308Win - Why the High Velocity?

[Shrike]

This post didn't garner any attention in the pinned 308 Win thread that is going on 16 years old, so I thought I'd post it here:

I have been doing some chrono work with my 308 and a new bullet/powder combo and seeing what seems like unusually high velocities. Wanted to get thoughts/recommendations related to whether you think I'm getting into dangerous pressures given the velocity. I have always used a Varget/175SMK combo and now trying the Nosler 175RDF and IMR 4064 combo I picked up a few years ago due to availability.

Rifle:
Savage 10FP-LE2B 26" BBL 1:10 twist

Old load:
44.4gr Varget
175gr SMK
Fed GM210M Primer
Winchester case
Avg Velocity: 2743fps

Note: This is approaching the max load of 45.0gr of Varget and never seen pressure signs, get plenty of reloads out of my brass, and have shot over 1000 of this load through the rifle.

New load:
43.1 up to 43.7gr IMR 4064
175gr Nosler RDF
Fed GM210M Primer
Winchester case
Avg velocity (43.1gr 4064): 2750fps
Avg velocity (43.4gr 4064): 2764fps
Avg velocity (43.7gr 4064): 2793fps with a weird spike to 2832fps on one of the shots

Note: This is nowhere near the max charge of 45.6(C) grns per Hodgdon's Reloading Data Center and their published velocity for the max load is 2728fps...I'm already exceeding that with a much lower charge. There were no signs of pressure. Their test barrel is only 24", but I didn't think 2" would make such a drastic difference, if that's what you all think it is.

The powder is about 1 year old and has been stored properly. All the chrono results above (even of my old load) were recorded at the same range session using a ProChrono DLX. I allowed the barrel to cool between shot strings.

 

[spife7980]

How was bolt lift and extraction? As light as an empty chamber or could you feel it resisting?
43 is max according to the nosler manual.
I don’t have any first hand experience but 4064 is faster than varget so I bet it’ll start spiking pressures up in short order with hot days or a bit more powder.

 

[straightshooter1]

This post didn't garner any attention in the pinned 308 Win thread that is going on 16 years old, so I thought I'd post it here:

I have been doing some chrono work with my 308 and a new bullet/powder combo and seeing what seems like unusually high velocities. Wanted to get thoughts/recommendations related to whether you think I'm getting into dangerous pressures given the velocity. I have always used a Varget/175SMK combo and now trying the Nosler 175RDF and IMR 4064 combo I picked up a few years ago due to availability.

Rifle:
Savage 10FP-LE2B 26" BBL 1:10 twist

Old load:
44.4gr Varget
175gr SMK
Fed GM210M Primer
Winchester case
Avg Velocity: 2743fps

Note: This is approaching the max load of 45.0gr of Varget and never seen pressure signs, get plenty of reloads out of my brass, and have shot over 1000 of this load through the rifle.

New load:
43.1 up to 43.7gr IMR 4064
175gr Nosler RDF
Fed GM210M Primer
Winchester case
Avg velocity (43.1gr 4064): 2750fps
Avg velocity (43.4gr 4064): 2764fps
Avg velocity (43.7gr 4064): 2793fps with a weird spike to 2832fps on one of the shots

Note: This is nowhere near the max charge of 45.6(C) grns per Hodgdon's Reloading Data Center and their published velocity for the max load is 2728fps...I'm already exceeding that with a much lower charge. There were no signs of pressure. Their test barrel is only 24", but I didn't think 2" would make such a drastic difference, if that's what you all think it is.

The powder is about 1 year old and has been stored properly. All the chrono results above (even of my old load) were recorded at the same range session using a ProChrono DLX. I allowed the barrel to cool between shot strings.

You didn't say what to what COAL you're seating them Nosler RDF's too, but I used a COAL of 2.840 just to see where the number fell and your Winchester brass affords you more case volume to help keep the pressure down. It looks to me like your powder might have a higher and normal burn rate, which produces higher pressure and velocity for a given weight. That could be due to the powder having dried out (less moisture than when new). QuickLoad uses a default burn rate much lower than what I'm seeing in your numbers. Here's what your numbers looks like with that particular COAL:

 

[Shrike]

How was bolt lift and extraction? As light as an empty chamber or could you feel it resisting?
43 is max according to the nosler manual.
I don’t have any first hand experience but 4064 is faster than varget so I bet it’ll start spiking pressures up in short order with hot days or a bit more powder.

Bolt lift and extraction were normal as if it we an empty chamber. Thanks for the Nosler data! I don't have that manual an only referenced Hodgdon's Reloading Data Center. Perhaps a lesson learned there. I'll definitely have to consider the hotter days to come here in New Mexico!

