Home Forums Hunting & Shooting Ask The Gunwriters IMR data - .280 loaded to .270 pressure...

Lou,

Several sources are starting to produce "full power" .280 loads. Nosler is a good example. As far as I can tell, even at "full power" for many rounds...IMR/Hodgdon/Win load data is consistently conservative.

As always, some data looks conservative. However, what I noticed is the velocities look low for the powder charges reported for some rounds - at least compared to other sources and my rifles. For other rounds, it is the other way around. The loads are not necessarily conservative, just look slow. I guess that is the variability of the process.

Lou

The latest trend: .....EVERYBODY wants to load their favorite cartridges to 270W pressures.

Sheesh--just buy a 270!

I be skeptical.
10-15 years ago several of us had virtually unlimited access to a couple Oheler Ballistic Labs-we bought strain gauges by the gross.......At 65K psi, the 3-4 280Rems we ran through the Ballistic Labs would show most/all the classic signs of over pressure, ejector marks, lots of case stretch, case head expansion, short case life, etc........

Casey

Casey: Do you remember the velocities of the 280 at those pressures?

I've been getting 3040 fps with 150g Nosler Partitions out of a 22" barrel in a Rem 700 BDL for a long time. No marks on case heads, no cratered primers. I use each case 10 times then throw them out. Each rifle is different so your rifle may be chambered tighter and may shoot a little slower. I use Norma MRP and Rem Mag rifle primers. I also only neck size so the case is marginally larger ... I've also gotten just over 3000 fps using H4831.

Chuck

According to one rule of internal ballistics, a 7mm cartridge on the same case as a .270 is capable of about .013% in extra muzzle velocity when driving a bullet of the same weight.

The .280 is supposed to have slightly more powder capacity than the .270 because the shoulder is slightly further forward, but I have measured the capacity of both cases with water and if there is a difference, it is so small that different weights (makes) of brass obscure it.

So if a .270 is capable of 3000 fps with a 140-grain bullet in a certain barrel length, then the .280 should be able to drive a 140 at around 3040 in the same barrel length, at the same pressure.

3040/3000 = 1.0133

1.3% increase

MD: 3040 to 3090 is about where I've topped out. In doing load development with R22, I've had 140's go faster, but I was not comfy over 3100.

It will also vary somewhat with the bullet. My first .280 had a 23" barrel, and I loaded the 139 Hornady Interlock to 3100 with H4831, with apparently very acceptable pressures. But we all know that sometimes doesn't mean much. However, the 139 Hornady has about the shortest bearing surface of any 7mm bullet in the 140-grain range, and does indeed tend to produce less pressure than, say, a 140 Partition or TSX.

But the reality is that there just isn't much difference in the .270 and .280, except for 175-grain bullets on the high end of 7mm, which apparently almost nobody loads in the .280....

John - thanks - that's the kind of information that is of real value and not often found. Best, John

Just to illustrate what MD is saying...here is a data run for QL using 139s and R-22. This was provide to me, so I don't have the ability to run H4831. I bolded the velocity and pressure that are just at 65Kpsi. Also, below that is a comparision to show what MD says about the 139 giving less pressure...which I have found to be the case as well. Also note, this velocity is in a 22" bbl.

Cartridge : .280 Rem.

Bullet : .284, 139, HDY BTSP 2825

Cartridge O.A.L. L6: 3.330 inch or 84.58 mm

Barrel Length : 22.0 inch or 558.8 mm

Powder : Alliant Reloder-22

Predicted data by increasing and decreasing the given charge,

incremented in steps of 2.0% 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

-20.0 83 48.00 2287 1614 26826 9668 81.8 1.496

-18.0 85 49.20 2349 1703 28648 10053 83.5 1.458

-16.0 87 50.40 2412 1795 30600 10433 85.1 1.422

-14.0 89 51.60 2475 1891 32694 10807 86.7 1.385

-12.0 91 52.80 2540 1990 34942 11174 88.2 1.350

-10.0 93 54.00 2604 2093 37355 11530 89.6 1.312

-08.0 96 55.20 2669 2199 39951 11876 90.9 1.271

-06.0 98 56.40 2735 2308 42744 12209 92.2 1.230

-04.0 100 57.60 2801 2421 45750 12527 93.4 1.191

-02.0 102 58.80 2867 2537 48991 12829 94.5 1.153

+00.0 104 60.00 2933 2656 52490 13112 95.5 1.117

+02.0 106 61.20 3000 2778 56271 13376 96.4 1.081

+04.0 108 62.40 3067 2903 60365 13619 97.3 1.047

+06.0 110 63.60 3134 3031 64801 13838 98.0 1.014

+08.0 112 64.80 3201 3162 69615 14033 98.6 0.982

+10.0 114 66.00 3268 3296 74844 14201 99.1 0.951



Cartridge : .280 Rem.

