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#6406494 - 08/13/16 10:30 AM First time using a chrono...kinda concerned
7six2 Online   content
Light Foot

Registered: 06/14/16
Posts: 33
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.

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#6406504 - 08/13/16 10:37 AM Re: First time using a chrono...kinda concerned [Re: 7six2]
red bluff Offline
Tracker

Registered: 07/08/12
Posts: 535
Loc: Texas, Erath
Unless you are seeing pressure signs I would run it and be happy.

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#6406525 - 08/13/16 11:01 AM Re: First time using a chrono...kinda concerned [Re: 7six2]
kmon1 Offline
junior

Registered: 09/27/06
Posts: 20287
Loc: Texas
If accuracy is good and no pressure signs roll with it. Some barrels are just faster than others.
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#6406529 - 08/13/16 11:06 AM Re: First time using a chrono...kinda concerned [Re: 7six2]
7six2 Online   content
Light Foot

Registered: 06/14/16
Posts: 33
I see no pressure signs, but since I'm new to reloadig I'll post a pic later when I get home.

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#6406567 - 08/13/16 11:40 AM Re: First time using a chrono...kinda concerned [Re: 7six2]
cblackall Offline
Woodsman

Registered: 05/12/16
Posts: 114
Loc: Lewisville, TX
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.

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#6406600 - 08/13/16 12:21 PM Re: First time using a chrono...kinda concerned [Re: 7six2]
Ritter Offline


Registered: 02/15/09
Posts: 246
Loc: Southern Oklahoma
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.
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#6406631 - 08/13/16 12:56 PM Re: First time using a chrono...kinda concerned [Re: 7six2]
BIGDOG1956 Online   content
Woodsman

Registered: 10/26/09
Posts: 234
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

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#6407253 - 08/13/16 11:15 PM Re: First time using a chrono...kinda concerned [Re: Ritter]
kmon1 Offline
junior

Registered: 09/27/06
Posts: 20287
Loc: Texas
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
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#6407570 - 08/14/16 11:24 AM Re: First time using a chrono...kinda concerned [Re: 7six2]
7six2 Online   content
Light Foot

Registered: 06/14/16
Posts: 33
I just realized that perhaps my 5R rifling is contributing to higher velocities.


Edited by 7six2 (08/14/16 11:46 AM)

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#6407630 - 08/14/16 12:19 PM Re: First time using a chrono...kinda concerned [Re: 7six2]
FiremanJG Offline
THF Celebrity

Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
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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#6409214 - 08/15/16 02:47 PM Re: First time using a chrono...kinda concerned [Re: 7six2]
Texan Til I Die Offline
Pro Tracker

Registered: 08/18/09
Posts: 1758
Loc: Central Texas
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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#6409401 - 08/15/16 04:31 PM Re: First time using a chrono...kinda concerned [Re: Texan Til I Die]
7six2 Online   content
Light Foot

Registered: 06/14/16
Posts: 33
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.

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#6414110 - 08/18/16 10:10 AM Re: First time using a chrono...kinda concerned [Re: 7six2]
onlysmith&wesson Online   content
Woodsman

Registered: 07/10/14
Posts: 211
Loc: Lewisville/ Foard County
I also have a 5R (Remington) and have thought I was getting a lot more velocity than published data.

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#6414131 - 08/18/16 10:24 AM Re: First time using a chrono...kinda concerned [Re: 7six2]
dee Offline
Extreme Tracker

Registered: 04/10/10
Posts: 4664
Loc: Red River way
Rifling type won't affect velocity much. When it does typically lower groove means faster.
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#6414215 - 08/18/16 11:34 AM Re: First time using a chrono...kinda concerned [Re: 7six2]
onlysmith&wesson Online   content
Woodsman

Registered: 07/10/14
Posts: 211
Loc: Lewisville/ Foard County
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.

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