260 Rem. QL OBT/Node Help

[longrangehunter]

Hey Guys,

Once again I've run out of powder (H4350), and 139 Scenar bullets for my GAP 260.

I thought I'd switch to a different bullet too, the Berger 140 Hybrid Target. Although I was able to order more Lapua Bullets last night after testing the Berger's and not liking them so much only to realise I have no powder left!

Neither of which I really care to do, why fix what ain't broke! I have 4 lbs. of RL-17, and 3 lbs. of H4831SC.

140 Berger Hybrid Target P/N 26414 (Note: this bullet will have to jump further to fit in the AI Mag Box)
H2O Cap. = 55.16 grs. (Lapua brass)
24" BBL.

What's the charge wt. Node/OBT using RL-17, or H4831SC. Mag Box OAL 2.890" max (usable 2.850")

(My prior OBT/Node using H4350 was 42.7 grs/139 Scenar @ 2.240" CBTO= COAL 2.800" at 2750 fps avg. velocity). Super accurate load.

Thanks in advance!

 

[TackDriver284]

With 24 inch barrel, OBT fast node is 1.2282, slower node is 1.3084

Hope that helps.


With 2.890 OAL and H4831SC:

Cartridge          : .260 Rem
Bullet             : .264, 140, Berger Hybr #26414
Useable Case Capaci: 48.001 grain H2O = 3.117 cm³
Cartridge O.A.L. L6: 2.890 inch = 73.41 mm
Barrel Length      : 24.0 inch = 609.6 mm
Powder             : Hodgdon H4831 SC

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% 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

-10.0   93    41.49   2466    1890   40177   9008     91.0    1.437
-09.0   94    41.95   2495    1935   41543   9131     91.6    1.414
-08.0   95    42.41   2524    1981   42941   9251     92.1    1.393
-07.0   96    42.87   2553    2027   44424   9368     92.7    1.371
-06.0   97    43.33   2582    2073   45947   9484     93.2    1.350
-05.0   98    43.80   2612    2120   47527   9596     93.7    1.329
-04.0   99    44.26   2641    2168   49166   9706     94.2    1.308
-03.0  100    44.72   2670    2217   50870   9812     94.7    1.288
-02.0  101    45.18   2700    2266   52637   9916     95.2    1.268  ! Near Maximum !
-01.0  102    45.64   2729    2316   54478  10017     95.6    1.249  ! Near Maximum !
+00.0  103    46.10   2759    2366   56389  10114     96.0    1.229  ! Near Maximum !
+01.0  104    46.56   2788    2417   58377  10207     96.4    1.210  ! Near Maximum !
+02.0  105    47.02   2818    2469   60443  10297     96.8    1.192  !DANGEROUS LOAD-DO NOT USE!
+03.0  106    47.48   2848    2521   62599  10383     97.2    1.174  !DANGEROUS LOAD-DO NOT USE!
+04.0  107    47.94   2877    2574   64841  10466     97.5    1.156  !DANGEROUS LOAD-DO NOT USE!
+05.0  108    48.41   2907    2627   67177  10544     97.8    1.138  !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    103    46.10   2901    2617   67798  10137     99.6    1.139  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba    103    46.10   2575    2061   46145   9592     88.6    1.345

With 2.850 ( usable )OAL and H4831SC

Cartridge          : .260 Rem
Bullet             : .264, 140, Berger Hybr #26414
Useable Case Capaci: 47.447 grain H2O = 3.081 cm³
Cartridge O.A.L. L6: 2.850 inch = 72.39 mm
Barrel Length      : 24.0 inch = 609.6 mm
Powder             : Hodgdon H4831 SC

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% 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

-10.0   93    41.22   2464    1887   40304   8924     90.9    1.435
-09.0   94    41.68   2493    1932   41679   9046     91.5    1.413
-08.0   95    42.14   2522    1977   43106   9165     92.1    1.391
-07.0   96    42.59   2551    2023   44584   9282     92.6    1.369
-06.0   97    43.05   2580    2070   46120   9396     93.1    1.348
-05.0   98    43.51   2610    2117   47712   9507     93.7    1.327
-04.0   99    43.97   2639    2165   49366   9616     94.2    1.306
-03.0  100    44.43   2669    2214   51086   9722     94.6    1.286
-02.0  102    44.88   2698    2263   52872   9824     95.1    1.266  ! Near Maximum !
-01.0  103    45.34   2728    2313   54730   9924     95.5    1.247  ! Near Maximum !
+00.0  104    45.80   2757    2363   56662  10020     96.0    1.227  ! Near Maximum !
+01.0  105    46.26   2787    2414   58670  10113     96.4    1.208  ! Near Maximum !
+02.0  106    46.72   2817    2466   60762  10202     96.7    1.190  !DANGEROUS LOAD-DO NOT USE!
+03.0  107    47.17   2846    2518   62942  10287     97.1    1.172  !DANGEROUS LOAD-DO NOT USE!
+04.0  108    47.63   2876    2571   65210  10368     97.5    1.154  !DANGEROUS LOAD-DO NOT USE!
+05.0  109    48.09   2906    2625   67576  10445     97.8    1.136  !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    104    45.80   2900    2614   68153  10046     99.6    1.137  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba    104    45.80   2573    2058   46368   9501     88.5    1.343

