When does velocity not equate to pressure?

[bowji john]

Of course it does - always

However - in the light of the offering by @Stalker1962 - may I offer my own application to the 'Wally award' ?

Today I was playing with peregrine VRG1's out of a 9.3 x 62

I usually load 62 grains of RL 17 for my Nosler partitions

Aha says I - know they are a about a mile longer so compressive loads are bound to be an issue

Now I don't have distance to the lands as a guide - my barrel is from the same school as Linda (the Linda) - If you are under 50 - never mind

I do have a mag size - so that became by COAL guide

So - having consulted all the 'recipe books' and QL - I chose to start my load dev at a load of 58 grains - 4 below my standard charge for the Noslers

QL gave me the thumbs up and a predicted MV of 2350 - a bit higher than I need but QL tends to over estimate MV and if it proves correct ''I can always drop the load a bit' says I

One round at 25m

BANG

Recoil much the same as ever

Case had no signs of pressure - all good

No stiffness to the bolt - no probs with extraction




Glanced at the reading on the Magneto V3 - velocity read 3350 !!!!

Went home for a beer

 

[Lateral]

John,

Bullet weight ?

If you’re right, I’ll be calling Ed

But are you sure you measured bullet velocity, and not muzzle blast ?


Mark

 

[bowji john]

Hi Mark

286 grain

I did wonder about gases confusing the reading

Summat don’t make sense

Other than me of course!

 

[zambezi]

Glanced at the reading on the Magneto V3 - velocity read 3350 !!!!

Given the normal recoil, ease of extraction, absence of extractor signature on base, and no significant primer cratering, surely something is off with the chrono?

I have had optical chrono mis-reads if there was any residual oil in the barrel [i.e. forgot to dry patch before going shooting]. Not sure how the V3 would trip over that.

Have you checked the V3 bayonet for any distress? I am just wondering if rust or other flotsam from the moderator passed or impacted the bayonetbefore the flight of the bullet.

Regardless, I would pull the remaining rounds and re-measure charge.

 

[zambezi]

I tried to run up your cartridge in the GRT profiler, and that program does not have a database entry for the 286gr Peregrine VRG1.

But it did have an entry for the 286gr Nosler partition. When I input all that, it reckons that 55gr is a hot load. Some ways off your 62gr per the OP. But...there are a myriad guesstimates and default settings in such a mock up.

Happy to run specific query if you want to supply case volume, seating depth, etc.




By way of cross check, I had a look at my Nosler reloading manual. It does not list RL17 for the 9.3x62 cartridge and the max load in RL15 is 58.5gr for the 286gr Nosler partition.

 

[bowji john]

I tried to run up your cartridge in the GRT profiler, and that program does not have a database entry for the 286gr Peregrine VRG1.

But it did have an entry for the 286gr Nosler partition. When I input all that, it reckons that 55gr is a hot load. Some ways off your 62gr per the OP. But...there are a myriad guesstimates and default settings in such a mock up.

Happy to run specific query if you want to supply case volume, seating depth, etc.

View attachment 232870


By way of cross check, I had a look at my Nosler reloading manual. It does not list RL17 for the 9.3x62 cartridge and the max load in RL15 is 58.5gr for the 286gr Nosler partition.

That graph does tell a different tale to QL

I’ll have to study it later

A max of 58.5 for RL 15 makes sense as it is quite a bit faster that 17

I’ve chosen it for the 404 j as I’m restricted by vol with those long Bullets

 

[zambezi]

I’m restricted by vol with those long Bullets

I played about with the seating depth. By tweaking that value with even a 1mm deeper insertion [tending toward a reduced case volume] has a significant impact on pressures.

That stands to reason. But perhaps the rate at which that pressure increases [as we stuff longer copper bullets deeper into the cases to retain workable COAL] is less obvious.

55gr RL17, 7mm insertion:

 

[bowji john]

I played about with the seating depth. By tweaking that value with even a 1mm deeper insertion [tending toward a reduced case volume] has a significant impact on pressures.

That stands to reason. But perhaps the rate at which that pressure increases [as we stuff longer copper bullets deeper into the cases to retain workable COAL] is less obvious.

55gr RL17, 7mm insertion:

View attachment 232875

I suspect compressed loads has played a significant part in my woes !

What is extra-ordinary though - with that MV (if correct) is that I can still type my problems on here !!!

No signs of pressure on case or action - that is hard to fathom

 

[Selous]

Duff velocity reading…. Nothing else makes sense. There are no other indications of high pressure so try a few more to see what velocity they are doing

 

[zambezi]

Duff velocity reading

Quite possibly.

