I’ve only used Nosler and Lapua brass in the past, but got a bag of Winchester brass in mail today for a 270 Win. Have read conflicting reviews on this brass, so I thought I’d play around with it a bit just to see for myself. Most of the case mouths were out of round but the flash holes looked to be fine. I decided to measure them all case base to datum. 44/50 measured 1.947-1.949”. 5 of the remaining 6 were either 1.946 or 1.950, with the last case measuring 1.9535”. My question is this...when I placed the case mouth/neck into the bump gage insert, the brass did not stop at some point on the shoulder, but rather seemed to drop down to the shoulder/body junction....as if the case body stopped the brass and not the datum. My insert is stamped with a “17” and the package says it’s for cases in the 30.06 family. Anything I should be taking from this occurrence? Thanks.
Brass or bump gage insert?
- Thread starter Jody Simcox
- Start date
SAAMI uses a datum measurement of .375" The 270 win and 30-06 use the same one. The shoulder angle is the same.
If using a #17 Sinclair??
Sinclair Bump Gauge Is different.
Here is where i throw all compatitors into the scrap bucket. The old methods work best. Size for a crush fit when closing the bolt. Simple.
If using a #17 Sinclair??
Sinclair Bump Gauge Is different.
Here is where i throw all compatitors into the scrap bucket. The old methods work best. Size for a crush fit when closing the bolt. Simple.
I’ve had the same issue with Sinclair comparator inserts for a 220 Swift. Sized cases had shoulder to base lengths varies more than 0.005”. Also it was probably “a few” out of 50.
When I used an insert for a different shoulder angle 28* on the Swift (Swift is 21*) cases I didn’t see the variation.
I’m still trying to figure it out.
I don’t get the variation in base to shoulder with 4 other cartridges with different shoulder angles.
I’m thinkin the insert is off.
When I used an insert for a different shoulder angle 28* on the Swift (Swift is 21*) cases I didn’t see the variation.
I’m still trying to figure it out.
I don’t get the variation in base to shoulder with 4 other cartridges with different shoulder angles.
I’m thinkin the insert is off.
Those cases may have been fired in different chambers or some sized in different dies.
Doesn't matter much what gauge datum diameter is used. All 270 chamber shoulders are not the same exact angle. Same for FL sizing dies.
A crush fit of case to chamber typically opens groups one to several tenths MOA; the reason benchrest winners decades ago had to full length size their neck sized cases when bolts started crush fitting in battery. Bolt heads seated enough different to change the direction the barrel whipped during bullet's barrel time. Much worse if bolt faces were not squared up.
.001" case head clearance to bolt face (when in firing position) is perfect for best accuracy and case life. That's what mikecr was suggesting.
Doesn't matter much what gauge datum diameter is used. All 270 chamber shoulders are not the same exact angle. Same for FL sizing dies.
A crush fit of case to chamber typically opens groups one to several tenths MOA; the reason benchrest winners decades ago had to full length size their neck sized cases when bolts started crush fitting in battery. Bolt heads seated enough different to change the direction the barrel whipped during bullet's barrel time. Much worse if bolt faces were not squared up.
.001" case head clearance to bolt face (when in firing position) is perfect for best accuracy and case life. That's what mikecr was suggesting.
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butchlambert
Site $$ Sponsor
Didn't see where he mentioned that it was new or unfired brass,
“Got a new bag in the mail today”....took some measurements before I touched the brass. Typically brass gets caught about mid-shoulder by the insert. These factory new, unaltered cases got caught by the body it appears....maybe that’s where the .375 diameter is...
The #17 Sinclair "comparator bodies are machined to fit particular shoulder angles of cartridges. Rather than measuring to the datum line." No datum is used.
Just compare fired brass and dont size to much.
butchlambert
Site $$ Sponsor
I saw the new bag, but nothing about new brass. Measure it after fireforming it
I assume it was factory new brass, but actually only said “unprimed” brass from Cabelas. Measurements from the bump gage insert were 1.948before firing and 1.952 after firing..this very evening I backed my sizing die off 1 1/2 turns and cycled these 3 pieces...measurement with bump gage insert is now 1.953”. Only sized about 2/3 of the neck with a slight bulge noted as compared to the sized portion of the neck. Also, overall case length has gone from 2.53” (before and after firing) to 2.57” after this partial resizing...I’m unsure what to make of all this.
A crush fit shows the brass is fully expanded to the chamber. It will be the maximum head to datum measurement.
Then bump the shoulder back .002"
Fired brass doesnt always fully expand to the chamber on 1 firing. May take 3 or more depending on the powder charge.
A starting load may make shorter cases with no neck diameter expansion.
Then bump the shoulder back .002"
Fired brass doesnt always fully expand to the chamber on 1 firing. May take 3 or more depending on the powder charge.
A starting load may make shorter cases with no neck diameter expansion.
jepp2
Gold $$ Contributor
A couple of years ago I picked up some new in the bag Winchester 204 Ruger brass. Some of the brass was not properly formed and on that brass even after firing a stout load, the case head to datum was still over 0.010" short and the shoulder wasn't square. It had a much darker color, like the composition was different than the brass that was normal. Even the interior of the case neck showed different forming marks.
I realize that isn't your problem, but just recognition that Winchester has some quality issues at times. Out of round mouths are to be expected.
I realize that isn't your problem, but just recognition that Winchester has some quality issues at times. Out of round mouths are to be expected.
As the case body got squeezed down, the shoulder and neck moved forward. The die moves up or down about .072" per turn.
If the die was lower in the press, the shoulder would've been pushed back a few thousandths. Turning the die 1/10" on its circumference changes its height about .002". Link below was used to print die labels on label paper.
http://i860.photobucket.com/albums/ab170/jepp2/DieAdjustment-1.j
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