Peculiar 1st Cold-barrel Shot

3deers · Nov 6, 2015

I have a peculiarity with a particular rifle, a semi-automatic Browning BAR that I have owned for many years.

Most groups with a given ammunition (usually I use Remington Core-Lokt 180g - 308 Win -- but the same phenomenon happens with other ammo) will print shots #2, 3, 4, and 5 of a 5-shot group into a 1-1/2 inch group, sighted in for 2 inches high at 100 yds. The very first shot, however, almost always prints 5 inches low, and a couple inches left. If I immediately shoot a second 5-shot group, all five shots will group. If I let the rifle cool completely (like a 1/2 hour) the same low-printing 1st shot often happens again.

Has anyone ever heard of this? Can anyone offer an explanation, or a fix to this problem?

truck driver · Nov 6, 2015

I saw this also out of a clean cold barrel and one of the guys suggested that there was oil in the barrel and to wipe the barrel dry with a degreaser before shooting. I did that before my next range day and it grouped just fine.

Anonymous · Nov 6, 2015

I've seen this before, the issue is that you manually chamber the first round, the other 4 are cycled by the semi auto action.

When you chamber the first round just hit the bolt release and let the action do the work, if you ride the bolt it will make the issue worse. Not that unusual with semi auto guns.

ElmerThud · Nov 7, 2015

I don't know about semi-auto rifles, but I've had this with bolt action rifles & my K95...since I started running a meths soaked patch through & clearing the barrel of any oil/solvent residue, the problem reduces significantly.

Not sure how a carbon fouled barrel can produce the same phenomenon though. I've not had that happen, but Hodgemans explanation seems logical to me.
Cheers, ET

preacher · Nov 9, 2015

Yep, it's mainly the difference in the chambering action. On my older Belgium made BAR 270 ( which has no bolt release lever) I have to bring the bolt all the way back and let it go to chamber that first round. If I ride it in, it may not even lock into battery and if it does it throws it out of the group. I had an accurized Mini 14 that no matter what you did , that first round went 6" out, then the rest went into 1.5". I sold that thing.