cracked base on .270 cartridge

[Pine Donkey]

I was shooting my son's .270 today and had a couple cartridges "blow out" around the base. I am not sure what is the cause. The gun is newly built on a Mauser 98 action. It has a douglas barrel, and we shoot reloads. The reloads are in winchester brass, 54 grains of IMR4350, CCI 200 primers, and speer 130 grain boat tail soft points. The brass has been shot 3 or 4 times and the gun has had only about 100 rounds through it. Below is a picture of one of the cases, the crack goes about half way around the case. Only 2 of 12 shells did this. Thanks to all who are willing to give some input on the situation.

 

[308Nut]

That is to be expected when full length resizing the same case over and over. As the case expands and gets resized repeateadly, brass moves forward starting from where it os cracked. It gets thinner and thinner until you get what you just got.

 

If this is happening with only a couple of resizes, it almost definately is from setting the shoulder back at least .005-.010" from when it was extracted.

 

You might want to try neck sizing only and only run them full length when they start to get tight in the chamber. When you do FL size, try not setting the shoulder back more than .0005" (1/2 of on thousands NOT 5 thousands) per resize. That is one of the biggest culprits (setting the shoulder back too much). You will have to sacrifice some time and fire formed brass to set the die so as to not set the shoulder back more than .0005-.001"

 

Hope that helps!

 

M

 

 

[elkhunter]

I find this to be very common with 300 win mag, 270 and 243 loads. After I have shot the brass 2 to 4 times i notice cracks towards the base, that's when i start throwing them away. Take a close look at the brass before you reload them, you can see small cracks at the base, toss em into the trash.

[oz31p]

if the brass is from this 270 as stated earler neck size only. I have found it to be a more consistent final product its easer to do and the brass will ladt much longer. I have some 300wm brass that is on its 9 loading.

[Red Rabbit]

In addition to the excessive resizing, the problem could also be due to excessive headspace in the chamber as you mentioned it was a new rebarrel. Chamber should be checked with a no-go gauge.

 

 

[.270]

if you reload a lot, you see this regularly. every time you shoot it, the case stretches. until if finally cracks just above the base. every time you reloade, inpsect your brass. you can catch them most of the time, before this happens. i full length everything, because i reload for hunting and i don't ever want a tight round in a situation where i need to be able to reload quickly. anytime you shoot, you need to vigilant about all aspects. cracked cases are part of reloading and shooting. Lark.

[308Nut]

In addition to the excessive resizing, the problem could also be due to excessive headspace in the chamber as you mentioned it was a new rebarrel. Chamber should be checked with a no-go gauge.

 

+1 RR. That is another very good point. Excessive headspace is another major cause of case/head separation.

 

elkhunter,

 

If you are seeing this with only two to three resizes, try setting your die back a bit (where the shoulder just kisses the die) or neck sizing. This will allow for much longer brass life than what you are getting.

[shaynec]

I see it when that brass was fired in more than 1 gun.

[azmetalman]

I have been shooting a .270 Ruger M77 for over 30 years. Never had any casehead separations. The advise given in the previous replies is excellent and I suggest you check each and every item mentioned. Any of them or a combination of them may be the problem.

I neck size all brass except my designated hunting rounds. Hunting rounds are those that have been fired and full length sized no more than 2 times. Once when new and once after the first firing. After that I retire them to target round duty. New brass is relatively cheap when you consider how many new cases you actually use over time. I make it a practice to examine every case, regardless of the "duty" category, at the time of firing and after sizing. Overkill??? Maybe but it makes me feel better.

You can make a cheap and effective tool to check for potential head separation. Take a paper clip and straighten it out. Grind or hone one end to a VERY sharp point. Next use a pair of needle nose pliers to bend the wire 90 degrees just behind the point. This bend must end up short enough to fit into the mouth of the case. Now insert the bent end all the way to the bottom (case head) of a previously fired case. You can slowly scratch up and down in the area of potential separation and feel the sharp tip follow a shallow depression in the case wall. This is evidence of a thinning of the case wall caused by stretching and it is where a head separation will occur if the case is fired a few more times. If the point catches in a small groove...throw it away now. This is crude but effective method.

I don't keep neck sized cases for more than 5 additional loads once they enter the target category.

I recommend you keep your cases in batches. That way you know the history of each group and won't need to worry about their future performance.

I hope this helps.

[Pine Donkey]

Thanks for all the pointers. I will be looking at all these things.

[sjvcon]

In addition to the excessive resizing, the problem could also be due to excessive headspace in the chamber as you mentioned it was a new rebarrel. Chamber should be checked with a no-go gauge.

+2 on RR note of checking the headspacing. This is a common symptom when headspacing is incorrect.

[Red Rabbit]

What was determined to be the cause of the case separations?

[Pine Donkey]

I was pushing the shoulder back too far when reloading. Many people we very helpful and taught me how to adjust the dies to just "bump" the shoulders. I also checked the chamber with a go-no go gauge. They gun is fine, it was just my adjustments to the dies that was off. This gun is a very good shooting gun out to 600 yards. It also performed well on my buck last week. Thanks to all who gave advice.

[Red Rabbit]

Good that it was just a simple die adjustment to solve the problem. Starting over with new brass now?