recomendations for heavy 5.56 loads

[kritos666]

I just got a new barrel for my LMT 18" 1-7"

Id like to run 90 SMKs if I can. This is strickly for long range work target work. 600-1k yrds. I am OK with it being limited to one shot at a time.
I have heard issues with the throat not being deep enought to take the longer pills. Has anyone had any experince with this?


Any input is apreciated.

 

[forrestgump01]

The 1 in 7 is perfect for the 90's , the problem you are going to have is getting enough velocity with the 18 in barrell ! . Especially for 1000 yards. You might want to think about mid 70 to the 80 grainers .
Most of the guys shooting 223 at 1000 yds stay away from the 90 grn and run the 80 grn bullets . Even with a 26 in barrell and the right powder the 90 don't seem to perform as well as some of the 80 grns. Maybe someone else can chime in.

 

[kritos666]

sounds like the 80gr bergers are in my future. I did wonder about the barrel length. Thanks for the reply.
Always open to other input.

 

[George63]

75 hornady, 77 SMK or Nos CC - all great performers at mag length, maybe not at 1000 but over 800 there are so many better tools for the job than an 18" 5.56 - why beat your head against a rock

 

[kritos666]

.. Oh agreed there are better tools. It just fun for me... I had never taken it past 800 till this summer. On a whim I decided what the heck. and after working out the dope, made 3 hits out of 5 on a 12" target... and called it a day

Its all just a fun challenge for me. Im not into competion or anything. so if it works great, if not thats OK. I don't even take my GAP10 out unless im going 700+ so the AR has filled that slot and it a lot cheaper to shoot. Now if I can find a place that is longer than 1200 to strech my 6mm CM GAP Id be a happy camper

 

[George63]

with the projectiles I mentioned it would be cheaper - the price of the exotics may put it over a 175 SMK to load

 

[kritos666]

good point ... plus I have 77 Noslers already

Thanks for the info

 

[Ultraman550]

69 SMK and 77 CC Noslers have worked well for me out of a 16" 1:7 shooting to 750. I didn't get to 800 because I was doing load testing and only had 2 sets of 10 for both grain bullets. I liked the Noslers the best out of the two but I'm also going to try something in the 80. I agree on challenging yourself though. That's the fun part.

 

[FancyFreddy]

The 1 in 7 is perfect for the 90's , the problem you are going to have is getting enough velocity with the 18 in barrell !

Bingo!!!

For any distance out beyond 600yds and that heavy of a bullet, you are likely to need a longer barrel. I found this out as well a few years back. With a 77gr SMK or Nosler and a 24" 1:10 they will stabilize but I need a 1:8 for my 18".

But, report back with how it goes. Just because I gave up with >77gr and <20" barrel doesn't mean someone else should.

 

[leid]

OP,
Here is the 80gr. VLD over 5.56MM pressure TAC seated over-mag-length in LAPUA brass at 750yds. & 100yds. fired from 18" SS 1x7.7 Krieger/CLE barrel. 80gr. JLK did not group well and 90gr. JLK was not stable from 1x7.7 barrel. No surprise there as I asked CLE to make the barrel to ideally shoot factory MK 262 or equivalent 5.56MM 77gr. SMK handload. Was shooting steel @ 750 with a 5.56MM pressure 77gr. SMK seated to mag length in LC brass the same day. Both loads shot about even until the wind picked up, then the VLD showed a definite advantage. Just watch the temperature if using TAC. TAC yielded high MV with very low ES/SD at full NATO pressure. Quick & dirty thermal stability test numbers on TAC & H4895 are listed below. Go with a 24" or 26" barrel if you can to get the necessary MV preferably with a thermally stable single based powder like H4895 or one of the newer propellants if you can find some to test. I have a lifetime of hearing loss so must hang a can on the end of whatever I shoot to help keep the hearing I have left. 18" barrel plus the can is as long as practical for me now but I used to shoot an un-suppressed 24". Good luck with it!

Edit: Brass life is pretty sad near full NATO pressure (62,350 PSI). Primer pockets get loose quickly. With a longer barrel, you don't have to push the brass nearly as hard to get the needed MV.

80gr. VLD over 5.56MM pressure TAC seated over-mag-length COAL 2.390" in virgin LAPUA brass at 750yds. & 100 yds.: MV 2822 with SD 6.24 FPS


77gr. SMK over 5.56MM pressure TAC seated to mag-length COAL 2.255" in virgin LC brass@750yds same day/same condition: MV 2827 with SD 10.04 FPS


Thermal Stability of 77gr. SMK over 5.56MM pressure TAC in LC casing seated to mag-length COAL 2.255" fired in 18" SS 1x7.7 Krieger/CLE barrel:
+135F: 2861 FPS
-10F::: 2755 FPS
---------------------
106 FPS over 145 degrees F

Thermal Stability of 77gr. SMK over 5.56MM pressure H4895 in LC casing seated to mag-length COAL 2.255" fired in 18" SS 1x7.7 Krieger/CLE barrel:
+135F: 2741 FPS
-10F::: 2737 FPS
-------------------
4 FPS over 145 degrees F with SD 18.19 FPS

 

[jkonzal]

If you can find some, try IMR 8208 XBR with 77gr pills.

 

[bruddah]

If you can find some, try IMR 8208 XBR with 77gr pills.

I agree. That powder and the SMKs are a deadly combination.