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lengthofpull
09-23-11, 18:26
Hello all,
Long time reader, first time poster here. I am getting ready to have the kind folks at Rainier build me a "precision" upper and I have a few questions first. I have used the search function here to answer most of my questions but I have a few other items I haven't found anything on. If anyone could point me in the proper directions that would be great.

This is going to be a 20" Lothar-Walther SS barrel, Vltor MUR upper, and Apex rifle length hand guard. I have no need for iron sights and will be using a 4.5x14 scope on it. I will be shooting no further than 600 yards with most work done inside of 400. I have no plans for suppressor use.

Targets will be sage rats, coyotes, 12" steel gong and whatever targets i staple to a piece of plywood to try and outshoot my old man/his 223 bolt gun.

1. On a precision upper, what recommendations can be given for gas block selection? There will be no iron sights on this gun so I have no need for a rail. Just get a decent low-profile one?

2. For a muzzle device I am looking at the Vortex. I am not sure I believe that it "helps align exiting barrel gas to improve accuracy with all bullet types" but I am willing to have an open mind if someone presents data. A question I have for folks who have the vortex or other open prong style muzzle devices is do you find that foliage gets stuck in it when you're tromping through the woods? I want something that just does flash suppression, at this time i am not interested in a comp or break.

3. The barrel comes with a matched bolt, however I believe (not sure) it is a DPMS which i am not thrilled about. I have a spare daniel defense bolt and I am going to do accuracy comparisons with both to see if the matched bolt offers any substantial accuracy gains. If this is the case is bolt carrier selection as critical as bolt selection from a reliability standpoint (assuming the key on the carrier is staked properly).

Thank you for your time.

Belmont31R
09-23-11, 18:42
Lo Pro's are fine. Just make sure the barrel is dimpled for the set screw.



Ive never noticed a difference in accuracy with different muzzle devices. A2's work really well and only cost about 10 bucks with the crush washer. If you have money to burn or need a can mount thats one thing worth spending money on.


I would rather use a mil spec type bolt than anything DPMS.

a0cake
09-23-11, 20:40
Hello all,
Long time reader, first time poster here. I am getting ready to have the kind folks at Rainier build me a "precision" upper and I have a few questions first. I have used the search function here to answer most of my questions but I have a few other items I haven't found anything on. If anyone could point me in the proper directions that would be great.

This is going to be a 20" Lothar-Walther SS barrel, Vltor MUR upper, and Apex rifle length hand guard. I have no need for iron sights and will be using a 4.5x14 scope on it. I will be shooting no further than 600 yards with most work done inside of 400. I have no plans for suppressor use.

Targets will be sage rats, coyotes, 12" steel gong and whatever targets i staple to a piece of plywood to try and outshoot my old man/his 223 bolt gun.

1. On a precision upper, what recommendations can be given for gas block selection? There will be no iron sights on this gun so I have no need for a rail. Just get a decent low-profile one?

A pinned block is preferred over set screws for reasons of durability. If you do go the set screw route for whatever reason just make sure the barrel is dimpled for it. Rocksetting the GB can also help if you use set screws. Getting a rail that covers the GB is an added layer of protection. But really, there is no reason you have to do any of this. Just get it pinned. I had an issued MK12 (set screw GB) turn into a single shot on me after taking a nasty fall on rocks.

2. For a muzzle device I am looking at the Vortex. I am not sure I believe that it "helps align exiting barrel gas to improve accuracy with all bullet types" but I am willing to have an open mind if someone presents data. A question I have for folks who have the vortex or other open prong style muzzle devices is do you find that foliage gets stuck in it when you're tromping through the woods? I want something that just does flash suppression, at this time i am not interested in a comp or break.

I've only run the Smiths on MK48's and M14's. On the 48's there was obviously no observable difference in accuracy (it's a MG). Flash suppression was impressive.

However, on the EBR's we were able to notice a moderate POI shift at 200m+, depending on whether or not you let the Vortex stop vibrating before taking another shot. In other words, POI was different based on whether the Vortex was still doing its tuning fork act from the previous shot or not. Disclaimer: those 14's were not accurate to start with and exhibited unpredictable behavior, so I cannot attribute the POI shift to the Vortex with absolute certainty. But the phenomenon was conceivable enough for us to switch back to the standard FH

3. The barrel comes with a matched bolt, however I believe (not sure) it is a DPMS which i am not thrilled about. I have a spare daniel defense bolt and I am going to do accuracy comparisons with both to see if the matched bolt offers any substantial accuracy gains. If this is the case is bolt carrier selection as critical as bolt selection from a reliability standpoint (assuming the key on the carrier is staked properly).

