A law enforcement officer has fired 1.000's of  rounds through 4 magazines on full auto without a failure, yet when he fires short bursts he experiences jams and bolt problems. Anyone have any suggestions? Thanks in advance for your help.

CP

Stronger mag spring needed.

Quoted: Stronger mag spring needed.

ditto on the stronger mag spring, either SAW red or Wolff Exta Power

Quoted: A law enforcement officer has fired 1.000's of  rounds through 4 magazines on full auto without a failure, yet when he fires short bursts he experiences jams and bolt problems. Anyone have any suggestions? Thanks in advance for your help. CP

Need more details.  What kind of malfunctions?  F/T eject, F/T extract, F/T feed, etc.  What configuration is the weapon?

Don't laugh....but, It likely is the way this individual is holding/shouldering the weapon

Hotgun

My LMT wasn't getting enough gas and acted like that.  

That could be a need for new gas rings on the bolt or a FSB installed in such a way that it partially covers the gas port.

Hotgun- no chuckles here- I'm the guy in question.hough,
I shoot a rifle match that requires five rounds per magazine, in the positions of standing, kneeling, sitting and prone.  The gun is kept on semi auto for the firing.  Last summer I started having problems with two magazines- early Brownell's manufacture, and well taken care of.  I started having failure to feed and eject issues with the magazines.  They were marked and set aside.  One of the other good ones started doing the same thing- failing to feed properly, round partly fed out of the magazine, ejection issues- the next round being fed into the gun was getting in the way of the extracted case, and I forgot to add that the bolt was not being held back from all three.  All of the problem magazines drop free from the gun.

The match after I shot with different magazines (same manufacturer) and had no problems at all.  

My inclinations are followers followed by the springs.  

The gun in question is a Doublestar 20" HBAR A2 style, Miculek comp.  The problems have only happened a handful of times- enough that I have concerns over the magazines.

Now the kicker of it- the magazines work fine in my M4 Commando on full auto.  I would figure problems would show up quicker in FA than in semi.  No feed/ eject/ bolt closure issues- worked like they should.  No mag dumps, just 2-6 round bursts fired.  No problems.  A couple days later, same problems revisited in the other gun.  

Any thoughts and advice are appreciated.  The problem mags are being kept out of rotation until they are fixed- and will probably be range mags after this.

Two different rifles......not quite what I believed, based on the initial post. What I described can easily happen with FA guns in some (even experienced) hands.
With the second weapon added, of course some mechanical discrepancies possibly arise (Colt vs. other). Feeding the last few rounds of a magazine is sort of an acid test for the magazine, so this scenario adds a twist. My conclusion is that the combination of the xyz weapon, along with possible characteristics of the early mfg. mags are = problem with the xyz rifle. IE, I suspect the mags, but the rifle's characteristics (possibly ammo) are likely contributing.

Best I can do from here.
Good luck,
Hotgun

Gotcha.  Another possible cause (?):  the Doublestar has an extended bolt release installed, DPMS manufacture.  It's the model with two pads.  

A couple of other guys I shoot with have not been able to get theirs to work properly. Noticed tonight that there is some play in it.

Could be fouling in the magazine, considering it;s an SBR.