In my final articles, Issues for the DMR half 1 and half 2, I got here to the conclusion that a DMR can be greatest suited with an optic system which targeted extra on velocity than precision. Targets will all the time current at unknown ranges and just for a number of valuable seconds, so it’s in the most effective curiosity of a contemporary rifleman to make use of a quicker, however much less exact BDC based mostly methods. Alone, a bdc is a superb software, however to actually full the ideas which I’ve labored on, we have to pair a BDC with a rifle that gives a flat trajectory and a bullet that gives decreased wind drift… insomuch as we will. In 5.56 this implies a cautious number of a load designed to 1) match the BDC with the flattest capturing setup we will and a couple of) ship superior efficiency in accuracy and diminished wind drift.
All Outa Time to Dial:
Perceive that for a BDC reticle to be helpful, it should get us inside vary to permit the trajectory arc to intersect with the goal. The human physique is just so tall, and solely so large… Just a little little bit of wind drift at 300 may push you off a couple of inches, however the human physique is large sufficient to take in a little bit of wind error and land successful. Likewise, in case you estimate distance, hopefully will probably be inside the margin of error for successful. Perhaps it’ll hit low (goal was additional away you then estimated) or it’d hit excessive (goal was nearer than your estimate). A poor hit inside the margin of error (arrow to the knee?) is best than no hit in any respect. To make sure a *greater* hit chance, we’d like the flattest capturing projectile out there in order that error in vary estimation can nonetheless land successful.
Let’s do a psychological train. Think about a Pink Rifleman utilizing a AK47 with a scorching new BDC system. You possibly can calibrate a BDC for 7.62×38 simply as simply, however notice that the stadia are going to be much more separated in comparison with a 5.56 BDC. That’s as a result of 7.62×39 is pokey and sluggish, and thus the 100 yard step stadia markings are additional unfold aside. As we estimate vary, it turns into extra important that we get it proper with the 7.62 as our margin for error diminishes. A number of yards off the actual vary, and the spherical will hit the filth or fly over the top. The trajectory of seven.62×39 is just too punishing of errors. Your arrow to the knee with 5.56 is perhaps an arrow within the dust with 7.62×39 for the very same vary estimation error.
So to be *extra* helpful, a BDC must be matched with a rifle system that squeezes out as a lot velocity as attainable. Your vary estimate won’t ever be good. So use a projectile which flies as flat as potential to mitigate the error you will enter into the system. In my case, I would like my 5.56 as speedy as potential. A rifleman acknowledges that velocity (and RETAINED velocity) does certainly matter. A 20 it have to be so it shall and thus it’s! Aaahhhmen.
The Trijicon ACOG:
There are lots of fashions to select from. Loads of good arguments for and towards this and that mannequin. After proudly owning and promoting two (now on my third) I’ve two fashions in thoughts which might be notably suited properly to a DMR type construct.
My first selection for my 20 inch DMR is the TA01 ACOG. This mannequin is a “legacy” mannequin that hasn’t had a lot in the best way of improvement. It’s a easy reticle with three cross bars and effective BDC stadia. It doesn’t function fiber optic illumination. It’s naked bones. Tritium and laser etched reticle solely. With all of the nifty options that different fashions include, why select the oldest product on the road?
The TA01 does some issues nicely. It’s calibrated to 55 grain ammunition from a 20 inch barrel. This satisfies the speedy projectile / BDC facet. The drop stadia are tight and intently spaced. It’s because the 55 grain bullet has a really flat trajectory inside 600 yards. The opposite merchandise that I favor with this ACOG over one thing like a TA31F is that the reticle is all the time eye-catching. For those who ever shot a Ta31 collection beneath cowl, you’ll word that the reticle washes out. When it washes out, you’ve got a tiny black chevron. That’s not quick. It’s onerous to seek out. It was one of many largest disappointments I had once I received my first ACOG.
The TA01 collection avoids this by use of its giant crossbars. Capturing from indoors to out nonetheless provides you an amazing the power to bracket the goal and FIRE. As well as, the TA01 is extra reasonably priced than its brother and sister fashions. Additionally full red-line illumination at night time means the BDC works after darkish. How far. To 800 yards. That’s kinda loopy, however I’ll take it!
Enter the ACSS:
This can be a good selection as nicely. It contains a bigger circle dot reticle and provides wind holds with numerous different strategies of vary estimation. It’s calibrated for the 62 grain XM855 out of a 20 inch rifle. Nothing in any respect incorrect with this mannequin besides the reticle would, for my part, nonetheless wash out a bit from capturing underneath cowl or when used with a light-weight. It’s a trade-off. I feel both system (ACSS and TA01) are appropriate optics for a DMR.
