Question about 9mm - Unique/147Gr. Load

[Bobby H]

Just loaded three sample loads with 147gr. Montana Gold bullets, O.A.L. 1.1" on all loads and got the following results:

1. 4.5gr avg. - 1,022fps

2. 4.6gr avg. - 1,004fps

3. 4.7gr avg. - 976fps

Why is my velocity going down as the load increases. All loads were once fired, mixed brass.

Thanks for your help.

[freakshow10mm]

I've seen this happen with other powders. Best example is 10mm running Longshot with a 180gr bullet. 9.2gr is faster than 9.5gr. No gain in velocity, accuracy, nothing. No change other than burning more powder.

I wish I could help you explain it, but I can't. If you aren't getting faster or more accurate, why burn more powder?

[Bobby H]

I actually was reducing my load trying to lower the velocity(and power factor). I guess I will try a few at 4.4 and 4.3 gr and see what I get.

[tac_driver]

Minimum OAL(inches) 1.13

Bbl Length 4

Primer CCI 500

Powder Charge Weight(grains) Unique 4.3

Velocity(fps) 954

Above is the data taken off the Alliant website.

4.3 is the MAX for that powder bullet combination

When you see velocity dropping as the charge is increased it is a Hi pressure sign in most cases.

Edited February 26, 2010 by tac_driver

[TonyT]

I gave up using Unique in pistol loads although I do use it for 28 ga. shotshell. At one time Alliant/Hercules listed 4.1 gr. max with the 147 gr. FMJ, a few years later they listed 3.5 gr. as maximum, now it's 4.3 gr. - I am a great believer in consistency and do not appreciate unexplained variations of this magnitude.

[freakshow10mm]

Generic answer is when lots change or the formula changes, the data will change. Also the testing protocol might have changed between manual editions. For some time they have used the +2 SD method but might have changed to the +3 SD method and data changed in the manual due to this.

[cookselk]

I used 4.0 grs. of Unique with the MG 147 seated to 1.130", Win Brass, my chrono said 903 fps average for 10 shots. When I was chronoed at area III last year they got 942 fps. I have also used this same combo with the Ranier 147 and Remington 147 (REM--a very accurate bullet!). The Ranier went 918 and the Rem went 923 fps.

[dubels]

It is weird that you got 976FPS with 4.7 grains at 1.10 OAL. Lyman list the max load at 4.5 gr at a OAL of 1.115 goin 1039fps. I am loading 4.0 gr behind a 147 Precision Delta Bullet. I am going to go out today to test out different OAL. I have a batch loaded at an OAL of 1.115, 1.125, 1.13. Hopefully I can get to chrono out at my local club.

Edited March 31, 2010 by dubels

[dubels]

I tested out my loads and like Cookselk reported I got 905 fps average out of a PD 147 TC FMJ at 1.13 OAL and 4.0gr of Unique. My favorite load out of my test batch is 4.0gr of Unique behind a 147 TC FMJ at 1.15 OAL. It comes out to about 893 FPS and a 130PF.