Hi. Just joined the site and looks very informative. I have reloaded for general hunting purposes for years now for all rifles in 222, 243, 308, 30-06, 7x57, 7mm, 270. I have just purchased a 300 Win Mag Sauer. I started by loading Sierra gamekings 165gr and got magnificent groups. 6mm. However i experienced bullet failure with some heads retaining 50gr when retrieved. So i decided to move to Nosler Accubonds. The problem I have experienced is that when using the Noslers even at the lowest recommnded powder charge I am blowing the cases up. The backs blow off and the cases get dented. I have played with overall length but this has made no difference. I am using S365 (South African powder), Winchester magnum primers and Hornady brass. I have been told it is pressure related. Is this correct? Why am I getting such high pressures at the lowest range. This has not happened previously with any other loads I have developed. Any suggestions?

quote:

Why am I getting such high pressures at the lowest range. This has not happened previously with any other loads I have developed. Any suggestions?

Please post a pic so that we can see what you are referring to. Right now I'm not sure if the head is tearing off or what the situation is.

My immediate suspicion is a head separation. How many times have you loaded the cases? Do you full length resize? Can you post a pic of an unfired case? Does is have a light ring above the web section? Do new cases do the same thing?

Bend a paper clip and feel the inside of the case. You can easily feel the thinning of a looming head separation just above the web of the case.

Let's see those pictures.

I am not sure what he is asking about.

Is this what the OP is talking about?

Yes that is exactly what is happening on the cases when fired. However i get up to 3 dents in the case. In addition to this the back (head) of the case separates leaving the remainder of the shell in the barrel.

You are experiencing potentially dangerous total head separations. This is generally due to an excessive headspace stuation and or continual oversizing or both. The problem can be the brass or the rifle. New brass will probably not do this (but you didn't reply regarding how many times this brass was loaded). Have a gunsmith check your headspace with a no-go gauge in case it is the rifle, although the fact that you haven't had this before makes me think that is possibly not the rifle. Is this a new rifle?

Don't shoot it until you have checked the headspace. The action seems to have done a good job of keeping the hot gasses out of your face and eyes so far; don't tempt fate.

It may just be that you are oversizing your brass, but I'd check the rifle first.

I've never seen the dents with that but I guess there is a bunch of gas that needs to go somewhere.

Can you answer some of the questions in my previous post to assist in determining what the most likely cause is?

Hi. The brass is new brass. Never before fired. I did full length resize before firing. The rifle is a new rifle. I initially loaded with the Sierra Gamekings which are a much shorter head and experienced no pressure problems. Which also leads me to believe it is not the rifle. With the longer Nosler Accubonds maybe it is pressure? to answer some of your questions :-

"My immediate suspicion is a head separation. How many times have you loaded the cases?FIRST TIME Do you full length resize? YES Can you post a pic of an unfired case? WILL DO Does is have a light ring above the web section? DO YOU MEAN ON THE BRASS. YES A LIGHT RING IS EVIDENT Do new cases do the same thing? THESE ARE NEW CASES
"

Thanks for the help.

I am struggling to upload the photos but the brass looks identical to the pictures above

Looks to me like you have a major head space problem.

Get the rifle checked by a good smith before shooting it any more.

If it is a single head separation, it could have been a flawed piece of brass. I thought when you get the oil cans in the shoulders, it indicated low pressure. Although the ones I've seen showed considerable smut on the necks.

I agree, get the headspace checked out as a first step. Any gunsmith who builds rifles should have the gauges in 300 WM. New brass should not do this! Have you ever fired factory ammo (not recommending you do until this is resolved, but asking)?

As you have played with seating depth it seems this has happened a few times.

Let us know what the gunsmith finds. With a new rifle don't be tempted to repair anything. You need to return it if there is a problem.

Thanks. I will have the firearm checked out. I misunderstood your question on it being a new rifle. If is new for me but i purchased second hand.
I have shot factory ammo with no problems and also the sierra gamekings. My thoughts were the longer nosler heads with more bearing space giving me excessive pressures. As said i will have it checked out but will also get some new brass and check that I haven't oversized the cases currently. Will let you know what transpires. Thanks for the help

You stated you full length sized the new brass. My guess is that you pushed the shoulder back too far and now have the head space issue. When starting with new brass, all I do is run the expander ball thru the case mouth just enough to make the case mouth round again. Typically, new brass doesn't need to be full length sized prior to firing.

