Pistol Caliber Carbine Quest
Part 2
 

 
          In Pistol Caliber Carbine Quest Part 1 I talked about my search for a Pistol Caliber Carbine. I purchased the Rock River Arms LAR R9 competition model. I shot a dozen different types of ammo through it with NO MALFUNCTIONS! I had heard that there were issues with the 9mm AR15’s so I was very happy with my choice.
 
As I stated in the last chapter, I always sighted my work AR15 carbines in for 50 yards. When shooting in closer than that there was not much elevation change. With a 5.56 round, a 50 yard sight zero was also correct at 200 yards. I decided to sight my R-9 in for 50 yards just because that is what I am used to. So I went to our Club’s 50 yard bench range. I was equipped with my High Power spotting scope and rifle bench rest. I tried multiple types of ammo. I was using an Aimpoint Comp M3 with a 4 MOA dot. I like this set up a lot. I use an 8 ½ X 11” piece of poster board with a ¾” black paster in the middle for my sight in targets. I set the sights or scope to shoot about 1” high so that the group is clearly visible. Remember I am used to long range rifles that should be going into one hole or at least a clover leaf at 200 yards so I don’t use a big target. This way I can punch holes in the target and keep it in a three ring binder. I should digitize but I am locked in the 20th century. 
 
My First run was with some Winchester White box 115 grain FMJ ammo. The group was pathetic. Well actually there was no group. I guess you could call it a pattern. Sort of like a shot shell pattern.  Well maybe it just doesn’t like that ammo. I tried some Winchester White Box 124. The results were the same. Then I tried some 124 grain coated lead bullets. These shoot like a laser in my son’s HK VP9SK. I was finding it hard to even locate the hits. Copper plated bullets were no better. This was very frustrating considering Rock River says this barrel will shoot 1.5” groups at 50 yards. Something had to be wrong. I examined the barrel using a Hawkeye bore scope. The machine work looked to be fine. The chamber for the round was exceptional. The only criticism I had was that the muzzle crown could stand to be lapped better but in a 9mm this might not matter.
 
Well I am older and I needed a new eyeglass prescription so maybe it was using the Aimpoint in the bright sun at 50 yards. Undaunted, I bolted a pair of YHM 1.5” risers to the top of the upper receiver. I put my Leupold MKIV 6.5 X 20 Tactical scope on top. I grabbed a box of almost every type of 9mm ammo I could find in my shop and off to the range I went. I started with the Winchester White Box 115. I did a little better. This 115 ammo now shot a 7 ½” group. Well that was the ones on the 8 ½ x 11 paper target. No I am not kidding, a bunch missed.
 
Next up was the Winchester White Box 124 NATO. This made a sort of group, 4 inches. Okay but not what I had hoped for from Rock River’s custom barrel.
 
I tried some CCI Brass Blazer 115 ammo. This produced another 4 inch group at 50 yards. Maybe this barrel is just ammo sensitive?
 
Moving on I shot some 124 grain +P+ Federal Hydra-Shok that I had left over from my HK P7 days in the late 1980’s. I think this was circa 1989. This gave me a 2 inch group at my 50 yard target. Now we are talking! Maybe this likes ammo with a higher velocity?
 
Thinking that the R9 barrel wanted hotter loads, I used some IMI Uzi 115 grain +P++ sub machine gun ammo that we used in MP5’s back in my prior life. The Uzi was meant to be shot out of sub machine guns and not pistols. It was pretty hot as I remember. Good, good, this made a group 2” wide X 2 ¾” tall. Clearly velocity was a factor with this barrel. 
 
Now before I go on, let me state that I have learned from working with long range target rifles that no two barrels are alike. No two barrels will behave the same. I consider Rifle barrels to be just like finger prints in that no two are the same, not ever. So for this particular R9 stainless fluted barrel speed seemed to be the answer.
 
Next up were some slower rounds. Don Smith is a retired law enforcement officer. He is on the Board of Directors of the International Association of Law Enforcement Firearms Instructors. Don is one of the shooters that organize the Steel Practices that I have come to enjoy. Don will only shoot 147 grain ammo in 9mm. It doesn’t matter if it is out of his Glock, STI Open 2011, or one of his carbines. With Don’s choice in mind I brought out some old CCI 147 grain gold Dot that we used in suppressed MP5’s. This Gold Dot was slow so it didn’t make noise in the MP5SD. This 147 Gold Dot produced a 1 ½” group with a flyer just a little further out. Wait a minute. I thought this barrel liked faster bullets? Well the R9 liked the fastest ammo I had and the slowest ammo I had.
 
The last ammo I tried with the 20 power scope at 50 yards was some very new Browning 147 grain FMJ. This has been on sale at a couple of the local stores so I thought it was worth a try. This shot about 1” groups with a couple trigger jerks.  I am getting happy again.  
 
Back at the shop, I pondered the results I got at the 50 yard range. What was the same about the 147 grain bullets, the 124 +P+, and the UZI ammo? Why was it different from the 115 and 124 grain ammo? I decided to pull a sample bullet from each of the different ammunition I shot. As you can see in the photo of the different bullets lined up, the WW 115 has a really short bearing surface on the side of the bullets that rides in the barrel lands. The Hydra-Shok, the UZI, the 147 Gold Dot all have a much longer bearing surface. So I have to surmise that 9mm carbine length barrels like longer bearing surface bullets. I did some on line searching of the forums to see if anyone else saw similar results. I could only locate a couple people who were trying to get better 50 and 100 yard accuracy out of the 9mm Carbines. The consensus was that lead and copper plated bullets were ruled out immediately. After that it pretty much seemed barrel specific. I shopped around for some bullets to reload. I settled on Zero 147 grain JHP. These bullets have a long bearing surface. This might be my answer.
 
Although I have many brands and types of smokeless powder on my shelves, I prefer to use VihtaVuori powders in pistols. The VV burns very cleanly. Although most use VV320 powder for 9mm, I prefer the VV340. The slower powder seems to keep the muzzle down. The faster burning VV320 gives just a little more recoil and therefore muzzle climb. This is not what one wants for shooting steel targets as fast as possible. Based on my reading, I decided to try VV340 loads of 3.9 grains, 4.0 grains, 4.1 grains, 4.2 grains, 4.3 grains, and 4.4 grains. WARNING 4.4 GRAINS EXCEEDS THE RECOMMENDED LOAD DATA. I was shooting a carbine so I thought this would not be a problem. As with any reloading article I will state that one should never start with the heaviest recommended powder load. It is best to start at the lowest and work your way up. Look for pressure signs as you shoot the stronger loads. Stop at once when you see signs of cratered or flattening primers, swelling or splitting of cases etc.

Yet another 6.5 Grendel first, Amend2 is going to make magazines for the Grendel. This is a really unique design. The lower part of the magazine is double column. The follower feeds the rounds up into a single column. The rounds will only enter from one side. Look for these on the Harbour Arms Website in April.