Brass Pattern; How much of a factor in accuracy?

berettaprofessor · Apr 16, 2017

I finally got some Hodgdon CFEBLK to try in my 300BO AR (carbine barrel) and shot it today. I loaded up 11.6 grains behind a Hornady 208 A-Max, a load right out of the Hodgdon 2017 manual. All hand-weighed charges and exact to 11.6 grains. Twenty pieces of brass ejected over about a 6 foot diameter circle from my 2:30 to 4:30 about 8 feet out. No signs of high pressure on the brass. My previous load for this round was IMR 4227, 10.1 grains behind the same bullet (also right out of the 2017 Hodgdon manual), and it ejects everything in about a one foot circle at my 4:00 (I shot it today under the same conditions, 15 rounds). The latter load sure makes the brass easy to find

So my question; I was not really shooting benchtop to test accuracy today, but was shooting off-hand at a 6 inch target from roughly 25 yards out so the AR was aimed at roughly the same spot, plus or minus my shaky hold. From the brass ejection pattern, can I reasonably conclude that the IMR 4227 load is going to be more consistent accuracy--wise in this gun? Or does it mean anything at all?

For those who have been wondering about CFEBLK, I can't feel any difference in recoil between the two powders and the Hodgdon manual listed speed of the Hornady 208 A-Max is about the same for both. I will tell you that the 300BLK powder has very tiny grains with a few larger ones mixed in and it seems to get spread over the benchtop by bouncing off the scale pan, which I wasn't crazy about.

Kaldor · Apr 17, 2017

Probably doesnt mean anything at all

A pointer to keep very fine powders that tend to bounce out of pans? Use a small plastic shot glass to drop powders into, then transfer into scale pan, if using a drop. A plastic pan also has less bounce, but will probably require tuning the balance on your scale to account for the different pan.

macgrumpy · Apr 17, 2017

It means that the IMR powder produced more consistent pressures that were slightly less than the other powder. Whether that means that it was a more accurate load is hard to say, it could be since the pressures and resulting velocities would be more consistent (better standard deviation) if the load was a good match to the barrel.

hdwhit · Apr 18, 2017

berettaprofessor wrote:
From the brass ejection pattern, can I reasonably conclude that the IMR 4227 load is going to be more consistent accuracy--wise in this gun? Or does it mean anything at all?

Reading the pattern of ejected brass (particularly from an AR) is a little like reading tea leaves. So many things, like chamber pressure, cleanlinees of the rifle, uniformity of the brass, how smooth the brass was, consistency of the bullets, etc. can influence where ejected brass falls that there is inevitably some subjectivity in the analysis unless you started out consciously trying to control all the variables.

Like macgrumpy said, it's pretty safe to assume the IMR produced more consistent pressures, but whether that translated into greater accuracy is hard to say. After all, you can consistently produce a recoil impulse that throws off your stance or grip and the accuracy will be less than an inconsistent recoil impulse that doesn't bother the shooter.

mdi · Apr 18, 2017

I have noticed a different "ejection pattern" with different loads in my Garand. Lighter loads landed farther forward to mebbe 1:00 (brass hits the op rod handle) and heavier loads farther back some to 4:00 (brass is deflected less by op rod handle). Actually a similar occurrence with my 1911, heavier loads eject farther to the rear than lighter loads...

GooseGestapo · Apr 21, 2017

My M1's and Carbine act exactly opposite. Hotter loads are thrown further foward due to op-rod throwing them foward. I.E. service level ammo.
A cast bullet load with a 155gr PTGC, over 35gr of H4895 are thrown over my right shoulder.

Likewise with the .30Carbine, 14.7gr of H110 under a 110gr FMJ are thrown foward, a 90gr Coated cast RN over 12.0gr of #2400 is thrown over my right shoulder.

Brass Pattern; How much of a factor in accuracy?

berettaprofessor

Member

Kaldor

Member

macgrumpy

Member

hdwhit

Member

mdi

Member

GooseGestapo

Member

Similar threads