280 AI & 150g ABLR

[bboswell]

Does anyone have experience loading this round using Viht N-165?

I then went to Viht N-165. I am seeing some signs that I can get the accuracy I need out of this but I am extremely surprised at how far my velocities and pressures are off from Nosler load data. I hit hard bolt lift @ 62g which is a full grain short of MAX but I'm getting avg velocity of 3165 which is over 100 fps faster than the MAX load is shown to produce. This even though my barrel is 2" shorter than the test barrel.

What in my mix could cause my results to be so far from the book or have others seen this as well?

 

[Ridgerunner665]

Something is wrong, no doubt...

Measure your case capacity and let me know what it is..... how to do it can be found here... viewtopic.php?f=4&t=30761

You say hard bolt lift, are there any ejector marks on the case head?

And tell me about your chrono set up and lighting.

 

[nvbroncrider]

Maybe the lot of powder you have is faster than normal.

 

[bboswell]

Something is wrong, no doubt...

Measure your case capacity and let me know what it is..... how to do it can be found here... viewtopic.php?f=4&t=30761

You say hard bolt lift, are there any ejector marks on the case head?

And tell me about your chrono set up and lighting.

Thanks for your help.

My chrono is a ProChrono Digital as seen here http://www.competitionelectronics.com/p ... o-digital/. It is not expensive but it has served me well for several years. Shooting was done mid-day with good sun light.

Yes there were ejector swipes on the case heads.

As far as case capacity I will have to get back to you, all of the reloaded cases have been sized but I still have 40 once fired factory loaded Nosler cases that I can measure once my water sits till tomorrow.


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[Ridgerunner665]

I have had that chrono for a good while myself...on my 3rd one, shot the first 2, lol.

I get more consistent results by placing the chrono in the shade...I still have that chrono, but I mostly use the MagnetoSpeed these days.

I was doubting your chrono pretty hard until you said you had ejector swipes too....

Given the ejector swipes and assuming the velocity is correct...

You're probably running a little over 70,000 psi with those loads...it takes about that much to show good pressure signs in a 280 Ackley.

 

[bboswell]

Hate to say but I doubted my results enough to try again the next day which was very overcast and results were consistent.

Hard bolt lift, great velocity, and 3 shot group in the .3's.....


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[bboswell]

Something is wrong, no doubt...

Measure your case capacity and let me know what it is..... how to do it can be found here... viewtopic.php?f=4&t=30761

You say hard bolt lift, are there any ejector marks on the case head?

And tell me about your chrono set up and lighting.

Case capacity is 71.9 based on 10 case average


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[Ridgerunner665]

Dang....that is low.

You'll be better off using 280 Remington data.

Probably not what you wanted to hear...but its the truth.

 

[Ridgerunner665]

Give me a few and I'll run some QL projections to illustrate what I'm saying.

 

[bboswell]

Dang....that is low.

You'll be better off using 280 Remington data.

Probably not what you wanted to hear...but its the truth.

Nosler data says 64.8g water which actually caused me to remeasure making a smaller "bubble" above the case.

 

[Ridgerunner665]

OK...the cold hard facts...and you're not the first I've had to explain this to...seems some people don't know how to properly ream a 280 Ackley chamber, which should come out to be 74 grains case capacity (+/- 1 grain for allowable reamer variance).

I have a couple of 270 Winchesters that I load for on a regular basis...one belongs to my wife, the other to a good friend.

The case capacity of those 270's is as follows:

71.3 grains for the Browning (my friends rifle), and 69.7 for my wifes FN made Winchester Featherweight.

OK, the 280 Rem has its shoulders pushed forward .050" from what 270 Rem does...so, figuring in that .050" more room in the case we can make a safe bet that a 280 Rem should have a capacity of around 1 grain more than the 270, QuickLoad agrees. (defaults are 67 grains for the 270, 67.9 for the 280)

 

[Ridgerunner665]

Dang....that is low.

You'll be better off using 280 Remington data.

