Midwest Powder 669

9

95GTSpeedDemon

New member
Bought a jug on sale. it said it was similar to win supreme 780. i knew its more suited for magnums, but im trying in .243w & 6.5cm. loaded some test rounds based on data i scrounged. 780 should burn faster than H1000 but slower than H4831 is the general consensus i read. superformance is supposedly close in burn.

Fired test rounds, they are slower than i was expecting. So, trying to estimate new loads to work up is where im stuck.
22" 6.5CM, SL brass, 129gr Hornady spire point, 2.787 COAL, 44.1gr of mp669 was 2474fps
46.5gr 2545fps
20" .243w, SL brass, 100gr SP, 2.675 Coal, 45.7gr MP669, 2694 fps
108gr Berger Elite, 2.879 coal, 46.5gr, 2770 fps
108gr Berger Elite, 2.879 coal, 41.1 H4350, 2908 fps

if i OBT that data under superformance, is there any degree of accuracy of pressure its going to estimate with a higher charge?
 
Should work well. Just start off low and work your way up. Im glad they offer this powder to the reloading community. Natchez wanted $60/lb for Power Pistol in their latest sale? Of course this is before tax and shipping.

I picked up some IMR Blue to load 45auto from American Reloading. Using new primed Norma cases from Raven Rocks along with a new Precision Delta 230gr FMJ. Should work out to be around 30 cents for a new round which isnt too bad in todays market. LPP brass.

Supposed to be here Thursday.
 
$170 for 8lbs. I mean, its worth trying.
Its got to be much slower burning than they described. Im missing 100-150fps with .5gr to go for max book load of 47gr.
H4350 is on the money for a 108, but hodgen's data is wonky between the 107 & 108, so who knows.
 
It burns more like H1000. Too slow.

MP 666 seems to be like ramshot hunter. Probably more suitable for your need.

-TL

Sent from my SM-N960U using Tapatalk
 
(tangolima: It burns more like H1000. Too slow.)

ummm depends on the gun, i had a bolt 243 that just loved h1000 and 105amax but not all combos can stand that slow of a burn rate, it "might be too slow" but it might work well... just have to test.

edit; missed the 20" , no that is probably too short for that to work right. i had a 24" tube.
 
I fired 5 at 46.5gr, the group wasnt as good as the 5 of h4350 with the same bullet and coal. I wonder if the 20" barrel is part of the issue, too short for that slow of powder.

I did shoot some min loads of h4350 one day, just 3 for a test, 2500fps those 3 grouped tight.

Im going to swap the barrel, it hasnt shown great potential to shoot better than .8moa
 
yeah too slow burn rate for the combo 'tube length / bullet weight / bullet construction' will cause excessive blast energy when the bullet exits the barrel, and thereby degrade accuracy.
 
Unless your barrel is very short (under a foot), the same powders that produce maximum velocities in longer barrels will produce the maximum velocity your shorter barrel is capable of. Note that the SAAMI standard velocity and pressure test barrels for your calibers are all 24" long. So, if you see a velocity printed on a major manufacturer's box with no barrel length given, by default, it will be 24" for those chamberings.

The packaging images for MP 666, MP 668, and MP 669 all say they are like Supreme 780, but then give progressively slower velocity as you go up through those powder numbers for the provided charges of 69, 68, and again 68 grains for the 175-grain BTHP in a 300 WM. So they are not identical. QuickLOAD thinks they are all faster than the slowest offerings by the usual suspects, but slower than the 4350 and similar rates by those same sources, tending to fill a gap in relative burn rate. Even though Supreme 780 is discontinued, Hodgdon still has data for it for that bullet design, and a linear extrapolation suggests a 68 or 69-grain charge of it would have produced about 150 fps more velocity than the MP powders' published numbers.

Further confusing the issue is that the 300 WM has more brand-to-brand cartridge case internal volume variation than most cartridges, with about an 8-grain water capacity spread among various common brands, and we don't know whose cartridge cases or primers were used to test by Midwest Powders. So, it is clear that likening this to 780 is a major simplification. Nonetheless, sticking with 780, but tweaking its properties to produce MP 669 matching velocities and looking at other powders that produce those same velocities (with a 24" barrel; I can't know for certain that's what MP used in their testing, as they aren't a major brand and may not do things to SAAMI standards or may have used one of the 26" barrels common to 300 WM), I wind up with pressure predictions of right around 40,000 psi. That's not great for slow powder combustion consistency, and unless the powder is so bulky that you can't squeeze more into the case, their recommended 300 WM charges are almost certain underloaded. High velocity SD would tend to confirm ignition irregularities.

The bottom line is that it looks like your 6.5 CM pressures aren't much over 45,000 psi at most. I would be looking at heavier bullets to give the powder more time to burn, though you need to start the load workup over if you do that. If you have or know someone who has a Pressure Trace, I would be looking at making some measurements. Unfortunately, that instrument is discontinued so a used one would be all you could buy.
 
im trying to remember if it was .243 or 6.5cm, both with new starline brass; i filled up the neck to the very top of the case at like 50gr of mp669 i believe, i believe 48gr was the bottom of the neck. ill have to check my notes. either way, its likely going to sit on the shelf for some larger cased caliber.
maybe ill do a .264wm instead of a creed, i can dial up or down the speed that way.
 
95GTSpeedDemon said:
im trying to remember if it was .243 or 6.5cm, both with new starline brass; i filled up the neck to the very top of the case at like 50gr of mp669 i believe, i believe 48gr was the bottom of the neck. ill have to check my notes. either way, its likely going to sit on the shelf for some larger cased caliber.
maybe ill do a .264wm instead of a creed, i can dial up or down the speed that way.
Click to expand...
Good idea. Are you going to try MP 666? I'm eager to know how it goes.

-TL

Sent from my SM-N960U using Tapatalk
 
Thanks. I may get some myself. It is in-stock. It should replace ramshot hunter nicely. I was hoping mp669 can replace ramshot magnum. Too slow unfortunately.

-TL

PS. Now it is out of stock.

Sent from my SM-N960U using Tapatalk
 
Last edited:
6.5cm, starline brass unfired. Fired case 52.4gr H2O, this is 51gr mp669 thats been vibrated down just a little. Doesnt drop like stick powder ������
DDfPJ7b


https://imgur.com/a/tvpzfgX

see attachments
 

Attachments

  • .243 mp669.JPG
    .243 mp669.JPG
    93.5 KB · Views: 22
  • 6.5cm 22in mp669.JPG
    6.5cm 22in mp669.JPG
    31.5 KB · Views: 26
You must log in or register to reply here.
Back
Top