Loss of velocity with colder weather

Pilotscrappy

Sergeant of the Hide
Jul 21, 2018
111
28
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#1
So I tried searching this and got mixed opinions.

My questions is I chronod my load this summer in about 90 degrees of heat. My velocity on my rounds was average 2730fps.

My load was 140gr eld match over 42.1 gr of h4350. 6.5CM 24" stock barrell on ruger rpr.

I just went to the range yesterday to chrono and it was colder (about 50 degrees) and my velocity has slowed to about 2675 ish.

I thought h4350 was temp insensitive?
Is it normal to slow down that much with cooler weather?

Also do I need to be loading more powder to get velocity back? I'm also wondering if I am now out of my accuracy(speed) node?

I've only been reloading for about 4 months so I'm still learning.

Any help appreciated thx guys
 
Dec 26, 2013
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Edmonton, Alberta, Canada
#2
I ran the same test but all in about 5-10 minutes. I had a control batch, a hot batch and a cold batch. I just used the dash heater in the car and a zip lock bag + ice. I found basically no difference.

My guess is that something else changed between then and now. It my be worth running a similar test just to rule everything else out. Could you have been closer to the lands before? Maybe you need to remeasure?
 

FatBoy

Chris Hayes, Nashville TN
Jul 29, 2001
895
332
63
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Nashville, Tennessee
#3
what chrono? If it's not a magnetospeed are you 100% positive you have it the extract same distance from the muzzle and open the same amount if it's a folding chrono?

Did you change the lot of powder or use different brass?

If you still have one loaded, pull one down and check your powder weight again.
 
Likes: Boss334OP
Dec 1, 2011
316
13
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MN/ND
#4
Should not see that much variation over such a small temp change. I see around 30fps drop between 70* and 0*. (42.3 H3450 140RDF Starline CCI450 @ 2770 *for reference only)
Something else is going on... Moisture or lube causing degradation, maybe? Scale running cold for these?
 

Pilotscrappy

Sergeant of the Hide
Jul 21, 2018
111
28
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#7
Chronograph is a cheap caldwell one.
And also it was very overcast here the other day versus when I did it on a hot sunny day.

In regards to seating depth I have kept that constant I have been seating just over Sammi specs. I'm at coal 2.815 I think? I'll have to look at my notes when I get home.

Also worth noting is I haven't noticed any accuracy changes to speak of, groups are still tight with bullet holes touching each other when I do my part.

Perhaps my chrono was being inaccurate?
 

TacticalDillhole

Standby to get some
Jun 26, 2012
2,951
1,596
113
N. Carolina
#8
Chronograph is a cheap caldwell one.
And also it was very overcast here the other day versus when I did it on a hot sunny day.

In regards to seating depth I have kept that constant I have been seating just over Sammi specs. I'm at coal 2.815 I think? I'll have to look at my notes when I get home.

Also worth noting is I haven't noticed any accuracy changes to speak of, groups are still tight with bullet holes touching each other when I do my part.

Perhaps my chrono was being inaccurate?
Yeah. It’s def the chrono.
 
Likes: Max

FatBoy

Chris Hayes, Nashville TN
Jul 29, 2001
895
332
63
45
Nashville, Tennessee
#9
Probably the chrono. If you had access to 600 yards the same day, you could confirm with the come up.

Once I find a load that works and has numbers I like, I don't ever run it over a chrono again unless something changes in accuracy or Ibhave to change powder, etc.
 

Pilotscrappy

Sergeant of the Hide
Jul 21, 2018
111
28
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#11
So I went to range today and chronod again as it's a sunny day. Still about 50 degrees.

Velocity today was reading around 2715-2720fps

Same exact load /same batch of ammo from last time.
So clearly the chrono was being inaccurate.

Is it super important to have the chrono at the same distance from the muzzle everytime? I haven't been measuring it really I've just been going about 10-12 paces from the muzzle and setting up the chrono. This could be another reason of the inconsistencies?
 

TacticalDillhole

Standby to get some
Jun 26, 2012
2,951
1,596
113
N. Carolina
#12
So I went to range today and chronod again as it's a sunny day. Still about 50 degrees.

Velocity today was reading around 2715-2720fps

Same exact load /same batch of ammo from last time.
So clearly the chrono was being inaccurate.

Is it super important to have the chrono at the same distance from the muzzle everytime? I haven't been measuring it really I've just been going about 10-12 paces from the muzzle and setting up the chrono. This could be another reason of the inconsistencies?
I’ll be real honest, Caldwell stuff is pretty much junk. Invest in a magnetospeed if you can. It will do you so much better. Even better would be a labradar but that’s pricey so I’m not trying to spend your money but the MS is pretty much the minimum I would recommend. The optical chronograph are just to finicky and subject to a lot of atmospheric interference
 

FatBoy

Chris Hayes, Nashville TN
Jul 29, 2001
895
332
63
45
Nashville, Tennessee
#13
It's pretty important to have it the same and square to the muzzle. I like 10' on non-magnums or magnums with a can. 15' for magnums without a can.

Light is also important, but I don't see a cloud making a 100fps difference.

I use an Ohler 35p and have zero issues.
 

Pilotscrappy

Sergeant of the Hide
Jul 21, 2018
111
28
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#14
I’ll be real honest, Caldwell stuff is pretty much junk. Invest in a magnetospeed if you can. It will do you so much better. Even better would be a labradar but that’s pricey so I’m not trying to spend your money but the MS is pretty much the minimum I would recommend. The optical chronograph are just to finicky and subject to a lot of atmospheric interference
Yeah I figured the caldwell was pretty much bottom of the barrel. Considering I spent like 60$ on it. Anything quality in our sport seems to be expensive.

I have shot with guys @ the range who were using the Labradar and it's a super nice setup.
I've never seen the magnetospeed In person, I'll have to check those out and do some research if I want that or just save for the Labradar.

I honestly bought the caldwell just so I could get rough numbers on my rifles.

But thanks for the info, Def seems like my chrono is lacking and that should be a upgrade I will need to do.
 

Pilotscrappy

Sergeant of the Hide
Jul 21, 2018
111
28
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#15
It's pretty important to have it the same and square to the muzzle. I like 10' on non-magnums or magnums with a can. 15' for magnums without a can.

Light is also important, but I don't see a cloud making a 100fps difference.

I use an Ohler 35p and have zero issues.
Good to know, I'll start measuring when I set it up and see if that helps with my consistency on the unit.
 

Max

Descendant of John Adams
#16

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Max

Descendant of John Adams
#17
I’ll be real honest, Caldwell stuff is pretty much junk. Invest in a magnetospeed if you can. It will do you so much better. Even better would be a labradar but that’s pricey so I’m not trying to spend your money but the MS is pretty much the minimum I would recommend. The optical chronograph are just to finicky and subject to a lot of atmospheric interference
Since owning a magnetospeed, I am so over regular chronos. I found them to just be a pain in the ass....
 

Max

Descendant of John Adams
#19
There are good ones and if you are good, you can get downrange velocity if you can shoot through it without killing it.
I had a good one. A CED. It even spoke. The problem was setting it up, not shooting it (I never did) , light conditions and the Wyoming wind blowing it over and breaking the freakin “sails”. I mean seriously what a freaking hassle. I’d get to the range early then realize there was not enough light. Then the wind would kick up or clouds would roll in or too much sun. The magnetospeed it just so easy by comparison.