Bullet : .284, 140, NOS AccuBond 59992

Cartridge O.A.L. L6: 3.330 inch or 84.58 mm

Barrel Length : 22.0 inch or 558.8 mm

Powder : Alliant Reloder-22

Predicted data by increasing and decreasing the given charge,

incremented in steps of 2.0% 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

-20.0 87 48.80 2369 1745 29731 9994 84.2 1.442

-18.0 89 50.02 2435 1843 31855 10376 85.8 1.403

-16.0 92 51.24 2501 1945 34142 10751 87.4 1.365

-14.0 94 52.46 2568 2050 36607 11116 88.9 1.328

-12.0 96 53.68 2636 2159 39265 11470 90.4 1.284

-10.0 98 54.90 2704 2272 42135 11811 91.7 1.242

-08.0 100 56.12 2772 2389 45238 12137 93.0 1.200

-06.0 103 57.34 2841 2508 48596 12445 94.2 1.160

-04.0 105 58.56 2910 2632 52233 12735 95.3 1.122

-02.0 107 59.78 2979 2759 56185 13004 96.3 1.085

+00.0 109 61.00 3049 2889 60478 13251 97.1 1.049

+02.0 111 62.22 3118 3023 65151 13473 97.9 1.014

+04.0 113 63.44 3188 3160 70254 13669 98.5 0.980

+06.0 116 64.66 3258 3300 75831 13836 99.1 0.948

+08.0 118 65.88 3328 3443 81929 13973 99.5 0.917

+10.0 120 67.10 3398 3589 88583 14079 99.8 0.886

The trouble with QL data is that it is theorectical. In actual practice, it can be pretty far off. I've seen it in others and I've done some myself. In my book, there is no substitute for starting low, working up and then testing in the warmest temperatures you will be hunting, with loads that are 5% over that. If you get no pressure signs there with broken in brass, you are going to be OK.
This bussiness of chasing the last 100-150 fps. is a mistake. Rifles and components simply vary too much. If you must have more velocity, simply go to a bigger case. E

Understand QL data is a predictor only with a set of invariable parameters applied to an inexact science. Still, like all other "load data" it's a resource. And valuable if used correctly. Dangerous if not. Some people call seeking maximum safe performance "squeezing out that last 150fps". I call seeking max safe performance for a given round just that.

JB: Well, it's interesting to look at the pressure/velocity data that 280 posted here on the 140 AB.. It indicates that it takes about 60,000 psi to get a 140 to around 3050 or so. I never knew the pressures of my loads, but my impression was that the load seemed OK at 3050-3100.So some of the loads may have been a tad over 60,000. But it takes a jump all the way to almost 65000 to get 3118 fps. I do not think the extra 70 fps is worth the extra strain.

I've seen the big difference in the Hornady bullet in working with the 338-225 Hornady vs the 225 Nosler Partition. I learned the hard way to NEVER substitute a Nosler partition after working up the load with an equal weight Hornady Spire Point.

I called Nosler today to ask about their .280 data. The new Nosler #6 puts their best accuracy load of 57grs of R-19 at 3152fps from a 26" bbl. Most data I see, adds @40fps for 2" of bbl...so a 24" bbl would be @ 3110. However, they claim this load data is loaded at or under SAAMI max of 60Kpsi! NOT up to .270 SAMMI standards of 65Kpsi...so they said.

My barrels have always been 22", in both 270 and 280.Yeah, I can see them hitting that with 26" barrels.Long barrels solve all kinds of velocity "problems"...

As long as some people want to push the pressure envelope into the danger zone, why not just raise the pressure limit of the 280 and be done with it? The limits are just there for ideal conditions, very strong modern steel rifles, no reloading errors or firing conditions and absolutely perfectly uniform components.

Just one favor, though. When you blow yourself or a loved one into obliviion, say hi to Murphy for me. We're old buddies.

Wayne

I got a T/C Encore ProHunter back in March of this year with a 280 Remington barrel and looked at loads for about three months. One of my Dad's friends had been loading since the early 1940's. He gave me all of his loading stuff in 1975 when me moved overseas to work. So I have most of the loading data that has been published from 1940 to current. I choose the 280 data from one of the early Speer books. It was suggested to use the middle range loads for the autos and pumps and the high end loads for bolt guns. I choose 53.5 grs of H-4350 with a 140 gr Ballistic Silvertip, CCI LR BR primer in a W-W nickel plated case and they shot all into the same hole at 100 yards. Their length is longer that you could use in a typical rifle. I have not checked them in my chronograph, but I am guessing they will be in the 3100 fps range. I hope all is well in our shooting community, Merry Christmas to all!
Good shooting!
Marcus.

RIGHT!

FWIW My 22" M77 280 put out slightly over 2800fps with 57gr of R-19......