40s&w vvelocity fluctuating

[mclement29]

Just started loading 40s&w for my glock 22 with lonewolf ported barrel. ..loading 3.5gr promo (reddot)...charge varies +/- .1gr behind lee175tc (drops 178gr)oal 1.13 in mixed once fired ....problem I'm having is I'm getting 100-125fps variance. What could be causing this?

[sargenv]

Are you sure your bullets are in fact all the same weight? Some powders in some guns don't work that well. Promo might be that way with your current bullet.. Also wonder if the chrono is far enough away from the muzzle of the gun.. wondering if it is picking up burning powder granules from the muzzle..

[mclement29]

The bullets drop between 177.4 and 178.8....wouldn't think it's enough difference for 125 fps......was thinking of trying some of all same headstamp and see if that helps any...just hoping I can get this promo to work out as I have 8lbs of it....if not o well have to try another powder

[AggieEE]

Another potential problem is the mixed cases. How much weight variation is there between cases? Weight = volume. I don't know how sensitive Promo is to volume/pressure variations but...... How far are you shooting? Is the velocity variations showing up in your groups? I have no idea what kind of velocity variation factory ammo has, sometimes ignorance really is bliss.

[Jupiter7]

Could be the porting? Try bumping the charge .1 and see if it tightens up.

[mclement29]

Started at 4.0gr....still had 848 to 960 fps....thinking the mixed brass is most of it.

[osteodoc08]

Well, a 0.2 grain variance +-0.1 gr for a 4gr load is up to a 5% weight variance. 5% is 5%. Not bad at all really (for plinking ammo) for such a small case, until you start mixing brass......any setback at all for any of the bullets? Any neck tension issues? Where at in the shot string are you seeing your outliers? These little cases can be sensitive. Promo is considered an equivalent of Red Dot.

On the other hand, if no pressure signs, used as plinking ammo, gun functions fine, who cares? I know I wouldn't.

[mclement29]

Started at 4.0gr....still had 848 to 960 fps....thinking the mixed brass is most of it.

[mclement29]

First shot 848, 2nd 830,3rd 748,4th 825,5th 760 and so on.....its just plinking ammo for under 15yds.....no biggie just like to have consistency. ...my "groups" look more like shotgun patterns anyway..lol

[Jupiter7]

I've never sorted brass for .40. Also never weight sorted boolits for .40. The most accurate pistol load I've loaded and currently load is in .40. I just haven't seen mixed brass and a variance of 1-2grs boolit weight either side of avg. as detrimental to accuracy or internal ballistics. I will say that I use AA5 and it is very consistent when dropping powder charges.

[bobthenailer]

A+ on mixed cases being the cause of your problem!

At one time i did a test with a very accurate load in 38 special , I loaded the same load in 13 different headstamp 38 special cases, group size went to 3X larger and velocity spreads went to over 100 fps .

[mclement29]

Thanks everybody. ...who's got a good load for lee175tc with herco

[tazman]

I found data in a Sierra handbook for Herco with a 180 jhp. The data should be very close with a 175tc.
Starting load was 5.2gr max was 6.5gr. It was listed as producing higher than average velocities.
I have no idea how old the data is. It was in one of those booklets that reprints everybody's data.
I am going to try it out as I have a pound of Herco with nothing pressing for it.

[hithard]

green dot is a good one if you can find it, shouldn't be to hard, check connies components out of Washington. call them though as they don't always' update their web site

[tazman]

Thanks everybody. ...who's got a good load for lee175tc with herco

I tried out Herco with a Lee 175tc tonight. I loaded 5.8 grains in mixed brass with a Remington small pistol magnum primer.
It functioned perfectly and shot accurately in 2 different 40cal pistols.
Looks like I found my backup powder for 40 cal.