You didn't say what to what COAL you're seating them Nosler RDF's too, but I used a COAL of 2.840 just to see where the number fell and your Winchester brass affords you more case volume to help keep the pressure down. It looks to me like your powder might have a higher and normal burn rate, which produces higher pressure and velocity for a given weight. That could be due to the powder having dried out (less moisture than when new). QuickLoad uses a default burn rate much lower than what I'm seeing in your numbers. Here's what your numbers looks like with that particular COAL:

View attachment 8086827

I don't have the measurements in front of me for COAL but believe I am 0.005 off the lands....although that's no help for COAL since every chamber is different. I can tell you this is not a compressed load for whatever COAL I'm running, but it's close! These cartridges were loaded from a fresh 8lb jug of 4064 about a year or so ago and I always store my powders tightly sealed in their original container at room temp, but do not have humidity controls. That could definitely be a factor, but would have had to dry out pretty quickly just opening a fresh jug. I suppose it is a good thing I was using a chrono to question things before I loaded up more/hotter loads. The data I provided is the highest I went and I will definitely stay under 43 gr and/or around the 2700-2740fps area as the absolute max.

Thank you both for your responses!

 

[918v]

Which cases are you using? Win commercial that weigh 156 grains or Win military?

 

[JoshPutman]

Just so you're aware, you can find Nosler load data on their website for free.

 

[Shrike]

Which cases are you using? Win commercial that weigh 156 grains or Win military?

I am using Winchester commercial. Not the military.

Also, I have recently checked out nosler's website. Thanks!

 

[b6graham]

different powder and bullet can make a big difference

2" can be 50+ fps

loading data from one test barrel doesn't mean a whole lot in reality

 

[ma smith]

 

[918v]

I am using Winchester commercial. Not the military.

Also, I have recently checked out nosler's website. Thanks!

Weigh the brass to make sure it isn’t mis-stamped. looks to me like you have heavy brass and your loads are meant for light brass with more capacity.

 

[Haney]

Weigh the brass to make sure it isn’t mis-stamped. looks to me like you have heavy brass and your loads are meant for light brass with more capacity.

C'mon man , what are the chances the brass is stamped incorrectly ? None . Why the constant bullshit, give up .

 

[Chris M.]

This post didn't garner any attention in the pinned 308 Win thread that is going on 16 years old, so I thought I'd post it here:

I have been doing some chrono work with my 308 and a new bullet/powder combo and seeing what seems like unusually high velocities. Wanted to get thoughts/recommendations related to whether you think I'm getting into dangerous pressures given the velocity. I have always used a Varget/175SMK combo and now trying the Nosler 175RDF and IMR 4064 combo I picked up a few years ago due to availability.

Rifle:
Savage 10FP-LE2B 26" BBL 1:10 twist

Old load:
44.4gr Varget
175gr SMK
Fed GM210M Primer
Winchester case
Avg Velocity: 2743fps

Note: This is approaching the max load of 45.0gr of Varget and never seen pressure signs, get plenty of reloads out of my brass, and have shot over 1000 of this load through the rifle.

New load:
43.1 up to 43.7gr IMR 4064
175gr Nosler RDF
Fed GM210M Primer
Winchester case
Avg velocity (43.1gr 4064): 2750fps
Avg velocity (43.4gr 4064): 2764fps
Avg velocity (43.7gr 4064): 2793fps with a weird spike to 2832fps on one of the shots

Note: This is nowhere near the max charge of 45.6(C) grns per Hodgdon's Reloading Data Center and their published velocity for the max load is 2728fps...I'm already exceeding that with a much lower charge. There were no signs of pressure. Their test barrel is only 24", but I didn't think 2" would make such a drastic difference, if that's what you all think it is.

The powder is about 1 year old and has been stored properly. All the chrono results above (even of my old load) were recorded at the same range session using a ProChrono DLX. I allowed the barrel to cool between shot strings.

Shrike - Did you ever get the answers you were looking for?

The velocities you are/were getting with 44.4gr. of Varget in a 26" barrel seem normal to me. I recall testing 44.1 Gr. of Varget w/ new Lapua Brass, COAL 2.822" with 176 gr. A-tips in my XCRM 20" barrel (Gas piston, long stroke) and getting nearly 2600 fps but 2638 fps with 42.2 Gr. of H4895 is where I found a node, at around 2640 fps.

Using Varget, adding another 25 fps for each additional inches of barrel so, 6 inches x 25 fps and the velocities you are getting is what I would be expecting... I know several highly experienced shooters/reloaders that use 44.5-45.0gr. of Varget to shoot 175 Gr. bullets in 308 with great success.

Eventually I am going to give it a go as well, I just did not have enough case capacity in new Lapua brass to make it work with Varget for now...

Hope you are still using your Varget load of 44.4 Gr.? I know the SDs and ES were absolutely incredible, right under 44.0 gr. of Varget (accuracy was lacking however). Can't wait to give it another try with fire-formed brass with 44.4-45.0 gr. of Varget. Best - Chris

 

[matt33]

I'm not sure if it's helpful, but with 44.2 grain of Varget, a 175 Sierra Match King, CCI BR2, and Lapua brass with a COL of around 2.82" I average 2,692 FPS through my 26" Sako TRG-22 in .308.