• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Brass or bump gage insert?

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.
 
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.
Sinclair Bump Gage Inserts are used to measure the amount of shoulder bump when setting up full length sizing dies. Our Bump Gages install in either of our comparator bodies and are machined to fit particular shoulder angles of cartridges. Rather than measuring to the datum line , these gages indicate off of the shoulder of the case to get a better, more easily assessable measurement of how much you are actually sizing your cases.
:confused:

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.
 
My thinking is inline with 243winxb. Our chambers, like our dies, vary quite a bit. So it really is easiest to just fully fire form your cases, and then bump ~1-2thou as needed, using pretty much any gage (it's just off crush fit-by free bolt handle drop).
 
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.
 
Last edited:
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...
 
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.

SAAMI-
DATUM


A reference plane, point or diameter that provides a base for calculations and measurements.

Just compare fired brass and dont size to much.
 
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.
 
I wonder about the decapper Rod bottoming out prior to complete cycle.

A second thought- how many thousand is 1 1/2 turns
 
I wonder about the decapper Rod bottoming out prior to complete cycle.

A second thought- how many thousand is 1 1/2 turns

Depriming spindle has been removed, I use a separate die for that. I believe a full turn of a die with 14 TPI equates to roughly .071”.
 
Try setting your headspace without the bushing.
I'm not sure why a crush fit would be beneficial
 
Last edited:
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.
 
Yes of course fully Fire formed..

I had misunderstood what you were getting at.
My bad
 
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.

Brass Color1.jpg
 
Just dinking around I've used a 45 ACP empty case as a comparator should touch closer to the case shoulder junction.
As pointed out as long as they chamber it doesn't really matter until they are FF
 
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.
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

image (1).jpeg
 
Last edited:
I suppose Guffey and I are the minority using a feeler gauge under the shell holder
 

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Forum statistics

Threads
166,291
Messages
2,215,947
Members
79,519
Latest member
DW79
Back
Top