8.5” CMMG 1 in 7 twist 300 Blackout is the platform. No can as of yet.

I am expecting more out of this set than it can give me as far as accuracy goes. I’m reloading so what’s the best load to load for this specific set up and what should I expect.

At the end of the day I would be happy with a 6” shot group at 100 yards. If you can help me please do. I have no preference as far as bullet weight goes. I am using LilGun powder. I’m hoping to achieve my goals with this powder as I already have it.

As always thanks ahead. I’m just starting reloading so I’m green..

I don't shoot 300 BO so not much help there

If you provide more info, more people will be willing to contribute 30 seconds telling you what they know.

First question with a 300 BO, do you want sub sonic ammo or supersonic ammo?

Do you care which bullet you use?

You mentioned powder, which ones? ( your edit beat my reply. :) )

There is no suppressor now, will there be in the future?

I've repeatedly had 3 holes touching at 50 yds with a red dot sight. And I've only got 8 inches. 150gr Hornady Interlocks over about 17 gr IMR 4227 and a CCI400 primer crimped about 1/8 inch behind the cannelure (2.220" IIRC) running 1780fps. 

Hornady 150gr flat base soft point. #3031

15gr Lil-gun

CCI-400 Primer (or your favorite small rifle primer)

OAL- 2.100"

I'm using a crimp in the canalure of course only because my tests showed that my bullets when not crimped were walking forward (OAL getting longer) when the bolt would slam closed.

I'd imagine you could substitute any good quality 150gr flat base bullet and end up with good results. The Hornady's are inexpensive available and have worked in every .308" groove diameter caliber I've ever used them in.

Motor

To you question... ANY successful loads with the 8.5” barrel using the Lilgun powder as stated. No suppressor as stated but possible in future.. not stated. Thanks ahead

Is this shot group using a short barrel? 8.5” range? Thanks

I am a big fan of Barnes 110gr bullets. I have some lil gun but haven’t used it yet.

If your goal is a 6” group at 100 yards you shouldn’t have any trouble with that regardless of load. If you can’t get there I’d look at scope/optic mount, barrel torque, etc before monkeying with the load.

I don't know why you are concerned about Lil-gun in a 8.5" barrel. Have you looked at the load data on the container? It's a .410 shot gun powder which means it's at least a fairly fast burning powder and should work fine in your pistol length barrel.

Motor

I do apologize for lack of knowledge as I’m just starting. New with a short barrel and new with reloading. At this point I just want to know that the build will perform using whatever load it takes the best.

I was told and read that the tighter twist likes the heavier grain bullets.
So I picked up some Sig Sauer 220gr OTM yesterday.

I will go to range Wednesday to hopefully make some sense with build. Starting at 25 yards.


As far as optic goes.... it’s an old school  Sight Mark red dot...
maybe this is my failure point as when adjustments are made you have to shoot a few rounds to actually see the change in optic.

I will post results. Thanks for baring with my lack of knowledge.

You don't say, but there's not much point having with a short barrel rifle in 300Blk if you're not going to use a suppressor, so I assume that you are planning on getting one in the future and are accordingly looking to load sub-sonic.

When you made the decision to sacrifice both barrel length and velocity, you will need to look to bullet weight for your terminal effect, so that means optimizing a powder choice to a heavier bullet.

Also, a 1:7 twist rate is a fast rate for a 22 caliber barrel, it is super fast for a 30 caliber barrel.  A fast twist rate is needed to stabilize long projectiles (which are also heavier since the only way to get longer projectiles of a given diameter is to make them longer - but twist rate has to do with length).  But, as the diameter of a projectile increases, the speed at which the outer edge of the projectile is moving increases.  At sub-sonic velocities this is not a problem, but if you were shooting 30 caliber projectiles at high velocities out of a 1:7 barrel, you could easily have your bullets coming apart on their way to the target.  



A suppressed short barrel rifle is essentially a pistol with a buttstock.  It is a weapon for police and special operations forces to use in a surprise assault that may lead to close quarters combat.  Typical ranges would be across a room or front yard; 5, 7, maybe 12 yards.  It is not for distance use.  Personally, I would practice with it at the distances where it could (and would) be reasonably employed.



Well, you ask for the "best load" and then constrain the selection to a single powder.  Nobody knows what the "best load" for your rifle is.  And certainly nobody can say whether that "best load" is going to be achieved with Lil'Gun.  You need to discover the "best load" by following a proper load development process.  

Personally, given your super fast twist rate, short barrel and need for subsonic velocities with your future suppressor, I don't think Lil'Gun is an optimal choice.  Based on my past experience, I would look to powders such as H4227/IMR-4227, Accurate Arms 5744, Accurate 1680, or H4198/IMR-4198.  Keep in mind that even though I reference them as H4227/IMR-4227, because they are similar, H4227 and IMR-4227 are different powders and the load data is not necessarily interchangeable.

You can accept powder recommendations, but don't ever accept a load you get off an internet board.  You don't know if I've got 40 years reloading experience with no failures or am a sadist looking to give you the nickname "one eye" or "lefty".  Based on published information, select a powder that looks suitable.  Beginning with the Starting Load (and if no Starting Load is published, take the given load and back off 10% for your Starting Load) and then incrementally heavier loads looking for accuracy and pressure signs.  Stop if you reach the Maximum Load or if you get pressure signs.

Good luck.

I believe I’ve reached a good load. Using the lil-gun at 17.0gr with the 147gr without crimp. With COAL @ 2.140

I was able to make a three shot group inside of the one inch target at 25yrds.
I started with 14gr and worked up four different loads to the 17gr. As I’ve stated I’m new and learning more everyday.

I also believe a change in my optic was a large contributor to my outcome. I previously had an older sightmark red dot that was all over the place. I swapped it out yesterday with another ed dot I had on a different build. It was a Meopta M-Rad with a 3moa.

As always I appreciate the advice.

Now, make 25 more (5 five shot groups) and test again to see if it stays put.

If not, then adjust the charge by a few tenths of a grain less and more, re-test.

You're probably in the ballpark right now but it may change.

I have a myriad of 300 Blackout rifles and bbl lengths.  Overwhelmingly I use H110 for supersonic and AA1680 for subsonic 220gr loads.   I have fixed magnification optics, red dots, and variable magnification optics.  My worst performing Blackout is much better than 6" at 100yd; I'd be very upset if getting 6" groups.  But the real reason I'm posting is to say this:

In load testing any of my Blackouts, even if a red dot will be the final optic to be mounted and used or even if the Blackout will only be used at close range, I always mount a scope of the highest power I have handy even if the scope looks huge compared to the short bbl and test at longer ranges, normally 100yd.  That way I eliminate or reduce sighting error of a zero magnification red dot.  Once I have the most accurate load, then I mount the red dot or whatever optic I intend to use on that Blackout and sight it in with the accurate load.  Even if I can't shoot as accurate with the lower power optic, I know the load is good and the rest of shooting is up to my ability.

I have a 1/7 10" .300 and the bullets most certainly do not "come apart" at 2300fps+ verified on a chrono.

There's plenty of reason to own an 8-10" .300 with no suppressor, maybe not for you but that is entirely subjective and not at all indicative of everybody's feelings on the matter.

http://www.300blktalk.com/forum/viewtopic.php?t=84309

Good enough for Rsilvers its good enough for me.. and anyone else for that matter.

The rest of your advice is solid.