6 creedmoor eratic pressure spikes

[alinde88]

So here's my delema, I have an MPA 6 creedmoor that has shot lights out for about 1400 or so rounds, I shot 1000 109 lrht over 39.3gr of h4350 in peterson srp brass, at 10 loadings I was loosing primer pockets left and right and tossed most of them and got lapua brass, I shot 300 berger 115 hunting out of them over around 40gr of 4350 with no issue, I tried 107 smk's and couldn't get them to shoot. Then 109s came up and I bought another 700 of them, went to do a work up with the lapua brass, h4350 and the 109s and they have horrible pressure signs, like I'm swelling cases at 36gr, I cleaned the shit out of the barrel and checked with a borescope and there is zero carbon ring, but the odd part is that I can load 36 gr it will shoot one with zero pressure signs then the next identical load will swell a case, anyone ever had this issue ? I'm lost and said screw it and ordered a barrel but would like to know what the issue was

 

[Ranger188]

You were shooting Peterson brass first, then switched to Lapua.
Anytime you change something (like brass), you need to work up a new load.
They have different internal volumes that affect pressure.

 

[DLT]

You were shooting Peterson brass first, then switched to Lapua.
Anytime you change something (like brass), you need to work up a new load.
They have different internal volumes that affect pressure.

I agree with a new load work up being needed but isn’t 36gr of H4350 close to a starting charge and he was having trouble ? I shoot a 6 creed also and have a little brass trouble going on, in my case I believe it’s just a warm load that lasted 9 firings

 

[alinde88]

You were shooting Peterson brass first, then switched to Lapua.
Anytime you change something (like brass), you need to work up a new load.
They have different internal volumes that affect

I agree with a new load work up being needed but isn’t 36gr of H4350 close to a starting charge and he was having trouble ? I shoot a 6 creed also and have a little brass trouble going on, in my case I believe it’s just a warm load that lasted 9 firings

Yah I was definatly doin a load work up, the odd part is just that combo of components no matter what would give pressure spikes well below anything that should swell brass and push primers. Also loading 4 gr less powder than I was before with a heavier bullet is what's odd. No matter what I did with that combo it was crazy scary pressure signs

 

[alinde88]

You were shooting Peterson brass first, then switched to Lapua.
Anytime you change something (like brass), you need to work up a new load.
They have different internal volumes that affect pressure.

If you actualy read my post you see that It literaly says I was doin a load workup, the problem is that no matter how low I went on powder charge it was blowing primers and swelling cases, I know i need to work up a new load anytime I have a component change

 

[Zero333]

Did you check the H2O capacity of the Peterson brass ???

What barrel length and velocity are you getting with the 115 gr VLD Hunt. ???

Did examine the firecracking in the throat when bore-scoping the barrel ???

 

[Shane Roya]

Mic the 109's , they could be wrong size.

 

[SmokinJoe]

Case length a little long for your chamber?

 

[243winxb]

I can load 36 gr it will shoot one with zero pressure signs then the next identical load will swell a case,

Neck tension, bullet hold may need increased? If bullets move to soon on primer firing, strange things may happen.

Brass Trim length needs checks & chamber measured .

Check scale for correct powder amounts.

The 36 gr load would seem to a good starting load? But brass does make a difference. Check case volume.

Has all tumbling media been removed from the brass, before loading?

Just guessing.

 

[6.5 forever]

Were you checking speeds to see if was matching your pressure signs?

 

[AM_ARixon]

I know you said you checked for carbon ring, but those are exact symptoms of a carbon ring, and 6 creedmoors are very susceptible to carbon rings even with H4350... Was the bore perfectly clean because typically standard cleaning chemicals and techniques do not remove carbon rings. Did you check right at the mouth of the case? typically you have to use a compound and really scrub it out, or some guys with rings in the neck have had to go in with a reamer and cut it out.

 

[SBS]

How about loaded neck diameter with the Lapua vs. Peterson? If larger, could be right on the edge where some that are slightly larger may be too tight, as there is always slight variations in necks in a lot.

 

[Walt Krafft]

1500 rounds of max pressure 6 creedmore and your barrel is toast.

 

[FrankG]

1500 rounds of max pressure 6 creedmore and your barrel is toast.

^^^^^ Walt beat me too it!

The barrel is toast most likely. Pressure test barrels in 6CM and they only get about 800-1200 rounds out of them. Actually the number is probably on average is under a 1k rounds. Prior to 6CM coming out if we wanted to do testing we did barrels in 243win. because you basically smoked the barrel in about 800-900 rounds. Same thing here... pressure test barrels in 243win and they normally don't make it past 900 rounds and they are junk. Due to wear and the roughness of the throat they start to see a velocity loss and an increase in pressure. When these two things happen at the same time .... they pull the test barrels and throw them away. They no longer can count on them/trust them for p&v testing.

You can maybe milk it for accuracy for a bit yet... but it's just going to keep giving you problems.

Later, Frank
Bartlein Barrels

 

[alinde88]

I know you said you checked for carbon ring, but those are exact symptoms of a carbon ring, and 6 creedmoors are very susceptible to carbon rings even with H4350... Was the bore perfectly clean because typically standard cleaning chemicals and techniques do not remove carbon rings. Did you check right at the mouth of the case? typically you have to use a compound and really scrub it out, or some guys with rings in the neck have had to go in with a reamer and cut it out.

Yah I use boretech and a camera to make sure, that was my initial thoughts was maybe a carbon ring bit cleaning didn't helpn

 

[alinde88]

^^^^^ Walt beat me too it!

The barrel is toast most likely. Pressure test barrels in 6CM and they only get about 800-1200 rounds out of them. Actually the number is probably on average is under a 1k rounds. Prior to 6CM coming out if we wanted to do testing we did barrels in 243win. because you basically smoked the barrel in about 800-900 rounds. Same thing here... pressure test barrels in 243win and they normally don't make it past 900 rounds and they are junk. Due to wear and the roughness of the throat they start to see a velocity loss and an increase in pressure. When these two things happen at the same time .... they pull the test barrels and throw them away. They no longer can count on them/trust them for p&v testing.

You can maybe milk it for accuracy for a bit yet... but it's just going to keep giving you problems.

Later, Frank
Bartlein Barrels

Yah it's getting a new barrel this week, I knew it was pretty much toast but was tryin to milk it out while I waited for a barrel

 

[alinde88]

Were you checking speeds to see if was matching your pressure signs?

I was and it was running real fast, like 3100+ when it would do it

 

[alinde88]

Neck tension, bullet hold may need increased? If bullets move to soon on primer firing, strange things may happen.

Brass Trim length needs checks & chamber measured .

Check scale for correct powder amounts.

The 36 gr load would seem to a good starting load? But brass does make a difference. Check case volume.

Has all tumbling media been removed from the brass, before loading?

Just guessing.

You were shooting Peterson brass first, then switched to Lapua.
Anytime you change something (like brass), you need to work up a new load.
They have different internal volumes that affect pressure.

If you read my post you would see I had this issue while doing a LOAD WORKUP lol

 

[alinde88]

How about loaded neck diameter with the Lapua vs. Peterson? If larger, could be right on the edge where some that are slightly larger may be too tight, as there is always slight variations in necks in a lot.

Also checked that, between loaded and fired rounds I had about .004 clearance for the neck, I shot this brass with different it only started with the 109s

 

[RED DIRT]

Incase i missed it, What did the bullets diameter measure ?