F T/R Competition 308 AR for F-class & long range shooting

[Tx_Flyboy]

As the title implies, I am slowly putting together a 308AR for use in F-class & long range shooting (Palma, 600 & 1,000yard prone competitions).

I already have a 308AR that i use as my hunting rifle...it has a 20" lightweight profile barrel with a collapsible stock. The length of the barrel & the thinness of it means its not suitable for the task (not enough MV & heats up too quickly).

I am looking for open-minded advise from shooters in the above competitions and most importantly, those that are not hostile to ARs or use of something they themselves would not consider "optimal".

I want to make something clear off the bat
1. I do not want a bolt action rifle.
2. I am well aware that the mission above probably calls for two (2) separate rifles (a 308 for FTR & a "better" long range caliber).

Plan for the build is as follows:

1. DPMS stripped lower
2. DPMS Lower parts kit
3. Geissele match trigger
4. Brux AR-10(they will make it with a DPMS barrel extension) barrel thinking 28-30" finish length.
5. A2 Stock with 3# lead weight to balance out the rifle & further decrease felt recoil.
6. Circular free float handguard of some-sort.
7. I have an upper, gas block, and the remaining components lying around.
8. A set of front and rear globe sights. I need recommendations as my research into these has not started yet.

Please constructively critique this build. I intend to shoot either 208AMAX or 225gr Hornady BTHP exclusively in order to get the maximum possible resistance to wind drift. Elevation is a non-issue as distance to target is known and fixed.

I reload, therefore tuning the rifle for accuracy is not an issue.

Thanks in advance for your input.

 

[varmitslayer]

Re: 308 AR for F-class & long range shooting

I used my R-25 stock with an 18 in barrel. There are a lot of things that can be done to the AR platform to dial it in. you have touched on almost all of them. for me the trigger group and optics were key areas for me to improve my rifle. Another note about using the AR and I think it is absolutely key is curtesy, I made sure I shot from the last position so as not to fling hot brass on my nieghbor. I'm sure a brass catcher will accomplish the same thing. This was my first shoot so this is my observation from my own rifle. stock trigger was heavy and my optics were too low power to see where I was hitting. I plan on the x32 by 50 optic for the future. Good luck with your build looks like you have a good shopping list going. I would also add in good Bipod to your list as well.

 

[eracer]

Re: 308 AR for F-class & long range shooting

You want to have fun shooting at long range? Take that AR out there and blast away.

You want to have a chance at being competitive in F-class? Against purpose-built bolt guns?

Sorry. But like I said, get that gun out there and shoot to the best of your ability. Nothing wrong with having fun.

 

[Boblor]

Re: 308 AR for F-class & long range shooting

An AR platform is fairly rare in FTR and Palma but go for it. Remember for Ftr you have a weight limit of 18.18 pounds that is your rifle, scope and bipod. I like 20 power or more in a scope for Ftr shooting.
You mentioned Palma shooting,and a better long range caliber, remember Palma shooting requires .223Rem or .308 Win. ctgs. and in the U.S.A. any weight bullet for those ctgs. Ftr also requires the same ctgs. Other calibers will put you into F open class or Match Rifle or Any Rifle in non F class matches.

Centra makes a AR iron sight for the flat top and a front sight.

Bob L.

 

[XTR]

Re: 308 AR for F-class & long range shooting

If you want to participate grab it and come on out. Remember, by the NRA High Power rules <span style="text-decoration: underline">you must single feed</span> so get a bobsled follower or something similar, put on a bipod and get the best high powered glass you can afford.

That said, to stay super sonic all the way to 1000 you need to push either 175s at at least 2650 (and that's iffy at low DA) or 155s at about 2850. You will need all the barrel you can get. Most F class competitors are shooting 30" or more. An extra 15 to 20 FPS per inch adds up when you add 10 inches.


The problem is that you will be shooting against guys pushing 185s in the high 2700s and 155s at close to 3000 (or higher). You will be giving up oven an inch of windage per MPH of wind. Even if you start reading wind like the guys on the US-FTR team I'd bet you'll still give up 5 to 8 points per match, and until then you'll be shooting in the 160s and low 170s while everyone else is shooting high 170s and 180s.

