20 inch barrel 338 Lap loads

sharpshot50

Private
Hessian
Online Training Access
Minuteman
Oct 25, 2011
89
63
24
Missouri
I run 89.0 Retumbo behind a 300 SMK in my 20” AXMC barrel. I’m headed out the door for work but I can snag the OAL this evening.

I found anything over 89 causes a sticky bolt and anything over 90 causes the bolt to stick so badly that it has to be opened either with a rubber mallet or with assistance from a rod down the muzzle. This is true with both barrels I own, which are 20” and 27”.

Additionally, both barrels are chambered in such a way that bullets need to be seated quite deeply in the cases to avoid having them jammed into the lands. This is not really a problem for me because the 89gr load produces half-inch groups at 300 yards when I’m shooting well and even when I’m not doing particularly well, it’s still easy to shoot under 1.5” groups at that distance.

I do believe some more load development could be done that could lead to heavier loads. Comparing to other people’s loads, 89 grains of Retumbo is a pretty light load and I feel like the rifle can probably handle a “closer to typical” load with some work, I’ve just been happy enough with the current load that I’ve not taken the time.

Also, for what it’s worth, I can swap back and forth between the two barrels and the point of impact shifts about 1/4 to 3/8ths of an inch at 100 yards. The shorter barrel impacts shift just a hair to the left of where the longer barrel impacts.

I hope this helps.

Edited to add: the OAL I'm running right now is 3.625"
 
Last edited:
  • Like
Reactions: DownRangeThermal

brianf

Private
Belligerents
Apr 8, 2010
1,314
1,089
219
42
NY
a while ago alot of guys were getting 92 of retumbo, might be a faster lot of powder.

that being said, thats alot of noise and recoil with out a can for 20"

guess your wearing plugs and muffs