264 WM heavy bolt lift

[bigedp51]

He had hard bolt lift with ONE cartridge. He also said that cartridge had something on it.
I have traced, both 180gr BT'S and 180gr Accubonds with identical loads, no significant difference in pressure was noted, in my rifle.
There are more causes for hard bokt lift than just the brass expanding, a cratered primer can cause hard bolt lift, oil, grease etc etc.

lightbulb

And since the OP is the only one with the rifle and case in his hands the rest of us are only guessing as to what the actual problem is.

Below was published at the CMP website and explains why oil or grease increases chamber pressure. But I do not think the OP dipped his cartridges in resizing lube.

When the "Tin Can" Changed History by Dick Culver

http://www.odcmp.org/1101/can.pdf

 

[AG74]

I'm the OP and went back out yesterday to determine if case lube was indeed the problem, or not.


I first gave the chamber and bore a good cleaning to establish there was nothing on the chamber walls, nor an excess of copper buildup in the bore.

I fired three rounds of Nosler Custom ammo in 130 NAB. Advertised velocity from Nosler is 3100, they clocked in at about 3000 in my rifle. I used these three rounds to establish a baseline for velocity, accuracy, and bolt lift, fired brass condition, etc.

I let the barrel cool and fired three of my 140 NBT cartridges. All three were examined to ensure no lube, grease, etc remained. I chambered and ejected all three prior to firing, to ensure there were no problems.

All three clocked in at 3200+/-15 and shot a group comparable to the Nosler custom ammo, just over 1" at 220 yds.

Bolt lift on #1 was stiff, #2 was normal, #3 quite stiff.

No other signs of over pressure on the cartridges themselves to indicate flow. Primers normal, no ejector marks at all, etc.

The only anomaly in the cartridges I can think of is that some of these have been once fired and neck sized, the others (about half) have been fired twice and neck sized both times.

My thought is that the twice fired brass expanded to the chamber size twice, and on this third firing lacked the elasticity required for normal extraction.

Thanks for the input on this problem; I think FL resizing the brass and backing off the load a grain or two is in order.