Add in that it won't take you long to start trying to squeeze another 50 FPS out of your rifle and start making hotter loads, in a gas gun I'm betting your brass and your rifle will suffer.

You can do it, you'll be welcome at any match you go to, but you'll be spending money on a system that will be seriously handicapped in ways that cannot be overcome and it gives you no advantages in exchange.

 

[Denys]

Re: 308 AR for F-class & long range shooting

Tx_Flyboy, I would suggest you come to watch a long range match at Bayou Rifles; it's on the first Sunday of every month, registration ends at 7:30AM.

http://www.bayourifles.org/

If you're already aware of the club or are a member, please accept my apologies, I do not know who you are.

BTW, XTR makes excellent points, but they should not totally deter you from your goals.

 

[Tx_Flyboy]

Re: 308 AR for F-class & long range shooting

XTR,

Thanks for all the advise. However, you you seem to not have run the numbers on the 208 & 225 in a ballistics software.

In it i mentioned that i intend to shoot 208 AMAX (.649 G1BC) or 225gr HPBT (.711 G1BC). Both of these rounds, lauched at a measly 2500fps (achieveable from a 20" barrel in an AR) will require 155s traveling at 3100fps or 175SMK at 2950 fps to match them in wind-drift.

I am about to call Brux Barrels, and will ask for a 29-30inch barrel or the longest feasible barrel i can put on my AR.

With such a barrel, i should be able to get 2700fps or more with the 208 and maybe 30fps less withe the 225gr bullet. At those velocities, they are pratically untouchable by 155s or 175s from any 308 in terms of wind-drift. The only thing they give up to the lighter bullets is Elevation and recoil (more on that later).

As far as recoil goes, I cannot handle the recoil from any 308 bolt gun. I can withstand 3-5 shots before flinching sets in. With my AR, i can shoot 150+ rounds in a sitting and not feel in the least bit fatigued.

I figure that a semi-auto rifle close to 18pounds, felt recoil even with the heavy bullets will not be a factor (this better be the case).

Could you please advise why you think this platform is limited?

My current stock rifle has produced consistently sub-mao groups, and i dont feel that i'm giving up anything to a bolt gun. Since this new build will be have a match barrel chambered by Brux, i dont see that i'm that much in the hole.

Denny,

I am a member of Bayou rifles... i intend to come out and witness a match, but i dont think i'll be deviating from my plan.

Once again, Thanks to all that have provided input.

 

[Denys]

Re: 308 AR for F-class & long range shooting

When you come to a long range match, just ask for me.

That said, I understand your parameters, let me share a few thoughts with you. Before I go further, you should know that I have a lot of experience shooting F-class (F-T/R) with an AR rifle, all the way to 1000 yards, though in .223. I do shoot a bolt rifle in .308 now.

The AR platform is a joy to shoot prone, and you can make it even better with a few adjustments.

The first thing you need to look at is the stock, I would suggest a MagPul PRS. It is heavier than the A2 stock and it will allow you some adjustment; shooting prone, you want longer LOP, or at least I do.

The AR is hard on brass due to the ejection, but you can adjust and tame that. The first aspect will be the gas port location. If you are going for a long 28-30 inch barrel (and you should,) you will want to have the gas port moved further out by one or two inches to help deal with the gas port pressure during dwell time. Talk to Brux about that and see what they suggest. They may recommend a smaller gas port also.

You might want to get a Carrier Weight System from David Tubb to increase the weight of the carrier and thus reduce the velocity of the carrier. Along with the CWS, I also use his C/S spring.

I like Tubb's target grip and I find it's the best I have ever used for prone shooting. I have long fingers and that grip suits me, well, like a glove.

You might also want to get a through-the-triggerguard bolt release so you do not have to break position to release the bolt. A Geissele trigger is a given. The Bobsled has already been mentioned, make sure you get one. You will also want a good wide bipod.

Optics will be critical on the rifle, something with a top magnification in the 30X or more.

