300BLK, finally got to shoot it!

View · by **Scratch** on Thu Jan 15, 2015 11:39 am

So I've had my first 300BLK build completed now for a month or so. I've got prepped brass, primers, bullets, dies, case gauge, etc... Everything I need except powder. Can't seem to find it nearby.

But oh how I wanna shoot it!

I'm new to the cartridge, and really want to know how accurate it will be. I know that I have a short barrel (10.5") so it's not going to be the most accurate, but it shouldn't be that bad...
Ugh... If I could just get some powder, I could find out!

Well I was at Cabela's the other day and had some points to use up. Of course they didn't have powder, but they had ammo! As much as I hate buying factory ammo since I have a Dillon and am all ready to load, I was just dying to shoot it. So I bought a box of cheap ammo. This was Remington UMC 120gr OTFB, so I wasn't expecting super tight groups but thought I'd get to see what the cheapest ammo can do, and it can only get better.

I have a Primary Arms Advanced Micro Dot for this, but since I wanted to check accuracy, I thought I'd use a scope on it. I had a 1-6 power scope on a QD mount handy that was already sighted in on another rifle, and figured it should be close, so I pulled the red dot off and put on the scope.
I used a large sheet of white card stock so if the POA/POI was off, I'd still be able to see some groupings. The target was at 115 yards.
Here's my temporary setup:

To my surprise, the POI was very close. About 2" high and 2" right, not bad for not adjusting the scope at all! Here's my first group of five shots, about a 2-1/8" group:

Here's my second group of five, about a 3" group:

Here's where things got weird, this is my third group of five, about a 3/4" group:

And finally my last group of five shots, about a 2" group:

All 20 of these shots were taken with "maybe" ten seconds between trigger pulls. All 20 rounds were loaded in the magazine at the beginning, there was zero wind, there was no chance for the barrel to cool down between any of the shots, and the last group was about the same as the first two groups... Why then did the third group kick so much ass?

View · by **shooter115** on Thu Jan 15, 2015 6:22 pm

You missed just right :mrgreen:

View · by **UnaStamus** on Thu Jan 15, 2015 7:42 pm

It's entirely possible that your shooting position is changing between the strings. You could be altering where and how you shoulder the gun, how you rest it/prop it up, how you are gripping, or how you are working the trigger.
Shooting an AR accurately is different than shooting a bolt rifle accurately and requires different shouldering, bipod loading and trigger manipulation.

There is a possibility to a mechanical/internal problem, in which case I would recommend that you use a chamber gauge and ensure that you have a properly spec'd chamber. If that's spot-on, make sure that your loads are all within specs dimensionally with neck, throat, OAL, etc. Stuff like that.

Keep in mind that Remington UMC is not all that consistent or accurate. In the world of metallic practice ammo, UMC has been on the lower end of quality compared to a lot of other things I've used.

View · by **AFTERMATH** on Thu Jan 15, 2015 8:03 pm

Did you call your shots?

View · by **Deputyhiro** on Thu Jan 15, 2015 9:00 pm