Good luck!

Are you sure it is the caliber you think it is?
Something is WAY off and the gun should not be fired again without knowing the chamber dimensions.

quote:

posted 25 June 2013 14:07
Hi. Just joined the site and looks very informative. I have reloaded for general hunting purposes for years now for all rifles in 222, 243, 308, 30-06, 7x57, 7mm, 270. I have just purchased a 300 Win Mag Sauer. I started by loading Sierra gamekings 165gr and got magnificent groups. 6mm. However i experienced bullet failure with some heads retaining 50gr when retrieved. So i decided to move to Nosler Accubonds. The problem I have experienced is that when using the Noslers even at the lowest recommnded powder charge I am blowing the cases up. The backs blow off and the cases get dented. I have played with overall length but this has made no difference. I am using S365 (South African powder), Winchester magnum primers and Hornady brass. I have been told it is pressure related. Is this correct? Why am I getting such high pressures at the lowest range. This has not happened previously with any other loads I have developed. Any suggestions?

"any suggestions"

"Why am I getting such high pressures at the lowest range?"

There is a conflict, then there is the advise you have received, I do not know what you consider 'lower range'. the dents at the shoulder can be caused by low pressure, meaning, there is not enough pressure to force the case to seal the chamber, when that happens it is possible to have pressure on both sides of the case as inside and outside. When the pressure inside the case drops the pressure outside the case that is traped between the chamber and case cause the case to collapse causing the dents.

Then the case head separation, in the perfect world of the magnum belted case the case is held to the rear of the chamber, when fired the front of the case (case body) fills the chamber, meaning the shoulder does not move forward, part of the case body becomes part of the shoulder and part of the shoulder becomes part of the neck.

MEANING! THE case does not stretch between the case body and belt, but? by your description that is what happened.

I am the fan of cutting down on all that case travel, to accomplish that I am forced to ignore the belt, I size/form magnum cases to head space on the shoulder of the case against the shoulder of the chamber, I am not a fan of reduced loads. The window between mimimum and maximum is very narrow.

F. Guffey

Even if the belt stops the case from going right forward into the chamber, excessive headspace from issues with the lugs and lock-up will still cause problems.

By the description I am assuming this is a Sauer 80, or 90. These bolts lock up at the rear and are not a true rotating bolt. As you rotate the bolt handle three lugs come out at the rear of the bolt body and provide lock-up. This means that you can get a degree of "bolt compression" so to speak.

You may want to remove the bolt and whilst holding it in your hand, twist the bolt handle as if cocking it so that the lugs appear. The first thing would be to check that they do in fact all come out and then you can also inspect the surfaces and see whether they look very worn etc. This may confirm the suspicion most posters here have.

Either way, get a 'smith to take a look.

Then, again, there is "this does not happen with other loads he has used" and 'the cases are new.

Then there is the African powder, I do not know how slow the powder burns, I have powder from 50 cal type pull-downs, even thought I got the powder cheap it was not a bargain.

F. Guffey

1. Have a gunsmith take apart and clean the bolt and rifle to ensure the locking system is in good order and functioning as inteneded.
2. Have the headpace checked.

If 1& 2 are correct:

3. Start with new brass.
4. Open up the necks to 33 caliber with a 338 expander.
5. Neck them back down 30 caliber until they will just chamber. You have created a "false shoulder" for the cartridge to headspace on, rather than depending on the belt.
6. Fire full loads with a powder having a burn rate like 4350 or 4831.
7. The case will now be fitted to your chamber and should NEVER have to be full length resized for the normal 6-8 round case life of the 300 WinMag. If for some reason it does start to exhibit hard chambering, buy a shoulder bumping die that does not mess with the case's body.

Would help if we knew who made the rifle, the model, the burn rate of your powder, the brand of cases and dies and so on.

What you are experiencing is a clearly unsafe situation probably due to cases that are sized too short (heads coming off) and powder charges that are too low to expand the case neck/shoulder to prevent gas leak back (the dents).