As for your choice of bullets, that will have to be something you have to try out. My current thought is that a mix between velocity and BC is something to keep in mind. I currently shoot a 180gr bullet with a G7 BC of about .296 and a muzzle velocity a little above 2850FPS. It's done pretty good for me so far.

If you let me know when you plan to come to an LR match, I would bring that AR so you can see what I'm talking about with the various upgrades. My email is in my profile.

 

[Tx_Flyboy]

Re: 308 AR for F-class & long range shooting

Thanks a bunch for your advise Denys.

I have thought about all the items in your recommendations though i did not list them.

I think i'll do this a little at a time.

Yesterday i aquired:
1. DPMS stripped lower
2. DPMS LPK
3. JP 308 Enhanced bolt.

I will be sending the latter to Brux for headspacing to the new barrel.

Regarding attending a Long range match, I may not have my 308 completely built in a month, so i may bring my 20" hunting model just to have fun & gain valuable experience. I will definetly contact you so we can meet & brainstorm some more.

Thanks again for the constructive advise. I am new at this, so i very much appreciate all the input.

The fact that you've done this with a .223 gives me hope. If i can launch the heavy bullets fast enough & accurately enough (10 ring is 1MOA, so really sub-moa is all that's needed...on paper).

I really hope this endevaor is not a fool's errand, but at this point, i'm cupped & committed.

 

[wadebrown]

Re: 308 AR for F-class & long range shooting

I would recommend an adjustable gas block as that will allow you to tune the ejection and ease the damage to the brass, the buffer and others. Brux may be able to put a small enough gas port so that is not a problem.

Most gas ports can be easily moddded to make them adjustable.

 

[Tx_Flyboy]

Re: 308 AR for F-class & long range shooting

Thanks wwbrown.

I just ordered the Brux AR-10 (DPMS) barrel...its got a 12-14week lead time...plenty of time to fret about my decision to go against the grain.

Keep the advice coming...now i need to know about globe sights and which ones y'all recommend for a front sight.

Additionally, is there an advantage in buying a FFP riflescope for these long range matches? Could the mil subtensions aid in correcting for wind-drift?

 

[memilanuk]

Re: 308 AR for F-class & long range shooting

They could... might even be useful on the larger iron-sight target face. But my stance is if you are shooting targets, get a target scope which are pretty much all (last I checked) SFP for a reason - as the magnification goes up, you can hold finer.

Plus, you don't *need* stadia / reticle-based hold-offs - thats what the scoring rings on the target face are for

As far as front sights... I'd say pass on any of the older 18mm stuff. You'll need a fairly tall front sight tower to accomodate an AR or Tubegun based setup. I have a 22mm RPA 'Texas Tallboy' (or something like that) on my AR space gun and it works fine. 30mm front sights are the current 'fad'... Riles, Porter, RightSight, Centra Goliath... all should work pretty well. Plan on spending north of $500 for the front sight (including aperatures, diopter, sun shades, level, etc.) if you go with a new 30mm sight though.

 

[Tx_Flyboy]

Re: 308 AR for F-class & long range shooting

Holy crap!

$500 for the front sight alone? What about the rear sight?

I'm gonna ask a stupid question: I have a 1/4 x1/4 min pinned sight on an AR carry handle...what does this give up to say a phonix or the ones u mentioned besides looking funny when co-witness with a globe sight?

This thing is getting rapidly expensive

 

[memilanuk]

Re: 308 AR for F-class & long range shooting

Eh, looks like I might have been off a bit

http://www.auburnscouts.com/stallingsmachine/rightsight.htm

Although I could see the Riles setup knocking on the door...

http://www.rilesmachine.com/

Sure seemed like I spent at least that much, trying this, trying that, you know the drill. The one thing I found out the hard way (in terms of $$$) is that if you go with one brand of aperature or lens, don't bother trying mixing and matching. Getting all the threads to line up was not worth it; stick with one brand and call it good.

If the rear sight is a good one pinned by someone who knows what they're doing (like Holliger @ White Oak) it might do okay. I don't think it's going to have anywhere near the same range of adjustment or repeatability as say a Warner or clones there of. The big thing thats going to bite you is that 1/4x1/4 is based on the sight radius of a Service Rifle - which is very very short in comparison to a real Match Rifle sight which is designed for a ~36" sight radius (counting roughly 6" of receiver plus 30" of barrel).

