The burst may actually be doubling from a 'milked' trigger. Done that myself. Incidentally, I believe it completely proper to grease the area of the Op rod that rubs the barrel, some M1 guys I talk to don't do it
Possibly is your problem a bad valve in your gas cylinder lock screw allowing too much pressure blow-by?
Here's some info from TM9-1275 "Ordnance maintenance US Rifles, Cal .30, M1 M1C and M1 D" June, 1947, which I have condensed
42. Short recoil
Short recoil stoppages, often confused with feed stoppages, occur in rifles which are underpowered, [and] therefore do not drive the operating rod completely to the rear. When a rifle is underpowered and subject to short recoil stoppages, it will usually close on an empty chamber or fail to eject the fired case, closing with the spent case in the chamber. This is the type of malfunction which most frequently occurs in the rifle....[snip]
[causes]
a. undersized piston
b. oversized gas cylinder
c. undersized barrel at splined section
d. carbon or foreign matter in gas port of barrel
e. carbon in gas cylinder
f. operating rod binding
g. valve leak in gas cylinder lock screw
h. defective operating rod spring
i. bolt binding
j. foreign matter, burrs, and improper lubrication
k. rusty or ringed chamber
44. failure to feed
Feed failures, as in the case of short recoil stoppages, may cause the weapon to close on an empty chamber. This may be caused by excessive bolt speed, when the bolt moves so rapidly on the forward stroke that the ammunition does not have time to attain the proper feed position. The condition is often caused by unauthorized modification of the weapon, such as increasing gas port diameter. It may also be caused by any of the following reasons:
a. insufficient rearward travel for bolt to pick up next round due to short recoil (see paragraph 42)
b. long ejector
c. worn or improperly formed follower