different, primers too..... hell maybe the 250PT had a little bit of change of bearing surface between now and then. I think the rifle its-self would be the biggest factor, but it could all add up!!! Maybe the pressure testing equipment changed also????? That being said- it does seem to be an extreme spread. also i agree that noslers advertised velocities typically seem a bit high. Now I have an example for you:

I have a M70 25-06. It likes 51g IMR4350 and 110AB, at 52g the primer starts to crater just a bit. Bolt lifts fine, no marks on brass velocity is 3148 average. Just a wonderful load for my rifle. My friend owns a savage 25-06 and wanted to try some 110AB's...... so we took some of my loads and went to the bench. They were full length sized and chambered just fine. Set up the chrony and he fired BANG!!!!! Chrony said 3280 :shock: He said it kicked harder than it ever has, smoke came out of the back of the bolt, it was all we could do to open the bolt, the primer fell out of the case when we finally got to it!!!!!! both barrels are 24" needless to say we didnt shoot anymore

This is why we all agree to :

START LOW!!!!!!

:lol: