Building a varmit type AR

[raptrbreth]

I plan on building a varmit style AR upper so have been reading up on it. Some of the reading has led me to believe that some extra work might have to be done to make the upper more precise. I have built a few uppers now but am wondering what a gunsmith might do 'extra' that makes the upper better. Thanks for any input.

 

[natdscott]

The following is a list of things that can be done, have been done, and MAY provide benefit. Not saying I do all of them, but not sayin' I don't either.

First and foremost, a good barrel. By good barrel, I mean Krieger, Bartlein, Lilja...you get the idea. Call Wisconsin and get on their list. Oh, and make double-certain that you get the blank rough contoured BY the barrel maker. I have it on excellent authority that AR-15 barrels delivered by Krieger are FINAL contoured before final lapping.

Slightly oversized (+0.001"), and custom-made barrel extension. Likely requires hand-fitting to the upper receiver, and may STILL be glued in.

Custom ground live-pilot reamer based on either prints of intended round, or better, 3 dummy rounds of intended ammunition. Interchangeable pilot used at the nearest 0.0002"

Gas port drilled between lands, sized large enough to fully function, but not more. Consideration given to moving gas port forward for heavy long range loads need not be given to the faster powders typically used in varmint loads. Gas port can also specifically be drilled into a lead slug to avoid burrs.

Bolt overrun set to a bare minimum for function in the intended environment. Usually, smiths don't like to go less than about 0.005" overrun. Ask nicely, and explain your purpose, and some can be convinced to go a might shorter. But don't get greedy...the AR-15 does not blow up well.

Bolt trial-fit with a variety of firing pins to ensure that the pin fit has oh...about 0.001" clearance. This is about the only way to reduce/remove tendency to crater, as the bolts are too hard to drill and install a bushing, and nobody I'm aware of makes custom pins (though they could).

A GOOD milspec MPI/HPT bolt with bolt tail, BCG bearing surface, and rear of locking lugs ground as the last operation.

A good float tube like Bill Geissele's with index lugs, and ability to be made--and HELD--to perfect parallelism with the upper receiver. At least, if you have any intent to mount a scope forward. If not, then just get a good float tube that is rigid enough to hold up to abuse, and not flex under firing conditions.

All of this above being mounted to a good forged upper receiver. Billet is okay too. Just choose a good one, or let your smith, and put the receiver on tooling to determine if it's action face needs squared. This is a reallllly persnickety thing to do on a rifle who's bolt floats...but it has been done.

Finally, it should be made 100% certain all other normal procedures like gas tube alignment and float, and barrel nut torque are followed.

Feed this thing a diet of good brass, prepped as it can be, with NO quarter given to the mentality that "it's just an AR". Use Berger or Sierra bullets, premium powders, and BR primers.

You won't be disappointed.

-Nate

 

[padawan]

I plan on building a varmit style AR upper so have been reading up on it. Some of the reading has led me to believe that some extra work might have to be done to make the upper more precise. I have built a few uppers now but am wondering what a gunsmith might do 'extra' that makes the upper better. Thanks for any input.

Does varmit=accuracy for your goals? Our rule of thumb is barrel+loads to match, trigger, glass. Then its up to the person pulling the bang switch.

 

[Tactically Fat]

distances you'll be shooting these varmints?

if out to 250 yards or so - a typical run-of-the-mill AR SHOULD probably do it without issue - even with an inexpensive scope. My reasoning for this: I was able to hit a 2" steel square at 211 yards with my cheap AR + cheap red dot, repeatedly, while shooting prone and off a rest. And I'm way way way worse at shooting rifles than I am handguns. I THINK that I'd probably be able to hit a 3-4" target at 300 if I were similarly supported and if I knew how much to hold over. (As it was, I had a 50/200 yd zero on the rifle).

So - how far do you want to shoot?

