H4350 weird velocity

[King_beardsly]

I have a feeling something went terribly wrong with my hand load. I loaded up some loads about a month ago and finally shot them yesterday to finish off my load development and things got a little weird. I shot the same charge weight when it was roughly 45 degrees out and got an average of 3056, any yesterday it was right around 85 degrees yielding an average of 3141. I'm know the h4350 is apparently temp stable but an 85fps swing over 40 degrees seems a bit extreme and I think there might be something I'm missing.

 

[Milo 2.5]

Did it dawn on you to not fire at least one to pull and verify charge weight?

 

[King_beardsly]

I didn't notice the huge swing until I was inputting all the data into excel to keep track of all my load data and saw the huge swing in velocity. I'm thinking I should have gotten a temp reading off the ammo since it got left in my truck for several hours before I could get to the range.

 

[spife7980]

You got 85 fps difference over 40° for 2.125 fps/°

Ive gotten 61 fps over an 85 degree swing for .72 fps/°

You are getting a good jump in velocity there but Im not certain its all due to temp.



I suspect that you got a bit more neck tension/bullet grip adding into the system after the period of time due to brass hardness/spring back and/or bullet welding.

I know Ive had rounds that shoot noticeably faster after they have been sitting on the shelf for a bit. Doesnt happen to me every time but it has happened often enough that I try to not shoot ammo thats been sitting for a long time in any event I would care about scoring highly in.

Some people think its voodoo but I think that a bit of galvanic corrosion/electrolysis/cold welding etc is going on.

Load a few of them up again and see if its shooting like it was before or if they are still shooting faster.

 

[Milo 2.5]

I didn't notice the huge swing until I was inputting all the data into excel to keep track of all my load data and saw the huge swing in velocity. I'm thinking I should have gotten a temp reading off the ammo since it got left in my truck for several hours before I could get to the range.

That may be it, but even if the ammo was ambient temp, you should be able to feel it, and feel if it is warmer still. Ammo itself cools or warms to ambient temps rather quickly, sunlight on it, or on a loaded mag can cause issues.

 

[John Glidewell]

how many rounds down the tube. Could be barrel settling in and speeding up or combination of things already listed above.

 

[King_beardsly]

I'm going to load up fresh loads for this weekend and see where my velocity ends up at. I might of rushed into load development with out enough rounds down the tube, I think I'm sitting around 125 right now and I think I was around 50 with the first round of hand loads.

 

[ShtrRdy]

I suspect that you got a bit more neck tension/bullet grip adding into the system after the period of time due to brass hardness/spring back and/or bullet welding.

I know Ive had rounds that shoot noticeably faster after they have been sitting on the shelf for a bit. Doesnt happen to me every time but it has happened often enough that I try to not shoot ammo thats been sitting for a long time in any event I would care about scoring highly in.

Some people think its voodoo but I think that a bit of galvanic corrosion/electrolysis/cold welding etc is going on.

Any idea what ammo manufacturers do to avoid this ?

 

[spife7980]

Any idea what ammo manufacturers do to avoid this ?

They use more tension so the welding isn’t as drastic of a difference, some crimp, some brass has some sort of waxy film, the weird paints, idk, all sorts of shit. Reloaders use graphite amd mica and moly and so on.

 

[AIAW]

Any idea what ammo manufacturers do to avoid this ?

If you plan on shelving precision hand-loads you could always load as you normally do except seat the bullets out long. When you are read to take them out, seat them to your desired depth. That last seating will break the "weld" (if it formed). Good to go from there.

 

[MangoFett]

I only saw 18fps different between freezing temps and high 90's temps with h4350 in my 260 so I doubt it's the temp.

 

[King_beardsly]

I'm going to have to check through a few things and see if I over looked something simple. I'll load up some stuff tonight and double triple check through everything.

 

[260284]

I'm going to load up fresh loads for this weekend and see where my velocity ends up at. I might of rushed into load development with out enough rounds down the tube, I think I'm sitting around 125 right now and I think I was around 50 with the first round of hand loads.

Both of my Bartlein barrels sped up at 60 and again at 150 or so.

 

[King_beardsly]

I think I found my issue, it seems in my haste to load up ammo I never put into account the possibility of a different length to ogive between lots of bullets. It seems I was jamming the bullets into the lands instead of jumping them, might explain the speed jump and slightly flatter primers.

 

[spife7980]

Pays off to buy in bulk. Eliminate variables where possible.

Also, damn. Lots of variation there. What bullet and how far off?

 

[King_beardsly]

I'm definitely going to buy in bulk next go around. I just measured the new lot of berger 105 hybrids and they have a different of .02 base to ogive.