Velocity Guesstimate

[CMBTshooter]

I need some help with guesstimating velocity of 175gr Nosler Custom Competition and 43.0 gr RL-15 out of a .308 Win.

 

[DrMike]

Here's a QL projection built on a 22 inch barrel. With 43 grains, you are projected to reach 2568 fps. If you want a tad more velocity, you should be able to boost charge weight to 45.0 grains, boosting velocity to 2681 fps.

Cartridge : .308 Win. (SAAMI)
Bullet : .308, 175, Nosler CC HPBT J4 53952
Useable Case Capaci: 47.891 grain H2O = 3.110 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length : 22.0 inch = 558.8 mm
Powder : Alliant Reloder-15

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-20.0 78 34.40 2073 1669 28275 6480 89.2 1.532
-18.0 80 35.26 2122 1750 30069 6684 90.3 1.494
-16.0 82 36.12 2172 1833 31958 6884 91.4 1.457
-14.0 84 36.98 2222 1918 33963 7079 92.5 1.422
-12.0 86 37.84 2272 2005 36093 7268 93.4 1.387
-10.0 88 38.70 2321 2094 38354 7450 94.4 1.351
-08.0 90 39.56 2371 2184 40756 7624 95.2 1.313
-06.0 92 40.42 2420 2276 43307 7791 96.0 1.276
-04.0 93 41.28 2469 2370 46017 7950 96.7 1.241
-02.0 95 42.14 2519 2465 48897 8099 97.3 1.207
+00.0 97 43.00 2568 2562 51961 8239 97.9 1.175
+02.0 99 43.86 2617 2660 55221 8370 98.4 1.143 ! Near Maximum !
+04.0 101 44.72 2665 2760 58692 8490 98.9 1.113 ! Near Maximum !
+06.0 103 45.58 2714 2861 62390 8598 99.2 1.083 !DANGEROUS LOAD-DO NOT USE!
+08.0 105 46.44 2762 2964 66334 8695 99.5 1.055 !DANGEROUS LOAD-DO NOT USE!
+10.0 107 47.30 2810 3068 70545 8781 99.8 1.028 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 97 43.00 2685 2800 61989 8083 100.0 1.091 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 97 43.00 2411 2258 42313 7994 91.9 1.284

 

[JD338]

I would guess 2500 fps


JD338

 

[CMBTshooter]

Thanks guys, I loaded up to 44.0 grs and groups were all over the place. The only one that was decent was 43.0 grs and that could use some improvement. I know for sure I wasn't shooting my best.

I did shoot this group today with the 180 E-Tip and 40.5 gr RL-15.


I don't know what my problem is, but I think I have my scope mounted too high making it pretty difficult to get a repeatable cheek to stock weld. A lot of my groups look like this.
View attachment Group.jpg

I know this rifle can shoot better than this I just can't get past my own inconsistencies.

 

[RiverRider]

I feel your pain. I discovered this weekend that I've been holding my .25-06 all wrong. Using the wrong technique I've managed a few outstanding groups despite my errant ways, but after three lousy groups this weekend I decided to firm up my hold, and bingo. Now I have to revisit some loads I've skipped over. I guess that's the way it goes when you start load development on a new and unfamiliar rifle.

 

[DrMike]

Accuracy lies in the details, to be certain.

 

[nvbroncrider]

Consistency weather that is on the bench or at the range. Do the same thing every time and you will get consistent results.

 

[338 Ultra]

Thanks guys, I loaded up to 44.0 grs and groups were all over the place. The only one that was decent was 43.0 grs and that could use some improvement. I know for sure I wasn't shooting my best.

I did shoot this group today with the 180 E-Tip and 40.5 gr RL-15.
View attachment 1

I don't know what my problem is, but I think I have my scope mounted too high making it pretty difficult to get a repeatable cheek to stock weld. A lot of my groups look like this.


I know this rifle can shoot better than this I just can't get past my own inconsistencies.

Not my Rifle not my load but if it was me I would be pretty stoked with the groups in the targets you posted considering the bullet you are using and the size of the game it would be used on based on the weight and the construction nothing inside of 350-400 yards should survive it if you do your part.

 

[onesonek]

I have found, once you start approaching max for a particular rifle, I will find about 2 nodes it likes. Just above starting, and just below the rifle's max.. Usually in mine, a 1/2-1 gr. on the top and bottom ends, depending on case capacity to begin with. But once I push much beyond that last one, I see things go to pot in a rather big way with group size. It could be you are seeing that, and just reaching the limits of that rifles likes. Then I back off to that last accurate load, and if desired play around a bit within a .10 or so, along with seating depth if I want to see if I can tighten it up some. Somtimes a slightly slower powder if one has room/capacity may warrent a try.
Also, the manuals are only guides, as guns/chambers vary. I have some tight ones, that won't let me come close to listed loads. But the velocity is close to book. Mine just hit pressure limits quicker. It is just a educated guess if one don't chrono them.
Then too, sometimes the extra fps more just ain't worth the risk, and really isn't worth the gain down range.
I have had middle loads do some really weird things too. Just never know what the gun's own idiosyncrasies are.