7.5 x 55 Swiss Case Separation

[PCCUSNRET]

I was trying out some new reloads today in one of my Swiss K-31's and noticed the brass appeared to be separating after only one reload. The load wasn't hot and 5 shot groups were running from 1" to 2" @ 100yds. The round on the left has a Hornady 168 gr A-Max with an O.A.L. of 2.915 and the case was cut to length at 2.180. If you look closely you can see a line around the bottom of the case where it is starting to separate. You can also see from the piece of brass cut in half that there is a deep groove on the inside of the case. In the rounds that started to separate I had resized the brass with a Redding die and used 44.5grs and 45grs of Varget. I also shot 10 rounds that were resized on a RCBS die and used Prvi 168gr. HPBT's with 44.5grs. of Varget. There were no signs of separation in the cases that were resized with the RCBS die. It appears that the angle of the neck is not as steep on the brass sized with the RCBS dies and the brass sized by the Redding die seems to be pushed back 35 thousandths of an inch more than the RCBS die. This is the second time I've run into this problem shooting the Swiss rifles. I really don't believe the problem is caused by the gun but by something I am doing in prepping the brass. I've been told that bad headspace in a gun can cause this but I think there must be another explanation. Any suggestions? Thanks in advance!

Chuck

 

[R.W.Dale]

IIRC one of your sets of dies is cut for the K11 chamber and the other for the K31 but I can't for the life of me remember which is which.

 

[PCCUSNRET]

Krochus, Thanks, but would that make a difference? I have both of these guns and I shoot reloaded GP-11 brass in both. Would pushing the neck back too far cause brass to separate like this? I also shot 10 rounds out of a 1911 today that were sized in the RCBS dies and I can't see any signs of separation in this brass.

 

[R.W.Dale]

I also shot 10 rounds out of a 1911 today that were sized in the RCBS dies and I can't see any signs of separation in this brass

A little research shows the RCBS dies are cut for the K11 chamber and the Redding for the k31 so RCBS dies loading ammo for the K11 would have the shoulder pushed a bit too far back than necessary for the K31

Are you sure you used the redding dies wit the K31?

more
http://www.surplusrifle.com/shooting2006/swissreloading1/index.asp

Would pushing the neck back too far cause brass to separate like this?

No but pushing the shoulder back too far most certainly will. Which sounds like what you're doing. This is a long shot but lets try this angle

You have two die sets am I correct in assuming you have 2 shellholders? If so what do they measure as shown in the pic below?

 

[PCCUSNRET]

You have two die sets am I correct in assuming you have 2 shellholders? If so what do they measure as shown in the pic below?

I do have 2 shellholders and they both measure .141. I have just resized 2 pieces of brass using the Redding and the RCBS dies. You can see in the photo that it appears the Redding is setting the neck back just a bit more than the RCBS. I had both dies set all the way down to where my RCBS Rock Chucker cams over slightly. Should I try backing the Redding die off slightly or should I just use it for the 1911 and the RCBS for the K-31's? I also have a neck sizer for this round but it normally only works once and then I have to full length resize. Thanks again for your help.

Chuck

 

[R.W.Dale]

OK your redding set seems to simply be pushing the shoulder back too far as you have them set in your press. This is one of those occasions where a proper case gauge would be invaluable but I doubt you can buy one for 7.5x55 K31 specs.

Anyhow yeah you'll just have to experiment with backing the size die away from the shell holder till you're pushing the shoulder back no farther than is necessary to ensure easy chambering. Which will be a tricky operation with a straight pull rifle. But should be worth the trouble in terms of brass life.

At this juncture it's pointless to affix blame on one piece of equipment. You could have a combination of factors working against you like a slightly shallow die sizing brass for a rifle with a slightly long chamber. Sometimes you size die just has to be setup exactly right for a particular gun.

I also have a neck sizer for this round but it normally only works once and then I have to full length resize.

