• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Pressure issues, need some help

DLT

Silver $$ Contributor
First off I want to start by saying this is a home build rifle. Origin action with a factory savage 6 creedmoor barrel. I owned another rifle this barrel was on which was all factory and it was a hammer. I sold the whole rifle, they rebarreled it and I bought the original barrel back (it always shot well). I installed in on this origin to play until I decided on what chambering to switch to. Now the fun part. I have been shooting 39.5 of H4350 with a 107smk around 3050fps with out much of a hiccup.
Today I decided to try Vv-n160. Looked up their load data and decided on a safe charge at 39.5gr. I loaded up 4 and hit the range.
First round was 3150, and blew the primer out. The case did not stick. I pulled the other 3 loaded rounds and came down 1 whole grain to 38.5gr.

The first round I was scared and pointed it into the pond and pulled the trigger, speed was 3,014 with no pressure signs so I fired the other 2 into a single hole. Excited, i went and loaded 3 more but the first one locked the bolt and stuck the case. I was able to get it out thank goodness.
I rechecked my scales they were zeroed and set to the correct charge weight. The rifle has .005 clearance of headspace from the go gauge. Could that be my problem ? I have measurements written down and my tools on hand if you want to ask any questions.

I want to add Vv load data was using small primers where my brass is large rifle. I am also bumping my fired rounds .001.
If it’s not the headspace causing it or the large primers for small primer load data I’m at a loss.
 
Last edited:
You switched powders. Your brass/primer/bullet combo does not like the new powder.
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.
 
I would guess, based on the information you provided, it's the large primers and that powder.
Again, based on the information you provided, ignition and burn rate isn't consistent with your combination.
I personally would cease using the new powder.
Did you happen to record the velocity when the primer blew the first time and the action locked-up the second time? I'd bet the velocity was off quite a bit.
 
Back it off, obviously.

A really good and thorough barrel cleaning always helps and never hurts.

I am so enamored with VihtaVuori N150 that I can't possibly criticize your plan to use that powder.

Your rifle is not VihtaVuori's rifle. Unless you have the same brass, same primer, same powder, all from the same lot numbers, any results you have are subject to the same variations everyone else suffers.

A lot of people run maximum loads with no ill effects. I don't even try.

I use a chronograph and take barrel length into consideration. I develop all of my ammo somewhere below maximum velocity, somewhere below maximum powder charges, seeking accuracy above all else. I'm weird like that.
 
Wait...

You set the headspace up .005" beyond the go gauge.

Then you bumped the shoulder back another.001" on previously fired cases.
The cases that you fired from this setup?
Or that barrel before you screwed it on the new action?

Where are you seating the bullets?
Jam?
Or a set distance off of the lands?
 
Wait...

You set the headspace up .005" beyond the go gauge.

Then you bumped the shoulder back another.001" on previously fired cases.
The cases that you fired from this setup?
Or that barrel before you screwed it on the new action?

Where are you seating the bullets?
Jam?
Or a set distance off of the lands?
Yes headspace is .005 over what a go gauge measures. I set it up at the time with a sized piece of brass that was previously fired in that chamber so to me the head space would have been very close as the brass had already been fired and sized back down a few firings. If I was using new virgin brass and had the headspace on the excess side I could absolutely see it causing a big problem, but my brass is only growing .001 and I’m bumping it back .001. I’m .020 off the lands. Measurements are as follows using my hornady headspace comparator

gauge measures 1.529
At 1.534 I get a snug bolt close with 3 pieces of scotch tape on back of gauge
1.533 is my sized brass dimension
1.534 is my fired brass dimension
 
Last edited:
I would guess, based on the information you provided, it's the large primers and that powder.
Again, based on the information you provided, ignition and burn rate isn't consistent with your combination.
I personally would cease using the new powder.
Did you happen to record the velocity when the primer blew the first time and the action locked-up the second time? I'd bet the velocity was off quite a bit.
The first time it happened today was round no. 1 on my Garmin was 3110 fps. I knew that was bad hot. The next 3 AFTER I came down 1 grain was 3016, 2988, and 3014. They was not a hard bolt lift, no stamped case head, no wild velocities. I loaded up 3 more identical rounds and the first one blew the primer out and got stuck in the chamber it was 3090.
 
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.
you experienced lot to lot variation
do not trust just one load manual
I have about 15 load manuals and when I work a new caliber or new powder
I reference at MINIMUM 4 of those books from different years to find a safe starting load
not simly just grab one from the first book I read
You need to do the same, or start much lower when trying out a new powder you dont have any experience with previously
Powders speeds can change from the year any particular load manual you reference was published
Powder does not stay the same exactly from lot to lot, pound to pound, week to week, year to year, decade to decade
The only thing that will stay the same is that particular Jug of powder you are using, ONLY
If you happen to buy another jug, (what I do, is pour them together and roll it around a little to evenly distribute the kernels to try and equalize the burn characteristic to be closer to what I had previously)
But only mix the same exact powder together, dont mix different brands or types etc.
Such as -have Old lot of W-748 / mix with new lot of W-748 = more equalized to the Old Lot
Vs whatever speed the new lot may be which could be a faster burn rate and act totally different than all the loads I had previously worked up with W-748
Which would then require starting at least 5 grains lower, and work up new loads ALLLLLLLLLL over again
Its just how Powder works due to the nature of how the cotton and/or glycerin was Nitrided at the time the powder was made and the distribution of the exact percentage of the mixture of the 2 if it is high energy double base powder, IE: getting the exact same powder from lot to lot - is more complicated than making a pot of coffee
Start LOW
 
