QL for a unique situation - Dr Mike!

[frankm]

Dr Mike... I ve got a unique situation where a QL prediction could be of great help. Here’s short summary. Wanting to use D Tubbs Final Finish bullets in my new 221 Fireball factory barrel. Have had great luck with David’s product in past. Catch is they re only coating the 77 Sierra MK in 224 diameter and there’s no data to be found. They said the bullet will not hurt my 1-14 twist barrel... just will tumble, have no accuracy once it leaves barrel.

Could you run a QL prediction on:

221 Fireball
77 gr Sierra MK
1.900 OAL
24” barrel
H4198 powder

I m thinking around 13 grs might be a mid pressure load but that’s a total guess and not willing to try it without some predicted data.
Appreciate any help you could provide!

 

[DrMike]

Cartridge          : .221 Rem Fireball
Bullet             : .224, 77, Sierra HPBT MatchK 9377G G7
Useable Case Capaci: 16.591 grain H2O = 1.077 cm³
Cartridge O.A.L. L6: 1.900 inch = 48.26 mm
Barrel Length      : 24.0 inch = 609.6 mm
Powder             : IMR 4198

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   89    12.24   2187     818   34568   3741     97.9    1.414
-09.0   90    12.38   2207     833   35539   3776     98.1    1.399
-08.0   91    12.51   2227     848   36536   3809     98.4    1.384
-07.0   92    12.65   2247     864   37561   3842     98.6    1.369
-06.0   93    12.78   2267     879   38613   3873     98.8    1.353
-05.0   94    12.92   2287     894   39694   3903     99.0    1.337  ! Near Maximum !
-04.0   95    13.06   2307     910   40802   3932     99.2    1.321  ! Near Maximum !
-03.0   96    13.19   2327     926   41945   3959     99.3    1.306  ! Near Maximum !
-02.0   97    13.33   2346     941   43117   3986     99.5    1.291  ! Near Maximum !
-01.0   98    13.46   2366     957   44321   4011     99.6    1.276  ! Near Maximum !
+00.0   99    13.60   2385     973   45557   4035     99.7    1.262  ! Near Maximum !
+01.0  100    13.74   2405     989   46832   4058     99.8    1.247  !DANGEROUS LOAD-DO NOT USE!
+02.0  101    13.87   2424    1005   48140   4079     99.9    1.233  !DANGEROUS LOAD-DO NOT USE!
+03.0  102    14.01   2443    1021   49483   4099     99.9    1.220  !DANGEROUS LOAD-DO NOT USE!
+04.0  103    14.14   2462    1037   50866   4118    100.0    1.206  !DANGEROUS LOAD-DO NOT USE!
+05.0  104    14.28   2481    1053   52279   4135    100.0    1.193  !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     99    13.60   2465    1039   53435   3855    100.0    1.190  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba     99    13.60   2269     881   38238   4059     96.0    1.356

The bullet will likely tumble, and accuracy will be atrocious; however, the purpose is not to develop an accurate load, but to polish the lands. The bullet will accomplish that purpose. I believe the company is correct in the assertion that the barrel will not be hurt by the bullet. Perhaps you can make up some loads that you intend to shoot for testing after the polish. If they are at hand, you'll be inclined to use them quickly.

 

[frankm]

Thanks Dr Mike! Looks like 12-12.5 grs would be ample to send polishing bullet down the bore. I agree that the bullets would most likely tumble and definitely be inaccurate but goal is to smooth bore. Didn’t want to mess up barrel/twist with a long unstableness bullet but Mr Tubbs said it wouldn’t hurt anything; just go down range very inaccurate!

Thx for your help and Merry Christmas to you Sir!

 

[DrMike]

And a blessed and glorious Christmas to you and yours.