Fireforming belted cases with false shoulders goes back several decades as all belted cases are manufactured way undersize because they have to chamber in any rifle, the belt handles the headspace chore and "back in the day" they were usually not reloaded.

DON'T SHOOT IT AS IT IS !!!!!

Gentlemen,

S365 is fairly close to 4350. I haven't checked the OPs loads.

Are you sure these Noslers weigh what you think they weigh?

quote:

Originally posted by postoak:
Are you sure these Noslers weigh what you think they weigh?

And I guess we should ask if you ever measured the velocity and if so what it was.

quote:

Originally posted by postoak:
Are you sure these Noslers weigh what you think they weigh?

Verified Diameter?

A friend of my Dads got some .311? bullets mixed in with .308 but that was a looong time ago and I couldn't tell you whose bullets they were. Close enough to go unnoticed until they were fired.

The top picture is before firing and is typical of over lubrication for sizing. The bottom picture is head separation and indicates that the case, from shoulder to case head, is shorter than the chamber from bolt face to shoulder. It does not matter whether the headspace is caused by a faulty rifle or whether it happens in the loading procedure.

http://www.gsgroup.co.za/faqsizerdie.html

Just to keep the thread alive a bit. Biggsma is a friend of mine and out hunting until early next week.
I do know that it is not a case of too little powder as suggested, but interesting commentary.
I'm sure that he will appreciate the input on his return and provide more details.

Hi All. Sorry back after a long break (hunting). I have had the rifle checked out by a gunsmith. There is no head spacing problem. He is of the opinion I have over sized the brass when doing full length resizing. He did some of his own reloads to show me that rifle was fine. On my loads we blow the heads off and get powder burns all the way back on the cases. He also cut open some of my reloaded brass to show me the stress areas and how i had damaged the cases. So i guess it is back to the drawing board with some new brass. I will certainly take in all comments previously posted when i try this reloading again. Thanks for all the guidance

Set up your sizer die like this:

http://www.gsgroup.co.za/faqsizerdie.html

Still...he should be able to set his dies up like manufacturer states...use a published starting load...and NOT get case head seperation.

Gotta be more to the story if the rifle is OK.

Setting it up according to my method takes care of any deviation from perfect. Deviation from perfect is very common with production rifles and dies.

Production rifles do not cater for the reloader. Even if the rifle has a small headspace problem, it can be accommodated with the die setting.

Right...but we are talking catastrophic failure here from a rifle that presumably is fine (according to smith) and shot factory loads fine.

You should not have to set the sizing die up specifically for that rifle to load moderate loads and NOT get case head seperation.

I have measured die sets where the sizer die was 0.30mm too short. Setting such a die to the top of the shellholder, as most die manufacturers instruct, will result in a reloaded cartridge that is catastrophically too short from the shoulder to the base. Use a shellholder, of a different make to the die set, that is a fraction lower and tolerance stack up will spoil your day every time.

Factory ammo will be free of problems in the rifle but ammo reloaded with such a sizer will separate very quickly.

quote:

You should not have to set the sizing die up specifically for that rifle to load moderate loads and NOT get case head seperation.

Sadly, decades of experience by thousands of reloaders have proven this is not true. As Gerard explains, not all dies/shell holders are the same. Even reloading manuals (Speer in particular) recommend setting the die to match the chamber. Do that, and these problems will disappear.



.

Well...I guess he could have gotten a really bad die. And if that were the case...his first reloads with the Sierra bullets would have seperated as well. (Go back and read the whole story from the start)

But if every round had to be specifically sized to match a rifle chamber...there would be no factory loaded ammo sold.

See below from Gerard's own website:

"It is quite common for a sizer die to be set up incorrectly for an individual rifle. The manufacturers of die sets give instructions that will work for the set up of their dies, regardless of the specification of your particular rifle. These settings are general settings that will work with any rifle. In effect, if you use these settings, you will make reloaded ammunition that is very similar to factory ammunition and will probably get similar results. Manufacturers of rifles and cartridges follow manufacturers specifications so that the largest possible cartridge will fit in the smallest possible chamber in a rifle made for a particular cartridge."

So...I am still skeptical that the sizer was all of the problem.

