What does temp stable mean?

At -40, It's closer to .001" on a 1.00" diameter object. Which will actually generate more pressure. More so on 416r stainless.

When I shoot the old .283" Norma bullets in my 7mm WSM, and I shoot the exact same bullet, but the newer .284" diameter bullet. The newer one creates more pressure with the same powder change.
 
Alot of CNC mills use thermal expansion to hold the endmills/cutter in the tool holder now. Nothing more than heating the holder, placing the tool in, cooling it off, then chucking it up and using it. You can use it in manual mills as well. Has very minimal runout, and uses the same principle of thermal expansion.

Holding your micrometer the wrong way, or too long results in a improper reading as well. Metal contracts and expands way more than you think. And a typical mic only ready down to .0001. the larger the mic, the more it changes, and the more improvement it is to use it right, and have the environment you are in temperature regulated.
 
https://x.com/i/grok/share/AIsKGHxPliqqjtqlEFtFmxhGj

Denver Steve - That is really interesting that such a method is used to chuck tools - so simple, and similar to the blacksmith putting the rim on a wooden wheel. I wonder if a metal which has a lower coefficient of expansion would grip tighter because of the range of expansion would be less. (Just a silly wonder).

Also I wonder if pistons of aluminum and blocks of cast iron change enough in size from temperature change to make any difference in how they turn over in the cold - I suspect that being hard to start has a whole lot more to do with the type of lubricant - so I'm suspecting that the same goes for barrel bore - It could even be that copper jackets are more or less slippery in cold. There might be some simple explanation for the occasional increase in velocity in cold. I notice that near the muzzle is the place for barrels to rust because of moisture - which would be from water condensing inside the barrel - usually less than two inches, but I suppose that it could get in further and freeze as a hoarfrost ( like frost on an extension cord) - even a very thin frosting might allow the bullet to accelerate at a higher rate for the last inches of the barrel - but that would affect only the first shot. I can experiment with this - breathing down a cold barrel before shooting over the chrony.

As a rule, any rule we make has weaknesses - requiring that we admit weakness in understanding - my supposings are more wrong than right - so real data like we saw early in the topic is great stuff to listen to.

And I'm off to get the sleds fired up for when the grandkids come.
 
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I found the one test I did with my 7-08 that I lost 30fps from 70F to -10F with WW760, wasn't overly concerned about that for inside of 300yds. Was surprised to see how many of Todd's tests increased in the cold. Seen people talking more about speeds increasing with heat than I ever have with cold, in various posts on the subject, especially with stuff like pierced primers and whatnot related to pressures. Something of an endless argument once again, different expansion and contraction rates on barrel materials, bullet materials, powder moisture content, primer vs load size vs temp and so many variables involved, that it's probably a mostly unsolvable question. All you can really go by is the empirical data, and that's pretty thin pickings when it comes to cold weather and a large variety of powders.
 
some updates from recent shooting in -12c (ammo was left outside for a few hours before shooting when temp was -17c) Velocity measured with Garmin Xero

22 ARC 88 ELDm / N550
+24c 2860 fps
-12c 2804 fps
- 1.6 fps per degree

6mm ARC 100gr TGK / Leverevolution
+28c 2820 fps
+15c 2752 fps
+3c 2734 fps
-12c 2718 fps
- 2.5 fps per degree

6mm Creed 109gr ELDm / RL23
+21c 2838 fps
-12c 2850 fps
- 0.4 fps per degree

6mm Creed 110gr SMK / Ramshot Grand
Summer testing to come
+3c 2896 fps
-12c 2914 fps
- 1.2 fps per degree

6.5 Grendel 120tgk / Alliant AR COMP
+28c 2502 fps
+7c 2517 fps
-12c 2522 fps
0.5fps per degree

260 Rem 120NBT / Alliant RL16
Summer testing to come
+14c 2911 fps
-12c 2915 fps
0.2fps per degree

5.56 Ruger 40gr SBK / Dominion 8208BR
+28c 3434 fps
+5c 3408 fps
-12c 3329 fps
2.6 fps per degree

5.56 Ruger 55 Vmax / Dominion D8208BR
+28c 3004 fps
+5c 2919 fps
-12c 2957 fps
1.2 fps per degree

280Ack 160gr LRX / RL26
Summer testing to come
+14c 2821 fps
-12c 2824 fps
0.1 fps per degree

280Ack 165gr TGK / Viht N555
+28c 2776 fps
+12c 2774 fps
-12c 2748 fps
0.7 fps per degree

280Ack 190gr ATIP / Viht N565
+21c 2623 fps
-12c 2612 fps
0.3 fps per degree

308 Win 165gr NAB / RL15
+16c 2659 fps
-12c 2616 fps
1.5 fps per degree
 
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