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First time using a chrono...kinda concerned #6406494 08/13/16 03:30 PM
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7six2 Offline OP
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So I've recently started reloading and like many folks I started my load development without a chronograph. I worked my way up and found a powder charge and seating depth that my rifle likes with a particular 168gr bullet. Yesterday I finally acquired a Magnetospeed chronograph and checked my velocity. My loads were for a .308 bolt-action using Federal brass, CCI BR2 primers, 168gr HPBT bullets, and 43.7gr of IMR 4064. The speeds I was seeing averaged at about 2770fps. I'm setting this up for distance shooting but to me that seems kinda fast for that powder charge.

My Savage rifle does have a really short chamber...with my cartridges set to the recommended 2.800 COAL im only .005 inches from the lands. This particular load that I chronoed is set to .010 off the lands. Although it did shoot better at .005 off.

I also checked velocity on a load that I've found to be very accurate for the 178gr AMAX and it was 2680fps. The MagnetoSpeed is new to me but its operation and set up seem pretty simple and straightforward. Now I'm concerned that I need to go back and work up lighter loads. I'd love to hear yall's opinions.

Re: First time using a chrono...kinda concerned [Re: 7six2] #6406504 08/13/16 03:37 PM
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Unless you are seeing pressure signs I would run it and be happy.

Re: First time using a chrono...kinda concerned [Re: 7six2] #6406525 08/13/16 04:01 PM
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If accuracy is good and no pressure signs roll with it. Some barrels are just faster than others.


lf the saying "Liar, Liar your pants on fire" were true
Mainstream news might be fun to watch
Re: First time using a chrono...kinda concerned [Re: 7six2] #6406529 08/13/16 04:06 PM
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I see no pressure signs, but since I'm new to reloadig I'll post a pic later when I get home.

Re: First time using a chrono...kinda concerned [Re: 7six2] #6406567 08/13/16 04:40 PM
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Good accuracy and more velocity than expected sounds like a win to me, as long as there's no excessive pressure signs. If you're comparing your velocity to what the book says your velocity should be, don't. Rarely is that ever going to match up. Too many variables at play with different barrel lengths, powder lots, etc.

Re: First time using a chrono...kinda concerned [Re: 7six2] #6406600 08/13/16 05:21 PM
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Keep in mind also that IMR 4064 is not like the IMR Enduron or Hodgdon Extreme powders. You will see an increase in velocity as the ambient temperatures rise. This might account for why you are seeing a near maximum charge velocity from a middle charge weight.

You might try cooling a few rounds sealed in a plastic bag in ice and compare their velocity to rounds that have been sitting in the sun.

Re: First time using a chrono...kinda concerned [Re: 7six2] #6406631 08/13/16 05:56 PM
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My 7 Mag chronograph very well it's shot 250 to 300 foot per second faster than the loads of indicate some loads have are just faster in a barrel than others

Re: First time using a chrono...kinda concerned [Re: Ritter] #6407253 08/14/16 04:15 AM
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Originally Posted By: Ritter
Keep in mind also that IMR 4064 is not like the IMR Enduron or Hodgdon Extreme powders. You will see an increase in velocity as the ambient temperatures rise. This might account for why you are seeing a near maximum charge velocity from a middle charge weight.

You might try cooling a few rounds sealed in a plastic bag in ice and compare their velocity to rounds that have been sitting in the sun.


Very valid point Ritter


lf the saying "Liar, Liar your pants on fire" were true
Mainstream news might be fun to watch
Re: First time using a chrono...kinda concerned [Re: 7six2] #6407570 08/14/16 04:24 PM
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I just realized that perhaps my 5R rifling is contributing to higher velocities.

Last edited by 7six2; 08/14/16 04:46 PM.
Re: First time using a chrono...kinda concerned [Re: 7six2] #6407630 08/14/16 05:19 PM
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I had a Savage 24" .308 that would push a 178 A-Max 2700 fps with 44.2 gr of Varget. That is on the upper end, but I think you're fine.


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Re: First time using a chrono...kinda concerned [Re: 7six2] #6409214 08/15/16 07:47 PM
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Originally Posted By: 7six2
I just realized that perhaps my 5R rifling is contributing to higher velocities.
So you're shooting the 10T, right? I had similar results with mine. Found a legitimate one hole load with the 168 Amax and was hoping to get at least 2600 out of it and on my Magnetospeed it averaged 2680.


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Re: First time using a chrono...kinda concerned [Re: Texan Til I Die] #6409401 08/15/16 09:31 PM
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Originally Posted By: Texan Til I Die
Originally Posted By: 7six2
I just realized that perhaps my 5R rifling is contributing to higher velocities.
So you're shooting the 10T, right? I had similar results with mine. Found a legitimate one hole load with the 168 Amax and was hoping to get at least 2600 out of it and on my Magnetospeed it averaged 2680.


Thats right, Savage model 10. More and more this rifle is proving to be a keeper.

Re: First time using a chrono...kinda concerned [Re: 7six2] #6414110 08/18/16 03:10 PM
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I also have a 5R (Remington) and have thought I was getting a lot more velocity than published data.


An unethical shot is one you take, that you know you shouldn't.
Re: First time using a chrono...kinda concerned [Re: 7six2] #6414131 08/18/16 03:24 PM
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Rifling type won't affect velocity much. When it does typically lower groove means faster.


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Re: First time using a chrono...kinda concerned [Re: 7six2] #6414215 08/18/16 04:34 PM
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I'd like to see a fully dimensioned drawing of the rifling, I don't know the depth. It does stand to reason that the radius feature on the lands would increase contact with the bullet, leaving more gas pressure behind, increasing velocity.


An unethical shot is one you take, that you know you shouldn't.
Re: First time using a chrono...kinda concerned [Re: 7six2] #6414603 08/18/16 09:16 PM
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More contact means more resistance.

Krieger sells both and will tell you their tests show no discernable advantage to the 5r but if you want one they can build it at a cost. Biggest claim to the 5r is ease of cleaning but I've not been able to tell a difference. I won't be paying extra for my next one.


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Re: First time using a chrono...kinda concerned [Re: 7six2] #6429311 08/29/16 03:58 PM
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UPDATE: I went ahead and backed down to my next lowest accuracy node with the 168gr for now. That still gives me 2700fps with 42.5gr of IMR 4064. Should extend the life of my brass and I still get 1/2 MOA accuracy.

As for the 178 grain AMAX...I'm still working on that load; but it seems that the 168s may work better for me.

Re: First time using a chrono...kinda concerned [Re: 7six2] #6430698 08/30/16 09:14 AM
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Have you tried Berger Hybrids or Hornady ELD's?

Re: First time using a chrono...kinda concerned [Re: spg] #6430891 08/30/16 01:09 PM
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Originally Posted By: spg
Have you tried Berger Hybrids or Hornady ELD's?


The Hornady ELD's have my attention but are not available in 168gr. I would try the 178s but the prices are still high. Haven't really looked into Bergers.

Last edited by 7six2; 08/30/16 01:10 PM.
Re: First time using a chrono...kinda concerned [Re: 7six2] #6433949 09/01/16 03:28 AM
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Just FYI for comparison:
42.8 grains of IMR 4064, 168gr SMK is supposed to match FGGM and is a standard load used by M1A match shooters with slight variation based on the rifle. 41.75 grains of IMR 4064 with a 175gr SMK is another "standard". Neither are near max but work in gas guns without creating undue stress on the components.


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