300 win mag overpressure

[Prostockstan]

Can anyone help me with an overpressure and possible undercharged load? went to the range today and had a primer blow out two holes and burn my bolt-face. Chamber is a PTG 300 win mag tactical match. 3.620 OAL .020 jump to lands 208g ELD, 72.6 g of reloader 22 powder. once fire formed federal brass, neck sized and pockets cleaned, Winchester large rifle primer.

 

[Berger.Fan222]

It does not seem like an undercharge situation to me. A few things to check:

.300 Win Mag brass is all over the map in terms of volume. Volumes from 88 grains of water all the way to 95 grains of water are common. I'd measure the capacity of five cases and compute your mean and standard deviation. If your capacity (weight of water to the top of the neck) is closer to 88 grains, that load may be hot on the overcharged side.

There are times with the .300 Win Mag and extruded powders, that standard large rifle primers give a significant ignition delay. Normal is < 3 milliseconds, but these can delay (from firing pin strike to ignition) 50-100 milliseconds. Some experienced shooters can hear the click - boom delay and know what is happening, or it can be diagnosed in an audio recording.

In any event, these delays cause a much different firing sequence than normal, because the primer detonation compresses the powder in theback of the case into a ball of compressed powder (it can be seen clearly on some misfires) which then ignites with all the powder squunched up against the back of the bullet with an air space in the back of the case. This may be the cause of your overpressure. The cure is to use magnum primers. In my experience, this is more likely to occur on the low end of recommended load ranges, which would be your situation if your cases have a volume of 92-95 grains of water.

 

[Homerange]

Can anyone help me with an overpressure and possible undercharged load? went to the range today and had a primer blow out two holes and burn my bolt-face. Chamber is a PTG 300 win mag tactical match. 3.620 OAL .020 jump to lands 208g ELD, 72.6 g of reloader 22 powder. once fire formed federal brass, neck sized and pockets cleaned, Winchester large rifle primer.

See my reply in another thread for the possible cause:
http://forum.accurateshooter.com/posts/36791573/

 

[XBBR Shooter]

It does not seem like an undercharge situation to me. A few things to check:

.300 Win Mag brass is all over the map in terms of volume. Volumes from 88 grains of water all the way to 95 grains of water are common. I'd measure the capacity of five cases and compute your mean and standard deviation. If your capacity (weight of water to the top of the neck) is closer to 88 grains, that load may be hot on the overcharged side.

There are times with the .300 Win Mag and extruded powders, that standard large rifle primers give a significant ignition delay. Normal is < 3 milliseconds, but these can delay (from firing pin strike to ignition) 50-100 milliseconds. Some experienced shooters can hear the click - boom delay and know what is happening, or it can be diagnosed in an audio recording.

In any event, these delays cause a much different firing sequence than normal, because the primer detonation compresses the powder in theback of the case into a ball of compressed powder (it can be seen clearly on some misfires) which then ignites with all the powder squunched up against the back of the bullet with an air space in the back of the case. This may be the cause of your overpressure. The cure is to use magnum primers. In my experience, this is more likely to occur on the low end of recommended load ranges, which would be your situation if your cases have a volume of 92-95 grains of water.

Since the weight of brass is ~ 9 times that of water, in order for a 300 WM case to hold 95 grains of water (7 grains of water more than another case @ 88 grains), it would have have 63 grains (of brass) lighter than the case that held 88 grains of water - it is simple high school physics.

The problem with trying to determine volumetrics of cases with water, is that no one ever makes sure the cases are the same size all over.

The accurate ways to do it is, 1 - put the cases in a "body die" and fill them with water - that way the case walls are constricted to the same outside dimension, so the volumes are compared under the same conditions - or 2 - weigh the cases, as brass confined in a chamber under pressure will be fully against the chamber walls, so internal volume, ergo, the weights will be directly related to the inner volumes.

Primers do not make balls of powder - the flame from the primer flashes through the entire powder space in micro seconds (it takes about 2 millionths of a second for a primer to be completely consumed). The entire powder charge is consumed in in 1 to 2 milliseconds.

 

[savagedasher]

Since the weight of brass is ~ 9 times that of water, in order for a 300 WM case to hold 95 grains of water (7 grains of water more than another case @ 88 grains), it would have have 63 grains (of brass) lighter than the case that held 88 grains of water - it is simple high school physics.

