Factory norma ammo over pressure according to quickload?

[Kryogen]

I have tested an old box (10-15 years?) of 308 norma magnum, and it chronos at 3130 fps or so.

The new factory ammo is around 3040 fps.

According to quickload, I can't get anything over 3035 FPS without being over pressure.

70.5 RL19 gives me 3044 fps, no pressure signs
71.0 gives around 3050, flat primers
71.5 hard extraction.

From that I determined that 70.5 was a safe load in that rifle.
According to quickload, I am still over pressure at 3044

Your point of view? Maybe I should cut the next reloads to 70.0 to lenghten brass life? I already have a few that have loose pockets from being fired factory load + 2 reload (might have been the over max loads)

 

[Andy]

Quickload is a software package, it's not pressure testing equipment. It does a good, but imperfect job estimating pressure and muzzle velocity, but is for me, it's simply a sanity check that augments other sources of info. IMO Quickload is just ahead of "Pressure Signs" for least reliable estimator of pressure - for those who can't afford pressure testing equipment, a good chronograph is your best friend.

 

[jethunter]

What Andy said. And there is no relevance comparing Quickload RL19 results to Norma factory ammo.

 

[Loyalist]

What does the pressure look like in quick load with a NORMA powder, which is what I assume Norma
Factory uses

 

[CanAm]

factories rarely use canister powders

 

[9.3mauser]

I would switch to a slower powder... RL 22 or H4831. RL 19 is likely a little too quick to give top velocities without pressure signs.

 

[jethunter]

factories rarely use canister powders

exactly.

 

[Kryogen]

So if I am 1 whole grain below stiff bolt, how safe is that? Primers look on the flat side of fine.

 

[john92awd]

Like mauser said, a slower powder would do the job.

 

[cosmic]

1 grain below is 1.4%, not very much margin there. Why push the limits of the brass and the action, when you can go to a slower powder. Not to mention throat erosion which varies with the load cubed...
And BTW - Max accuracy rarely occurs at or near max load.

 

[stubblejumper]

So if I am 1 whole grain below stiff bolt, how safe is that? Primers look on the flat side of fine.

One grain is not much when you are talking 70 grains. If you are seeing stiff extraction at 71.5gr, I would probably reduce the load by at least 1-1/2 grains, likely 2 grains. As for quickload, is is a calculation, it can only estimate pressure, and then only on known pressures, you don't know what powder blend is being used in the factory load.

 

[H4831]

[QUOTE=cosmic;12761937----- Not to mention throat erosion which varies with the load cubed...


Where and when were the tests done to prove this theory?

 

[H4831]

"---And BTW - Max accuracy rarely occurs at or near max load."

The greatest bench rest shooter of all time is usually considered to be Warren Page.
In his book, the accurate rifle, he states, "There is only one way to load the 308 and that is full."

For loading heavier calibres for long range shooting, he says, in effect, the fellows load each of their rifles to the highest pressures the rifles will take, with Norma 205 or H4831.

I guess nobody told these guys that they should load light for better accuracy!

 

[Eagleye]

I have tested an old box (10-15 years?) of 308 norma magnum, and it chronos at 3130 fps or so.

The new factory ammo is around 3040 fps.

According to quickload, I can't get anything over 3035 FPS without being over pressure.

70.5 RL19 gives me 3044 fps, no pressure signs
71.0 gives around 3050, flat primers
71.5 hard extraction.

From that I determined that 70.5 was a safe load in that rifle.
According to quickload, I am still over pressure at 3044

Your point of view? Maybe I should cut the next reloads to 70.0 to lenghten brass life? I already have a few that have loose pockets from being fired factory load + 2 reload (might have been the over max loads)

All of that older Norma Mag ammo graphed north of 3100 fps. Norma bluntly stated that the original load was 76.7 grains of now obsolete N205. [Replaced by the nearly identical MRP] I have a written statement from Norma precision to verify that loading.

I am a big fan of the 308 Norma Mag, and have several rifles so chambered. 75.0 grains of MRP will usually give just over 3000 fps in a 24" barrel. I can almost always reach 3100 or slightly higher with MRP, IMR 7828, Vihtavuori N165 & N560. I have had close to the same results with Reloder 22.

These loads do not mark brass in my rifles, nor do primer pockets loosen within 5 firings. Extraction is easy and silky smooth.

