brass longer on one side after firing

[Willoughby]

Ive noticed my 3006 brass grows longer on one side after firing
what causes this to occur ? is it my reloading or is it the chamber causing this
its in a savage 110 -so the barrel is easy to change -
the load is once fired rp brass -208 amax 54grains H4350-cci lr primers
I assume its the chamber but would like your opinions
thanks in advance

 

[watercam]

Have you indexed a cartridge, fired it and determined which side, relative to the chamber/locking lugs, is growing?
How did you determine that one side is growing longer than any other. If it is in the trimmer, which trimmer is it?

 

[bugman]

if this is an unturned neck OD chamber, IMO, it is different thickness on sides of the case neck brass. Could also be chamber-related....rough/tool marks on one side equals more friction and can cause unequal fired lengths. In this case a borescope is your friend.

 

[ARshuter]

I gotta ask. What makes you suspect the chamber?

 

[jlow]

If this is unturned brass, check the thickness of the neck. My guess is the brass has uneven neck thickness (which is not unusual) and this extend all the way down the case. As you fired the round, brass gets pushed up passed the shoulder into the neck, this is why the neck gets longer and you need to trim. Thicker area may push up more material making that side grow longer.

 

[Willoughby]

all the brass was trimmed to same length and inside -outside chamfered before firing -
after firing the brass is noticeably longer on one side
I found this when measuring col to see if they needed trimmed before reloading
I found all case necks were longer on one side
like the brass had flowed more on one side
I load for several cartridges- & have never seen this before -that's why I assume its the chamber
I get 3-4 loadings before needing to trim on other rifles

 

[watercam]

There is a theory that brass that is thicker on one side than the others 'bananas' when firing. Similarly if ones bolt face is not square (or one lug is not making contact with it's abutment) the same thing can happen. It is not visually apparent but measurable. Did you check the concentricity of the body of this particular batch of brass? Are your lugs lapped? Bolt face trued?

 

[bigedp51]

If brass has unequal case wall thickness the case when fired will expand more on the thin side and warp. When full length resized the warping increases and the base of the case can end up no longer 90 degrees to the axis of the bore. The end result is the warped banana shaped case as explained below. This problem is worse when civilian SAAMI cases are fired in military chambers with larger diameter chambers. And very prevalent with cheaper grade .223/5.56 blasting ammo made from cases that are seconds and have a large variation in case wall thickness.

 

[jlow]

all the brass was trimmed to same length and inside -outside chamfered before firing -
after firing the brass is noticeably longer on one side
I found this when measuring col to see if they needed trimmed before reloading
I found all case necks were longer on one side
like the brass had flowed more on one side
I load for several cartridges- & have never seen this before -that's why I assume its the chamber
I get 3-4 loadings before needing to trim on other rifles

None of the above it going to make any difference if your brass has uneven thickness inside. Are you even reading the response and understanding what we are telling you?

 

[Willoughby]

None of the above it going to make any difference if your brass has uneven thickness inside. Are you even reading the response and understanding what we are telling you?
reading yes
understanding ....probably not
I think your saying I have case neck thickness issues
and maybe some head thickness issues
Ive only been reloading for about 4 years
but just basic reloading - and no -I don't measure neck thickness - or run-out

thanks for all the response's
greatly appreciated

 

[Preacher]

Thats where one of those Junke machines would come in handy...
Besides a Hawkeye, a ball mike is also your friend, get you one...

 

[Brians356]

after firing the brass is noticeably longer on one side
I found this when measuring col to see if they needed trimmed before reloading

I'm curious, how much longer on one side?

And how exactly did you measure the difference, if you did? Or is it something you just eyeballed when applying the caliper, or squaring up cases on the trimmer?

 

[243winxb]

If bolt face is not square to the chamber (or one lug is not making contact with it's abutment) the same thing can happen.

 

[jlow]

It’s not a problem but if you don’t understand what we are saying, the best thing is to ask. It is a bit hard to respond to a poster’s question when they ask a question but the answers looks like they are being ignored.

It is really not rocket science but cases are extruded in the manner described in this article:

http://www.accurateshooter.com/technical-articles/how-cartridge-brass-is-made/

What you should get from this is this is rarely done absolutely perfectly and if it is done off centered, the resultant brass will have thicker wall on one side. This different in thickness is not just at the neck but all the way down the side of the case. This is quite common but sometimes it can be off enough that it can cause a problem.

As mentioned in my earlier post. When you fire a round, some of the case material will inadvertently move from the body of the case towards the neck. How much usually depends on how hot the round was loaded. As the brass moves up around the shoulder and into the neck, the neck gets longer and this is why you have to trim to maintain a constant neck length. When one side of the case is thicker, more material will move up from that side and this is likely the reason why you see your brass longer on one side after firing.

If you don’t have tools to measure the brass, this will indeed make it difficult for you to do trouble shooting. This of course is the reason why we spend money to get tools. We can give advice and guess at possible reason for your problem but in the end, you will need tools if you want meaningful answers.

 

[fdshuster]

I see by your original post that it's RP brass, far from being my favorite. Try a small amount of Lapua or Winchester. I stopped using RP many years ago because of manufacturing defects, like radical differences in case neck wall thicknesses. One side of the case neck with neck wall thickness of .0135", and the other side .009", measured with a ball micrometer. "Banana" shaped cases that had runouts of .012" under my Sinclair concintricity gauge, loose primer pockets, and the list goes on and on.

Maybe I just had a single bad lot, and maybe that's your problem also, but I know since I stopped using it I've never had those problems again.