Temperature readings were taken with a cheapo laser thermometer I bought at the local auto parts store. It might be accurate and shows a reading of somewhere between 94 degrees and 98 degrees on bare skin. Probably accurate enough for its intended use.
Temps were taken in the same spots on both guns. Both guns were measured before and after firing. For the sake of continuity, I tried to get readings off the same spots on the two different guns. Upper temps were taken on the right side of the receiver in front of the ejection port. Bolt carrier temperatures were taken with the carrier still in the receiver through the ejection port at the scallop that clears the dust cover. Temps on the bolts were taken with the carriers removed but bolts still in carriers. Temps were taken on the top of the bolt at 12:00.
I started with a Colt M4 (SOCOM fat barrel) and my Ruger SR556C. Both guns were measured at the barrel at an external temp of 73.5 degrees.
I started with the Ruger on the Colt F/A lower. I ran one mag on full-auto, locked the bolt open and took temperature readings. I then let the gun sit with the bolt locked open for thirty seconds and then took a second set of readings. I did this for a total of five magazines.
I then put the Colt lower back on the Colt and repeated the above.
After this, I allowed both uppers to cool and then fired 90 rounds through both guns on full-auto. The guns were then set aside for one minute with the bolts locked open before temps were taken.
Please note that I didn’t have the time or the ammo to try this with the HK416. I hope to have a chance for the same test(s) on Tuesday.
Here's what I came up with:
First column after firing, second column after sitting for thirty seconds.
Colt M4
And the same measurements on the RugerCode:Mag 1: Flash hider 141 88 Barrel 86 89 Gas Block 103 109 Upper 82 85 B/C 83.5 84.5 Bolt 90.5 84.5 Mag 2: FH 120 95 B 100.5 90.5 GB 136 141 U 96 99 BC 95 96.5 B 111.5 94 Mag 3: FH 136 123 B 115.5 89.5 GB 138.5 156 U 103.5 109 BC 106 106.5 B 121.5 108 Mag 4: FH 165 132 B 136.5 123 GB 179.5 157 U 115.5 118 BC 115 115.5 B 124.5 112.5 Mag 5: FH 164 143 B 151 135 GB 183 179.5 U 123.5 125 BC 121.5 121.5 B 126 119
Finally, both guns after ninety rounds and then a 1-minute cooling period:Code:Mag 1: FH 82 87 B 113 122 GB 104 120 U 76 74.5 BC 78 74.5 B 78 74 Mag 2: FH 95 90 B 150 96 GB 121 116 U 77.5 81 BC 79 83 B 77 75 Mag 3: FH 117 106 B 146 156 GB 174 166 U 83 89.5 BC 84.5 89.5 B 76.5 75.5 Mag 4: FH 124.5 123 B 156 216 GB 165 214 U 96 93 BC 91 93 B 80.5 79.5 Mag 5: FH 120 106 B 203 198 GB 168 208 U 90 94.5 BC 94.5 98.5 B 87 85
Code:Colt Ruger FH 317 340 B 349 360 GB 258 278 U 135.5 106.5 BC 109.5 77.5 B 90.5 77.5
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Originally Posted by ForTehNguyen
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