A puzzle for the group

[PvtGreg]

Hi All,

Last weekend I went to the range with 25 56-50 of Starline's best along with 25 of my own cut down 32 gauge brass.  I had never before shot both at the same time.

The load was bullet - 350 gr RCBS-82309 over 9.2 gr trailboss for both.  Loaded in the same session and using bullets from the same lot.  The range was 100 yards and I was benched.

-Shooting the Starline brass first, ALL my 5 round groups were between ~3 and 4in.

-Shooting the cut down 32ga brass second, ALL my 5 round groups were between ~5 and 7in.

OK - so I figured this was a fluke - so I loaded 25 more Starline and 25 more cut down brass, same load as before.

-Shooting the cut down 32ga brass FIRST, ALL my 5 round groups were between ~5 and 7.5in.

-Shooting the Starline brass second, ALL my 5 round groups were between ~2.5 and 3in.

All the hits were clustered around center.

Any thoughts other than Starline makes good brass?

Thanks - Greg

[matt45]

My first guess would be that the 32 guage stuff is thicker and the expansion at ignition is not as uniform, but that is only a slightly educated guess (w/out an oehlar it would be tough to prove).

[Herbert]

flash hole sizes can affect acuracy,the larger the flash hole the more acuracy gos off in my experince

[PvtGreg]

FYI - third range tryout for Starline vs 32 ga brass.  Results confirmed.

As per Herbert's comment - I confirmed that the primer hole for the Starline is about 10% bigger than 32 ga brass. 

Also a second factor may be that I'm using magnum pistol primers on the 32 ga brass (they only take large pistol primers) and standard rifle primers for the Starline.

[Herbert]

It has all so been my experiance that the weakest posible primmer will give the best acuracy with BP.I even use a under primmer wad in my BP loads,no need for this with smokless but I have never had any luck with magnum primers.If the 32 ga cases have smaller flash holes they should be very good for BP loads with proper anealing

[Capt'n Jack]

How well do the 32 brass shells grip the bullet?  Could be the Star cases give better powder ignition due to better grip on the bullet.  Do not think BP needs this but does like compression so???