This is why I tell folks not to bother with neck sizing for guns other than turn bolt actions

BTW is this a problem that just sprang up outta nowhere with a rifle you have had no problems with previously or is this a new to you gun? E

 

[PCCUSNRET]

BTW is this a problem that just sprang up outta nowhere with a rifle you have had no problems with previously or is this a new to you gun?
E

This happened before in another Swiss K-31 and I was led to believe that the headspace was bad in that gun so I put it away and haven't shot it in several years. Yesterday I discovered some of the brass that I had sized and primed from back when I had this problem before. I loaded up about 40 pieces of this brass yesterday in different loads of Varget to see if I could come up with a good load using the Hornady 168gr A-Max bullets. I will try shooting some fresh GP-11 rounds through this gun and then try reloading using both of these dies to see if I can get this sorted out. I do think I will try backing the Redding off a little as it does appear to be pushing the neck back further than necessary for these rounds to fit in this gun. Thanks again for your help.

Chuck

 

[PCCUSNRET]

Here is a photo of the ones that separated before in the other K-31.

 

[navyretired 1]

This is one of those times when a chamber cast with cerro-safe would answer ever question, with a chamber cast you know exactly what the chamber looks like and can load to that size. There is no doubt that the cases are lengthening in chamber and the only question is why. They have to grow a lot to get head seperation in one firing based on my wildcat fire forming experience. I've pushed shoulders out 0.025 without any problems and then get from 5-10 reloads before I trash.
I'm with Krochus as I seldom neck size except for target ammo, and if I do I try every round thru action to ensure no long cases(firing pin removed).

 

[NCsmitty]

Swiss straight pull bolts do not have the camming power to overcome some tight fitting ammo, compared to regular bolt actions and you're sizing to allow both rifles to feed without problems.
From your description, it seems that you are setting the shoulder back on the cases, and it's compounded by having two rifles, with different chambers, that you are feeding.
To eliminate the separation, you'll probably need to segregate the two rifle's brass and pay closer attention to fitting the brass to each chamber.



NCsmitty

 

[PCCUSNRET]

I have some of this brass that I hadn't resized yet and found that I could back the Redding die a complete rotation off the shellholder and the brass would easily load into the K-31. The problem I see is that the even though it fits, the neck isn't completely resized. I can see that there is still about an 1/8" not sized. If I bring the die down just enough to complete the sizing of the neck is it going to push the shoulder back? Is this what is meant by partial resizing? I can see by the marks on the brass that I will have to use the full length die to resize this brass but I don't think I'll need to bump the shoulder back as much as I did with the ones that separated. Thanks again for all the help!

 

[R.W.Dale]

I have some of this brass that I hadn't resized yet and found that I could back the Redding die a complete rotation off the shellholder and the brass would easily load into the K-31. The problem I see is that the even though it fits, the neck isn't completely resized. I can see that there is still about an 1/8" not sized. If I bring the die down just enough to complete the sizing of the neck is it going to push the shoulder back? Is this what is meant by partial resizing? I can see by the marks on the brass that I will have to use the full length die to resize this brass but I don't think I'll need to bump the shoulder back as much as I did with the ones that separated. Thanks again for all the help!

were these cases fired or new? If new you cannot use them as a reference for setting up your FL die because they come from the factory already sized to spec.

As to sizing, as you run the die into your press farther and farther you size more and more of the case up until the shellholder bottoms out against the die. This is an infinitely adjustable variable. Somewhere on your die threads between only sizing the neck and pushing the shoulder back too far is where you want to be. Where the neck is fully sized and the shoulder on a fired case is pushed back only a few thousandths to allow for easy chambering. The only way to find this sweet spot without a case gauge is to size some fired cases and see if they,ll chamber. But pay attention to the bolt handle and make sure it's going 100% of the way into battery. Because determining those last few thousands on a k31 gets kinda tricky.

And remember in this process you're setting up the Redding dies for the K31 and that particular K31 ONLY!

 

[PCCUSNRET]

were these cases fired or new? If new you cannot use them as a reference for setting up your FL die because they come from the factory already sized to spec.

