Why the heck is the first round out of my gun always dropping the shot 1-2mins low???
Shooting a AR10....the rifle groups3/4moa solid but when I first load the mag and release the bolt stop there is always a flyer....

I would give it 99% odds that it is you and not the gun. I can usually be counted on to throw one curveball myself and have know several people that do the same with certain rifles.

The first round out of each mag, or the first round of the day?  I remember our DM's talking about hot and cold barrels.  I don't know anything about it, so if anyone does know the answer I'm all ears.  

its the first round on each mag reload...clean or dirty is consistently low. If its becaus how much force the bolt is traveling when you release the bolt stop then whats the best way in releasing the bolt???

When the gun cycles...does the bolt travel faster or slower then when you release the bolt stop?...as opposed to pulling back the charging handle etc...

Quoted: I would give it 99% odds that it is you and not the gun. I can usually be counted on to throw one curveball myself and have know several people that do the same with certain rifles.

+1

Sorry...but its not me...its a repeatable phenomenon. 1st round of every mag...

Load a Mag and hit the Bolt release,  then drop mag and pull charging handle slowly to eject round.  Check for damage to round...???  Just a thought

Ricky

I have been hitting the bolt release for the first round for over twenty years and I have never noticed any accuracy difference in releasing the bolt release to strip a round as opposed to the bolt carrier cycling via the gas system. If it were an issue of releasing the bolt stop affecting accuracy on that first shot, I would be concerned about safety. If it is only the first round every time stripping a round out of the mag that causes an accuracy problem, I would be concerned about bolt lockup.

First thing I would do is check a series of magazines to determine if it is a magazine issue. I would check to see if the follower is bad, hanging up the bolt hold open causing the rifle to not lock up properly. I would also check the bolt release to make sure it isn't snagging the bolt carrier on a full mag causing a bad lockup problem. I'd check for sheared off bolt lugs and bolt cam pin hole wear/cracks as well.

If your barrel is clean on the first few rounds, it will not print where the rifle is zeroed until the barrel is warmed up and just a little dirty. A cold barrel will print differently than a warm barrel.

I would bet any amount of money this is a case of you flinching and being a little anxious when you take your first shot. After three or four rounds, the brain will adjust to the chaos involved in rifle fire and you will calm down. I have seen this MANY times and after many years of rifle shooting, if I am not calm when I place my first shot or if my mind is elsewhere, like stressing about work, it will affect my shooting. Ruling your shooting out as the possible cause so fast will not wear well will experienced rifleman. EVERY rifle I own is a better shooter than I am.

The Oly Ultra Match I had always threw the first round. It wasn't much, about 3/16" on average high and right. If you are doing groups, either single load or hold off for the first.

To see if it's a bolt lock up problem, fire 29 rounds from a 30 round mag, switch the safety "on", drop the mag, put a full 30 rounder in, and fire that mag.  That way the bolt won't be catching, and bolt lockup will be consistent all the way through that second mag.  

Quoted: Sorry...but its not me...its a repeatable phenomenon. 1st round of every mag...

ok well then eleminate the one factor that is different on that shot from the rest of the shots then. It is not the barrel temp or fouling or magazine if it is on every mag so you can eleminate that, so try using the charging handle to load instead of the mag relaese. Do this on several magazines. Once you have eleminated that then all mechanical faults are out of the way. Only one thing will be left then.

Quoted: Quoted: .. but when I first load the mag and release the bolt stop there is always a flyer.... Right there. The key to accuracy is consistancy.  My best guess is the foce of the bolt carrier group going forward is different from when it's released from the bolt stop compared to when firing (when the bolt carrier goes all the way to the rear). I'm guessing the minute differences in bolt lock up could be contributing to the difference. Also, if the bore is clean for that first shot you will get a different point of impact compared to a dirty bore(this is well known).   But I'm betting you're also seeing a the 'flyer' on every new magazine?

I suspect all of my AR's do this to some degree but it REALLY shows up in my heavy barrel varmiter.    I have learned to dump the first round from the mag into the berm when I am shooting groups.    I have found a load that will regularly shoot at about 1/2" at 100 yards but the first round is ALWAYS a flier.   It will often throw the last round out of the mag for some reason also.

Consitency is the key to accuracy.   Consistency in ALL steps of the process, from loading to trigger pull to how the gun functions.

Is the barrel nut tight?

Quoted: Quoted: Sorry...but its not me...its a repeatable phenomenon. 1st round of every mag... ok well then eleminate the one factor that is different on that shot from the rest of the shots then. It is not the barrel temp or fouling or magazine if it is on every mag so you can eleminate that, so try using the charging handle to load instead of the mag relaese. Do this on several magazines. Once you have eleminated that then all mechanical faults are out of the way. Only one thing will be left then.

+1

I was thinking both to DM's and Forest's answers.  Eliminate all everthing you can, and what's left over is the cause.  It's not heat or the groups would fly at the end of the string.  It's not mechanical or you'd see fliers randomly as your mechanical conditions change.  It's in how the bolt locks up, or how the first shot changes your hold or the rifle's rest.

Fire the first round while aiming it on another space on the target, then place all further rounds where you want them, problem solved.

Well I went out today and shot some more strings...Groups consistenly 3/4moa at 100yards..

BUT...consistently 1.5" low with the first round of the mag....I tried relasing the bolt stop, pulling back the chargin handle and releasing, locking back and pulling the back the handle..etc......different mags....

everything except for riding the handle back into battery....

getting pretty fustrating...

Last week I was shooting this thing at a torso sized steel all day long at 830 yards everytime but that first round...!!!!

Did you try a downloaded mag ?  Put one less than capacity in the mag and see if the lessened spring pressure makes a difference in lockup.

Pull the bolt back and hand load one round through the ejection port.  Load a magazine.  Then start firing.  If this improves the first round placement let the bolt go forward on a round and carrfully eject and mic the bullet seating deapth compared to the others.

These hand loads?

someone said it, but it may have gotten lost in the shuffle.  

Load a new mag while you still have a round in the chamber.  Then when you fire that round the bolt will strip the first round out of the new magazine with a normal cycle.  If that round out of the new mag hits normally, then you know it has to do with the lockup due to dropping the bolt manually.  If the first round out of the mag still hits low, then you know it has to do with the way the mag is releasing the first round and that is causing the issue.

basically..if its a lock up issue then you cant do much about it...? maybe a stronger buffer spring?

If the round is being compressed as it is being fed....what can you do? The problem is that it is consistently 1.5" low......there is such a thing as being compressed consistently that much?

I'll have to bring out a caliper to the range next time but I think it maybe a lock up issue....

Quoted: To see if it's a bolt lock up problem, fire 29 rounds from a 30 round mag, switch the safety "on", drop the mag, put a full 30 rounder in, and fire that mag.  That way the bolt won't be catching, and bolt lockup will be consistent all the way through that second mag.

Try what this guy said.

IMO it's you and not the gun.