.308 handload velocity question


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Goattman
January 10, 2013, 09:49 AM
I am loading once fired Black Hills brass.

Powder: 42.1g IMR 4064
Primer: CCI BR2
Bullets: SMK 168 HPBT

Dropping powder with RCBS chargemaster and checking with 505 scale, so I am confident of actual charge.

Rifle: Remington 700P 26" barrel no modifications

Chrono: Competition Electronics Digital (12' from barrel)

Outside, 35 degrees, and sunny.

Bullets are chronographing at 2480 fps average, SD 27 fps

This is lower velocity than I expected. I was expecting in the 2600 fps range, only because this is what BH chrono at in summer.

Is the velocity I am experiencing what others see as well or no?

If No, any suggestions why?

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Walkalong
January 10, 2013, 10:31 AM
From Hodgdon online data:
168 GR. SIE HPBT IMR IMR 4064 .308" 2.800" 41.5 2518 43,800 PSI 45.9C 2766 58,800 PSI

24" barrel.

Does sound a little slow. What OAL?

USSR
January 10, 2013, 10:38 AM
Goattman,

The primary problem is your Black Hills brass was made by Winchester, hence it has the Winchester's large case capacity. So, you essentially have a very light charge. Secondary causes are low temperature and mild BR primers. You've got plenty of room for more powder in that case, and you might want to also consider a hotter primer such as the Fed 210M that Hodgdon used in their load data. Hope that helps.

Don

Dthunter
January 10, 2013, 12:58 PM
You definitely have room to increase your powder charge. Just do so incrementally (1 grain at a time). Eventually you will either reach your velocity
Goal or find high pressure signs. Every gun is a little different, and thats the beauty of reloading. You can tailor your load to the specific firearm.

Remember, above all, accuracy is found where the rifle likes it. It may be at a lower velocity, or a higher velocity. Just feed the rifle what it likes.
Generally speaking, all my .308's are most accurate at or
Near max velocities published in the loading manuals.

Have fun, and be careful As You work up in pressures.

Goattman
January 10, 2013, 01:00 PM
Walkalong, 2.800" OAL.

918v
January 10, 2013, 02:43 PM
Increase your charge.

SlamFire1
January 10, 2013, 05:12 PM
This is what I got in my Ruger M77 Mk II with a 26" barrel and LC90 cases.

So either your barrel is not as tight, the cases a bit bigger, or my primers a bit hotter.

I would say bump your charge to 42.5 and 43.0. That should get you around 2600 fps.


Ruger M77 MKII
26 " Barrel 1:10 twist


168 Nosler 42.0 grs IMR4064 Lot2449 LC90 CCI#34 OAL 2.750"
27-Nov-06 T = 60 F

Ave Vel = 2594
Std Dev = 22
ES = 67
High = 2629
Low = 2562
N = 10
excellent accuracy

41 Mag
January 11, 2013, 06:21 AM
To be honest with the average your posting your not that far from where you think you should be IMO. I have seen WAY bigger discrepancies.

There can also be a number of other influences as you mentioned the temp between dead summer and winter, chamber dimensions, brass dimensions, powder lot, bullets and so forth. Could be as simple as the primers. Only testing will tell.

One thing I have found many times is that what I expected a load to be was not always what it actually was. It could also be as simple as the lighting on your chrono as well. Sometimes the brighter it is the further off my readings are. I try to use something like a target clothes pinned to the top of the screens to give me as close to a standard as possible. It helps when it goes from bright sun to a cloudy day in keeping my readings a bit more consistent.

But like others have mentioned it is simple to creep up on your charge and see where your at there as well.

Trent
January 11, 2013, 10:39 AM
Cloudy days means your chrono needs a shield. It's "too bright".

It's the reverse of what you'd expect, but sunny days are actually "darker" to the chrono (from it's viewpoint) than cloudy days, where the whole of the sky is lit brightly. It's harder for a shadow to be picked up by the sensors when the light source is "everywhere" above it.

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