As to sizing, as you run the die into your press farther and farther you size more and more of the case up until the shellholder bottoms out against the die. This is an infinitely adjustable variable. Somewhere on your die threads between only sizing the neck and pushing the shoulder back too far is where you want to be. Where the neck is fully sized and the shoulder on a fired case is pushed back only a few thousandths to allow for easy chambering. The only way to find this sweet spot without a case gauge is to size some fired cases and see if they,ll chamber. But pay attention to the bolt handle and make sure it's going 100% of the way into battery. Because determining those last few thousands on a k31 gets kinda tricky.

And remember in this process you're setting up the Redding dies for the K31 and that particular K31 ONLY!

Thanks Krochus!

These were fired cases. Don't believe they were fired in this gun but they were fired in a K-31. Before I resized them the bolt wouldn't close without applying extra force. Once I resized just the neck (without pushing the shoulder back) and the base of the brass (I believe this is called the head of the brass) it chambered easily in this gun. I did the same to some of the rounds I fired last week that didn't show the signs of separation and they chambered easily also. I won't know for sure until I load these up and fire them but I believe the problem was caused by overworking this brass and not a head space problem with these guns. I'll let you know what I find out next time I get to the range. Thanks again for all the help.

Chuck

 

[PCCUSNRET]

I had a very interesting conversation with a fellow from RCBS today. I called to verify that the RCBS die set that I have is the correct set for the Swiss K-31. He told me that RCBS only makes one die set for the 7.5 x 55 Swiss and they are for the 1911 Schmidt Rubin. This didn't sound right to me because I have read on numerous boards and various retailer's web sites that the RCBS die set 33501 is the one to use for reloading for the K-31's. He also told that the set I have is no longer made by RCBS. It is labeled "Part Number 17101 Die Set 7.5 SR". Anyone else load for the K-31 using either of these die sets?

 

[PCCUSNRET]

Finally got a chance to shoot this gun again and now I am more confused then ever with the results. I shot a total of 30 rounds, 10 GP-11 and 20 reloads using GP-11 brass from a different batch. In the photo below, there is an unfired GP-11 round on the left, a once fired GP-11 case from the same batch in the middle and a twice fired case on the right. If you look closely, you can see the neck on the unfired round is quite different than the two rounds that have been fired. What's really strange is the round in the middle is showing signs of head separation and there are no signs on the twice fired case. I cut both pieces in half and found there was a groove inside the piece of brass in the middle and none visible on the twice fired case. The case on the far right was first fired in another gun and FL resized with Redding dies that were cut for the K-31 rifle if that would make any difference. I was expecting if there was going to be any signs of separation that it would have been from the brass on the right, not the brass that hadn't been reloaded yet.

In the second photo there is a piece of brass that appears to be almost "twisted", with spiral dents starting about 1/2" from the base extending the full length of the case to where the neck begins. This piece came from one of the ones I reloaded.

I'm beginning to think this gun may be ready for retirement. My next experiment is to try it with some Graf and Prvi Partizan ammo to see if this makes any difference. All of the GP-11 brass used in the test was dated 1978 and 1979.

Is there any way to check the head space on one of these old Swiss K-31's to see if the gun is shot?

Thanks for all your help!

 

[243winxb]

Make small shims like in the link.

Is there any way to check the head space on one of these old Swiss K-31's to see if the gun is shot?

You can make homemade gauges to fit on the head of the case and then try to close the bolt*. Soda cans measure around .0035" See if you can close the bolt on 1, then 2, then 3 shims. When you set up your FlRS dies, make shims out of the same soda can, put a hole in center for decapping pin.Put shim between shell holder and FLRS die. Start FLRS with 2x.0035" shims. See if brass chambers, make sure that bolt if fully closed before firing. OR >] Put tape on the cartridge head till action will not close, then measure the case from head to mouth to find the thickness of the tape. Follow link to bottom of page. http://www.surplusrifle.com/shooting/headspace/index.asp

 

[Canuck-IL]

I have read on numerous boards and various retailer's web sites that the RCBS die set 33501 is the one to use for reloading for the K-31's.

That's odd - I did a lot of reading before buying dies and the only die set I ever saw recommended for the K-31, specifically for longer brass life, was the Redding set.

