Hello
After looking at 55gr and 62gr bullets, it’s time to take a look at the 68-69gr HPBT weight class.
The previous workups are here;

https://www.m4carbine.net/showthread...-P-15-Sport-II

https://www.m4carbine.net/showthread...-P-15-Sport-II

Again, shooting this new stock S&W M&P 15 Sport II with a 1-9 twist 16” barrel, topped with a Lucid HD-7 Red dot sight.

For this exercise the Sierra 69gr HPBT Match bullet will be shot. The Sierra bullet is about .898” long.

I know this kind of ammunition needs to be shot with some good glass at distance. I’m looking at some scopes, but haven’t decided which one yet. That’s’ coming up later..

The first thing I do is examine some factory ammo. The two that I grabbed was the Federal 223 Rem 69gr Gold Medal Match loaded with the Sierra bullet, and some Hornady Frontier 223 Rem 68gr HPBT Match, loaded with their 68gr HPBT bullet with a cannalure. This sample has a length of .917”.

https://postimg.cc/gallery/vhy10aqi/

https://postimg.cc/gallery/1ts3ch8uy/

I couldn’t find any Sierra bullets locally at the time, so I picked up some Hornady 68gr HPBT without a cannalure. When I measured their length I found them to be roughly .983” long! So it looks like Hornady makes two completely different 68gr HPBT bullets. I would have thought that the two would be the same length, one just has a cannalure and one does not, but that doesn’t appear to be the case.



I loaded up a few rounds with the longer non-cannalured bullet and it was painfully obvious that this bullet is much too long for this 1-9 barrel after shooting a few groups..

So, when the Sierra bullets arrived, I loaded up some test ammo, seating the bullets at 2.255”, no crimp.
Lake City brass was used throughout.
All the targets circles are 4".

Velocity data was taken with an Oehler 33. Screens centered 15’ from muzzle.
All of the targets were shot at 50 yards.

This will be the first time using Varget and 2000-MR in the line-up.

I shot an initial group with the Federal ammo at my range behind the house, but made the mistake of shooting after a full day of work around the property. That didn’t work out so well. But an average of five rounds came in at 2601 fps at 82°F.



On range day it was cooler, I was well rested and ready to shoot.. The Federal ammo shot much better..



So, after looking at this, two things came to mind.
First, there is no doubt that the Sierra 69gr bullet will shoot in this 1-9 barrel. And second, boy have I got some work to do!…

The velocity was lower this time as the ambient temp was 30° cooler.

Also shot two groups of the Frontier ammo;



The slightly longer Hornady bullet didn’t do quite as well..

With both the Fed and Frontier I shot one group, recorded data, and then shot a second group while the barrel was warm.

Ok, here is how all the handloads went;

Here is all the data I was working off of;







Well there is definitely an array of personalities as to how each powder handles this bullet weight out of the 16” barrel.
Now that a quality bullet is being used here, a lot of powders are showing potential.

The next day I shot a group with 26.4 grs. AA2520 as 26.1 wasn’t showing any pressure signs. It was a bit warmer and the weather was quite different. This group was pretty good, but this one was a bit warm..



Also shot a third group with the Frontier load when it was warmer, to see if velocity or group size would change. No difference either way. I any case it seems the Frontier load is not temperature sensitive.



Here is a graph for all of this;



Looking forward to see what this rifle could do with some glass on it..

Bear in mind this is all relative to one rifle, one shooter, one place and time, one set of components. Change any one variable and this could all change. Don't accept this as loading data. You must do your own work ups with your rifle.