The problem with trying to determine volumetrics of cases with water, is that no one ever makes sure the cases are the same size all over.

The accurate ways to do it is, 1 - put the cases in a "body die" and fill them with water - that way the case walls are constricted to the same outside dimension, so the volumes are compared under the same conditions - or 2 - weigh the cases, as brass confined in a chamber under pressure will be fully against the chamber walls, so internal volume, ergo, the weights will be directly related to the inner volumes.

Primers do not make balls of powder - the flame from the primer flashes through the entire powder space in micro seconds (it takes about 2 millionths of a second for a primer to be completely consumed). The entire powder charge is consumed in in 1 to 2 milliseconds.

Excessive head space . ?
Quick check check the shoulder set back . Comparing fired case to un fired case .
I also like mag primers when loading over 50 GR of power . Good luck Larry

 

[M-61]

Can anyone help me with an overpressure and possible undercharged load? went to the range today and had a primer blow out two holes and burn my bolt-face. Chamber is a PTG 300 win mag tactical match. 3.620 OAL .020 jump to lands 208g ELD, 72.6 g of reloader 22 powder. once fire formed federal brass, neck sized and pockets cleaned, Winchester large rifle primer.

Is this a load you have used before without problems? Why the choice of LR and not mag primers.( just wondering)

 

[savagedasher]

Was the one time cases shot in your chamber? Larry

 

[Berger.Fan222]

Primers do not make balls of powder - the flame from the primer flashes through the entire powder space in micro seconds (it takes about 2 millionths of a second for a primer to be completely consumed). The entire powder charge is consumed in in 1 to 2 milliseconds.

Maybe you will stop confusing your bogus theories with experimental reality.

The pic below shows the powder dumped from two .300 Win Mag loads that failed to ignite the powder, even though the primers detonated. Note the two balls of powder in front, just as I described. The other 18 of 20 cartridges fired, but with a 50-100 millisecond delay after the primer detonated.

The DoD spec for delay between primer detonation and powder ignition is 3 milliseconds, and there are ways for measuring this accurately. I think some documentation I saw showed about a 0.2 millisecond delay between primer detonation and powder ignition when things work well. I read another paper somewhere about a problematic situation with delays of 50-100 millisecond delays.

The key to fixing this in the .300 Win Mag was to use a magnum primer.

 

[XBBR Shooter]

Maybe you will stop confusing your bogus theories with experimental reality.

The pic below shows the powder dumped from two .300 Win Mag loads that failed to ignite the powder, even though the primers detonated. Note the two balls of powder in front, just as I described. The other 18 of 20 cartridges fired, but with a 50-100 millisecond delay after the primer detonated.

The DoD spec for delay between primer detonation and powder ignition is 3 milliseconds, and there are ways for measuring this accurately. I think some documentation I saw showed about a 0.2 millisecond delay between primer detonation and powder ignition when things work well. I read another paper somewhere about a problematic situation with delays of 50-100 millisecond delays.

The key to fixing this in the .300 Win Mag was to use a magnum primer.

View attachment 984642

100 milliseconds is 1/10th of a second - if the ignition of a 300 WM took 10th of a second, you would not be able to hit anything with it - yet it is a popular 1,000 yard round - as to your little balls, they are not normal ignition, they are from failure to ignite.

I shoot a 1,000 yard rifle in 300 WM, I have space in the loaded case, and I use a standard primer (BR-2), and I have no problems.

 

[Berger.Fan222]

100 milliseconds is 1/10th of a second - if the ignition of a 300 WM took 10th of a second, you would not be able to hit anything with it - yet it is a popular 1,000 yard round - as to your little balls, they are not normal ignition, they are from failure to ignite.

Perhaps you failed to catch that the description was attempting to diagnose an unexpected result in a .300 Win Mag that also used regular (non-magnum) primers. We're not discussing a load that is working well in normal use. We are discussing a developmental load that is behaving oddly.

You may not be able to hit anything with that ignition delay, but other than the delay and the misfires, the shooter actually shot sub MOA groups. Improve your follow through and you can too. Nothing tests follow through like an ignition delay.

I shoot a 1,000 yard rifle in 300 WM, I have space in the loaded case, and I use a standard primer (BR-2), and I have no problems.

Is anyone so stupid as to think that because a standard primer ignites a 300 Win Mag case full of powder for you that it will work well for everyone else, regardless of what powder and bullet and case they are using?

