300 Blackout Subsonic accuracy a joke???

[RDA]

15 shot hand loaded subsonic group at 300 yards from a 9" sbr using iron sights

Any chance of getting a picture we can discern something from or can you give us the cliff notes of your results?

Thanks.

[dellet]

15 shot hand loaded subsonic group at 300 yards from a 9" sbr using iron sights

Any chance of getting a picture we can discern something from or can you give us the cliff notes of your results?

Thanks.

Right click, open image in new tab/window, then enlarge.

Pink paper is 12" wide silver thing is a ruler.

Pretty good with irons at 300

[rebel]

Damn good with irons at 300.

[RDA]

15 shot hand loaded subsonic group at 300 yards from a 9" sbr using iron sights

Any chance of getting a picture we can discern something from or can you give us the cliff notes of your results?

Thanks.

Right click, open image in new tab/window, then enlarge.

Pink paper is 12" wide silver thing is a ruler.

Pretty good with irons at 300

I can see it now that you fixed it. Originally it was just that small thumbnail type picture and clicking on it gave you another small picture that you couldn't enlarge. I'd be pretty happy with those results with fixed sights.

[Dr.Phil]

Dr. Phil,
My 5.56 12" barrel is very accurate as is my MWS .308 from LMT. That is why I was surprised to have trouble with 300 blk. I have actually been very impressed with the MRP system, it is my favorite AR and I own a gun shop and can choose pretty much whatever. I'm always interested in squeezing the most accuracy out of it though so let me know how your shim project works out!

Cool...
I've always been an LMT fan as well.

I'm in the process of working with the LMT MRP product line technical manager to figure out what the issue is.
My latest tests were perplexing.
@ 100 yards, it would print a .41" three shot group and then the open up to 2.17" after the last 2 shots were fired in a five shot group.
The other thing that concerns me with this barrel is that the gas port is located half on / half off the leading edge of the rifling.
I know Krieger has identified this as a cause of accuracy issues in their barrels.

The barrel bedding concept regarding LMT MRP is also intriguing to me.
I think that as long as it is done properly so that you do inadvertently create a mechanical lock between the barrel assembly and the upper, there could be significant gains in accuracy to be had there.

I'll be sure to post up some updates of the thread I created for that project once I get done working with LMT on the issue.
(I suspect that they will replace the barrel assembly with one that they pre test for me.)

[Antinimby]

Check out this video: https://www.youtube.com/watch?v=XW5bxUuW8Ek

[Kill By Number]

Dr. Phil,
My 5.56 12" barrel is very accurate as is my MWS .308 from LMT. That is why I was surprised to have trouble with 300 blk. I have actually been very impressed with the MRP system, it is my favorite AR and I own a gun shop and can choose pretty much whatever. I'm always interested in squeezing the most accuracy out of it though so let me know how your shim project works out!

Cool...
I've always been an LMT fan as well.

I'm in the process of working with the LMT MRP product line technical manager to figure out what the issue is.
My latest tests were perplexing.
@ 100 yards, it would print a .41" three shot group and then the open up to 2.17" after the last 2 shots were fired in a five shot group.
The other thing that concerns me with this barrel is that the gas port is located half on / half off the leading edge of the rifling.
I know Krieger has identified this as a cause of accuracy issues in their barrels.

The barrel bedding concept regarding LMT MRP is also intriguing to me.
I think that as long as it is done properly so that you do inadvertently create a mechanical lock between the barrel assembly and the upper, there could be significant gains in accuracy to be had there.

I'll be sure to post up some updates of the thread I created for that project once I get done working with LMT on the issue.
(I suspect that they will replace the barrel assembly with one that they pre test for me.)

What types of ammo did you use in your testing so far?

[Dr.Phil]

What types of ammo did you use in your testing so far?

I did a complete ladder workup with the 125 SMK, CCI 400 primers, N110 Powder & H110 Powder.
That ladder determined 17.2 grains of N110 & 18.6 grains of H110 to be the optimal charge weights for this barrel using the given components.
The 17.2 grain charge weight would consistently shoot .41" three shot groups at 100 yards, but they would open up to over 2" when 5 shot groups were shot.
The 18.6 grain charge weight would consistently shoot 1.6" 5 shot groups at 100 yards.

I also tested some factory loads for a baseline.
Remington Premier Match 125 SMK = 1.8"
Gorilla Ammunition 125 SMK = 2.1"

[Kill By Number]

I figured out the culprit as to why I couldn't get any subsonic loads to group for me. I shot last night with 2 different LMT MRP .300blk guns, one with AAC SDN-6, one with Gemtech Sandstorm silencers. Same shooter, distances, range, ammo, etc.

The first group is the Gemtech silencer and Silencerco ammo (which I am now a big fan of!). I am glad to see accuracy is possible in the platform.
https://www.dropbox.com/s/pxk49xwfdyuqr ... 6.JPG?dl=0

BUT the second pictures are of the SDN-6 silencer at 25 yards and 100 yard (without the silencer this gun shoots well). This shows bullets don't always travel in a linear MOA at every distance. 25 yards (4 moa), 100 yards (12 moa). The holes aren't keyholes and bullets must be going through the air in a corkscrew pattern is all I can guess. Something is not concentric with this setup, either the flash hider, silencer, or barrel shoulder and is causing wildly bad accuracy. (sidenote this AAC SDN-6 shoots great with 5.56 mounted on a different flash hider / barrel)
https://www.dropbox.com/s/v21by9uu0pxx2 ... 7.JPG?dl=0
https://www.dropbox.com/s/sgnwx9xjkqsd6 ... .JPG?dl=0
Any ideas on what is happening here???

[Sithlord]

I'm glad to see I'm not the only one with MAJOR issues when adding a suppressor to my rifle.

I had a post earlier about it: viewtopic.php?f=141&t=94169

I haven't posted more about it because it's still being diagnosed. But, the latest, in my case, is:

1) Suppressor + Upper sent back to suppressor manufacturer. They identified a (potential) issue with the barrel threads, worked around it, shot decent groups.
2) Upper was returned, I shot it, and had horizontal stringing suppressed. Worse, subs looked like they were going in at a 45 degree angle.
3) Took suppressor + upper to FFL. They shot it with my handloads and factory. NO ISSUE with accuracy or keyholing.
4) I shot it, and again had horizontal stringing suppressed (although not as bad). Rounds were going in almost horizontally at 25 yards when suppressed. Moved the target out to ~40 yards - all holes were good (circular, no signs of tumbling) but a 12" 5-shot spread (when suppressed).

So, a different FFL is going to shoot it tomorrow. If they don't have issues, but I still do, then the FFL has asked to video tape me magically making rounds keyhole. To take as many variables out as possible, half of the tests I conducted in #4 were with MBUIS. Even at 50 yards, I got a respectable grouping (4 shots almost touching, same elevation) UNSUPPRESSED.

I'd show pics, but its beyond embarrasing...