Last edited:
Do they use different brass, different volume?
They used Lapua small rifle primer brass, starting at 37.2gr and max charge at 41.2gr. I just assumed since n160 was slower than h4350 I should be able to start at 39.5. It was too hot so I came down to 38.5 and apparently it’s too hot as well.
 
you experienced lot to lot variation
do not trust just one load manual
I have about 15 load manuals and when I work a new caliber or new powder
I reference at MINIMUM 4 of those books from different years to find a safe starting load
not simly just grab one from the first book I read
You need to do the same, or start much lower when trying out a new powder you dont have any experience with previously
Powders speeds can change from the year any particular load manual you reference was published
Powder does not stay the same exactly from lot to load, week to week, year to year, decade to decade
Start LOW
I thought i started low enough almost 2gr below their max. I used that same canister in 22 creedmoor and didn’t have any mishaps. Different rifle and bullet weight obviously but nothing crazy happened. I have not been able to find any more load data unless Nosler has it which I did not look for. Sierra didn’t use it and nor did hornady.
 
Could anything catastrophic have happened to my bolt or bolt head on my origin ? Is there anything I need to look for ? I am for sure going to take the rifle apart and use the go gauge to get headspace at the bare minimum like I always do except on this job. I did all my measurements after it was installed using a piece of brass and thought it should be fine
 
I thought i started low enough almost 2gr below their max. I used that same canister in 22 creedmoor and didn’t have any mishaps. Different rifle and bullet weight obviously but nothing crazy happened. I have not been able to find any more load data unless Nosler has it which I did not look for. Sierra didn’t use it and nor did hornady.
Gotcha, I understand more now, did not have much data to go by.
regarding the two different calibers
I have even seen listed in load manuals, the same manual in fact
One particular powder may react SLOWER in a smaller case
and the Opposite as well, May react FASTER in a LARGER case
------------
The exact opposite of what we instinctually think it should do
its beyond me how or why any powder could act faster in a larger case
Such as going from 22-250 to a 308, but the powder act as if it a FASTER powder.
------------
As far as any damage to your rifle, look for any flame cutting on your bolt head or where the firing pin hole is
Check your recoil lugs
Look at the chamber OD for any possible signs of swelling
First main 3 off the top of my head which could be easy and obvious to check
I think you'll be alright though, 100 fps faster than expected is not really out of the realm of a safe mishap
------------
BTW I headspace using my sized brass too, I see nothing wrong with matching the chamber specifically to your FL sized brass
 
  • Like
Reactions: DLT
Just looked at noslers data and they used n160 with a large primer and max out at 41.5gr at 2949 fps with a 24” barrel
 
Gotcha, I understand more now, did not have much data to go by.
regarding the two different calibers
I have even seen listed in load manuals, the same manual in fact
One particular powder may react SLOWER in a smaller case
and the Opposite as well, May react FASTER in a LARGER case
------------
The exact opposite of what we instinctually think it should do
its beyond me how or why any powder could act faster in a larger case
Such as going from 22-250 to a 308, but the powder act as if it a FASTER powder.
------------
As far as any damage to your rifle, look for any flame cutting on your bolt head or where the firing pin hole is
Check your recoil lugs
Look at the chamber OD for any possible signs of swelling
First main 3 off the top of my head which could be easy an obvious to check
I think you'll be alright though, 100 fps faster than expected is not really out of the realm of a safe mishap
I know the case head itself swelled .030 in diameter
 
I know the case head itself swelled .030 in diameter
That sounds like a lot, more than the brass should be allowed to grow I'd check the size of your chamber at that location where the head swelled.
Something seems strange, almost as if maybe your lot of brass could also be much thicker than normal
Have you weighed it and compared to what that brass should or typically weighs?
 
I want to add Vv load data was using small primers where my brass is large rifle. I am also bumping my fired rounds .001.
If it’s not the headspace causing it or the large primers for small primer load data I’m at a loss.

That, I think, is a great indication of the difference in weight of primer compound between large and small rifle primers, and the effect that the mass of primer compound has on velocity, or it's equivalence to grains of powder.

Your mass of powder is relatively small, a large rifle primer adds a substantial percentage of "powder power" to the burn, and accelerates the burn rate, over a small rifle primer.

My suggestion is to come down a full 10 percent from the small rifle primer load, and retest, working back up. This also irons out any issue of the current brass having less case capacity than the old.
I know the case head itself swelled .030 in diameter
The expansion of the case head on virgin brass should be around 4 thou in a small case. On RUM brass, I take it to 8, allowing many firings. This 30 tells you there is excessive pressure, not just a little more.

Excessive pressure creeps in when the cases are too long.

I'd also guess your brass needs trimming. Measure the case length of the fired and full length sized cases. Have to be full length sized. Ask me how I know and how long it took to realise.
 

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Forum statistics

Threads
166,810
Messages
2,223,502
Members
79,917
Latest member
Joe The Licensed Plumber
Back
Top