Lots of folks regularly use RCBS, Lee and Hornady (who I believe NOW offer an alternative set just for the 31) and are satisfied but the Redding is (was, if you now count Hornady) the only set SPECIFIC to the K-31 chamber vs the 1911. See the reference on SurplusRifle under reloading for the K-31.
/Bryan

 

[918v]

I suggest you take your once fired brass and size it in either die, but adjust the die to bump the shoulder only enough for the bolt to close. This will take trial and error, but will eliminate your casehead separation issues. Screwing the die to touch the shellholder without considering headspace is dangerous.

 

[918v]

The Redding dies aren't "better", they're different. They make 2 different 7.5x55 FL sizing dies. One is the standard specs. No matter what 7.5x55 Swiss rifle you have, it will FL resize the case small enough. The other FL sizing die is made specifically for the K31, which has a slightly larger diameter chamber. Not longer over all, not longer to the shoulder, just slightly larger diameter. The K31 specific die allows for the slightly larger diameter and doesn't work the brass as much as the standard size dies.

http://www.calguns.net/calgunforum/showthread.php?t=42186

 

[Canuck-IL]

Who said 'better' anywhere in this thread?

The post above notes - "specifically for longer brass life."
/B

 

[243winxb]

Load data.

Hodgdon data does not list Varget. Varget would seem to fast, and your load to hot. Different brands of brass can give high pressure with starting loads.(Prvi Partizan in 308win) H4350-44gr. w/ 168gr looks like a better/safe load. I do not own or have i ever owned a 7.5x55, so take it for what its worth.

 

[918v]

Who said 'better' anywhere in this thread?

The post above notes - "specifically for longer brass life."
/B

Nobody said "better." I was using the quote to illustrate internal differences between 7.5mm Swiss dies.

 

[PCCUSNRET]

That's odd - I did a lot of reading before buying dies and the only die set I ever saw recommended for the K-31, specifically for longer brass life, was the Redding set.

Lots of folks regularly use RCBS, Lee and Hornady (who I believe NOW offer an alternative set just for the 31) and are satisfied but the Redding is (was, if you now count Hornady) the only set SPECIFIC to the K-31 chamber vs the 1911. See the reference on SurplusRifle under reloading for the K-31.
/Bryan

Bryan,

I started loading for the Swiss K-31 about 12 years ago. At the time there was very little information on the Internet about reloads for this round. I spent a lot of time on the Swiss Rifle board and this was where I heard that RCBS was the "only" die recommended by many for reloads for the K-31. At the time, I believe Redding was only making dies for the 1911 and a couple years later came out with a die specifically for the K-31 (which is the set I have). Pierre St. Marie was (is) a strong advocate of using the RCBS dies to reload for the K-31. If you follow this link you will see where he recommends bring the die down to the shellholder and then a bit more until the press cams over.

http://www.swissrifles.com/ammo/reload1.htm

This may be fine for some K-31's but not for at least 2 of mine. Whenever I load this way I get case head separation. Trouble is now, it appears that I have cases getting ready to separate that I have not even reloaded (the round in the center was not reloaded, it was a fresh round). The case on the far right was one of my reloads and there is no sign of case separation yet on this round and it was sized (gently) with the Redding die.

Would using another bolt change the head space?

Thanks for your input.

Chuck

 

[PCCUSNRET]

I suggest you take your once fired brass and size it in either die, but adjust the die to bump the shoulder only enough for the bolt to close. This will take trial and error, but will eliminate your casehead separation issues. Screwing the die to touch the shellholder without considering headspace is dangerous.

Thanks, but I never got the chance to reload this case that is showing signs of case head separation. I had planned to reload this brass by just gently bumping the shoulder back until the cases fit this gun but I never got the chance. These cases are already showing signs of separation after the initial firing. Thanks for your suggestion.

Best,

Chuck

 

[918v]

So that case you sectioned is only once-fired? In your initial photo, you mentioned the round on the left had signs of separation, but I don't see it. The empty case next to it does, but not the case on the left. All fired/sized cases will show a pressure ring in that area. The trick is controlling it.

The cases in post #15 appear normal, btw.