With 2.890 OAL and RL 17

Cartridge          : .260 Rem
Bullet             : .264, 140, Berger Hybr #26414
Useable Case Capaci: 48.001 grain H2O = 3.117 cm³
Cartridge O.A.L. L6: 2.890 inch = 73.41 mm
Barrel Length      : 24.0 inch = 609.6 mm
Powder             : Alliant Reloder-17

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% 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

-10.0   84    38.79   2568    2050   41170   9322     99.8    1.415
-09.0   84    39.22   2594    2092   42489   9386     99.9    1.394
-08.0   85    39.65   2620    2134   43853   9445    100.0    1.374
-07.0   86    40.08   2646    2177   45260   9499    100.0    1.355
-06.0   87    40.51   2672    2219   46713   9550    100.0    1.335
-05.0   88    40.95   2698    2262   48215   9599    100.0    1.316
-04.0   89    41.38   2723    2305   49766   9648    100.0    1.297
-03.0   90    41.81   2749    2349   51371   9696    100.0    1.279  ! Near Maximum !
-02.0   91    42.24   2774    2392   53029   9744    100.0    1.261  ! Near Maximum !
-01.0   92    42.67   2799    2435   54744   9791    100.0    1.244  ! Near Maximum !
+00.0   93    43.10   2824    2479   56515   9837    100.0    1.226  ! Near Maximum !
+01.0   94    43.53   2849    2523   58348   9883    100.0    1.209  ! Near Maximum !
+02.0   95    43.96   2874    2567   60223   9928    100.0    1.193  !DANGEROUS LOAD-DO NOT USE!
+03.0   96    44.39   2898    2611   62206   9972    100.0    1.176  !DANGEROUS LOAD-DO NOT USE!
+04.0   97    44.82   2923    2656   64238  10016    100.0    1.160  !DANGEROUS LOAD-DO NOT USE!
+05.0   97    45.26   2947    2701   66338  10058    100.0    1.145  !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     93    43.10   2921    2652   68785   9471    100.0    1.139  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba     93    43.10   2675    2224   45611  10226     99.0    1.342

With 2.850 ( usable ) and RL 17

Cartridge          : .260 Rem
Bullet             : .264, 140, Berger Hybr #26414
Useable Case Capaci: 47.447 grain H2O = 3.081 cm³
Cartridge O.A.L. L6: 2.850 inch = 72.39 mm
Barrel Length      : 24.0 inch = 609.6 mm
Powder             : Alliant Reloder-17

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% 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

-10.0   84    38.52   2564    2044   41180   9243     99.8    1.415
-09.0   85    38.95   2591    2086   42502   9307     99.9    1.394
-08.0   86    39.38   2617    2129   43868   9366    100.0    1.374
-07.0   87    39.80   2643    2171   45281   9420    100.0    1.354
-06.0   88    40.23   2669    2214   46738   9469    100.0    1.335
-05.0   89    40.66   2695    2257   48246   9518    100.0    1.316
-04.0   90    41.09   2720    2300   49802   9566    100.0    1.297
-03.0   90    41.52   2746    2343   51412   9613    100.0    1.279  ! Near Maximum !
-02.0   91    41.94   2771    2387   53076   9660    100.0    1.261  ! Near Maximum !
-01.0   92    42.37   2796    2430   54797   9706    100.0    1.243  ! Near Maximum !
+00.0   93    42.80   2821    2474   56576   9751    100.0    1.226  ! Near Maximum !
+01.0   94    43.23   2846    2518   58418   9796    100.0    1.209  ! Near Maximum !
+02.0   95    43.66   2871    2562   60323   9840    100.0    1.192  !DANGEROUS LOAD-DO NOT USE!
+03.0   96    44.08   2896    2607   62293   9884    100.0    1.176  !DANGEROUS LOAD-DO NOT USE!
+04.0   97    44.51   2920    2651   64335   9926    100.0    1.160  !DANGEROUS LOAD-DO NOT USE!
+05.0   98    44.94   2945    2696   66447   9968    100.0    1.144  !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     93    42.80   2918    2647   68902   9385    100.0    1.139  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba     93    42.80   2671    2218   45671  10135     98.9    1.341

 

[longrangehunter]

Thanks TD,

Now that's what I thought today when I shot 3 each @ 46.0; 46.5; and 47.0 using H4831SC and 46.5 had a perfect little triangle with two touching and one just off the edge under 3/4" on a single 1" round black dot.

