Weird pressure issue

R

reynolds357

New member
I am playing with new powders in my 6.5x284 hunting rifle. Lapua brass, 9 1/2 primer, magpro powder. I started load development at 59 gr. No pressure signs. 60, no pressure signs. 61, no pressure signs. 62, no pressure signs, but accuracy went South. 61 was most accurate. So, I headed the other way. 58 The bolt handle was hard to lift, extractor mark deep on brass, primer cratered. These pressure signs were consistent for all 5 shots. I loaded 2 more to verify no mistake, same results. I am going to drag out the Chrono, but did not have it with me.
 
What is min and max for your powder?

You can actually increase pressure when you go below the minimum charge. Pressure and velocity are not directly related.
 
I would cut your loads by a lot more than a couple of grains. Without pressure gages you don't know what your pressures are. And, without a chronograph you don't know what your velocities are. By and large, you are staggering around in the dark.

Phillip Sharpe has a excellent section in his book about a 100,000 psia round he fired that gave absolutely no pressure indications. He also showed it to lots of experienced shooters, all claimed normal pressures. He used that example to show that the "traditional" signs of pressure are unreliable. He also never claimed shooting 100K psia rounds were safe, they are not.

I also have a magazine article from the 1980's. Some handguner was loading way over max and not having pressure indications till he reduced his loads. The magazine tested his load recipe and, he was over 80,000 psia.

If you are having pressure indications with a reduced load, your pressures are over max with the reduced load. I don't know why you are not experiencing pressure problems with the increased loads, but I have absolutely no doubt, they are overpressure.

Cut your loads. Cut them by a lot.
 
CONFIRM YOUR LOAD DATA It seems +10 gr

Of course caution in all directions is called for. Indeed,you might have too much powder. Do check that out.

But a 6.5/284 will have a tight twist,heavy for caliber bullets,and its likely loaded warm.
Just the sort of round that CAN metal foul horribly.That makes it harder to
push the bullet through.

Maybe.

And sometimes the powder we pick is just fickle in that particular load.
-------------------------------------------------------------------------------------
!!!! ****I went to Hogdon's site and looked up 6.5/284.****!!!! CAUTION
I don't know what bullet you are using.
With bullets from 120 to 140 gr,most powders max load around 50 grs.

With a 120 gr bullet,the heaviest max load published with any powder was 58.5 gr of H-1000. Which is slow.
Max with IMR 4831 is 48.7

With the 140's,a max load of H-4831 is 49.5 gr

You are talking 58.59,60?? Gr Might you be 10 gr off?? That could get exciting.(I don't know MagPro powder)
 
Last edited:
No real advice on the specific loads but can't recommend going above or below the data using the slower powders.
I use a chronograph and load to velocity w/o going over the data max load. I've found several cases where I hit the listed velocity while still a few grains below the data so I stopped and was happy with it.
 
Starting published load is 57. Published max is 61.8.
Even though I did not have my chronograph with me, the groups consistently moved up the paper as powder charge increased. The 58 gr load was 2" lower than the 62. I cut the chamber myself. It is a long throat Norma chamber. The data is for the Winchester chamber. The data is conservative for the long throat chamber.
 
Last edited:
It helps if you list more complete information.

Bullet for one

Also have you fired this rifle with other powder , which ones, which bullet and how did it do?

Do the cases look complete smooth?

Its possible the Magnum primer is causing issues even though its a spherical power. Its not listed in my books as a standard though it says it is.


I would get a Hornady 9 or 10 and load up with another powder and check how it does, starting at minimums working up in 1/2 grain increments.

With a custom chamber and by hand there is a possibility of a chamber that is not a smooth as it should be.
 
Last edited:
Book list as close a bullet as I can find at 53 to 58 Magpro (120 GMAX is not a good match to sent to the next highest)

If its not bee fired with a magnum primer in the tests (they don't say) then that adds both a pressure aspect as well as potential erratic results at various powder levels.

