[swimmer]

The wire for this circuit is 14AWG.
It is about 30 feet max to walk from the panel to the last outlet but I suppose the cable length is much longer.

 

[swimmer]

Did you check the voltage at each receptacle along the way while the heat gun was running? I'd be curious as to what the voltages were along the run.

With the 13A heat gun in the last outlet, there is approx 1.0 to 2.5 voltage drop between outlets as you walk from the panel towards the last outlet

 

[swimmer]

vd = 2kil/kcmil = 2*12.9*13*l/6530


2.5 = 2 * 12.9 * 13 * l/6530

solving for l (the distance)

l=48' between receptacles (if I did the math right)


since you said you had approx 8' between receptacles,
the resistance seems to be 6x what it should be.
are the conductors severely degraded/corroded at the
splices (high resistance connection ?)

also might want to check my math (been a while since I used
that forumula)

Chap 9 Table 8 of the NEC lists the circular mils of #14 copper as 4110. I'm not sure where you got 6530.
So L = (4110 * 2.5)/(2*12.9*13) = 30.64 ft.
I don't usually do this without carefully listing units but I followed the example on http://www.mikeholt.com/technnical-voltage-drop-calculations-part-one.php and got the same results.

 

[swimmer]

I must have been using the online voltage drop calculators incorrectly yesterday.
I used 3 different calculators today and used the formula Vd = 2*K*Q*Amps*D/CM
Vd is in volts
K = 12.9 ohms
Q is approx 1.0 for conductors smaller than 1 AWG
Amps = 13A
CM = 4110 (Chap 9 Table 8)

Solving for distance, the formula and the calculators all give a approx 8% drop for approx 125 ft. As has been noted, 30 feet from the the panel to the far bedroom could use 125 ft. of cable.

So 8% voltage drop for 13A on 125 ft of 14AWG cable is to be expected