But with due regard to John's currently retained ability to enumerate ten blessings digitally, and with a nod to GRT, I think I would probably drop a few grains before re-testing.

It would be good to know the COAL or insertion depth so we can better model GRT or QL.

 

[markymark]

Do you think that part of the reason is that these are Peregrine bullets? My understanding is they only just lightly touch the rifling, riding the lands and grooves rather than engaging in them.

Meaning higher velocities can be achieved with lower pressure?

I doubt you would get the same result with any other lead free projectile.

 

[SamHuntVic]

John, it will be interesting when you test the Woodleigh Hydros, better let us know the difference.
Grant.

 

[Lancaster]

Do you think that part of the reason is that these are Peregrine bullets? My understanding is they only just lightly touch the rifling, riding the lands and grooves rather than engaging in them.

Meaning higher velocities can be achieved with lower pressure?

I doubt you would get the same result with any other lead free projectile.

A lot of the new, (post Barnes X) LFA bullets appear to be bore riders to a greater or lesser degree, the exception seems to be the Nosler E tips.

 

[Edinburgh Rifles]

Excellent news

Very low friction design.
Rather than removed material grooves from the shank to reduce friction/fouling/pressure, (old school technology), Peregrine use driving rings in relief.
The shank OD is LAND diameter
The ring OD is GROOVE diameter

Allows for use of faster powders, shorter barrels, compressed loads that would otherwise produce high pressure spikes and lower velocities.

They work extremely well in the current factory norm of 20” barrels
Where as i am struggling to make 3000fps on a client’s 130gr GMX load in .270
Comes out around 2990fps in his 20” Tikka T3 (using a stout load of RS60)

I use Peregrine 136gr in .308 and make 2950 in a 20” tikka (44-45gr N133)

Velocity is not always needed to make them work but higher terminal velocities with expanding/maintained mass monolithics will always work better at speeding up the expiration of the target animal.

 

[bowji john]

Excellent news

Very low friction design.
Rather than removed material grooves from the shank to reduce friction/fouling/pressure, (old school technology), Peregrine use driving rings in relief.
The shank OD is LAND diameter
The ring OD is GROOVE diameter

Allows for use of faster powders, shorter barrels, compressed loads that would otherwise produce high pressure spikes and lower velocities.

They work extremely well in the current factory norm of 20” barrels
Where as i am struggling to make 3000fps on a client’s 130gr GMX load in .270
Comes out around 2990fps in his 20” Tikka T3 (using a stout load of RS60)

I use Peregrine 136gr in .308 and make 2950 in a 20” tikka (44-45gr N133)

Velocity is not always needed to make them work but higher terminal velocities with expanding/maintained mass monolithics will always work better at speeding up the expiration of the target animal.

Hi Ed

Do you think that MV thatI measured is not a malfunction in the V3?

It scared me to death - I’ve never had 3000 ft per sec out of anything- let alone something half the size of my house

I shall seat less deeply next and come down a grain or two

I only require 2300 from them and the numbers at the moment are scaring me

 

[bowji john]

Quite possibly.

But with due regard to John's currently retained ability to enumerate ten blessings digitally, and with a nod to GRT, I think I would probably drop a few grains before re-testing.

It would be good to know the COAL or insertion depth so we can better model GRT or QL.

COAL was 3.290

I have some extra room in the mag so will increase that but fir next go

How can QL (which has been updated for Peregrine and RL 17, give a predicted vel that is so different from that measured?

Surely the MV is wrong. There was no noticeable increase in recoil either which I would have expected launching a 286 grain bullet at 3300 ft per sec!

Also … how can your reloading software give such different predictions to mine (QL)

 

[Andy RV]

No pressure signs, test them again.

I personally think your magnetospeed threw a wobbler.

 

[bowji john]

No pressure signs, test them again.

I personally think your magnetospeed threw a wobbler.

I will turn down the sensitivity- it was set at ‘standard’

 

[zambezi]

how can your reloading software give such different predictions to mine

Whenever I have found a widely differing prediction, it is usually because I have omitted one critical parameter, or left a faux default. I may have selected the wrong Nosler projectile...

Whenever GRT has solid data, it broadly agrees with reloading manuals, and other software models.

I will re-run GRT with the Nosler solid #29825 286gr grain data with COAL supplied above and double check all default values for foo wrt SAAMI.

[One complete mystery for me is why the user of GRT can change the starting pressure value. How many reloaders have the kit to measure that?]

 

[zambezi]

GRT also makes powder predictions based on published explosivity. The GRT model is then fine tuned by iterative user input.




Per GRT's statement regarding RL17, it is not as user calibrated as RL15 or RL16: