Perfecting a DMR

[TokenTech89]

A guide I found while on the internetz at work. Hope this helps out some people. I know it helped me out, despite me not using the gun in the thread.

http://www.airsoftsniperforum.com/showthread.php?t=892

[Star_folder]

Aw man.... and I was hoping this would be a question thread. That is a good thread though, lots of good information in it.

[Dominum]

That's one I haven't seen in a long while, but I remember it being reccomended to me a few years back. Still a great read with lots of useful info for AEG builds in general.

[TokenTech89]

it can be a question thread. like, what is a really good range for a dmr to be at as far as fps, range, and rof?

[Star_folder]

Well, that's an incredibly broad question, with a wide range of possible answers. Generally speaking, from what I've seen, 400fps with .25g bbs should reach out to 300ft when using .4g bbs. And then my L85 gets a very reliable 400ft out of it's 520fps with .25s. It's a hard thing to grasp, hard to fit it to a graph of what you should get, vs what you are getting. Seems like a DMR should be at least able to make 300ft body shots, with heavy bbs and a good hop, it's very possible.

As for FPS, I believe the higher the better. As it turns out, a .4g bb leaving your barrel with 3.5J of power, about 550fps with .25s, has 1J of power at the 100ft mark. Which is the same as being shot point blank with a 0ft MED gun. The lower the power level of your DMR, the less power it is at the 100ft mark. And let's be honest, how often are you actually engaging people at 100ft. Most of my engagements are 150-200ft. So, I believe you should top it out the best you can, and then make sure your internals can reliably handle that sort of power.

Rate of Fire. Some think it's stupid, for a DMR to have a rate of fire, but that translates into cycle completion, how fast you can pull the trigger. Those of you who have seem me on the field know I feather the trigger on the L85, it shoots very fast, on an 11.1v I get about 22rps, closer to 30rps on a 14.8v. I believe you should have a gun that does at least 20rps on full auto. It helps ensure cycle completion before the trigger can be pulled again, it also means you'll let off the shots quicker when you pull the trigger. Long trigger pulls and high torque gear sets slow down the rate of fire. Personally, I believe a DMR shouldn't have anything higher than 18:1 gears in them, the stock gear ratio. My L85's stock ratio is 21:1, just a tad higher than an M4's ratio, 18:1. And even with this "normal" ratio, I'm able to toss around this SP170 spring at higher rates of fire than some stock guns get.

Just some thoughts, like I said, incredibly broad question. lol.

[Frost]

so if you are currently shooting 448fps with .25 with a travel with .4s of 300 ft, would it be possible by upgrading the spring to increase the Fps 500-550 Fps with .25s to effectively reach 400ft with .4s? Also would the increased energy of the spring create more hop up spin therefore lifting the Bb even more?

[Star_folder]

so if you are currently shooting 448fps with .25 with a travel with .4s of 300 ft, would it be possible by upgrading the spring to increase the Fps 500-550 Fps with .25s to effectively reach 400ft with .4s? Also would the increased energy of the spring create more hop up spin therefore lifting the Bb even more?

It would not, FPS and range are not directly related to each other. Yes, the bb would go further, but not significantly so. Range has a lot to do with the bbs you're using, the quality of the hop up, and the consistency of the fps. At that point, the point you are at, a heavier spring will only get the bbs to their target faster.

When you start getting to the point where you are asking to reach, you have to start crafting a very high performance rifle. The hop up unit needs to be heavily modified and tuned so that you get a full contact of the contact patch. Having a system that will apply pressure directly down on top of the patch instead of an angle like normal chambers do is important. You also won't be able to do it unless you have access to a full chamber, OR, are willing to heavily modify the receiver. Sadly, guns like the RS SVD would require external modification to put in a longer contact patch.

You'll also need a good barrel, something smooth, very smooth, but something large enough to ensure the bb a stable flight path. Having a tight bore is not the best idea. After the bb hits the hop up, it's riding along the top of the barrel. Everytime it hits the sides of the barrel, a little counter productive hop is applied to it. That throws your accuracy off. You really shouldn't go smaller than a 6.03mm barrel because of this.