I have reported a problem with an extruded powder, a standard primer, and the same bullet as the OP. My problem was solved with a magnum primer. Because one load works with a standard primer, one would be foolish to be so confident that his will also.

 

[Nvreloader]

QL shows the following case capacity's for these brands of brass,

Fed = 92.0 grs
Norma = 95.5 grs,
T Brand ? = 87.5 grs,
Win = 93.8 grs,
300 Mag SAMMI = 91.99 grs,
No listing for Rem brand.

Tia,
Don

 

[Zero333]

Did this happen on the first shot ?

I'm thinking this could be a primer cup problem and not a hot load.

I've heard of primer recalls due to pinholes in the cup causing exactly what the OP stated.

 

[Homerange]

Did this happen on the first shot ?

I'm thinking this could be a primer cup problem and not a hot load.

I've heard of primer recalls due to pinholes in the cup causing exactly what the OP stated.

OH shit read the OP again more carefully......Winchester primers, well what can more be said, that's the problem.
Seen it numerous times with hot loads....one mate has a eroded ring completely around his firing pin from the bloody things. Stick with medium loads and you won't have a problem, hot loads don't use Winchester primers. Period.

Further info on Win primers in this thread:
http://forum.accurateshooter.com/threads/blown-primer-in-270-winchester.3882989/#post-36633408

 

[243winxb]

Winchester large rifle primer. Some may be defective. http://s338.photobucket.com/user/joe1944usa/slideshow/Firearms and Reloading/Primer Gas Leak Alliant list 71 gr with a 200 gr berger. In your tight match chamber, i would guess your load is over pressure also??

 

[FatBoy]

I use Win LR primers (as well as Rem magnums) in Win cases at 78gr of Retumbo under a 230 OTM shoved so far down in the case it looks silly. No leaks, no over pressure. Not saying that a guy can't get a bad lot, but the primer is probably not his issue.

I have read the Navy had issues with the 220s in mk248 mod1 ammo using tight chambers. Their brass is fire and forget, so having a big~ish chamber with a lot of "headspace" up front is not a big problem. It allows them to run way hot ammo in some mighty warm places and not have rifle or ammo failure.

I have to wonder if the neck sized brass is the issue, allowing the pressure to spike immediately as none of the energy is absorbed during the .020" shoulder blowing up to meet the chamber, like a A191 round/chamber does with new brass?

Could also have been some case lube or cleaning solvent in the chamber. Seen it a dozen times, never worked out well for the shooter or his brass.

 

[Homerange]

Winchester large rifle primer. Some may be defective. http://s338.photobucket.com/user/joe1944usa/slideshow/Firearms and Reloading/Primer Gas Leak Alliant list 71 gr with a 200 gr berger. In your tight match chamber, i would guess your load is over pressure also??

You're not kidding.
Winchester did have a bad batch/es from the research I did a couple of years ago so many shooters that I know are reluctant to use them now, such was the damage done to bolt faces.

Is anybody having problems with batches of recent manufacture?

 

[Zero333]

You're not kidding.
Winchester did have a bad batch/es from the research I did a couple of years ago so many shooters that I know are reluctant to use them now, such was the damage done to bolt faces.

Is anybody having problems with batches of recent manufacture?

I used hundreds of Win LR primers in the past couple of years for one of my brothers 308w loads. No problems.

During testing, Win LR primers consistently printed much smaller groups than BR-2 and 210M. Maybe because it's W-748 ball powder they were igniting.

 

[DaveTooley]

Can anyone help me with an overpressure and possible undercharged load? went to the range today and had a primer blow out two holes and burn my bolt-face. Chamber is a PTG 300 win mag tactical match. 3.620 OAL .020 jump to lands 208g ELD, 72.6 g of reloader 22 powder. once fire formed federal brass, neck sized and pockets cleaned, Winchester large rifle primer.

Please describe the two holes you mentioned . Were they on the corners of the primer? If so you have a bad lot of primers. Call Winchester for replacements.

 

[Sniper338]

Use federal magnum match primers!


Usually and caliber that says "magnum, or mag", needs magnum primers to help with the powder capacity... my stardard rule of thumb..

 

[MagnumManiac]

Use federal magnum match primers!


Usually and caliber that says "magnum, or mag", needs magnum primers to help with the powder capacity... my stardard rule of thumb..