Peterson pressure 6.5 cm

[il_cop]

Looking for some guidance here....

Tikka 20" 6.5 cm
Peterson brass once fired
143 ELDX .05 jump/ 2.24 cbto/ 2.88 coal
240 rounds down tube
OG 6.5
WLR primers

40 gr h4350
2595 avg.
45 es 15 sd
2577 - 2622

Heavy bolt lift and extractor marks on 1/4 cases

Just keep dropping the charge (?)
Seems super low already but velocity seems to track, though I'm seeing reports of higher charges and velocity here and elsewhere.


Tight chamber?
Is this just what the rifle's gonna give me?

Anything you can think of or recommend?

Appreciate it

 

[wind gypsy]

Extrapolating to my 24.3" CTR barrel, it gets about the same before getting sticky bolt lift.

140 Hybrids to low 2700s, 144 LRHT to around 2670 is about max i can run with Lapua or Norma brass and h4350 without frequent heavy bolt lift. Even that gets a little sticky time to time. So with the 4" of additional barrel length and larger capacity brass, that tracks close to what you're seeing.

I know others push em faster, maybe their tolerance for sticky bolt lift is higher than mine or they just have setups that dont show it as much.

Also, if you were shooting into the wind and it was cool out, i've had bolt thrust issues show up way earlier when shooting suppressed in such conditions.

 

[streamerfish]

Looking for some guidance here....

Tikka 20" 6.5 cm
Peterson brass once fired
143 ELDX .05 jump/ 2.24 cbto/ 2.88 coal
240 rounds down tube
OG 6.5
WLR primers

40 gr h4350
2595 avg.
45 es 15 sd
2577 - 2622

Heavy bolt lift and extractor marks on 1/4 cases

Just keep dropping the charge (?)
Seems super low already but velocity seems to track, though I'm seeing reports of higher charges and velocity here and elsewhere.


Tight chamber?
Is this just what the rifle's gonna give me?

Anything you can think of or recommend?

Appreciate it

Like you said, the velocity seems to track....Roughly 2600fps out of a 20" barrel is in the right ballpark.

Peterson brass is known to have lower case volume. I don't have direct experience with it, but lots of reports of around 1 grain difference out there.

So yeah, below 40gr may feel a touch low, but I wouldn't think really outside of expected range.

 

[hoooogan]

Also confirming that tracks. My SA Redline 20" starts to get a touch sticky at ~2620fps with 147 ELDM in Lapua brass and 41.0gr H4350.

 

[skipper907]

I would try shortening your coal. I personal shoot mine at 2.845 with 41.0 h4350 in Peterson brass and can be right on the pressure line.
I would load up 5 to 10 at 2.800 and maybe 2.845 and see how they shoot
if you loading .050 off and your coal is 2.880 it seems like your max coal is a little long

 

[wind gypsy]

I would try shortening your coal. I personal shoot mine at 2.845 with 41.0 h4350 in Peterson brass and can be right on the pressure line.
I would load up 5 to 10 at 2.800 and maybe 2.845 and see how they shoot
if you loading .050 off and your coal is 2.880 it seems like your max coal is a little long

I'm pretty sure I had to be over 3" COAL to hit lands with 140 hybrid or 144 LRHT in my CTR tube. Long throats in those tikka 6.5s.

Not disagreeing that shorter COAL might show less pressure but rather that the COAL at Jam doesn't seem unreasonable.

 

[skipper907]

I'm pretty sure I had to be over 3" COAL to hit lands with 140 hybrid or 144 LRHT in my CTR tube. Long throats in those tikka 6.5s.

Not disagreeing that shorter COAL might show less pressure but rather that the COAL at Jam doesn't seem unreasonable.

Ya with Berger bullets you will get a much longer coal compared to Hornady which will be shorter.

 

[il_cop]

What's the general consensus?
Drop the charge to 39.7 and keep the coal?
Or keep the charge @ 40 and shorten the coal?

Besides fixing the pressure issue, I'd like to tighten up the es... I'm assuming they're related.

So much for the painless method!?

This is the first rifle I've had to chase like this.

 

[wind gypsy]

Drop 0.3 and seat a little deeper.

That said, you're seeing pressure signs on 1 in 4 firings, meaning pressure signs are not an exact line like people pretend it is. Dropping powder charge less than 1% is far from a guarantee you wont still have some rounds exhibit pressure signs.

This is one of the reasons I pulled my CTR tube before it was dead.. If I was loading a shorty tikka 6.5 creed barrel, i'd probably lean towards 130 TMKS to get velocity.

 

[il_cop]

I'm fine if I land at 2550-75, no worries. Just want to get rid of the pressure.

I have a ton of 143s from another 6.5 build that I want to get through before I invest in 130s. But youre on point, probably the the better choice.