I shot them prone, off a bipod on the driveway in the snow. The last 3 shots were hard to see since it was almost 5 PM PST and the cold fog came in off the snow. I don't think they were producing enough pressure though since the brass looked wrinkled down the sides, and all the same funky look but got better as the charge went up. Weird but they were shot suppressed.

I'll post a picture after I get back from town.

Thanks TD

 

[TackDriver284]

I was bored and checked your OBT on your prior Scenar load, and it was spot on.

 

[longrangehunter]

I was bored and checked your OBT on your prior Scenar load, and it was spot on.

I've been doing this long before I ever read about such things, it's just that sometimes I second guess myself. That and I've grown used to doing this in less than 10 rounds! lol Mainly because I hate burning up a good barrel tinkering with every known combination, I stopped that at least 10 years ago.

Check out the 2004 Data for the 260 Remington. Way past what is written in any book these days! Funny thing is I'm using powder I bought on 12/20/2006.

So these were shot prone off a bipod, and a rear bag at 125 yards. I just wasn't interested in making this any more difficult and shot off my bridge to where my road turns so I could place the target stand in the roadway, and have the mountainside directly behind it.

So that's a .36" 3 shot group. The 47.0 was already too dark to really see the black dot well enough to actually shoot it with a lot of precision. I was rushing to just see what it would produce, and it was well past 4:50 PM PST.

I will need to retest it again, check the speed, and shoot it some more until I'm certain it's a good load.

Please note none of these were shot over my chronograph, and that's not often I do that dumb trick only because I like to know what kind of pressure is being developed. So please anyone reading this don't just copy what my rifle/powder/bullet combination was doing! After all the powder is a decade old.

 

[Dwh7271]

Nice shooting and great powder choice. My AI version of the 260 loves H4831.
Nice job TD on the nodes.

 

[longrangehunter]

Well not so fast.... three shots @ 8' from the barrel 2649, 2673, 2663 bare barrel no suppresser. I will test suppressed in a minute, I think it's slowing the burn rate.

Changed my mind, I'm going to increase the powder charge to 47.7, and test for speed bare barrel.

2715; 2730; 2726 fps.

 

[Dwh7271]

Check your PM.

 

[longrangehunter]

So I tested these loads using my 35P Chronograph and obviously I had to increase the powder charge for the expected velocity range.

Here's the skinny in the picture, although when I walked down the road to test for accuracy I realised I left my rear bag and shot three rounds without it. The first was the bulls eye, the other two weren't doing so well, my bad! So I walked back home to get the rear bag and those two went where they should.

The left side printed data is bare barrel, no muzzle brake, and not suppressed. The right side printed data is suppressed and at 8' from the muzzle, not the suppresser. I had to test those using a tripod with a Hog Saddle while I sat on the bench next to my front door, so I was not able to test those for accuracy.

Note: Please do not use my data in your gun without a chronograph and while working up! Sure the 2004 magazine says a max of 48.0 grs. using the 142SMK @ 2.780", but it also just so happens I had three unopened 1 lb. canisters from 2006 all from the same lot. So please work up slowly and don't just jump up like I did. I'm sure that sounds cocky, but I've tested enough to know what will produce the desired level I'm seeking through years of experience. Just play it safe and always use a chronograph when testing.

 

[longrangehunter]

Here's some interesting data I observed. Running a gun suppressed seems to level out the pressure curve of a given load. Look at the two, and you'll see it in the bare barrel vs. suppressed. Even the other data using a different bullet, and powder showed to lower the ES, and SD!

The 5 shot group in this picture was suppressed, and off the tripod while seated. Fairly stable platform to shoot from, but I was mainly looking only to see the velocity data.

 

[Dwh7271]

I agree.
The suppressed loads appear to definitely have less spread.
Do you think that's due to a slower powder having a more even burn with the additional length? Or does the suppressor add something else?
Really interesting.
I've heard that many loads seem to tighten up as far as group when suppressed but have no experience with that to say yes or no.

 

[longrangehunter]

I agree.
The suppressed loads appear to definitely have less spread.
Do you think that's due to a slower powder having a more even burn with the additional length? Or does the suppressor add something else?
Really interesting.
I've heard that many loads seem to tighten up as far as group when suppressed but have no experience with that to say yes or no.

