Erratic Velocity

slimjim · Posted: Tue Mar 20, 2018 5:37 pm Post subject: Erratic Velocity

Elvis turned me on to the a new load for the .270 Win using Hodgdon's Superformance. Superformance is not a standard .270 powder. Hodgdon does not list it in its loading data. I did find load data on BarnesBullets.com using Superformance with 130 and 140 grain bullets. Some reloaders are posting velocities around 3000 fps with 150 grain bullets. This was enough to motivate me to investigate using Superformance with Hornady's new 145 grain ELD-X bullet. The ELD-X with a BC of 0.57 (measured) with the muzzle velocity of a 130 grain bullet would really extend the .270's readn and could be considered a game changer.

I used new Remington and Winchester brass with magnum primers and a 3.370" COAL (mag length but still a ways from the lands. I started 55.5 grains and worked up to 57.4 grains without indications on pressure signs with the primer. Velocity peeked at 3000 fps at 57 grains then fell 100 fps with 57.4 grains - time to stop. However, velocity progression was not consist/linear like I typically find with a powder charge vs velocity ladder.

The only thing I can point a finger at is there was significant case capacity (empty) space in the case. Could this be causing the velocity variation? Is their a filler I can use to maybe improve the situation? I often use tissue stuffed into the case when I do reduced loads to keep the powder stack up against the primer.

Your thoughts and suggestions are appreciated.

slimjim · Posted: Tue Mar 20, 2018 6:10 pm Post subject: Re: Erratic Velocity

Here is a plot of velocities. I typically get a straight line. With good powders, it can be very linear.

English Mike · Posted: Tue Mar 20, 2018 7:48 pm Post subject: Re: Erratic Velocity

The .270 does seem to perform best with load densities at or near maximum.
I guess you could try a filler but I think there's more to it than that.

slimjim · Posted: Tue Mar 20, 2018 8:09 pm Post subject: Re: Erratic Velocity

English Mike wrote:

I guess you could try a filler but I think there's more to it than that.

I expect you are correct, English Mike. Just searching for any other possibilities.

SingleShotLover · Posted: Tue Mar 20, 2018 8:11 pm Post subject: Re: Erratic Velocity

Long cases seldom seem to do their best with less than 90% or more load density in my experience. Short (BR type) cases can get away with less sometimes. I always attribute results to uniformity of ignition related to powder position in the case. I generally try to choose a powder for any given cartridge that best fills the case, without compression, and is projected to generate the best velocity. I work up loads by starting well under maximum and work up by degrees (bigger cartridges with slower powders about .5 grains at a time and .2 grains with smaller capacity cartridges and faster powders) and watch groups sizes for the node that gives best accuracy.

Elvis · Posted: Tue Mar 20, 2018 11:31 pm Post subject: Re: Erratic Velocity

wonder if a magnum primer will help....... cant hurt to try.
or the old tip barrel up to sky before lowering down and firing shot while powder is still in rear of case..... or better still THROW THE PLURRY CHRONY AWAY and just get on with shooting Very Happy

Bushmaster · Posted: Wed Mar 21, 2018 8:21 am Post subject: Re: Erratic Velocity

Accuracy?

inthedark · Posted: Wed Mar 21, 2018 12:36 pm Post subject: Re: Erratic Velocity

I was told one time by a collector of old black powder and smokeless powder rifles that you can use course ground corn meal as filler in a cartridge to keep the burning of the propellant more consistent. The idea being that you filled to case to 100% capacity to keep the propellant close to the primer or initiating element. That's all I (think) I know but I'll leave it to someone who knows more to correct me????

SingleShotLover · Posted: Wed Mar 21, 2018 3:16 pm Post subject: Re: Erratic Velocity

Problem there is that the corn meal has to be added as additional projectile weight. Might not be much, but has to be considered.

Vince · Posted: Wed Mar 21, 2018 4:33 pm Post subject: Re: Erratic Velocity

I’ve only known of Dacron “fluff” being used successfully as packing in cases with smaller powder loads, but I’m sure there are other things that are suitable.

It is my experience that powder loads filling the case to at least 90% to be more consistent in velocity and accuracy...with the appropriate powder of course.

I’m with a Elvis here...consider using a magnum primer Slim...should give better (and more consistent) ignition. Barring that, I would be looking at a different powder.

slimjim · Posted: Wed Mar 21, 2018 7:04 pm Post subject: Re: Erratic Velocity

Elvis, I should have mentioned I was using a magnum primer.

slimjim · Posted: Wed Mar 21, 2018 7:10 pm Post subject: Re: Erratic Velocity

Bushy, this rifle is a 1/2 moa with IMR4350. I haven't done any fine tuning yet but I'm haven't got below 1 1/2 moa yet.

I'm going to pack the excess space just for curiosity. Give me a week or two.

Bushmaster · Posted: Wed Mar 21, 2018 7:38 pm Post subject: Re: Erratic Velocity

I will try to be patient.

Elvis · Posted: Wed Mar 21, 2018 8:55 pm Post subject: Re: Erratic Velocity

ok....maybe Im missing something...maybe just dumb.
what kinda plurry graph is that????
I take it the blue dots mean you fired 10 shots????
so why is one stuck out in no mans land under 57???
why is only 56.5 showing 3 dots/shots
take out the 2 lower velocity readings ,one at 56 the other at again no mans land just under 57.5 and then have another look at your line,its pretty darn near straight and velocity spread/variation is pretty darn good....
from the little written about this powder,where it works its awesome where it dont its not flash and will have you pulling out hair.......
if Im reading it right your 56.5grn 3 shots have VS of 25fps or less???? and you pushing a 145grn pill at just under 3000fps...THAT ALONE would be an awesome load WITHOUT any more tweeking and says to me project worth time to continue.......but yeah the blue dot thing has me beat,surely there should be 3 dots per line or an average per 3 shots for each charge weight.

Aloysius · Posted: Thu Mar 22, 2018 2:19 am Post subject: Re: Erratic Velocity

Just to disturb you a little: I never use a filler (unless you call toilet paper wad in a cal. 12 filler material). With small amounts of powder (as f.e. reduced loads) I point my barrel high, tap slightly my rifle so that all powder is seated near the primer and shoot. (after aiming of course, not just shooting into the sky!)
And I see they recommend the use of magnum primer... I only use magnum primers with powder of a slow burning rate (fe: Vihta's N160, H1000,... ALWAYS magnum primers!). I would not recommend the use of magnum primers in your example. You don't crimp. I expect that the magnum primer already "unseated" the bullet before the powder ignits. This is an uncrontroled action, so you never know how much space is in the case at the moment the powder ignits.
So: try normal primers, no fillers and point your barrel a second to the sky before you shoot. That's far better than adding another variabel thing like a filler.
just my humble opinion.