Brass stretching in 6.5x55

[jetinteriorguy]

I picked up an old Swedish Mauser a couple months ago for s’s&g’s because I’ve always wanted one and have been interested in the 6.5x55 caliber for a long time. This rifle was manufactured in 1906 and seems to be in pretty nice shape, all numbers matching except the stock. Using the proper bushing for this caliber in the Hornady comparator I’ve measured the base to shoulder datum on fired brass vs. full length sized brass. The amount of stretch runs between.015” and .020” and I’m wondering if this is excessive. This is with Lapua brass that’s been twice fired.

 

[44 AMP]

hmmm....I think different folks will have different opinions about "excessive"...

You've got a Swede that has its 115th birthday this year. So, its probably one of the Swede versions of the 95 Mauser... is it one of the 96 "long rifles"? or a carbine? Not that it makes any difference for what you're asking, I'm just curious. I've had the carbine (and miss it, now..) and currently still have one of the long rifles.

Your Hornady gadget, tells you there's a 0.005" difference between fired brass and FL resized brass...

TO me that says your sizer die is working...

Now its likely someone will come along and tell you that .005" is too much, your brass won't last, you won't get accuracy, cats and dogs will be sleeping together, dead will rise and the world will end unless its .002"..etc...

Personally I don't worry about it. Nor do I measure it, or have the Hornady gadget to do it with. If your ammo chambers properly, the rifle shoots well, and your brass lasts the average amount of loadings, why go borrowing trouble??

I don't load for match/benchrest rifles, been loading since the early 70s, I don't have a comparator, and don't plan on getting one.

If you're really concerned about it, seems to me to be a fairly simple matter of adjusting your sizer die (screwing it out) just a tiny bit until the comparator tells you that you've reached whatever it is you consider the magic number.

 

[RC20]

The bottom line is you accept the chamber fire forming for that gun and then size it back as you are.

That is the same recipe that works for 303 with its generous chamber (also works for all other guns but the brass on a 303 back to original size cracks in 2 -3 firing)

Its a 100 year old gun with 100 year old tolerances in a world that has gotten much tighter and now built to now CIP European specification.

It did not start out as anything other than Swedish Military spec and tolerance, just like the 30-06 etc.

Its been rationalized to specs now like all the rest of those.

A new cartridge is formalized from the start but many are just averaged from the originals.

 

[jetinteriorguy]

I’m sorry for poor wording, what I mean is the brass is stretching from .015-.020”. As fired it’s 1.765-1.770” from the base to the datum point on the shoulder, but resized it’s 1.750”. My concern is if this will eventually lead to case failure prematurely. I’m also curious why the variation in the fired length, although most of the 30 rounds I checked were around 1.768”-1.770” with just a few at 1.765”.

 

[jetinteriorguy]

hmmm....I think different folks will have different opinions about "excessive"...

You've got a Swede that has its 115th birthday this year. So, its probably one of the Swede versions of the 95 Mauser... is it one of the 96 "long rifles"? or a carbine? Not that it makes any difference for what you're asking, I'm just curious. I've had the carbine (and miss it, now..) and currently still have one of the long rifles.

Your Hornady gadget, tells you there's a 0.005" difference between fired brass and FL resized brass...

TO me that says your sizer die is working...

Now its likely someone will come along and tell you that .005" is too much, your brass won't last, you won't get accuracy, cats and dogs will be sleeping together, dead will rise and the world will end unless its .002"..etc...

Personally I don't worry about it. Nor do I measure it, or have the Hornady gadget to do it with. If your ammo chambers properly, the rifle shoots well, and your brass lasts the average amount of loadings, why go borrowing trouble??

I don't load for match/benchrest rifles, been loading since the early 70s, I don't have a comparator, and don't plan on getting one.

If you're really concerned about it, seems to me to be a fairly simple matter of adjusting your sizer die (screwing it out) just a tiny bit until the comparator tells you that you've reached whatever it is you consider the magic number.

Oh yes, it’s the long rifle/Model 96. I have my eye on a Model 38 locally and it’s at a fair price given all the stuff that goes with it but I’m not sure I want all the extra stuff and price that goes with it. I have put the front and rear peep sight setup on it and am struggling with some weird light refractions I’m getting from my glass lenses but am getting it better playing with the extra diopters. I’m getting 3” groups at 50 yds and a little bigger at 75 yds. At 100 yds I can’t see a target clear enough to shoot a uniform group. The model 38 is setup with a scout scope which might be fun.

 

[Don Fischer]

Before this problem get's you crazy, do yourself a favor and throw that measuring device away. Then set your die up to partial resize and make your case's fit that chamber. Problem solved!

 

[44 AMP]

what I mean is the brass is stretching from .015-.020”....

OK, this changes things, somewhat, but still only a matter of degree.

What is the difference in overall case length, measured from base to case mouth between unfired, fired, and resized cases??

