Bad Idea???

[Lonewolf74]

Something I'm thinking about trying.

I got one of those Sinclair neck length gauges a while back and found that my actual chamber length is 2.670, so .050 over book max case length. This seems huge to me and would like to find a way to stretch the neck length out some so I'm closer to 2.660 or so.

Because of this I haven't been trimming my cases between firing but it bugs me they're not all the same length and possibly out of square.

Right now I'm prepping some more new cases out of the batch I bought and there all right around 2.610, book trim length but way short for my actual chamber.

So my idea! By accident a while back while setting my sizing die (Forster full length) I found out if I have the expander ball a tad too high it stretches the neck out some, about .010. So im thinking about doing this on purpose to all the cases and hopefully can trim them to square and be all the same at 2.620 or so as a starting point.

As a bonus I would think this would press all the neck walls to being very consistent in thickness.

So any reason this sounds like a bad idea?

 

[tbrice23]

I'll be perfectly honest with you, that sounds like a bad idea.
I'm pretty sure stretching your brass will make for some crazy amount of run out. The brass will stretch more on the thin side.

I make my own max chamber lenth guages out of once fired neck sized brass. Cut 1/2 the neck off with a dremel cut off wheel, seat a bullet deep, ream the cut off 1/2 of neck to have .001" or less tension on the bullet. Slip the 1/2neck on the bullet long then carefully chamber and eject the round and measure a few times.
Most of my chambers are .030" or so longer than saami except for my WSM chambers which are really close to saami.

 

[Lonewolf74]

Tbrice thank you for your thoughts, I did not think about this as being a possible side effect.

But in thinking about it I don't see how this could happen. The necks are stretched due to the expander being in the neck while the neck is still in the neck sizing portion of the die. I think the neck wouldn't have a choice but to stay true to the die. Any variance in neck thickness may be witnessed at the case mouth where it would be out of square due to the thin area being pulled/stretched more or less. I think side to side or off center as in run out would actually be the truest it could be from any die.

 

[Lonewolf74]

Aright I tried this with a few cases and it didn't work. No ill effects but I would only gain about .002 on the necks, not nearly as much as I thought it did before.

 

[Lonewolf74]

So my next question is asking some opinions. Do you think it's best to trim my brass so there all the same length?

Or trim them once to start out uniform and square then let them grow to whatever even though length will end up different across the lot?

I know having .050 clearance I'll never have to trim in the life of the brass but it drives me nuts not having them the same length.

 

[J E Custom]

Trim all of your brass to the same length and don't worry about the neck chamber length, It is fine. .030 to .050 thousandths is the recommended length longer than the case neck.

You have to have clearance to keep the case from jamming the neck into the chamber increasing the pressure excessively. closer tolerances don't improve accuracy and can only cause problems with pressures.

One reason I like the 40o shouldered cases is that they reduce the case growth.

J E CUSTOM

 

[Trnelson]

Exactly what said. It isn't a problem to solve or correct.
Square up your brass necks if you like, trim them back to specifications or select another safe length and run that. Especially if you have just one rifle chambered for that round. Keep in mind that they MAY OR MAY NOT fit safely in another rifle if left longr than specifications. My girls rifle has a very short neck and will not safely fire any of the brass from one of my rifles. I keep that brass in different safes, use different colored MTM bullet cases and different brands of brass to avoid any safety issues.

 

[J E Custom]

One other thing with short neck chambers is that if this area carbons up (Which they all do from firing) And the same thing happens to the length and the carbon has to be removed to keep pressure under control.

This is one of those things that can creep up on you if not watched because carbon is harder to remove and many solvents won't touch it.

J E CUSTOM

 

[Lonewolf74]

Thanks guy's, I don't know where I read it but I read a couple times that it's best to keep that clearance down to .005-.010 but I'm not gonna accomplish that so I'm not gonna chase it. Depending on growth I'll make my trim length between 2.620 n 2.630

 

[Lonewolf74]

One other thing with short neck chambers is that if this area carbons up (Which they all do from firing) And the same thing happens to the length and the carbon has to be removed to keep pressure under control.

This is one of those things that can creep up on you if not watched because carbon is harder to remove and many solvents won't touch it.

J E CUSTOM

How do you keep an eye on this and what do you do to remove it?

 

[J E Custom]

How do you keep an eye on this and what do you do to remove it?

I build a test gauge for my rifles using the actual reamer that was used for chambering and periodically check my brass with this gauge. Also I have a bore scope that I can use to look at the chamber if any chambering issues occur.

Maintenance with a good carbon remover should also keep this from happening. (Probably the best way without spending lots of money)

A good indication that your chamber has carbon fouling is a change is bolt closing, change in velocity and POI (Indicating an increase in pressure). This is another reason to have plenty of neck chamber length (The carbon will form sort of a forcing cone) and as long as the case does not contact this carbon ring, It is not to much of a problem.

J E CUSTOM

 

[flowhnun63]

I'll be perfectly honest with you, that sounds like a bad idea.
I'm pretty sure stretching your brass will make for some crazy amount of run out. The brass will stretch more on the thin side.

I make my own max chamber lenth guages out of once fired neck sized brass. Cut 1/2 the neck off with a dremel cut off wheel, seat a bullet deep, ream the cut off 1/2 of neck to have .001" or less tension on the bullet. Slip the 1/2neck on the bullet long then carefully chamber and eject the round and measure a few times.
Most of my chambers are .030" or so longer than saami except for my WSM chambers which are really close to saami.

i second this ^

 

[gohring3006]

What cartridge are we talking about?

 

[Rich Coyle]

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