Bergara 6.5 CM Oversized Chamber?

[Adipose]

I have a Bergara B14 Ridge chambered in 6.5 CM that I have been having a heck of a time finding a load that will shoot under MOA at 100yrds. Yesterday I tried to resize some of the once fired brass from this gun, I managed to get 2 of them sized but it felt like it needed excessive force on the press to get them sized, but chocked it up to maybe the die not being lubed up enough yet. On the third piece the brass is now stuck in the die.

When measuring the once fired brass as the base, all measure .472" which looks like .002" larger than SAAMI spec (.470"). My question is does .002" wider than SAAMI at the base seem excessive? Or is this within spec?

When I measure fired brass from a Tikka 6.5CM it comes out right at .470"

Trying to decide if this is a fluke or I need to send this back to have Bergara take a look at it?

 

[David_h]

Get a case gauge from Wilson or similar brand to check the size of once fired brass. These gauges are a "must have" for every reloader.

 

[BPollard]

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[243winxb]

SAAMI chamber .4714" plus .002" = .4734"

Will fired brass go right back into the chamber? If no, high pressure problem.

Clean die. Get RCBS 2, lube & pad. Skip the spray lube.
The first case placed in a clean die will need a little extra lube.

 

[Adipose]

SAAMI chamber .4714" plus .002" = .4734"

Will fired brass go right back into the chamber? If no, high pressure problem.

Clean die. Get RCBS 2, lube & pad. Skip the spray lube.
The first case placed in a clean die will need a little extra lube.

Thanks 243winxb, just looked at the drawings again and you are correct, looks like my fired brass is within spec, which makes me feel better.

I've always used Imperial Die Wax as my lube and haven't had an issue until now. I do have some RCBS lube and pad I will try.

I wasn't seeing any pressure signs on the fired brass to indicate over pressure. 40.5 gr H4350 with 143 ELDX. I also haven't tried rechambering any of the fired brass, but will try tonight.

 

[Mikecr]

When measuring the once fired brass as the base,

Where are you measuring,, the rim, or the web-line, or what?
How much is the new brass expanding there on 1st firing in that chamber?

 

[Hard rock]

Where are you measuring,, the rim, or the web-line, or what?
How much is the new brass expanding there on 1st firing in that chamber?

Thanks 243winxb, just looked at the drawings again and you are correct, looks like my fired brass is within spec, which makes me feel better.

I've always used Imperial Die Wax as my lube and haven't had an issue until now. I do have some RCBS lube and pad I will try.

I wasn't seeing any pressure signs on the fired brass to indicate over pressure. 40.5 gr H4350 with 143 ELDX. I also haven't tried rechambering any of the fired brass, but will try tonight.

Are you new at reloading

 

[Hydra6]

Are you setting the shoulder back too much? I learned a lesson the hard way I was pushing the shoulders back more than I need to = more effort and stuck cases

 

[WildBillG]

I know it is now frowned on but just neck size your brass.

 

[Adipose]

Where are you measuring,, the rim, or the web-line, or what?
How much is the new brass expanding there on 1st firing in that chamber?

Measuring at I guess what you would call the web-line. Shown with red arrow below.

New virgin starline brass measures 0.468" and once fired measures .472"

 

[Adipose]

Are you new at reloading

Only about 5 or 6 years now

 

[Adipose]

Are you setting the shoulder back too much? I learned a lesson the hard way I was pushing the shoulders back more than I need to = more effort and stuck cases

I am just slightly bumping the shoulder back .002"

 

[Mikecr]

Measuring at I guess what you would call the web-line. Shown with red arrow below.
View attachment 420683

New virgin starline brass measures 0.468" and once fired measures .472"

Thanks Adipose. IMO that is a huge amount of growth for once fired brass.
I doubt your brass will last very long even with use of a ring or small base die.
The reason I say this is because brass wants to go where it's been,, you can't stop it from doing that. And even at web thickness, anything over 1thou stretch is yielding.

If this is a reasonable load (any below max), I would sell off the gun, or if I just really liked it, have the barrel replaced with a good aftermarket and tighter chamber. But you also need to ensure there is enough breech support in the design, so that webs can't grow into difficult extraction.

I do a pressure test before working up a load, and while fire forming brass, for what I call 'MyMax'.
I take some culled brass with thickness variance or something and incrementally work up a higher charge for each case.
As I fire each, I measure the widest resulting diameter of the cases. I call this datum the 'webline', which you can easily see.
I'll watch the cases grow 1/2 to 1thou (that's normal to hi growth) and level off there. With a few increments higher in charge I'll see a step change of another 1/2thou. I stop & log that as MyMax charge, and with QuickLoad I get a good idea about the pressure present there.
This will be VERY close to published SAAMI max, so I suspect they're doing a similar test.
A sloppy chamber and poor breach support results in MyMax below SAAMI max. A tighter chamber and stronger action design results in MyMax a bit higher than SAAMI max (but not much).
This is with modern cartridges designed or tested for hunting, and more recently than 50 to 100yrs ago.
It's also a point where FL sizing will be required for reloading (which I don't and will never do).

Anyway, I just bring this up as my reference of big or small.
Also, I doubt Bergara will give a sh1t. Don't count on them..
Factory guns are designed enough for firing factory ammo, that's it. They're not designed for best in reloading.

 

[QuietTexan]

Get a case gauge from Wilson or similar brand to check the size of once fired brass. These gauges are a "must have" for every reloader.

You have to be careful which one you get. The Wilson gage is intentionally reamed oversize to use with a straight edge and their headspace micrometer, so it won't do anything for measuring body diameter past "so big that it couldn't rechamber in the rifle".

Sheridan Engineering, Hornady, and Lyman gauges are ammo-checkers in that they measure to a SAAMI spec to ensure chambering in spec chambers, but unsized brass should not fit in those.

RCBS and Whidden make screw-together headspace mic gauges that don't measure body diameter.

An anvil micrometer, or the .200 datum line kit from PMA are the best tools I've found for measuring web expansion.

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once fired brass

I am just slightly bumping the shoulder back .002"

You aren't "bumping the shoulders" on once-fired brass, you're oversizing the brass.

Normally I would say X2 on neck sizing or setting the FL die so high that it only sizes half the neck, if the case rechambers shoot it again, but in this case if you're really measuring +.004" expansion on the first firing that chamber is trash.

I've considered this for my B-14, I can't sell it in good faith to some poor unsuspecting soul who would think they're getting a deal on it:

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