Head separation and dimpled case body

[Area Man]

One too many reloads on a batch of 300 Win Mags and had a case head separation. What I have not seen before was dimples on the case wall just below the shoulder. Cause?

 

[MrMajestic]

Gases escaping from the separation leaking back between the chamber and case.

 

[Area Man]

Thanks.

 

[M-61]

Was this a new load you were trying?

 

[Area Man]

Was this a new load you were trying?

No I've used it before. Pressure is OK.

Are you seeing the "cratered" primer?

 

[BoydAllen]

Have you set your FL die to a specific, measured amount of shoulder bump, and removed the fired primer of the fired case, before you measured it? Head separations are not a forgone conclusion of many reloadings if this detail is handled properly.

 

['Freak]

Too many excessive for that particular chamber shoulder bump backs is my guess too.

 

[243winxb]

Dimpled case body

As already said

Gases escaping from the separation leaking back between the chamber and case.

The pressure was higher on the outside, than the inside.

 

[Area Man]

"Have you set your FL die to a specific, measured amount of shoulder bump, and removed the fired primer of the fired case, before you measured it? Head separations are not a forgone conclusion of many reloadings if this detail is handled properly. "

Thanks for the tip. No I have just been FL sizing them with the shell holder contacting the die base. I don't shoot the 300 very much and so I haven't been paying attention to such details, but I will now.

 

[jsthntn247]

Get the hornady headspace gauge set for your calipers and set your die to bump shoulders no more than .002.

 

[BoydAllen]

Using a once fired case, you can do just fine most of the time, just setting the die to put the shoulder so that it is where it came out of the chamber. This is because it takes more than one firing for the shoulder to move forward to the limit of the chamber. If you get a gauge you should check your cases as you size them. Differences in factory annealing can result in variations in shoulder bump at the same die setting, and if you happen to set the die using one of the softer cases, and don't check, you can end up with a tight bolt in the field.

 

[cdparker]

As the others have stated "get a gage" Your gage should sit on the datum point of the shoulder. Measure from the base of a fired case to the back of your gage. Do this with several cases and you should come up with a predominant measurement. Set your sizing die to set the shoulder back .002". If you don't have a gage, you can use a 12point socket that clears the case neck and rests on the shoulder of the case. It is a wee crude but it works. Make sure that everything is straight when you make your measurements. When you have your die set, put the socket back in your tool box for the next mechanic job you need to use it on. I have seen .300 WM reamers that were .023" long at the shoulder for what the die will set it to if you turn it in to bump the shell holder. As folks have stated--it is always best to set your sizing die based on the actual chamber in your rifle.
HTH

 

[Area Man]

Got out my Hornady head-space gauge and checked a fired case before and after running it through my FL die as I had it set-up. The FL operation was setting the shoulder back 0.025".

As they say on Mythbusters: "Well there's your problem."

 

[Area Man]

I thought for sure someone would comment on my cratered primer.

 

[jonbearman]

I honestly wish the die companys would provide a dvd to help people not induce dangerous head space issues.This has long been overlooked and should be addressed so beginners can actually understand how to start reloading safely.

 

[Dave T]

+1 on what jonbearman said

 

[cdparker]

AM- The cratered primer is a product of excessive sizing. Correct the sizing problem and the crater should correct itself. After you get things straightened out, take some more pictures.

 

[Area Man]

AM- The cratered primer is a product of excessive sizing. Correct the sizing problem and the crater should correct itself. After you get things straightened out, take some more pictures.

The "cratered" primer appeared on the first factory round I fired with this rifle. A M700 CDL that was purchased new in 2012.

OK. It was a bit of a trap. See attached pics. One is my new M700 and the other is my old M700VLS. Recently Remington began camfering the firing pin hole. I don't know why, maybe someone here knows.

 

[Area Man]

I honestly wish the die companys would provide a dvd to help people not induce dangerous head space issues.This has long been overlooked and should be addressed so beginners can actually understand how to start reloading safely.

I'm not a new loader but until recently I just followed the die makers instructions for die set-up. This is right out of the instructions for my Lyman die.

"Loosen the set screw in the die lock ring and back it off to give you room to screw the die into the press.
Lower the press handle until the shellholder is at its highest point. Turn the die into the press until its bottom edge makes firm contact with the shellholder. Exception: tungsten-carbide size dies (refer to as “T/C dies” from here on) for straight-wall pistol cases require a different setup. See special instructions below.
The “SIZE” die is now adjusted for either full-length or neck-resizing and decapping. Screw down the lock ring and tighten the set
screw."

 

[savagedasher]

A 300 win mag is a belted case. I think we have two or more problems. No 1 the gun mite have a head space problem. No 2 the dimpling probably was from excess lube. No 3 the cases were loaded too many times. Larry