#2358657 - 08/08/08 07:23 AM
a 470 range report - getting it dialed in
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UtahLefty
Campfire Kahuna
Registered: 03/18/06
Posts: 15780
Loc: Northern Utah
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This is with a Heym 470 using 500gr Woodleigh WCs and Norma brass,
Fed 215gm primers and H4831 (I like it because it fills the case and because I have a bunch of it on hand for the 416 and 270s).
Mostly I've been doing regulation testing and some windage drifting here and there.
What I've found after 50-60 rounds is that it's not too picky on the lower end of velocities- giving reasonable groups with several charge weights but once you get close to the crossing point, any little variation tends to give erratic grouping.
It also appears the charge/velocity relationship is quite linear (at least in the middle) giving pretty much 5-7 fps/grain change.
this is a 102 & 104 grain mixed target:
and here is 106 gr
the velocities:
102 = 2015 1.7"
104 = 2022 1.5"
105 = 2029 1.5"
106 = 2034 1.2"
107 = 2042 1.5" (?)
108 = 2050 crossed -2.0"
These have all been at 50yds (the stated regulation distance)-- I need to move it back now to 100 as I'm a little suspicious that 106 gr load may cross there.
I also need to get some idea of temperature sensitivity of H4831 as it appears a jump of as little as 20-30 fps could muck things up (tests so far have been at 50-58* F) Denton has graciously volunteered to donate his math skills once I get the data.
well, that's where I'm at so far....
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#2358662 - 08/08/08 07:26 AM
Re: a 470 range report - getting it dialed in
[Re: UtahLefty]
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hillbillybear
Campfire 'Bwana
Registered: 12/31/02
Posts: 11873
Loc: Western NC
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Good shooting , especially for a gun with that kind of recoil.
_________________________
"Yesterday is history,
Tomorrow is a mystery,
Today is a gift."
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#2358802 - 08/08/08 08:55 AM
Re: a 470 range report - getting it dialed in
[Re: hillbillybear]
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Roscoe
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Registered: 02/23/07
Posts: 56
Loc: Arkansas
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Good data. Let me know what your case life is with the norma brass. I had case separation problems in the past after only 2 firings.
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#2370129 - 08/14/08 11:05 AM
Re: a 470 range report - getting it dialed in
[Re: Mssgn]
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atkinson
Campfire Ranger
Registered: 03/04/01
Posts: 1769
Loc: Filer, Idaho, USA
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Your regulation is fine and its a shooter for sure, now all you have to do is sight it in.
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#2373956 - 08/16/08 11:23 AM
Re: a 470 range report - getting it dialed in
[Re: atkinson]
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toltecgriz
Campfire Tracker
Registered: 01/09/06
Posts: 7347
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H4831 is pretty stable. 4831SC slightly moreso. Unless you can coax a variance by heating, I wouldn't worry about it.
_________________________
"Be sure you're right. Then go ahead." Fess Parker as Davy Crockett
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#2375333 - 08/17/08 09:15 AM
Re: a 470 range report - getting it dialed in
[Re: toltecgriz]
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atkinson
Campfire Ranger
Registered: 03/04/01
Posts: 1769
Loc: Filer, Idaho, USA
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You have it down pat, quite messing with it and knock the sight over a tad and go shoot something..It won't get any better than you have it, don't change anything...
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#2376844 - 08/18/08 07:47 AM
Re: a 470 range report - UPDATED DATA
[Re: toltecgriz]
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UtahLefty
Campfire Kahuna
Registered: 03/18/06
Posts: 15780
Loc: Northern Utah
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tolt - I've learned from Denton that a (temperature insensitive) powder can be predicted to be insensitive only in the cartridge it was originally designed for. Any other cartridge the powder may prove useful for is a crapshoot - may not be sensitive, may be a little or a lot sensitive.
Also, barrel temperature is the key - not ambient temp or ammo temp.
I shot yesterday at 98* barrel temp (measured) and the "good" load crossed -- badly.
We've run a series of experiments chronographing pairs of loads at different temperatures (45*, 56*, 58*, 98*) - about 60 rounds in all.
then Denton worked his magic with the statistical analysis.
the skinny on H4831sc in (my) 470 NE:
-no statistical difference between barrels
-STD Deviation of 31fps MV
-1 grain of powder increase = 33 fps increase
the biggie:
temperature coefficient of (1.4)fps/degree F >> raise temp 1 degree = raise velocity 1.4 fps
in other words, +/- 24* F = +/- 1 grain of powder
For example, if it should happen that your max charge is 108 grains at 32 F, and you want the same performance at 92 F, you've got a 60 degree difference and need to reduce the charge by 60/24=2.5 grains, putting you at 105.5 grains.*
*special thanks to Denton for his letting me borrow his brain for a bit.
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#2414435 - 09/05/08 07:30 AM
Re: a 470 range report - the Latest
[Re: UtahLefty]
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UtahLefty
Campfire Kahuna
Registered: 03/18/06
Posts: 15780
Loc: Northern Utah
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well, I'm about out of testing time this season - get to hunt in 5 days.
I've settled on
104gr H4831sc for a temp range of 40-110*
106gr H4831sc for a temp range of 10-60*
(both work reasonably well in their temp range without crossing)
and it looks like I've got it pretty well sighted (these standing at 50,75,100,100 yds) I hope to use in on a moose hunt in a month
still to do:
-get a load for the solids
-check powder lot variation
-get a practice load (495gr HC + AA5744)
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#2423606 - 09/09/08 09:41 AM
Re: a 470 range report - the Latest
[Re: 340boy]
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atkinson
Campfire Ranger
Registered: 03/04/01
Posts: 1769
Loc: Filer, Idaho, USA
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Next time you get a chance use IMR-4831...It is a better double rifle powder than H-4831 in most every double that I have used it in....I also like RL-15 with a dacron filler...
I have shot a lot of Cape Buffalo with my reduced load of 85 grs of RL-15 and 5 grs. of Dacron at 2020 FPS with either a 500 gr. Northfork soft, cup point or Woodleigh softs and solids..It just hammers them and is mild of recoil... I also used the GS Customs flat nose solids with great success with this load...
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