Pressure signs?

[Ejcb]

Hi guys,

Managed to to test the 4451 / CCI450 / 147 ELDM / Lapua 6.5CM SRP brass combo at bisley.

I used a magnetospeed v3 on my 24" Tikka Tac A1 using an MK Machining mount, so the chrono wasn't attached to my barrel.

The wind 10 to 20 MPH from all angles, air and ammo temp was 21C, measured with a kestrel and laser thermometer respectively.

All loads grouped well despite the wind, so I focused on SD/ED and will shoot for groups another day in more favourable conditions.

The below 40.6 grain load had excellent figures, but is quite slow - however Tikka barrels can be known to be slow, however given the relatively warm ammo temperature of 21C, on a more common, cooler day I may see a lower MV, although the IMR Enduron range are meant to be relatively temperature insensitive - ( https://precisionrifleblog.com/2016/06/19/powder-temp-stability-hodgdon-extreme-vs-imr-enduron/#:~:text=That%20is%20very%2C%20very%20low,to%20large%20swings%20in%20temperature. - approx 68 FPS from -3 to 60C)

Unfortunately the other shots of the below series were not recorded, however they grouped very nicely at 600 and seem to have good SD/ES.

I did however notice some marks on the Lapua brass after their first firing, I am unsure whether this is brass wipe or smear from the virgin brass on the bolt face during fireforming, from bolt unlock and cartridge extraction, or from excessive pressure. 

In the picture below the 41.2 load cartridges have been arranged to place the ejector marks at the 6 o'clock position.

What are your thoughts?

 

[Catch-22]

I’d say that it doesn’t look like your usual ejector swipe as such, as most of the case head looks ‘swiped’. I guess that could happen as the bolt is rotated to unlock and the case head is scraping against the face of the action perhaps??

But if you look carefully at the ‘P’ in the middle picture and the ‘ree’ in the bottom picture, that looks more clearly like the ejector swipe, as it looks more distinctly round.

The primers don’t look flattened though.

[KABOOM]

1 hour ago, Ejcb said:

Hi guys,

Managed to to test the 4451 / CCI450 / 147 ELDM / Lapua 6.5CM SRP brass combo at bisley.

I used a magnetospeed v3 on my 24" Tikka Tac A1 using an MK Machining mount, so the chrono wasn't attached to my barrel.

The wind 10 to 20 MPH from all angles, air and ammo temp was 21C, measured with a kestrel and laser thermometer respectively.

All loads grouped well despite the wind, so I focused on SD/ED and will shoot for groups another day in more favourable conditions.

The below 40.6 grain load had excellent figures, but is quite slow - however Tikka barrels can be known to be slow, however given the relatively warm ammo temperature of 21C, on a more common, cooler day I may see a lower MV, although the IMR Enduron range are meant to be relatively temperature insensitive - ( https://precisionrifleblog.com/2016/06/19/powder-temp-stability-hodgdon-extreme-vs-imr-enduron/#:~:text=That%20is%20very%2C%20very%20low,to%20large%20swings%20in%20temperature. - approx 68 FPS from -3 to 60C)

Unfortunately the other shots of the below series were not recorded, however they grouped very nicely at 600 and seem to have good SD/ES.

I did however notice some marks on the Lapua brass after their first firing, I am unsure whether this is brass wipe or smear from the virgin brass on the bolt face during fireforming, from bolt unlock and cartridge extraction, or from excessive pressure. 

In the picture below the 41.2 load cartridges have been arranged to place the ejector marks at the 6 o'clock position.

What are your thoughts?

 

21c isnt very hot and the primers look fine, maybe a sign of pressure? how was bolt lift and extraction? Possibly compare some factory ammo  and if its the same and no other signs as mentioned above carry on. best wishes for good shooting.

 

[KABOOM]

i should have mentioned i have exactly one push feed plunger ejector action and i dont get marks on my brass shooting in temps around 30c. The rest are mauser type, true mauser, or Ruger no1 with a M-1 Garand because its kinda required by dna. Not that i recall the place i read it but , i have read some on primer flattening and how on firing the primer un seats slams on the bolt face and reseats. Tbh i look more to bolt lift and ease of extraction for pressure signs. I learned to confine my testing to the hottest times of year so my loads will be ok when i shoot the most. Powders that are not temp sensitive are used. 

[Ejcb]

On 7/12/2020 at 8:52 PM, KABOOM said:

21c isnt very hot and the primers look fine, maybe a sign of pressure? how was bolt lift and extraction? Possibly compare some factory ammo  and if its the same and no other signs as mentioned above carry on. best wishes for good shooting.

 

Hi kaboom,

bolt lift was fine, and the load is below the max load below: