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DPMS LR 308T - Lining up the sights


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Friends, this is a report from my first time out with my DPMS LR 308T and lining up the sights. (This is after my first try, when I discovered it wouldn't eject spent brass and sent it back on a 4-week trip to get a new extractor.)

 

For the rear sight I have a D&L Sports (Dave Lauck) CQB Iron Sight . It's an open notch sight, which I prefer, and may be the only such sight on the market for a picatinny rail -- aside from the peepers that you can 'flip' to give you a rear notch. It's adjustable for windage and elevation and held on with four (4) transverse mounting screws.

 

For the front sight I have the JP Enterprises Detachable Front Sight Base AR-15 with Lyman Globe Sight and I am using the Lyman post reticle/insert. It comes with Lee Shaver 'fine' inserts, but the notch in the D&L Sports rear sight is too wide to make them useful.

 

I called D&L and asked them if they made a narrower notch for their rear sight and they said no, they didn't, and I might wind up asking them if they would do a custom 0.60" notch for me.

 

To handle some of the recoil I have a Heavy XH Rifle Buffer and it makes the whole thing reasonable to shoot. To help save my ears I have a Bison Armory BRT Linear Compensator which is supposed to direct the muzzle blast away from me and downrange. While not as bad as the JP Enterprises Bennie Cooley compensator I had originally, it still made my ears ring.

 

Anyhow, with this setup and a target at 15 yards, I couldn't get on the paper, using a custom-printed target on an 8"x11" piece of paper. Bad news, and three rounds gone. Time to go back to the drawing board.

 

Using the handy-dandy calipers, I worked out the difference in rail heights, between the receiver rail and the rail on the gas block. Turns out, there is a 0.28" difference. With both sights mounted next to each other on the receiver rail, that means the front sight needs to sit 0.28" higher than the rear sight. Since the globe on the JP Lyman sight rides on an adjustable rail, I moved it up -- man, it was way off -- and I got on  paper the first shot. Five rounds later I sent one dead through the 3/4" bullseye.

 

Time to start moving the target further downrange to where I'm shooting at 100 yards, but had to quit as the farmer moved into the field I'm shooting into as background. I'll have to save the rest for another day. I don't know how good I'll do at longer ranges, as these open sights only give me 8" of sight radius.

 

First lesson learned -- Before trying to get on paper, mount the two sights on the same rail and make their height difference the same as the height difference between the receiver and gas block rails. It'll save ammo (at $1 per round or thereabouts) and a lot of guessing and head-scratching.

 

Second lesson learned -- the BRT linear compensator doesn't tame things down all the way. My ears are ringing and that ain't good. This is supposed to be a naked-ears hunting rifle. Short of adding a suppressor I'm open to other suggestions for a muzzle device.

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Wish I had something for you on the muzzle report brother, but it's a .308 and that muzzle will never ease up on your ears without some hearing protection or the aforementioned suppressor, even without a muzzle device you would still be hurting your hearing. Take care of those things brother, your hearing never recovers.

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Since I'm not getting ideal results from using the Bison Armory BRT Linear Compensator to reduce muzzle blast, I'm wondering -- has anyone tried out one of the fake suppressors on the market and noticed a reduction in muzzle blast?

 

This is supposed to be a hunting .308 so my ears will be naked, and I'm looking for options. I also noticed Kaw Valley has a linear comp offered through Joe Bob Outfitters but wonder if I'd just be getting pretty much the same as with the Bison Armory unit.

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Nothing is going to quiet the .308. Nothing short of a suppressor and subsonic rounds, which has already been mentioned.

 

 

Exactly. ANY device that serves to attenuate the report of a firearm (no matter how substantially or insubstantially) is considered to be a suppressor by Federal law. That is why you will find no devices outside of an actual suppressor that serve to reduce the muzzle report. 

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Exactly. ANY device that serves to attenuate the report of a firearm (no matter how substantially or insubstantially) is considered to be a suppressor by Federal law. That is why you will find no devices outside of an actual suppressor that serve to reduce the muzzle report. 

 

Actually, a linear suppressor isn't supposed to reduce the muzzle report, just redirect it downrange and away from the shooter. The result is supposed to be it's just as loud as before, just directionally loud.

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Just a quick update - the AR-15 / M-16 308 5 1/2" Flash Hider w/Holes from Northern Gun Parts is, from the shooter end of things, noticeably louder than the Bison Armory BRT Linear Compensator. So the BRT is at least doing something.

 

One thing I noticed when building a suppressor for a .22 is that the majority of muzzle blast -- for that caliber at least -- is the bullet going supersonic. With subsonic ammo it was quieter than an air rifle. If the same holds true for .308, there's no real solution without going with subsonic ammo, and I'm not going there.

 

BTW the BRT makes a huge fireball, easily visible in daylight. I'm not too happy with that. It wouldn't take an engineering miracle to combine a linear compensator with the features of a 3-prong Smith Vortex or something similar.

 

As far as lining up the sights, I'm getting 5/8" groups at 50 yards using open sights with a crappy little 8" sight radius. That makes me think I could have a sub-MOA gun if I was willing to put some glass on it, which I won't. I might eventually consider a holographic reflex sight like an EOTech. Parallax error from scopes drives me nuts, and so is peeking around the scope to get the scope lined up. Besides, I shoot with both eyes open and always have.

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I tell ya, shooting this iron with a crappy little 8-inch sight radius is just plain too 'fiddly' to be useful hunting in the field. Finding that last little smidgen of MOA is fine if you have the patience. I tried mounting an extra gas block at the muzzle and mounting the front sight there, but then you see the entire front sight assembly sitting in the rear notch. People who engineer open sights -- even Williams -- are darn lazy bastids except maybe those who build sights for Anschutz air pistols.

 

So about $300 in open sights just went into the parts box, maybe I'll try for some action on Ebay.

 

And then I went to the LGS (Scheels) and got a Trijicon RX30A-51. (Cost me about $100 less than at Brownells.) Uses ambient light and has a tritium insert for low-light conditions. No battery, and more importantly, no parallax. I'll be sighting that in today if conditions permit, and we'll see what sorts of groups I can get. The dot on the Trijicon is 6.5 MOA, which visually is pretty small, and that MOA coverage is pretty close to what you get with the front blade on open sights.

 

As far as managing muzzle blast, I'm going to look into having a machinist turn me out a "bloop tube" on a lathe and see what I can get with that.

Edited by gnatshooter
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