Question on bore sighting a M4

[wagon]

I bought this new-to-me CMMG M4 14.5" + FH, it has a FSB and a MBUS at the rear. When I was playing it with my bore sighter, I noted that @ 25 yds, the laser dot sits BELOW the FSB.

It makes me wonder if the BUS has ever been sighted in? Does it sound "normal" in the land of M4?

Or should I adjust the front sight down until the dot is right above the front pin?

Just try to save some ammo here ...Thanks in advance

[ucrt]

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I've never really had good luck with bore sighters.
I thought the cartridge-type laser BS would be the end-all. I bought one and bore sighted a deer rifle at 25-yards and then tried to shoot it at a 100-yards. The rifle wasn't even on the paper. So, much for saving ammo.

I guess if the laser isn't perfectly centered in the "cartridge" there is enough play in the bore to be off at a 100-yards.

Now, I "bore sight" by putting my upper on sand bags and look down the barrel at a target and adjust the sight accordingly. I've done it successfully at a 100-yards but itis kind of tricky. I generally do it at 25 to 50 yds. without fail.

But maybe its just me...

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[wagon]

Agreed, I don't expect the bore sighter can replace actual sight in. I have one of those cartridge-type from Cabela's, I have used it in my Mini-14, I first bore sighted it @25yd, follow by actual sight-in @ 25yd. Did you skip the actual 25 yd sight-in step completely?

Or may be I just got lucky with the set of bore-sighter that I have.

[ucrt]

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I bore sighted w/ the laser at 25 and went to a 100 to shoot. To me, if that doesn't work, what good is the bore sighter...it isn't saving any ammo??

On sandbags, I can line a target up in the center of the barrel at a 50 yards and I've always hit the paper. You have to back up 2' or so and move your eye around to get the target centered in the bore but it isn't too bad.

I've done this the most with scopes or RDS. It is a little harder with open sights because you don't have a cheek weld.
With a scope, RDS, or open sights, the hard part is to not move the upper on the sand bags while you adjust the sights. Next to impossible to do but if you move it (which you probably will) just line it back up.

If I take my time, I can use this technique at a 100-yards and hit the paper. The last time I did this sighting in a scope on an AR, I backed up about 2'-3' looking down the bore and managed to hit a 4" bulleye at a 100 ... but I wouldn't bet I could do that again.

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[wagon]

That's very cool, ucrt. I may try that this time.

[Jay Cunningham]

I bought this new-to-me CMMG M4 14.5" + FH, it has a FSB and a MBUS at the rear. When I was playing it with my bore sighter, I noted that @ 25 yds, the laser dot sits BELOW the FSB.

It makes me wonder if the BUS has ever been sighted in? Does it sound "normal" in the land of M4?

Or should I adjust the front sight down until the dot is right above the front pin?

Just try to save some ammo here ...Thanks in advance

Dude, don't use those stupid things.

Take it to the range and sight it in. Take your pick - but 100 yard zero is good. Get it on paper about 1.25" below POA at 25 yards, then confirm at 100.