Chamber sizing?

[dbooksta]

Is there a gauge or method to address the following problem?

I have a semi-auto .308 and I discovered that even after full-length sizing the cases they would not fully chamber without forward assist. Of course after full-length sizing they clear a case gauge, but that just confirms headspace and OAL.

I assume that the remaining problem is that at some point along the case body the FL sizer isn't squeezing the diameter down far enough for this particular chamber. Does that sound like the reasonable/likely explanation for the sticky chambering?

If so, how does one determine whether the gun's chamber is excessively tight or whether it's the FL sizing die not fully squeezing the case bodies into spec? Or what's the best solution?

 

[MALLARD]

Re: Chamber sizing?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dbooksta</div><div class="ubbcode-body"> Does that sound like the reasonable/likely explanation for the sticky chambering?

If so, how does one determine whether the gun's chamber is excessively tight or whether it's the FL sizing die not fully squeezing the case bodies into spec? Or what's the best solution? </div></div>

in order of your questions

yes it does

go and no go gages to check your chamer, the die i dont know.

the solution , are you sure you have set up your press properly so that the die base makes 100 % contact with the shellholder ? if yes

try another die ( redding body die , or lee f/l die is a good choice). If that fails , have one of the die makers look at your gun.

 

[ksthomas]

Re: Chamber sizing?

Sounds like you've run into a good candidate for a Small Base die. Use a headspace gage and make sure the shoulder's being bumped back at least .003"-.004" and you should be good to go. I'd also forget about the Forward Assist. If you're having chambering problems, the Forward Assist is only going to make it worse. Think of it as a button for making a SNAFU into total FUBAR in one quick punch. Been there, done that, and will never do it again. I now remove the pawl from my competition rifles so this CAN'T happen.

 

[MtnCreek]

Re: Chamber sizing?

What brass are you using and where did ii come from?
What die are you using?
Do you release the charging handle or slowly ease the bolt/carrier towards the chamber?
Are you crimping bullets?

 

[dbooksta]

Re: Chamber sizing?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MtnCreek</div><div class="ubbcode-body">What brass are you using and where did ii come from?
What die are you using?
Do you release the charging handle or slowly ease the bolt/carrier towards the chamber?
Are you crimping bullets? </div></div>

Lake City brass from Georgia Arms, and the initial Georgia Arms loads cycle fine. FL sizer is Lee, and I put a minimal crimp with their Factory Crimp die. Not riding the charging handle at all when chambering.

I bought a small-base sizing die and haven't tested it yet but expect that will solve the problem. But that seems like a coarse way of addressing the problem: After all, when it comes to case length and headspace we measure and adjust dies and chambers to thousandths. When it comes to body diameter we just say, "Regular or Small?"

 

[MtnCreek]

Re: Chamber sizing?

GA Arms uses milsurp LC brass, then they size them on an ammo load. I assume it sizes it min spec.

They chamber from GA Arms, but not after firing in your rifle.
Does a sized case chamber without bullet?
If no, turn the sizer in till it touches the shell holder, then lower the ram and give it an additional 1/4 to 1/2 turn. Check for function.
I bet that'll do it.

 

[dbooksta]

Re: Chamber sizing?

I have the Lee FL die touching the shell holder, and that doesn't do it.

 

[MtnCreek]

Re: Chamber sizing?

Give it an additional 1/4 to 1/2 turn. There's slack and flex in presses. That will take up the slack and account for the flex.

There's a chance your die is out of spec, but that's not likely the case.

 

[FLIGHT762]

Re: Chamber sizing?

Sometimes, that extra 1/8-1/4 turn after the die touches the shell holder will resize enough. Try it. Make a few dummy rounds so you're not having to cycle live ammo through the rifle.

I've had a few rifles where that extra turn made the difference, especially on a tight chambered gun.

 

[wilecoyote]

Re: Chamber sizing?

3588499 - 09/24/12 06:24 PM Re: redding body die, resizing [Re: wilecoyote] _ try that

 

[Grumpy61]

Re: Chamber sizing?

will they chamber with a bullet seated before crimping?

 

[dbooksta]

Re: Chamber sizing?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grumpy61</div><div class="ubbcode-body">will they chamber with a bullet seated before crimping? </div></div>

Nope.

 

[Kinsman]

Re: Chamber sizing?

I had the same type problem with some once fired, probably machine gun fired, mil surp brass. Small base die solved the problem for me....

 

[Sapper524]

Re: Chamber sizing?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Kinsman</div><div class="ubbcode-body">I had the same type problem with some once fired, probably machine gun fired, mil surp brass. Small base die solved the problem for me.... </div></div>

+1

I use Small based dies when reloading for Semi's. Saves a lot of headaches. I have a mild "universal" load ... Sized with SB die and will shoot fine to 800 yards in all my 308's.

175 smk
43.5 RL15
Win Brass
CCI 200
2.795 OAL

 

[dbooksta]

Re: Chamber sizing?

I'm eventually going to find time to use these observations to carefully measure my cases and try to figure out exactly what's going on.

As to my follow-up question here it sounds like the consensus is that: when full-length sizing is necessary you don't significantly reduce case life or accuracy by using a small-base die (as opposed to finding a way to minimize the resizing of the case body)?