Pressure issues, need some help

[DLT]

VV data for 6 CM with 108gr target bullets max load is 38.7 grains.

There is no load data for a 107, so it's good practice to use the next heaviest bullet data, 108 grains, and also the same type of bullet.

A SMK is similar to a Berger Target, not a Berger Hunter, notice the Hunter starts with 3 gr higher than the Target, and ends up at max 5 grains higher than the Target.

It means that the target bullet has a longer bearing surface than the hunter, and generates a higher chamber pressure, which is why you need to use data for similar shape bullets, not by weight alone.



The book says to expect 2759 fps from 37 grains of N160 with a 108gr bullet.

Your 300 fps over means, if all other parameters are correct, that the powder in the tin is probably not what you think it is.

Go look again. Sierra doesn’t make a 108 . The screw up is on them if some other mystery powder is in my jug. Either way if it is 38.7, I went down to 36.0 and still had stamped brass. I keep my powder separate. One on the table at a time. I will look and compare if anything else I have even looks similar to n160

 

[big5ifty]

I went down to 36.0 and still had stamped brass.

If you're 100% sure of the powder, mic the bullets. Don't use a vernier, a micrometer.

... and while you're at it, weigh the bullets.

 

[dellet]

I don’t think so.

*Update* today I sent my headspace with the go gauge. After it was set I used 1 piece of scotch tape (.0015- .002) on the back of the gauge and my bolt won’t close so I’m good there. I might have turned the barrel 1/16 of a turn from where it was. Anyway new lapua small rifle brass I started today down another grain so 37.5gr of n160 with a cci 450 primer and smoked and blew out the primer on the first shot at 3058fps. I came down another 1.5gr to 36.0 those 3 rounds stamped the brass hard with an average of 2967. Still over vv max velocity while being 5 grains below their max charge and 1gr below their starting charge. I give up on n160 not worth it to me. I Loaded 3 with 39.0gr of h4350 and had no pressure of any kind 2974 avg fps.

Not 1 thing has added up other than this power is hot as piss in this rifle. No explanation

You’re probably right on the powder, @Laurie has written about it a couple times and seems to think it’s hotter than the reloading tools predict.
but look at some numbers any way.

I believe all Savage rifle tenons are threaded 20 per inch. .050” per rotation, .005” on 1/10 rotation.

You switched to new brass, not only will that have less case capacity, it will have a longer neck due to a shorter body and possibly place the bullet closer to the lands, then you moved the lands closer to the bullet. All of this will raise pressure. Backing off only a grain from a known hot load was insignificant. I probably would have backed off at least 3-4 grains, you backed off 1 at first 2.5 total. Seems like enough. But wasn’t, keep in mind you basically changed rifles, brass and maybe primers. So reducing a known good by 10% would have been prudent. A known hot load needs even more.

You haven’t mentioned loaded length, is it all possible the bullet is jamming?

Some of your velocities with 4350 also seem high compared to book predictions, another indicator of possible tight chamber or bore or grooves, have measured those?

You have N560, in theory it should be a substitute for N160, yet reports have it as noticeably slower, might. So worth a try.

 

[DLT]

I still wonder if the powder isn't compromised in some way.

You’re probably right on the powder, @Laurie has written about it a couple times and seems to think it’s hotter than the reloading tools predict.
but look at some numbers any way.

I believe all Savage rifle tenons are threaded 20 per inch. .050” per rotation, .005” on 1/10 rotation.

You switched to new brass, not only will that have less case capacity, it will have a longer neck due to a shorter body and possibly place the bullet closer to the lands, then you moved the lands closer to the bullet. All of this will raise pressure. Backing off only a grain from a known hot load was insignificant. I probably would have backed off at least 3-4 grains, you backed off 1 at first 2.5 total. Seems like enough. But wasn’t, keep in mind you basically changed rifles, brass and maybe primers. So reducing a known good by 10% would have been prudent. A known hot load needs even more.

You haven’t mentioned loaded length, is it all possible the bullet is jamming?

Some of your velocities with 4350 also seem high compared to book predictions, another indicator of possible tight chamber or bore or grooves, have measured those?

You have N560, in theory it should be a substitute for N160, yet reports have it as noticeably slower, might. So worth a try.

i have not measured bore never had any issues. I did seat my bullets in deeper, I do have that much sense. I just didn’t come down near enough and I do believe that powder is a lot hotter than burn rate charts claim. I read somewhere over the weekend that it was closer to H4831 than H4350. I’m going to call bs especially on the n160 I have

 

[DLT]

If you're 100% sure of the powder, mic the bullets. Don't use a vernier, a micrometer.

... and while you're at it, weigh the bullets.

I did not weigh them but I did measure them. .243 I probably have 200 left out of a 500ct box

 

[dellet]

I have read it and stated on this thread couple of times that I had used this n160 powder in a 22 creedmoor testing. I went back to look at my notes and

i have not measured bore never had any issues. I did seat my bullets in deeper, I do have that much sense. I just didn’t come down near enough and I do believe that powder is a lot hotter than burn rate charts claim.

Not picking on you, but seating also raises pressure. It’s a case capacity issue. Kind of goes back and forth. Decreasing case capacity raises pressure, moving away from the lands can decrease pressure if the bullet was close very close.

If you set the barrel back .005” and seated the bullet .005” deeper, the chamber relationship stayed the same while internal case capacity was reduced. Higher pressure.