Nothing should move. Nothing. No barrel wobble, of the inner or outer barrel. Even a hair of movement will turn into much larger differences at range. Your hop up should be locked down in such a way it can't move on it's own. The hop up chamber needs to be sealed to the gearbox so it's not pushed forward with the shock of the piston or the pressure of the bb through the bucking.

Don't forget that a gun is only as capable as the person who holds it. Sometimes people need to take some time to just get used to their guns. Don't forget about the art of arching your shots, or adjusting your hop up if need be. Tilting your gun one way or another to counter act wind, etc. Learning your gun and how it performs is also very important in making a very long distance shot.

[Frost]

Tyvm star. I have already been able to do some tuning of my hop up and gained improvement and will look into barrel stabilization tomorrow. I do however have an extra 6.01 tight bore barrel mad bull 550mm. My thoughts on it after what you stated about barrels is that it is too long and too small of an diameter. Would glad for you to reaffirm this or disagree. Also will contact u later with the hop up improvement results.

[vanevery]

When you start getting to the point where you are asking to reach, you have to start crafting a very high performance rifle. The hop up unit needs to be heavily modified and tuned so that you get a full contact of the contact patch. Having a system that will apply pressure directly down on top of the patch instead of an angle like normal chambers do is important.

(Flat-hop Related)
Understanding this and tuning my hop-up with this specifically in mind is something that is becoming a break through for me in shooting long range.
Because my DMR is an AEG with a v2 hop-up unit, it raises and lowers at an angle.
This angle proves to be a hindrance at a given point no matter what your gearbox set-up is along with the BB weight you are shooting specific to it. The given point is specific to whatever set-up you are running and how your hop-up is tuned.

The hindrance is this: At some point all the performance that can be achieved at level hop has in fact been accomplished, yet your gun still has more range and accuracy to gain. This is dependent on adjusting for more hop.
With an angled hop adjustment, there is a point where adjusting for more hop becomes no longer a raise in hop, but a ramp launching your bb's.
I think of this "ramp" the same way I think of a standard bucking mound, it just gets in the way.
Being that I prefer to make my own Flat-hop nubs, I can customize the size, shape, and cut of the nub to counter act the angle of hop-up rise, and modify the hop-up arm to accommodate.
This negates the hindrance of the "ramp" to a measured degree and allows for more level hop in the raise of hop-up adjustment. This leads to more range and better accuracy at long range.

Don't forget that a gun is only as capable as the person who holds it. Sometimes people need to take some time to just get used to their guns. Don't forget about the art of arching your shots, or adjusting your hop up if need be. Tilting your gun one way or another to counter act wind, etc. Learning your gun and how it performs is also very important in making a very long distance shot.

Star is on the money here.
You the shooter are as important as the weapon in terms of accuracy.
When I first built a DMR that could consistently hit a target at 100 yards, I realized a couple things by spending time at the range.
One: the bi-pod I was using tends to lean to one side or the other. Sometimes the muzzle of the gun was not centered. I recognized this by the crosshairs of my scope sometimes leaning one way or the other. It is not much, so not always obvious by the feel of the gun. Correcting this immediately improved my accuracy.
Two: my breathing technique was all wrong for shooting a rifle. I am used to shooting real steel pistols, not rifles.
When I would breath, the stock of the gun on my shoulder would move the rifle up and down. This makes no difference shooting at 60 yards and in. At 100 yards, it matters.
So recognizing these points and making the appropriate changes greatly reduced my misses.

[Frost]

I agree with learning your rifle and perfecting your shooting technique. I have watched and read articles on technique and realize there is a certain way to breath and when to take your shot during the breathing process. Also that keeping the gun as stable as possible in the shot is crucial. I have not yet perfected it, but I am working on it.

@token tech I would love some more in depth info on your angled nubs along with some pictures if possible. :I don't completely understand it but it sounds like something worth looking into. And thank you for everyone's response to my questions.