IMO they do, first by evening or leveling out the pressure curve, and acting as a recoil/muzzle blast reducer. I think the data shows that by the reduced ES, and SD in the velocity.

I've never been a fan of muzzle brakes because of the shock wave/muzzle blast and my hearing in serious jeopardy around other people using them, but a suppressor takes both of those out of the equation.

 

[longrangehunter]

So I bought another 600 Lapua 139 Scenar's. I tested them w/ 42.0 grs. of RL-17 @ 2.240"CBTO = 2.800"COAL

Can someone run a QL with this info, so I can check the Btime. The case Cap. is 55.16 grs. of H2O.

Here is the data from this load, it looks as though I need go up for the 1.2282 OBT.

 

[longrangehunter]

I went out and retested w/42.5 grs. RL-17; BR-2 (above were typos) 2X Lapua Brass @ 2.240"CBTO=2.800" COAL.

I was unable to test for accuracy due to windy conditions today, but I did test 6 before this data at 125 yards prone, but the conditions weren't great and target was in the shade making seeing the orange dots very hard to see. (I was in the sun).

Very Low ES, and SD for a powder of this type, good speed. The gun had been cleaned on the data above, this data was with 11 shots through the gun prior to this which would have leveled off the velocity curve.

This was shot roughly 8' from the muzzle, suppressed.

 

[longrangehunter]

Long before the use of OBT I used to look for a flattening of the velocity even with powder charge increases. This usually told me I was at what is now known as what we see with OBT. Plus the POI would be unchanged even with these slight powder charge increases. This is what I always looked for while doing load development and as time, and time again proved to be the best possible sign of a good tune.

 

[SJB358]

Great thread Kevin. I'm watching and learning buddy.

 

[Dwh7271]

Kevin;
Check your COAL. I think the one listed is too short but may be wrong.
I'm running it for you but the 2.28 puts the ogive in the case.

 

[Dwh7271]

Used a standard COAL just to see. I can adjust later if you'dlike.
I think you have a node just above this load. 42.6 to 42.7 would be my guess. Next one is in the red zone around 44.6 or so.

Cartridge          : .260 Rem
Bullet             : .264, 139, Lapua Scenar GB458 6018
Useable Case Capaci: 45.773 grain H2O = 2.972 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length      : 26.0 inch = 660.4 mm
Powder             : Alliant Reloder-17 ?, Temperature: 40 °F

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.176% 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

-11.8   85    37.50   2500    1929   35972   8257     97.9    1.560
-10.6   86    38.00   2533    1980   37338   8355     98.3    1.535
-09.4   87    38.50   2565    2031   38758   8448     98.7    1.509
-08.2   88    39.00   2598    2083   40235   8536     99.0    1.483
-07.1   89    39.50   2630    2135   41768   8617     99.3    1.457
-05.9   90    40.00   2663    2188   43367   8694     99.5    1.432
-04.7   92    40.50   2695    2241   45013   8763     99.7    1.408
-03.5   93    41.00   2727    2295   46759   8827     99.8    1.384
-02.4   94    41.50   2758    2348   48559   8885     99.9    1.360
-01.2   95    42.00   2790    2403   50435   8936    100.0    1.337
+00.0   96    42.50   2822    2457   52389   8980    100.0    1.315  ! Near Maximum !
+01.2   97    43.00   2853    2512   54425   9021    100.0    1.293  ! Near Maximum !
+02.4   98    43.50   2884    2567   56548   9061    100.0    1.271  ! Near Maximum !
+03.5   99    44.00   2915    2623   58762   9100    100.0    1.251  ! Near Maximum !
+04.7  101    44.50   2946    2678   61067   9138    100.0    1.230  !DANGEROUS LOAD-DO NOT USE!
+05.9  102    45.00   2976    2734   63484   9176    100.0    1.210  !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 5% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 5% relative to nominal value:
+Ba     96    42.50   2885    2569   57908   8761    100.0    1.263  ! Near Maximum !
Data for burning rate decreased by 5% relative to nominal value:
-Ba     96    42.50   2743    2322   47262   9138     99.2    1.374

 

[longrangehunter]

Wow, that is interesting! Just looking at the previous QL w/the 140 Berger Hybrid, and RL-17 @ 2.850" COAL and comparing it with this one causes the B-Time (node) to change from #5 to 6. And like what Dewey said, the next node is way too fast!

Thanks for the QL Dewey, I made a typo on the COAL! My mind is not as sharp as it used to be I see! BR-2's vs. 4's, and the conversion from CBTO to COAL with those numbers I'm making mistakes.

Dewey, can you change that to a 24" barrel?

 

[Dwh7271]

Sure