Recently, I aquired a Vortex PST 4-16 SFP MIL/MIL scope in the mail. I finally got out to the range today and was able to mount it on my M14-DMR. My M14-DMR is the same gun I shot in the 2011 M1A match with fairly good results, but I changed the stock for a McMillan M2A that was an OIF bring-back.
Overview
A lot of people denigrate the M14 as a Sniper Weapon System as it is fairly fragile; which is fairly accurate statement. It's not as rock solid as the M24/M3 Ultra combo which is almost impossible to fuck up; but it is still a much more proven system than the M110 system. My opinion of the M110 comes from people that have gotten to use the rifle, and while it is very accurate, it is not very reliable. A lot of soldiers are/have been unhappy with the rifle because the tolerances is so tight that if you shoot it with the suppressor, you will have to clean it after a magazine. There have also been issues with trigger breaking. I think that the concept of a sub-MOA semi auto sniper rifle at the expense of reliability is silly...a reliable 1 MOA rifle is sufficient.
In order to use the M14 as an effective SWS, one has to pay very close attention to almost every little detail. The barrel cannot be free-floated, and it must have a certain amount of tension on it in order to shoot well. Changing the tension between the gas system and stock will alter the point of impact. Shooting the rifle with the bipod on concrete vs sand/dirt will change the point of impact also. Basically, you need to approach it with the idea that your rifle is a tuning fork, and that the slightest error will make it sing off-key.
Another major shortcoming for the M14 is the scope mounts. The Brookfield mounts work well like the one from Smith Enterprise work well, but they have a very specific procedure to mount them, and once they are mounted properly, they really should have green loc-tite applied to the screws. The screw that holds the mount into the side of the receiver needs to be properly torqued with a 65-inch-pounds, and if it is over-tightened, the screw threads will strip; this is to keep numbnuts from stripping the threads in the receiver itself. The mounts are also adjustable, and need to be carefully tweaked in order for the rifle to zero correctly; because the specs of the cut in the side of receiver where the mounts hook in is not very carefully controlled, it is not as simple as having a 20 MOA decline mount like you do on a bolt-gun.
Once the rifle is zeroed, you still need to check that the scope is going to have enough adjustment to zero at 100 and make it out to 1000. For .308 M118LR, that means having almost 45 MOA or 13 Mils of elevation, and having a little extra is a good idea so that you can have ample windage adjustments.
At the Range
I started the day at the range, and mounted the scope on the rifle. I had to remove the iron-sight because the scope would not clear the hood of my rear sight. I spent quite a bit of time dicking around with the mount; it needed to be adjusted so that I would have adequate elevation to reach 1000 yards, and still be able to zero at 100. I spent most of the day shooting off of sand bags because the bipod is too tall for the gun.
My overall view of the Vortex PST is that it is a very good scope. I did not have any problems with it, and it works as advertised. The turret/adjustments are much nicer than the Leupold Mark IV and M3A scopes that I also got to play with, but the glass on the Leupolds was noticeably brighter. However, I was able to resolve bullet holes at 200 yards that were on white paper, as well as on black pasters. I did not do any comparison with the lined/numbered charts, and I think my uncorrected vision (I am supposed to wear glasses but don't.) plays a part in how well I can resolve things. The shimmed zero stops work as advertised and are a good idea; I have my zeros written down so that if the turret shoots loose, I can tighten it back up, bottom it out on the zero stop, and count the clicks up from bottom.
After I had the rifle zeroed at 100 yards, I spent the rest of the time shooting groups at 100, and checking the adjustments on the scope. The scope worked flawlessly like it does in the youtube videos.
I do not consider myself a very talented benchrest/sandbagger. I probably shoot a thousand rounds off of a shooting mat for every ten I fire off of a bench. The M14 is one of the more difficult rifles to shoot accurately from a rest; the hammer is quite heavy, and if you dry fire the gun, you may notice the crosshairs shift when it falls. Trigger control can also be more challenging with the pistol grip stocks because the M14 trigger lever does not travel straight back like an AR15; the M14 was designed around a traditional stock, and the motion of the trigger reflects that. With that being said, doing well with the M14 comes back to paying attention to small details, and patience.
Since I like to brag, here are the measurements of my better groups.
I did a test on the elevation consistency toward the end of the day, after I hard fired 70 rounds through the barrel. I just wanted to use the last of the ammo I loaded for the rifle. The groups were as follows, with the farthest distance between shots listed. I measured from center-center with some calipers; that seems to be what the cool kids are doing.
* 3 shot group at +1 mil = .375
* 3 shot group at 0 mil = .990
* 3 shot group at -1 mil = .554
Earlier, I shot a 5 shot group off of the sand bags, and then off the bipod to check if/how much POI shift there is between the two. There was about a 1/2 minute shift upwards from using the bipod; however I am going to repeat the test when I get a shorter, more comfortable bipod.
* 5 shot group off sand-bags= .536 (elevation spread .200)
* 5 shot group off bipod= 1.401 (7 shots from the two 5 shot groups were within .800, 2 shots were thrown about an inch higher, and one was thrown about 1/2 inch high and left.)
There were other groups shot during the day, but I did not cut them out and put them in my data book. Realistically, I expect this rifle to do around 3/4 MOA; not much better, and not much worse. It and I might get more consistent in the future, but my training focus is not on shooting groups so I can claim my M14 is exceptional.
I finished up the day by shooting cold-bore shots at 100 and 200 yards with M118LR, which runs a little hotter than my hand loads. Impact at 100 yards was .9 inches right, and 1.06 inches high at 100 yards. Impact at 200 yards was 1.1 inches hight and .727 left at 200 yards.
Future Plans
With the rifle zeroed, and the scope working well, the next step is to get zeros out to 1000 yards, and to graft the data with clear tape to the stock, as well as loading ammo that will duplicate M118LR. I will probably replace the NM sight with a USGI sight, or modify the NM sight so that it will fit below the scope. A new, shorter bipod is also in the future.
Actually, OSUT/SOPC/SFAS is in the near future, and I probably wont see this rifle for a good 6-12 months.
