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7 mag reloading conundrum?

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Old 07-10-2011, 07:32 PM
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Join Date: Sep 2009
Location: Washington
Posts: 650
7 mag reloading conundrum?

I was testing 7 rem Mag loads today and had something weird happen. I was testing 140 gr Berger vlds and working my loads up. I started with the all loads .010 off the lands so oal to ogive was 2.650", all loads are using h1000. First load was 67 gr and velocities were 2715, 2732, 2743. Load 5 69.8 gr velocities 2930, 2930, 2956 and no pressure signs. Load 6 70.5 velocities 2982, 2969, 2969 no pressure signs. So everything is looking good. Test load 7 at 71.2 velocities at 2048, 2020, 2048 what the heck is happening? Test 8 to see it's 72 gr and velocities are 2290 and 2271 I didn't shoot the third because I wanted to make sure I loaded these correctly. Got home pulled the bullet and sure enough 72 grains. So what happened? The only thing I can think of is these 140 gr bullets have such a small bearing surface (.265) that when I seat them to .010 off the lands there isn't much in the neck to allow the pressure to develop properly, maybe 40% of the bearing surface is in the neck, is this logical at all? The 150 swift I measured had a bearing surface of .515 and easily allowed for long seating depth with plenty on bullet being seated. Also I use a redding neck bushing and size all brass so there is .002 (.282 ID) neck tension. Any help on understanding what happened would be appreciated. I'm thinking of going to 160 AB or 168 bergers because I'm thinking this must be a bearing surface issue. Thank you for any help in helping me learn something

Last edited by pyroducksx3; 07-10-2011 at 08:03 PM.
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Old 07-10-2011, 09:25 PM
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Join Date: Nov 2009
Posts: 57
Re: 7 mag reloading conundrum?

Maybe your chrono is jacked up? I shoot the same bullet/powder combo out of my 7STW and with 84 grains I get a little over 3,200 fps.
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Old 07-10-2011, 10:05 PM
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Join Date: Jul 2010
Posts: 140
Re: 7 mag reloading conundrum?

Seems like you should be getting higher velocity with 67 grains of H1000 and 140 grain bullets.

My 162 grain SST's are 3000 FPS with 68 grains of H1000
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Old 07-10-2011, 10:21 PM
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Join Date: Apr 2009
Location: Eastern Wheat Field near Bennett, CO
Posts: 538
Re: 7 mag reloading conundrum?

Could your problem be H 1000 being too slow for 7mm light bullets?
Do you have another powder like H 4831 to try with the 140 s ?

H 1000 should work great behind 160 AB and 168 vld.
At least it does for me.
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Old 07-10-2011, 10:24 PM
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Join Date: Sep 2009
Location: Washington
Posts: 650
Re: 7 mag reloading conundrum?

I'm not sure it was the chrono. I was getting 3009 out of a 270 with 140 gr sst's in their superformace ammo, 2478 out of a 300 savage with 150 ballistic tips and 40.5 gr ogIMR 4895, 813 fps with my 45 acp, 950 fps out of my 10mm glock 29, 1109 with my .22 lr and 2354 fps in a 303 British with factory 180 gr bullets the box said it would get about 2400 fps. All the reading from the chrono seemed good. I'm pretty sure there is a reason why I'm not getting the velocity I should, and not a chrono problem, I'm thinking it has something to do with the bullet not bring seated deep enough but this is just my reasoning and I don't have much experience or knowledge to back this up. I'm hoping somebody with both will be able to shed some light on this. I though the chrono might be bad also , like maybe it means 3290 instead of 2290 but it chronoed the 270 at around 3000 fps just fine. I'm learning that the equipment when it is functioning reliably ( as it seemed to read everything else just fine) is not lying and if it's telling me something is not acting right there is a reason why and not that it is broke.
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Old 07-10-2011, 10:34 PM
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Location: Washington
Posts: 650
Re: 7 mag reloading conundrum?

On hodgdons website it list the 140
Noslers partition (note I was shooting Berger vlds but) going I think around 3030 over 70 gr of h1000. I got 2982, 2969, 2969 with 70.5 gr of h1000 with no pressure signs do this is close to book but I was hoping to push em a little harder. What really throws me is why the velocity dropped to 2048 when I went up to 71.2 gr
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Old 07-11-2011, 06:06 AM
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Join Date: Dec 2005
Location: Tucson Az
Posts: 1,282
Re: 7 mag reloading conundrum?

I realize you had other rifles with their velocities reading correctly. Did you shoot any of them right after getting low readings?

I firmly believe the low readings WERE your chronograph. Sun angle can change readings. Were you starting to shoot later into the afternoon? Was one skyscreen shadowed? Were there partial shadows across one or both screen openings? Battery in good shape? There is no way you suddenly lost that much velocity.

Go back another day with the same load and just in case put in a new battery. Shoot with equal light on both screens. Repeat the same load, bet it reads fine.

Last edited by AZShooter; 07-11-2011 at 06:08 AM. Reason: typo
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