Bottle neck brass usually grows the most on it s first firing, and then a smaller amount with subsequent firings. This is why we set the trim to length at something like .01" shorter than the max length (though this varies with some cases), so that we can get several loading cycles (during which the case does stretch a bit) before it reaches the max allowable length, at which point, we trim it again.

The datum point you are measuring to, on the case shoulder is not telling you the overall length of the case. It is something you control with how much you size the brass. the case will stretch to the limit of the room in the chamber, then spring back some, and that can account for small variances between individual fired case measurements.

Generally speaking, a FL sizer die is supposed to reduce the case measurements to slightly less than the official minimum specs for the ammo, so as to ensure chambering in any "in spec" chamber, including those at the minimum end of the specification range.

so, yes, its going to leave the cases measurably less than the way they come of of the chamber. Measuring to the shoulder tells you the change in the base to shoulder but nothing else. And that change can be "set" to what you want, by adjusting your sizer die.

DO look at overall case length, AS WELL. You won't get good results from the "perfect" fit of the shoulder if the case neck is too long and over spec limits.

 

[jetinteriorguy]

I didn’t measure OAL before sizing but after sizing most of the cases were within .004” of each other and were all at least .005” shorter than the max length according to my Hornady book. I’ll check OAL after my next round of shooting. I’m well aware of sizing less than full length sizing, and will probably start doing this to extend brass life. I guess my biggest concern is if this much stretching and resizing is excessive to the point of base separation or is considered to be a reasonable amount if full length sizing.

 

[44 AMP]

I guess my biggest concern is if this much stretching and resizing is excessive to the point of base separation or is considered to be a reasonable amount if full length sizing.

The only answer to that is what your brass does in your rifle, with the amount of resizing you are doing.

The only way to find that out is to track one lot (batch) of cases through multiple loadings without changing anything, until you get signs of incipient failure. At that point, you have a base line to judge against. Then make a change to your sizing amount, and track that brass through multiple loading cycles until it reaches the failure point. and compare that number of firing with your first batch.

If you get 6 loadings now and 8 after making a change, is that worth it to you?
Or its also possible that you can make the change and still not affect the number of load cycles before the brass is worn out. Only shooting, reloading and shooting them and keeping track of the cases (each batch separate) will tell you what is happening in your gun with your cases.

Just because a tiny bit of less sizing ought to prolong brass life doesn't mean it will. It might, but every combination of rifle, die, brass, adjustments and other factors make each case potentially unique and the "usual" things might not happen. Only testing with what you have and do, will show if your set up falls within usual behavior, or outside it.

 

[jetinteriorguy]

Sounds like a reasonable plan. Thanks brutha.

 

[RC20]

Before this problem get's you crazy, do yourself a favor and throw that measuring device away. Then set your die up to partial resize and make your case's fit that chamber. Problem solved!

Kind of like sending a Probe to Mars, just kind of point at the planet and hope.

You need data to determine what your case length is in that gun, you then need to measure the sizing to see if you are pushing the shoulder back and how much.

Or you can use the die mfg instruction and really crush it back and split the cases in a few firings.

 

[jetinteriorguy]

The shoulder is being pushed back as I’ve previously stated, .015” to .020”. This is what concerns me if this is a more than acceptable amount. This is why I use the comparator because it measures to a predetermined datum point on the shoulder, as opposed to just measuring OAL which doesn’t necessarily tell how much the shoulder has moved, it only tells you how much the whole case has changed.

 

[Unclenick]

If you look at new brass, it is usually 0.002" to 0.003" below minimum chamber length. So, as Don suggested, you want to back the die out about 0.013" and resize again. That's just under a fifth of a turn. I wouldn't find it necessary to throw away the measuring tool, though. Just check that your cases are about -0.002" to -0.003" shorter from head to shoulder than they were when ejected from the gun after firing. That's enough resizing for reliable feeding from a magazine.

 

[RC20]

Yep

 

[jetinteriorguy]

Will do my friends. Given the variances in these lengths after firing would it be best to take the longest one and set your die to size them all a couple thousandths shorter or would it be better to pick the shortest case and size to that length?

 

[Unclenick]

Unless you have extracted the case so hard that you bent the rim and it is adding fake length to your measurements of the length of the case, the longest head-to-shoulder dimension will still be one that fits in the chamber, so it is not longer than the chamber and you want your resizing efforts to come out 0.002-0.003" shorter than that one. The others have either been fired at pressures too low to fireform the case fully or have developed so much spring from working that they would benefit from annealing.

 

[jetinteriorguy]

Thanks UN, that’s what I was thinking. This is a pretty moderate load which is probably why such inconsistent case lengths, and they all extract without any issues so I haven’t noticed any issues with the rims. I’m only shooting out to 75 yds since I can’t see targets clear enough with iron sights past that distance with the lighting at the indoor range where I shoot. At this range the medium load was most accurate. I sure miss my eyesight of my younger days. I’m using original style sniper sights which are aperture sights both front and rear, and I’m still playing with different combinations of apertures. I’m hoping with more practice to get consistent 3” or less groups at 75 yds.