Case expansion at the web after fired 1x. What is acceptable max?

[whatsupdoc]

Bored so I did some unscientific quick and dirty setup and measurements of Hornady 6.5 Creed ammo
fired in two different rifles. Mike was .221 from base.
Measured 10 pcs of new ammo then 6 each fired in two different rifles.

The correct way would be to measure and mark individual cases fire them then remeasure recording
each individual case.

Average head expansion was .001

 

[wboggs]

For years I have used 0.0015.
If you can get factory ammo, you can use the measurements for fired cases. Then reload the same brass and take measurements again. This has worked very well for me. At some point the expansion will equal factory and then get larger with increasing powder charges.
If you want to know the pressures with wilcats to a high degree of accuracy, you need pressing testing equipment.
The 0.015 has always proved to be a trouble free number for me.

 

[cem]

Agreed that using calipers no matter how expensive and good, Mitutoyo may be the best though mine are Starrett made in U.S., is not a good way to get actual measurements but may well be good for the delta or change. Again if the solid head on your brass is expanding that much it's a concern. If the solid head of factory loads is expanding that much it's a very real concern and maybe time for a chamber cast as an easy and obvious next step.

 

[M-61]

Case head separation is caused by the case stretching beyond elastic limits to fill the available space when base to shoulder space ………..- headspace is excessive

Yes. Don’t want to hijack but to your point:
And as arbitrary ‘bumping’ is a step in your reloading what do you think you are allowing to happen? To me you’re racing to that ‘elastic limit’.

 

[Lynn313]

Sounds like you had a significant runout problem when it was chambered or some type of chambering issue. The reamer could be at fault but id point toward the chambering process. Either way, get it measured and fixed before somebody gets hurt

Sounds like you had a significant runout problem when it was chambered or some type of chambering issue. The reamer could be at fault but id point toward the chambering process. Either way, get it measured and fixed before somebody gets hurt.

Dusty, thanks for looking at this. I don’t have the knowledge to understand significant run out problem tied to asking about the expansion at the web. Is this something any gunsmith that chambers would understand? Also, would they have the tools to measure?
Much Appreciated

 

[Dusty Stevens]

Dusty, thanks for looking at this. I don’t have the knowledge to understand significant run out problem tied to asking about the expansion at the web. Is this something any gunsmith that chambers would understand? Also, would they have the tools to measure?
Much Appreciated

Yes it means if you chamber a barrel with a bad setup the reamer can cut the base too big. That makes your cases expand too much

 

[jpretle]

An 'in depth' perusal of Bob Hagels' Guns Loads And Hunting tips would answer all of your questions...

 

[DaveTooley]

Yes it means if you chamber a barrel with a bad setup the reamer can cut the base too big. That makes your cases expand too much

Dusty
I don't think that's his problem. He had .003" expansion @.200". If it is a problem it didn't go away in .050" of travel.

.0025" expansion at the extractor groove means too much pressure for that lot of brass.

 

[Murray Brook]

Yes it means if you chamber a barrel with a bad setup the reamer can cut the base too big. That makes your cases expand too much

Is there an effect in accuracy or just case life.

 

[pdhntr]

PRE, CHE, RIP

I believe Ken Oehler also tested this using the Piezo system and the results mirrored Bramwell's.

Jim

 

[mikecr]

1thou is the most I would accept.
I used to use a blade mic & rig to measure, but found that calipers or a simple QC thickness MIC at the webline actually works better for my testing. The webline being the widest portion of any fired case. Normally I can see the point, but if not I can slide meaurement down the case until I hit it.
This works better because, as mentioned earlier, the webline will fall to a different datum depending on case manufacture. A cheap tool like this works really well:


Below the webline, like near extraction groove, I would be concerned at .0005" expansion.
More than that, whether I accepted it or not, the brass wouldn't be around for long.