Cold weather vs. Bullet hardness

[Hobbyman2007]

I did some shooting today with some 30 grain BBt’s In .22 cal. At the start of the session the groups were the usual 2+ inches at 50 yards . After the rifle and bullets got down to the outside temp my groups began to shrink . I’ve been using 40:1 lead tin mix . Does it make sense that lead would get harder when cold and would act like a harder bullet ? It was the best these BBT’s have ever performed and I’m starting to think they would shoot better with a harder bullet. Has anyone experienced this before . Here’ s apic of 100 yard target. Looks like I need to replicate whatever I did today .

[Bob H.]

Twenty years ago,  back when I was shooting a lot of cast bullets, I had many questions about cast lead.  I will tell you to do what I did,  I acquired a lead hardness tester.  Lead is a fascinating study, it has odd traits.  Lead hardens upon impact and within an hour the hardness will start to recede.  It does other strange things. 

BTW, I recommend testing samples of lager size,  I made a mould that would cast samples with draft 1/4" thick about 1" in diameter.

You are going to hate yourself and me for telling you to pull on this loose thread.  But,,,you will learn a bunch.

BobH.

[Ribbonstone]

Lead does odd things.

Use to be (and still can find it in the Lyman manuals) where casting with different hardness of lead would result in different diameters once cooled.  AHrder being larger than softer.

And running the same slugs though a sizing die would result in slightly larger sized bullets (again. harder being slightly larger).


Not that little bit of difference (normally in the 3rd or 4th decimal place...like something in the 1000ths/10000ths) didn't make a rat's rump when kicking them in the arse with 20,00psi (black poweder) or 50,000 psi.


But I will agree, it can make a difference when all you are booting them in the butt with is 3,000psi.

There just sin't a whole lot of obturation going on in solids based airgun slugs...so better to get them right to start with.

[pecor]

Expansion and Contraction of 2 different metals https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

[skorec]

They can be also other reasons to change group size and POI.
https://www.gatewaytoairguns.org/GTA/index.php?topic=139381.msg1407548#msg1407548

[KnifeMaker]

I don't think it would be noticeable in temp's we would be happy to live in.

I would suggest going to cast boolits  lot com. (Yes,that's how they spell it there LOL)!

Pose your question there where the experts know a thing or two about lead, and its various properties both with and without alloys.   

Knife

[Kinetic45^]

I'm going to say that between the temperature range of -50 F and 120 F that a human being might be out in, there will not be an appreciable difference in lead hardness.
You might as well wonder if a cold barrel was tighter than a hot barrel.

I wonder about 2" groups at 50 yards and think you need to look at what is causing that, rifle or bullets... and hardness would be way down on the troubleshooting list..

[pecor]

I'm going to say that between the temperature range of -50 F and 120 F that a human being might be out in, there will not be an appreciable difference in lead hardness.
You might as well wonder if a cold barrel was tighter than a hot barrel.

I wonder about 2" groups at 50 yards and think you need to look at what is causing that, rifle or bullets... and hardness would be way down on the troubleshooting list..

                                                                                                                                                                                     
                                                        X2 I Agree!    Coming from the Rim-Fire bench rest background we always let our guns and ammo come up or down to existing temps. Then Tune