Headspace is set when the extension is put on the barrel. Acceptable headspace is between 1.4646" and 1.4706." The point where a rifle becomes "unsafe" is 1.4736''. However, the Army uses 1.4730'' for an extra 0.0006'' of safety. A matched bolt simply means that they are checking headspace with various bolts and finding one in a healthy range. I don't know the exact extent to which this effects accuracy, but unless you are shooting from a rock solid platform, indoors, there is very little chance you will notice a difference. There are certainly a lot of more important factors when it comes to knocking out the X ring. I would personally use the "matched" bolt that comes with the rifle and keep the DD as a spare if that one goes, instead of switching back and forth...unless doing a comparison is something you just really want to do.


Thank you for your time.

.............................................................................................

a0cake
09-23-11, 21:41
Also, recommend splurging for a Geissele trigger. Of course, a trigger has no bearing on the inherent or potential accuracy of a rifle, but it will certainly help the shooter in exploiting a rifle's full potential. For regular use carbines, I see no reason to upgrade from a mil-std trigger, but for a precision build, the $220 for a Geissele SD-E is money well spent.

lengthofpull
09-24-11, 12:59
Thank you for your responses gentlemen.

aOcake, I did not know that a "matched bolt" was just a headspaced-checked bolt. I was under the assumption that it was precisely matched for the locking lugs to match up precisely every time. Thats good to know. I have read a post on here about the LW-50 barrel and its matched bolt showing slightly better accuracy, but it was a third hand report. Also, we're on the same page regarding the trigger.

In your experience how long does it take the Vortex to "settle down"? I realize there is likely a difference between 556 and 762 versions. Did you ever get branches/twigs/debris caught in it walking around or after setting it on the ground?

a0cake
09-24-11, 13:23
You're best off talking to LW (can't hurt to ask Rainier also) directly on what their own definition of a matched bolt is. It is likely that they check headspace with a variety of bolts on your barrel and select one that most closely meets what is optimal.

As for the Vortex, I wouldn't worry about things getting stuck in it. That never presented itself as an issue with the 48's.

About the POI shift issue, the manner in which we tested the Vortexes on the 14's was not in compliance with the scientific method because of lack of time and resources to do that kind of testing. The juice just wasn't worth the squeeze for us, given the possibility of having an issue. So we just chose to stick with the standard FH. I don't want to start a whole thing over the Vortex. There was simply the appearance of an issue regarding vibration and POI shift, noticed on one particular platform, so without the time and resources to do thorough testing, we chose not to use them for our own personal application.

Personally, I don't see a need for anything other than an A2 FH, unless a Suppressor will be used on the rifle, of course.

But, lots of people use and love the Vortex and AAC offerings, and more power to them. You just have to decide if it's worth it for you.



Thank you for your responses gentlemen.

aOcake, I did not know that a "matched bolt" was just a headspaced-checked bolt. I was under the assumption that it was precisely matched for the locking lugs to match up precisely every time. Thats good to know. I have read a post on here about the LW-50 barrel and its matched bolt showing slightly better accuracy, but it was a third hand report. Also, we're on the same page regarding the trigger.

In your experience how long does it take the Vortex to "settle down"? I realize there is likely a difference between 556 and 762 versions. Did you ever get branches/twigs/debris caught in it walking around or after setting it on the ground?

ALCOAR
09-24-11, 14:00
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MistWolf
09-25-11, 16:05
The Lothar-Walther barrel has a good reputation as an accurate barrel and compared to some others, is a good value. Little Crow Gunworks sells them for the best price I've seen going. You'll have to check for yourself, but when I bought mine, they advertised a 30 day money back guarantee if not satisfied, as long as the barrel isn't abused. Some accuracy guys claim barrels shoot better with matched bolts. Not carbine or plinker better, but precision shooting better (Fractions of an inch better, not whole inches better).

Without reliability as a factor, a clamp on gasblock is your best choice for accuracy. A pinned or a set screw gasblock could possibly cause a slight distortion on the bore which could have a negative effect on fine accuracy. This isn't to say pinned or setscrew gasblocks haven't been successfully used, just that this problem has cropped up from time to time.

The biggest problem using most muzzle devices having a negative effect on accuracy is from distortion of the muzzle from too much torque. Competition shooters have found that using more than a light torque can have a significant effect on accuracy