As Andy said so eloquently, QL is a software package. It is good stuff, but not the be-all, end-all. So many variants that it is simply a guesstimation, not etched in stone.

Regards, Dave.

 

[Gatehouse]

I have tested an old box (10-15 years?) of 308 norma magnum, and it chronos at 3130 fps or so.

The new factory ammo is around 3040 fps.

According to quickload, I can't get anything over 3035 FPS without being over pressure.

70.5 RL19 gives me 3044 fps, no pressure signs
71.0 gives around 3050, flat primers
71.5 hard extraction.

From that I determined that 70.5 was a safe load in that rifle.
According to quickload, I am still over pressure at 3044

Your point of view? Maybe I should cut the next reloads to 70.0 to lenghten brass life? I already have a few that have loose pockets from being fired factory load + 2 reload (might have been the over max loads)

Unless you have the exact powder of the day to run through QL, you aren't going to hget proper results. Garbage in = garbage out.

 

[Kryogen]

Ok thanks all.
That load works fine at 3040 fps and I will probably just keep it there.

 

[cosmic]

This is bread and butter mechanical engineering. In a nutshell, gas mass flow (and velocity) is proportional to load, and erosion potential is proportional to impingement energy (velocity squared). So, by increasing the gas flow by 5% you increase the erosion by 15%.

I refer you to "Combustion" by Joseph Singer P.E., page 23-21. Understandably, this book is not in common circulation, you might find that Marks Standard Mechanical Engineers Handbook offers a similar treatise on erosion.

 

[Eagleye]

This is bread and butter mechanical engineering. In a nutshell, gas mass flow (and velocity) is proportional to load, and erosion potential is proportional to impingement energy (velocity squared). So, by increasing the gas flow by 5% you increase the erosion by 15%.

I refer you to "Combustion" by Joseph Singer P.E., page 23-21. Understandably, this book is not in common circulation, you might find that Marks Standard Mechanical Engineers Handbook offers a similar treatise on erosion.

Typical of engineering....hard and fast rules that apply in some cases, but cannot make allowances for the nuances that change the goalposts.
There are so many small factors that are responsible for the rate of erosion in the throat of a rifle barrel. A set formula means little.
I have seen a 220 Swift barrel that had 2500+ rounds through it, and showed erosion that would normally be seen at 8-900 rounds.
On the other hand, I looked at a 6.5x300 Weatherby through the borescope...it was missing the first 5" of rifling from erosion. Round count? <300!!
Why the difference in these two chamberings, both of which are regarded as barrel-burners? Engineering cannot answer this easily.
Regards, Dave.

 

[cosmic]

Eagleye - I certainly agree with you that a universal formula cannot be applied across the board - as you cited above - each situation is unique. However, I think the formula is quite relevant to a given rifle and a given load. Whether the erosion rate is problematic is another story. If I had a barrel burner like a 220 Swift, and wanted to shoot it a lot, I would likely download it 5-10 percent from book to benefit the barrel.
On the other hand, I wouldn't be too concerned about erosion in an older lower pressure caliber like 30-30, 303 or 8 mm.

 

[Eagleye]

Eagleye - I certainly agree with you that a universal formula cannot be applied across the board - as you cited above - each situation is unique. However, I think the formula is quite relevant to a given rifle and a given load. Whether the erosion rate is problematic is another story. If I had a barrel burner like a 220 Swift, and wanted to shoot it a lot, I would likely download it 5-10 percent from book to benefit the barrel.
On the other hand, I wouldn't be too concerned about erosion in an older lower pressure caliber like 30-30, 303 or 8 mm.

Very sensible reply.
One of the major factors. IMHO, as far as barrel erosion goes, is heat. Continuing to shoot a barrel that is already piping hot is begging to accelerate erosion.

The Swift barrel I mentioned above was my own. It was fired with full power loads, always. [Why buy a Swift to shoot a 22-250, lol] BUT...was never fired "hot"
A Heavy barrel, which never saw more than 5 consecutive shots until it cooled. The Whby belonged to a friend who shot it so hot that water would sizzle on it.

Powder type, case design, barrel material, rifling twist, etc all factor in. Regards, Dave.

PS Sorry Kryogen, for derailing this thread a bit. D.