69gr BTHP SMK & RL15

[cj1026]

Guys I have been experimenting with some 69gr rounds and RL15. I'm shooting a 16", 1-7 twist, 5.56 chamber, free float AR. I've loaded 23, 23.5, 24, and 24.5g into Federal brass, sized and trimmed with CCI 400 primers. 24 grains got me 2552 fps with about 1" groups. 24.5 got me 2629 fps with about a 5/8" group. All shot a 100 yards 77 deg. no wind and no pressure signs.
My question is do you think it is safe to go any higher on my load? I would like to get 2700-2750 fps and still have good groups. Any thoughts?

[phish]

Work carefully up to 25 grains and keep an eye out for pressure signs. I never bothered to chrono my short line loads, they shoot to satisfaction and I already know the zeroes at the ranges I shoot them. I don't know what the "sweet spot" would be in terms for speed for the 69s.

http://www.whiteoakprecision.com/info-reloading.htm

[ar15barrels]

Quickload prediction:

Cartridge          : .223 Rem. (SAAMI)
Bullet             : .224, 69, Sierra HPBT MatchK 1380
Cartridge O.A.L. L6: 2.260 inch or 57.40 mm
Barrel Length      : 16.0 inch or 406.4 mm
Powder             : ? Alliant Reloder-15 ?, Temperature: 77 °F

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   90    22.50   2383     870   36214  10204     86.0    1.041
-09.0   91    22.75   2412     891   37376  10361     86.7    1.027
-08.0   92    23.00   2440     912   38575  10516     87.4    1.011
-07.0   93    23.25   2468     933   39814  10670     88.0    0.996
-06.0   94    23.50   2497     955   41094  10822     88.6    0.981
-05.0   95    23.75   2525     977   42416  10971     89.2    0.966
-04.0   96    24.00   2554     999   43781  11119     89.8    0.952
-03.0   97    24.25   2583    1022   45193  11265     90.4    0.938
-02.0   98    24.50   2611    1045   46651  11408     91.0    0.923
-01.0   99    24.75   2640    1068   48158  11548     91.5    0.910  ! Near Maximum !
+00.0  100    25.00   2669    1091   49716  11686     92.1    0.896  ! Near Maximum !
+01.0  101    25.25   2698    1115   51327  11822     92.6    0.883  ! Near Maximum !
+02.0  102    25.50   2727    1139   52992  11954     93.1    0.870  ! Near Maximum !
+03.0  103    25.75   2756    1163   54715  12083     93.6    0.857  !DANGEROUS LOAD-DO NOT USE!
+04.0  104    26.00   2785    1188   56497  12210     94.1    0.845  !DANGEROUS LOAD-DO NOT USE!
+05.0  105    26.25   2814    1213   58341  12332     94.5    0.832  !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    100    25.00   2829    1226   59672  12073     97.6    0.825  !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba    100    25.00   2473     937   40162  10795     83.2    0.988

[ar15barrels]

Can I get an amen?
Can I get a hallelujah brother?

[ness395]

24.6 gr of RE-15 in Prvi brass with 69 gr smk works great for me in my 20" barrel service rifle. Any more powder than that, and the groups start to noticeably open up.

[ocabj]

Randall's post supports my thought that 2750 fps with the 69gr in a 16" barrel is going to be on the hot side. I think it can be done in a NATO chamber, but be sure to use thick cupped primers (i.e Magnum) so you don't pierce or pop primers and chuck the brass after one or two uses.

[cj1026]

Randall thanks for the quick loads post.
I have a question. I made it to the range yesterday with some more loads. I worked up grains from my 24.5 load. 25 gr. was crap 1"-1 1/4" group, with no pressure signs. Now the 25.3 gr load was really good. 1/2" groups at 100 yards with an avg. 2749.8 fps. Temp was 87 yesterday. Just starting to flatten primers. Just a bit though. Do you think its safe? I know quick loads say NO! Also with quick loads it says for 25.25 gr. I should be at 2698 fps. Any thought on that? Is it just a ball park?

[ar15barrels]

Randall thanks for the quick loads post.
I have a question. I made it to the range yesterday with some more loads. I worked up grains from my 24.5 load. 25 gr. was crap 1"-1 1/4" group, with no pressure signs. Now the 25.3 gr load was really good. 1/2" groups at 100 yards with an avg. 2749.8 fps. Temp was 87 yesterday. Just starting to flatten primers. Just a bit though. Do you think its safe? I know quick loads say NO! Also with quick loads it says for 25.25 gr. I should be at 2698 fps. Any thought on that? Is it just a ball park?

Quickload is just a simulation.
Temperature changes things.
Case volume variations change things.
All sorts of gun factors change things too.

If you are getting 2750fps, scroll down through the quickload data and find 2750fps.
Then look at the pressure it shows.
While the charge may be wrong, the pressure and velocity probably correlate pretty well.

Cip spec for 5.56x45 ammo is around 62,000 psi.

[bruce_ventura]

Looks like you have a winner. If you're going to run hot loads, don't change a thing or else you will have to start over dialing in a load. Continue to look for pressure signs, especially when the barrel heats up. Be aware you have little or no room for error with this load.

If you're going to shoot 69 gr a lot and are concerned about barrel life, consider backing off to 24.5 gr. Then you have some margin for temperture effects, batch-to-batch propellant and brass variation, and balance errors.

[Darklyte27]

how bout the same 69 gr SMK in a larue stealth 20 inch 1/8 twist upper? its the ackley improved chamber.

some reason I think the 69 grs shoot better than the 77 gr ive loaded so far..

Please and thank you Randall