Question is still there, are you 100% sure you’re not jamming the bullet? It’s just something that hasn’t been asked or answered that is relavent

 

[DLT]

Not picking on you, but seating also raises pressure. It’s a case capacity issue. Kind of goes back and forth. Decreasing case capacity raises pressure, moving away from the lands can decrease pressure if the bullet was close very close.

If you set the barrel back .005” and seated the bullet .005” deeper, the chamber relationship stayed the same while internal case capacity was reduced. Higher pressure.

Question is still there, are you 100% sure you’re not jamming the bullet? It’s just something that hasn’t been asked or answered that is relavent

Yes. It’s just hard for me to believe the tiny things that I had off, caused that much destruction.

 

[10XSHOOTER]

If you're shooting over 35 grs of powder, stick with LRG rifle primers!
old school line of thought that still works today.
under 35 grs of powder SRP
35-65 grs LRG primers
over 65 grs LRG Magnum Primers

 

[big5ifty]

The fact that you can get predictable results with another powder, using the same bullets, brass and primers, is a strong confirmation that the problem is in fact what's in the VV container.

 

[SKWERLZ]

Yes I did but that doesn’t explain much to me as to what happened. I was using vv load data not a max charge. unless it’s a big no no to use large rifle primers in place of small rifle data. I just switched powders like any of us has done hundreds of times. I did not have my scale set wrong or use an out of line powder.

I have made mistakes before but with a little work or asking the right questions I found out and learned why things did what they did. Not sure about this go round.

Same primer, case, bullet and barrel as VV data?

Always work up.

 

[Doom]

Regardless of the cause you should advise VV/Capstone about this issue. IF nothing else the Load data is marked incorrectly but it sounds like something is amiss with the powder.

 

[DShortt]

The fact that you can get predictable results with another powder, using the same bullets, brass and primers, is a strong confirmation that the problem is in fact what's in the VV container.

My thoughts exactly.

2 or 3 rounds are fine, then a primer blows or the bolt sticks? Either that powder is wonky/mixed or that particular powder with that particular case/primer/bullet/seating depth results in inconsistent ignition.

I'd toss that powder. Before a catastrophe eventually ensues.

You aren't mixing primers, I presume? That's bad juju.

 

[DShortt]

Regardless of the cause you should advise VV/Capstone about this issue. IF nothing else the Load data is marked incorrectly but it sounds like something is amiss with the powder.

Weird thing is, unless I misread the thread, it worked fine in another rifle/cartridge.
So, I'm thinking he either messed up and dumped some different powder in this container between now and then, or he's got some primers that aren't all the same. Or he's got mixed brass. And the velocity wasn't off much between fine and a blown primer/stuck bolt?
There's only so many possibilities.

 

[DShortt]

i have not measured bore never had any issues. I did seat my bullets in deeper, I do have that much sense. I just didn’t come down near enough and I do believe that powder is a lot hotter than burn rate charts claim. I read somewhere over the weekend that it was closer to H4831 than H4350. I’m going to call bs especially on the n160 I have

So, explain to me how 2 or 3 shots can be fine, then you have a stuck bolt/blown primer?
There must be an inconsistency somewhere. And it's fairly significant.
Otherwise, every time you'd see the same result.
Did you use the same batch of primers in the cartridge that behaved normally? How many primers from this particular batch have you used?

 

[LCazador]

I know the case head itself swelled .030 in diameter

The case swelled .030" in diameter. That's 30 thousandths!! You're lucky to be here to post. Maybe it's .003" that's still way too much pressure expansion. I don't think H4350 is the wrong powder you're load is just a bit hot. Try fireforming 10 cases and start 2 grains less. Monitor head expansion from the virgin brass. If you're shooting stuff that was fired before, throw it away.

 

[DShortt]

The case swelled .030" in diameter. That's 30 thousandths!! You're lucky to be here to post. Maybe it's .003" that's still way too much pressure expansion. I don't think H4350 is the wrong powder you're load is just a bit hot. Try fireforming 10 cases and start 2 grains less. Monitor head expansion from the virgin brass. If you're shooting stuff that was fired before, throw it away.

Look at the photos in post #23 and you tell me.
Oy!
And he switched to VV N-160. And it doesn't happen every time.

 

[DLT]

Look at the photos in post #23 and you tell me.
Oy!
And he switched to VV N-160. And it doesn't happen every time.

Yep. It was 30thou. I got the brass at my uncles. I can measure it and post pictures next time I’m there. It’s a right hand action, but I’m a left handed shooter. I got gasses and what felt like grit, shot back into my face. Guess a left handed action would be safer. All I have ever had is right hand guns

 

[DLT]

Same primer, case, bullet and barrel as VV data?

Always work up.

No idea as they don’t list what primer or case. Only gives small primer and 26” barrel. I can’t be the only fool who has tried n160 in a 6creedmoor

 

[DLT]

So, explain to me how 2 or 3 shots can be fine, then you have a stuck bolt/blown primer?
There must be an inconsistency somewhere. And it's fairly significant.
Otherwise, every time you'd see the same result.
Did you use the same batch of primers in the cartridge that behaved normally? How many primers from this particular batch have you used?

The large rifle primers was fiocchi and I have used maybe 300 out of the 1500. And yes same primers

 

[DLT]

My thoughts exactly.

2 or 3 rounds are fine, then a primer blows or the bolt sticks? Either that powder is wonky/mixed or that particular powder with that particular case/primer/bullet/seating depth results in inconsistent ignition.

I'd toss that powder. Before a catastrophe eventually ensues.

You aren't mixing primers, I presume? That's bad juju.

No sir I am not mixing primers that is a big no no