Along with the other areas I would start at the lowest with another go to powder, using standard primers and carefully work up.
 
"I am playing with new powders in my 6.5x284 hunting rifle. Lapua brass, 9 1/2 primer, magpro powder. I started load development at 59 gr. No pressure signs. 60, no pressure signs. 61, no pressure signs. 62, no pressure signs, but accuracy went South. 61 was most accurate. So, I headed the other way. 58 The bolt handle was hard to lift, extractor mark deep on brass, primer cratered. These pressure signs were consistent for all 5 shots. I loaded 2 more to verify no mistake, same results. I am going to drag out the Chrono, but did not have it with me."

I'm not all that familiar with your cartridge or the powder you were using but I believe Magpro is one of the slower burning powders. What I think you experienced when you dropped to the 58.0 gr. charge was S.E.E., P.E.P. OR D.D.T. In other words Secondary Explosion Effect, Pressure Excursion Phenomenon or Deflagration To Detonation. They all mean the same thing. Potential KABOOM! Powders are designed to burn within specified parameters and once you go above of below those parameters strange things happen. Go above and velocity can take a big jump up, not change from the previous charge or actually give out a lower velocity which means you've gone too far. On the other end, drop below the normal starting load with a slow burner can produce the S.E.E problem which can result in a blown up rifle in some circumstances. Certain cartridges as well known to be affected by the too low charge high pressure problem. Two of the most well known are the .243 Win. and 7MM Rem. Mag. The 6.5x284 just may also be one of the cartridges that are more prone to the problem.
Paul B.
 
Weird thing is, I am not below the starting load listed in my data sheets.
Click to expand...

Well it seems you're over max with everybody else's data on your first loads and almost at max with your second loads . It is weird you did not have those pressure signs with the first loads but unless I'm missing what's going on here IMO I can see why you could/should be seeing pressure signs .

What data are you using ?
Is this a ball powder ?
If so that's a lot of powder to ignite , are you using mag primers ?
 
It is a ball powder so the Magnum primer may not be wrong but?

Its rated as close to the same as R25 and Retumbo (bottom of the chart)

http://www.adi-powders.com.au/handloaders/equivalents.asp

All its neighbors are high on the burn rate chart 126 (Magpro) and the others above to 141.

I too don't see those load levels, they are high

VNTH which is the closest burn rate is max at 43 gr.

Reloader 19 at one spot above it is 48.1
 
Last edited:
Weird thing is, I am not below the starting load listed in my data sheets.
Click to expand...

Weird thing is we are trying to help and its like pulling teeth to get where you got your data from

Saying over and over again that your data is good is not going to change the need for where you got that.
 
I don't load the 6.5x284 NORMA but I do use MAGPRO.

In my 7mmRM MagPro is the best powder I have found. Better than Retumbo, vvN560, vvN570, etc.

In my 300 WSM is another story: I got pressure 3 grains under maximum. And accuracy was bad with all charges I tried.

Maybe just try a different powder.

.02
 
I know were talking about 6.5-284, but my comparison is viable.
My .270 win uses Magpro and 150 grn bullets, max is 61 grains, but I found 59.5 most consistan accuracy, no signs of pressure.
Something about Reynolds data is strange.....
 
Ok my old data sheets from AA is where I got the loads. The new data is even weirder. 123 gr 6.5x284 win, 55.4 -61.5, Norma 53-58.9. They loaded the Win to higher pressure. Either way, the Win. Max load is always safe in the long throat Norma. BUT, the offending load is within the parameters. The non offending loads are outside the most conservative parameters.
Primer used and in data is L.R. non magnum.
 
Ok, go to Western Powder Companies published data and read it for yourself.
Click to expand...
notice when you do that their data for the Win is loaded to a considerable higher pressure than their Norma data. The Norma can always be loaded with more powder than the Winchester. It is in essence, a larger case due to the long throat getting the bullet further out of the case and giving more useable case volume.
 
You must log in or register to reply here.
Back
Top