N160 and a dirty bottom...

[gixer1]

I just tried out a batch of my first rounds with N160 for the 6.5CM and a bit of an oddity, I loaded up 12 x 120gr SP’s, 2 at 38.5gr and 2 at each 0.5gr increment up to 41gr, (my intention was just to get chrono results and look for pressure signs as there is no data for 120’s and N160, I also loaded up 10 x 140gr spbt’s, again in 2’s from 38.0 up in .5gr increments.

unfortunately the chrono wasn’t playing ball and wouldnt take any readings (low light as the sun was setting) so I shot all the 120gr rounds and 4 of the 140’s (trying to mess with the chrono) no speeds were recorded..

but what I did notice is all the 120gr rounds were touching so basically the same point of impact. The 120’s were about an inch apart however 3 of the 120’s and 1 of the 140’s had extremely sooty case heads on the rim...I guess this means throttle up but the soot was significant - is N160 a dirty powder??

OAL were as per Sierra manual.

regards,
Gixer

 

[Stevie/P]

Seat the bullet deeper or could be insufficient neck tension Sierra OAL is max length had this with my 6.5x55 seating the bullet another 20tho deeper did the trick for me

 

[Jax]

Did you have the soot on the first shot?Are you using a moderator?

ive had similar in the past after zeroing or load testing on particularly cold days. The cases came out wet and sooty. I put it down to gases cooling and condensing on the cases.

 

[rabbitter]

Morning Gixer

(Please ignore if no help. )

I've been playing with N150 and N165 recently as per my 6.5x55 thread.

One of the points that Viht mention in their blurb is that they make clean burning, temperature stable powders (which could be just blurb - sure).

It's been coldish - around freezing and I haven't had any sootiness. Has your brass all been fired the same number of times? If not, could you have some loose pockets? In my 6.5x55, I seated the Gameking SBT 140gr to Sierra's listed OAL and used Fiocci LRP primers.

As a side issue, is it possible that N160 is a bit slow for 120gr?

kind regards


Ian

 

[gixer1]

Sorry folks - I should have mentioned - brand new never fired lapua SRP brass, so neck tension should be pretty consistent. It was on sporadic shots - not all of the batch, same powder charge did not do it on both shots.

the seating depth on the 120’s was further in than on the 140’s...2.75” on the 140’s and 2.73” on the 120’s.

and yes, had a moderator.

regards,
gixer

 

[gixer1]

Morning Gixer

(Please ignore if no help. )

I've been playing with N150 and N165 recently as per my 6.5x55 thread.

One of the points that Viht mention in their blurb is that they make clean burning, temperature stable powders (which could be just blurb - sure).

It's been coldish - around freezing and I haven't had any sootiness. Has your brass all been fired the same number of times? If not, could you have some loose pockets? In my 6.5x55, I seated the Gameking SBT 140gr to Sierra's listed OAL and used Fiocci LRP primers.

As a side issue, is it possible that N160 is a bit slow for 120gr?

kind regards


Ian

Yes. Possibly. I was using Varget and hadn’t seen this issue but I had hang fires and my case fill was apparently very low.

 

[hendrix's rifle]

Sorry folks - I should have mentioned - brand new never fired lapua SRP brass, so neck tension should be pretty consistent. It was on sporadic shots - not all of the batch, same powder charge did not do it on both shots.

the seating depth on the 120’s was further in than on the 140’s...2.75” on the 140’s and 2.73” on the 120’s.

and yes, had a moderator.

regards,
gixer

Small primers, not a hot enough load? Could have given a bad burn (its been fresh where I am recently) and not ignited the powder properly

 

[gixer1]

My other thought was it’s due to the new brass and it not being fire formed to the chamber - I.e.- it may be better second time round?

regards,
Gixer

 

[Jax]

My other thought was it’s due to the new brass and it not being fire formed to the chamber - I.e.- it may be better second time round?

regards,
Gixer

Could potentially be the case if you have excess headspace.

Ive never had it, but I’ve read that excess headspace can cause the primer to be pushed out as it ignites and then it’s re-seated as powder burns and the brass expands

could be worth measuring the headspace of fired brass compared to the new brass just to check

this may explain why only the rim is sooty and not the whole case...

 

[Foxyboy43]

If not the new cases thought ( never had this problem with new myself) go deeper and/or crimp.

 

[Scooby-3]

You have got no where near enough powder in for 120gr bullets.

Check the Vihtavuori load data for other 120-140+ Bullets.

Viht is also very cautious so there max isn’t necessarily your max but work up

 

[gixer1]

You have got no where near enough powder in for 120gr bullets.

Check the Vihtavuori load data for other 120-140+ Bullets.

Viht is also very cautious so there max isn’t necessarily your max but work up

Actually for 160 with a 120gr bullet I am over the max already, not pressure signs but Vhit’s data is low.

 

[Scooby-3]

Actually for 160 with a 120gr bullet I am over the max already, not pressure signs but Vhit’s data is low.

Check the data for other 120 and up bullets, that particular bullet is an anomaly.

You have low pressure signs not high pressure, which potentially could be as dangerous

 

[Lateral]

Pictures can be deceptive, but the cases look like they're well used.

I'd be interested to see what they look like wiped down.

I can't understand why there isn't soot around the neck, just the groove ? I know it makes no sense, but it's almost like there's case head separation !

 

[takbok]

Actually for 160 with a 120gr bullet I am over the max already, not pressure signs but Vhit’s data is low.

Don't use the load data for the copper bullets, look at the 120gr jacketed bullet data.

As I've said, I don't think you'll get enough powder into the case to cause excessive pressure.

 

[gixer1]

Pictures can be deceptive, but the cases look like they're well used.

I'd be interested to see what they look like wiped down.

I can't understand why there isn't soot around the neck, just the groove ? I know it makes no sense, but it's almost like there's case head separation !

Hi Lat.

they are brand new out of the box cases, no signs of any damage.

I’ve never seen the groove with soot either to be honest, and it’s very thick soot.

regards,
Gixer

 

[gixer1]

Don't use the load data for the copper bullets, look at the 120gr jacketed bullet data.

As I've said, I don't think you'll get enough powder into the case to cause excessive pressure.

The problem is there is no data for the others...

 

[25 Sharps]

Actually for 160 with a 120gr bullet I am over the max already, not pressure signs but Vhit’s data is low.

You are comparing data for long, lead free bullets when you are using a short cup and core lead bullet

 

[25 Sharps]

Actually for 160 with a 120gr bullet I am over the max already, not pressure signs but Vhit’s data is low.

You need a faster powder or heavier bullet

 

[Loler UK]

I've have known this many times and would say Your shoulder is not sealing in the chamber early enough in the burn, likely because your head space is excessive/ your charge is too light / with too slow a powder.
can i see soot on the side of the cases as well as on the rim?

1st, clean the chamber, dirt and soot will hinder the seal.
2nd get a good head space gauge and measure a de-primed fired case and use this to set up your die so that you are not bumping back to far, if you use virgin brass you may find it's shoulder is a little far back for your chamber.

once this is done if it continues you have several options
1 apply crimp, this will encourage the case to expand and seal earlier
2 ladder up the charge, usual caveats apply to safety
3 use a faster powder
4 some people advocate a magnum primer to help seal the shoulder