Probably not what you wanted to hear...but its the truth.

Nosler data says 64.8g water which actually caused me to remeasure making a smaller "bubble" above the case.

Nosler data is quoting "usable case capacity"...measured with the bullet seated....totally different measurement.

 

[Ridgerunner665]

I'm still doubting your chrono....83,000 psi would have blown the primer, handily.

Cartridge          : .280 Ack Imp
Bullet             : .284, 150, Nosler Accubond LR 58734 G7
Useable Case Capaci: 63.190 grain H2O = 4.103 cm³
Cartridge O.A.L. L6: 3.330 inch = 84.58 mm
Barrel Length      : 24.0 inch = 609.6 mm
Powder             : Vihtavuori N165 ?

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.807% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms

+00.0  108    62.00   3165    3335    83563    10325    100.0    1.014  !DANGEROUS LOAD-DO NOT USE!

But either way, you are way over pressure....using N165, top speed for the bullet you're using is gonna be around 3,050 fps...no question about that.

 

[bboswell]

Now you have me curious. I have 8 cases here fired from a friends rifle built by a different builder. I will check capacity on them tomorrow.


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[Ridgerunner665]

For reference...mine is 73.9 grains.

 

[bboswell]

Y'all have me intrigued.

If the chamber is cut with proper headspace to handle factory loaded cartridges and the loaded loaded cartridge size is controlled by quality resizing dies where does this extra case capacity come from?

Again, not doubting your knowledge but extremely intrigued.


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[bboswell]

I'm still doubting your chrono....83,000 psi would have blown the primer, handily.

Cartridge          : .280 Ack Imp
Bullet             : .284, 150, Nosler Accubond LR 58734 G7
Useable Case Capaci: 63.190 grain H2O = 4.103 cm³
Cartridge O.A.L. L6: 3.330 inch = 84.58 mm
Barrel Length      : 24.0 inch = 609.6 mm
Powder             : Vihtavuori N165 ?

Predicted data by increasing and decreasing the given charge,
incremented in steps of 0.807% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step    Fill. Charge   Vel.  Energy   Pmax   Pmuz  Prop.Burnt B_Time
 %       %    Grains   fps   ft.lbs    psi    psi      %        ms

+00.0  108    62.00   3165    3335    83563    10325    100.0    1.014  !DANGEROUS LOAD-DO NOT USE!

But either way, you are way over pressure....using N165, top speed for the bullet you're using is gonna be around 3,050 fps...no question about that.

I doubt this chrono too


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[Ridgerunner665]

Y'all have me intrigued.

If the chamber is cut with proper headspace to handle factory loaded cartridges and the loaded loaded cartridge size is controlled by quality resizing dies where does this extra case capacity come from?

Again, not doubting your knowledge but extremely intrigued.

The diameter of the chamber...I think it often comes down to how many chambers have been cut with the reamer used....as it wears, each chamber is a little smaller than the last one it cut.

Head space is a measure of length.

 

[bboswell]

The diameter of the chamber...I think it often comes down to how many chambers have been cut with the reamer used....as it wears, each chamber is a little smaller than the last one it cut.

Head space is a measure of length.

I run a machine shop so that makes perfect sense.

But if factory ammo or resized ammo fits the chamber the only way to get this extra capacity is with a good deal of case stretch it seems.


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[Ridgerunner665]

The diameter of the chamber...I think it often comes down to how many chambers have been cut with the reamer used....as it wears, each chamber is a little smaller than the last one it cut.

Head space is a measure of length.

I run a machine shop so that makes perfect sense.

But if factory ammo or resized ammo fits the chamber the only way to get this extra capacity is with a good deal of case stretch it seems.

There has to be "some" case stretch...its just the way rifles work...the case needs room to feed easily under all conditions, and it also needs room to retract from the chamber walls so it will extract easily in all conditions.

Now if you're talking a tight chambered match rifle that is another monster...but the laws of physics still apply...less capacity will get you less velocity given equal pressure.