I selected a flat capturing projectile pairing for my rifle and now I want a way for working in wind holds. The thoughts’s eye is a really highly effective software, and by using some repeating patterns, we will extrapolate wind drops by way of thoughts’s eye visualization. With a BDC calculator, we will first develop a primary plan for our wind holds. Strelok provides us a visible of the reticle and goal, and with a little bit of creativeness we will see patterns the place we will apply repeatable holds.
The method is to think about silhouettes shoulder to shoulder. At 500 yards with full worth 10mph wind, your maintain can be a 3rd man standing shoulder to shoulder to your meant goal. At 400 the maintain can be an invisible man standing proper subsequent to your goal. At 300, maintain simply off the arm of the goal. At 200 and 100 yards, maintain good of middle of mass.
These holds are visually do-able and offer you a greater probability at successful with the 55 grain M193 than pure guestimation. Even a primary system is best than no system. Not the perfect spherical to shoot within the wind, however merely holding off utilizing psychological visualization may also help you in buck the wind. I might be hesitant to make use of the identical method at 600-700 as there’s solely a lot visualization you are able to do earlier than your simply aiming into the grass. I really feel 500 yards is the restrict of the method with this projectile.
When you have an ACSS system, then you’ve added holds to assist your capturing in wind; the holds on the ACSS are calibrated to 5mph crosswind and a 62 grain bullet touring out of a 20 inch rifle.
The ACSS is a extra science based mostly strategy and is superior to utilizing psychological imagery, however you continue to have to make use of SOME psychological imagery to shoot in 10mph crosswind. The additional ranging instruments are helpful in case you have time to make use of them, and the ACSS is a strong package deal save for the washout concern. I might add a supplemental purple dot so that you mitigate the wash out difficulty with a separate optic.
What About Variables?
One other good selection, however I prevented them primarily due to the added weight on a DMR. At a portly 9lbs, the HBAR is getting hefty. I would like the advantages of the heavy barrel, however the sacrifice is weight. Thus, I made the choice to make use of ACOG’s for the construct over the extra versatile variable optic. In most different circumstances, I might take a variable as they’ve so many further capabilities that it might take a separate article to cowl all of them.
There’s No Spoon:
Many shooters hate that a fastened BDC ties you to a single cartridge. In concept, sure this is able to be an issue, however in actuality you’ll find many different projectiles that match the BDC. The heavy, aerodynamic .223 loadings work amazingly properly with the TA01’s BDC. The 55 grain speedster contrasts rather well with the slower however extra aerodynamic 70+ grain bullets.
So the M193 TA01 reticle continues to be fairly helpful for the heavier match bullets. The trajectory curve strains up previous 300 yards very nicely and continues to be helpful out to 700-800 yards relying on the load. Additionally of word is how tight the wind holds turn into. Take a look at the 77 TMK Sierra at 500 yards… with a 10mph wind your maintain is good of the arm! Coupling these reticles with a 70+ grain loading will supply strong capturing outcomes and I intend to utilize them.
The ACOG nonetheless represents a top quality optic for a rifleman, although it has been eclipsed by the function packed variable optics as of late. For my part, a DMR advantages from the speed and accuracy of an extended heavy barrel. Since that is the route I selected, I additionally needed to mitigate the load with a lighter optic over a variable with mount. The ACOG TA01 and ACSS supply a fantastic pairing to a 20 inch gun and each function helpful parts for the rifleman. Whereas the TA01 is dated from a design standpoint, there’s nonetheless profit to its low mild BDC and helpful reticle which doesn’t wash out. The ACSS represents a extra function packed optic which provides the rifleman a lot better visible knowledge relating to wind holds, and would make one other wonderful selection save for the truth that washout continues to be an issue. Different ACOGS, such because the TA31 collection, lack each wind knowledge and in addition lack a strong, extremely seen reticle in hostile lighting circumstances… thus I might spring for TA01 or an ACSS system.
So for half four we’ll discover the statistics of my construct. Let’s pit a contemporary 10 inch carbine towards the 20 inch dinosaur and examine / distinction hit statistics utilizing some analytical software program. Very similar to accuracy, I consider hit proportion improves with incremental modifications: longer barrel, higher bullet, extra accuracy… all will add incremental enhancements to a rifleman’s hit price. With no squad of shooters to check in a managed setting, I’ll use the subsequent neatest thing to extrapolate some knowledge: The AB Analytics Package deal.