A factory round, or reloads fired on new cases for the first time, is unlikely to separate at the head. This typically happens at the third or later firing of the case, depending on how bad the mismatch is. The OP could tell whether this is so.

Bear in mind that, for the seasoned reloader, a case head separation at the third firing is 'very quickly'. Even a case head separation at 5 or more is indicative of having to set up more accurately.

Hi. I appreciate all the advice. Just another quick question. I tried the reloading procedure as per an earlier post of yours. I applied masking tape to the back of the head. On the second piece of tape I already had stiffness. I must admit to not even being able to measure something so thin with verniers. My question is on whether I could be using the incorrect shell holder and whether this would make a difference. Just looking at an internet chart of shell holders i see with lyman presses you should use a no5 shell holder. With an RCBS press (which i have) you should use a no4 shell holder? I have been using the no5 in the rcbs press. Could this be a problem.

You can stay with that shellholder as long as you set up the die to accommodate any difference that may be caused.

Masking tape is typically between 0.080mm and 0.100mm. If the bolt closes on two layers the die can be adjusted upwards by 0.160mm to 0.200mm.

Using a feeler gauge, do the adjustment and see what happens. If a feeler gauge is not available, use the clock face method described.

When checking a rifle chamber for headspace, a gunsmith will use a go and a nogo gauge. The bolt should not close on a nogo gauge but that would not make the rifle unsafe with factory ammo. There is a third gauge to check for safety called a field gauge. If the bolt closes on a field gauge, the rifle is unsafe. The difference between a go and nogo gauge is 0.100mm and the difference between a go and a field gauge is 0.300mm

Small differences make a big difference.

Hi Gerard. Thanks for all the advice. I will certainly try set the die up as such and will purchase the feeler gauge today to help. Interesting to note that I used one of my friends reloaded ammunition (with 180gr GS Custom heads) this past weekend and experienced no problems on the range with case head seperation. Just tried his loads and some factory ammo. All shot fine. On my reloaded rounds with the sierra heads whilst i didnt get case head seperation i got powder "blow back" all the way down the case body which i believe is an indication of incorrect sizing.

I am toying with the idea of purchasing factory rounds and using in my rifle after which i will purchase a neck sizing die and just use this. Do you think this could solve the problem.

Thanks once again for all the assistance.

I have a 300 win. mag in a Bar that had the opposite problem. The reloads wouldn't chamber. The auto didn't have the camming power to close the bolt. I had it run down to the shellholder. I sent the die back TO RCBS. They sent me a new die with the right size chamber. free It works fine now. Sometimes the dies can be a little off on chamber size. It was a small base die.

Blackened case bodies are generally an indication that the neck is not sealing in the chamber fast enough. Often this is because of a load that is too light, but you would need to look at the data and shoot your loads over a chronograph to be sure.

Neck sizing only will be a temporary fix and eventually your cases will probably not chamber in the rifle as the body expands as well and at some point the shoulder needs to be bumped back. My personal experience has been that this can happen faster in the rear locking Sauer designs than some other front locking lug actions.

What Gerard described is a way to bump the shoulder enough to fit your chamber, like a custom partial full length resize. This is the right solution.

By the way, beware of shooting other peoples reloads not developed in your rifle. I'll let Gerard tell you that those Sierras were bullets and not heads.

As AFRICAN LEADWOOD said, it is not necessary to throw more money at this by getting a neck sizer die. I have 34 die sets and do not own a neck sizer die at all. I also do not own a die set that does not have a proper lock ring. Lock rings on dies that depend on friction, is a cheap and dirty solution.

With terminology we get into some bad habits and, to help new reloaders and some older ones who were taught incorrectly, this is a useful referral.

Hi Gerard. Thanks for the information once again. I will keep you updated. I set up my dies as you mentioned and have loaded some catridges. Will test on the weekend and see if the problem has been resolved. I always seem to have one last question. What weight bullet do you recoomend for a 300 win mag. I have been loading 165gr. My mates is using the 180gr GS Custom with fantastic results. We have yet to recover a bullet from 15 animals shot at varying distances. I was looking for a flatter shooting bullet for open plains hunting and hence the 165gr