Warner is considered the gold standard... and is priced accordingly @ ~$550 for the rear sight... and figure on adding another Benjamin or so for a basic adjustable rear aperature. Stay away from the uber fancy aperature/diopter/whatever ones from Anschutz and such; too many moving parts and at least historically known for not holding up to centerfire recoil.

Phoenix Precision makes both front and rear sights; they don't make 30mm fronts but a 22mm works well enough unless you are really serious about running with the big dogs...

Biggest thing is don't fool yourself thinking that good quality 'iron' sights are a whole hell of a lot cheaper than a good scope. I'd say budget at least a grand for front and back together, or start looking for used.

 

[wadebrown]

Re: 308 AR for F-class & long range shooting

FFP are not needed nor optimal for F-class.

Not needed as you are shooting at a known distance so the ranging ability of the FFP is not needed.

Not optimal because you want a very small reticle so you can visualize and hold on different quadrants of the 10 ring for small holdoffs that you do not feel like adjusting your scope for.

I like my F-class scopes to be 1/8 MOA adjustments, for midrange matches the 1/8 MOA is very useful for me. For 800, 900 and 1,000 the 1/8 MOA is not as critical for me.

Whatever you do buy a scope that has turrets in MOA so you do not have to make the conversions between mils and MOA. The rings on target are laid out in MOA so having mil is an extra step that you may find cumbersome when you are in a hurry.

wade

 

[memilanuk]

Re: 308 AR for F-class & long range shooting

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wwbrown</div><div class="ubbcode-body">The rings on target are laid out in MOA so having mil is an extra step that you may find cumbersome when you are in a hurry.</div></div>

I found it to be more of a problem that the mil-mil scopes I've tried a) don't come with magnification above 24x and b) 1/10th mil clicks equate to (a little over) 1/3 moa, which is awful coarse for target shooting. Not insurmountable if you are using a tactical rifle in an F-Class match for practice, but certainly not what I'd be looking for if purposely setting up a target rifle...

 

[C23]

Re: 308 AR for F-class & long range shooting

An adjustable gas block that allows you to turn the gas system completely off perhaps?

I like the Noveske switchblock on my 5.56 barrel.

 

[Tx_Flyboy]

Re: 308 AR for F-class & long range shooting

Memilanuk,

Thanks much for all the info.

I think i'll budget about $500-$700 for irons (maybe Phoenix precision rear and a 30mm tube up front)...none of this is firm, but it seems like a good starting point for additional research. I am hopelessly lost when it comes to irons...they seem waaay more complicated than scopes.

Regarding scopes; the consensus is loud and clear...SFP with top end magnification 30X or higher.

I'm glad i already ordered parts for the build...had i taken the time to add up all the cash, i would have put his off for many years.

I'm scared and excited at the same time.

 

[Tx_Flyboy]

Re: 308 AR for F-class & long range shooting

C23,

Turning the gas block off turns the gun into a bolt action rifle...something i'm bending over backwards to avoid.

 

[Simon55]

Re: 308 AR for F-class & long range shooting

Sounds like fun .I have used a DPMS 308LR in NZ for the same with the 24" barrel using sierra 175 smks 42.5 gr varget 2580 fps . The 208 amax was going to be next on the list but have sold the rifle to a mate. However it did perform ok out to 900yrds and would maintain sub moa with 3mm clearance allowed for in magazine ,you will definitely have to single round load with it if you increase overall length to improve seating depths and powder capacity ,as magazine length is insufficient. We also found performance was very good with 155 gr sierra and 155 lapua.If you go for a 28*/30" heavy barrel you should have no problems achieving what you want single round feeding.

 

[ivycool]

Re: 308 AR for F-class & long range shooting

I like 20 power or more in a scope for Ftr shooting.
You mentioned Palma shooting,and a better long range caliber, remember Palma shooting requires .223Rem or .308 Win. ctgs. and in the U.S.A. any weight bullet for those ctgs.



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