 

[ROLEXrifleman]

Between the money for parts, tools, outsourcing work you can't handle in house either due to lack of tools or knowledge, down time, and a final product with no warranty you might be better off in the long run both financially and end product wise to buy a good at from the get go.
and define varmint type, cause that means different things to different people. To me that a sub moa ar past 400 yards and there ain't to many that can build that in their garage.

 

[natdscott]

Between the money for parts, tools, outsourcing work you can't handle in house either due to lack of tools or knowledge, down time, and a final product with no warranty you might be better off in the long run both financially and end product wise to buy a good at from the get go.
and define varmint type, cause that means different things to different people. To me that a sub moa ar past 400 yards and there ain't to many that can build that in their garage.

Amen, brother.

I love tinkering. I think if you can change oil on a car, you can probably assemble an AR, and even some bolt rifles, safely. I do scopes, bedding, triggers, reloads...lotsa things...

But when I have to have my AR rebarreled, it goes to White Oak in Illinois. If you are wondering...yes, that is a direct endorsement of their work. I know that John will build exactly what I ask, and that he and his crew will execute it as well as any humans on the planet. Their failure rate is about as close to zero as can be achieved, and that while delivering some of the most accurate AR rifles built.

-Nate

 

[raptrbreth]

More clarification. I can reliably hit black at 500 yards with irons. I want something that will hit sub MOA out past 500 with glass if I do my job. I am sure I would use it on varmits but for now only paper. The rifle is going to be my version of a DMR. From the sounds of it this is probably out of my skill level right now, might have to farm this one out.

 

[Tactically Fat]

I presume that you handload? Or willing to start?

I'm NOT much of a rifle shooter, and certainly no long distance shooter of any kind at all - but you're probably going to want the heaviest bullets you can find (77gr?) - and for extreme precision, they'll probably have to be handloaded and probably even single-loaded into the rifle due to OAL. Keep that in mind.

 

[NyleRN]

The following is a list of things that can be done, have been done, and MAY provide benefit. Not saying I do all of them, but not sayin' I don't either.

First and foremost, a good barrel. By good barrel, I mean Krieger, Bartlein, Lilja...you get the idea. Call Wisconsin and get on their list. Oh, and make double-certain that you get the blank rough contoured BY the barrel maker. I have it on excellent authority that AR-15 barrels delivered by Krieger are FINAL contoured before final lapping.

Slightly oversized (+0.001"), and custom-made barrel extension. Likely requires hand-fitting to the upper receiver, and may STILL be glued in.

Custom ground live-pilot reamer based on either prints of intended round, or better, 3 dummy rounds of intended ammunition. Interchangeable pilot used at the nearest 0.0002"

Gas port drilled between lands, sized large enough to fully function, but not more. Consideration given to moving gas port forward for heavy long range loads need not be given to the faster powders typically used in varmint loads. Gas port can also specifically be drilled into a lead slug to avoid burrs.

Bolt overrun set to a bare minimum for function in the intended environment. Usually, smiths don't like to go less than about 0.005" overrun. Ask nicely, and explain your purpose, and some can be convinced to go a might shorter. But don't get greedy...the AR-15 does not blow up well.

Bolt trial-fit with a variety of firing pins to ensure that the pin fit has oh...about 0.001" clearance. This is about the only way to reduce/remove tendency to crater, as the bolts are too hard to drill and install a bushing, and nobody I'm aware of makes custom pins (though they could).

A GOOD milspec MPI/HPT bolt with bolt tail, BCG bearing surface, and rear of locking lugs ground as the last operation.

A good float tube like Bill Geissele's with index lugs, and ability to be made--and HELD--to perfect parallelism with the upper receiver. At least, if you have any intent to mount a scope forward. If not, then just get a good float tube that is rigid enough to hold up to abuse, and not flex under firing conditions.

All of this above being mounted to a good forged upper receiver. Billet is okay too. Just choose a good one, or let your smith, and put the receiver on tooling to determine if it's action face needs squared. This is a reallllly persnickety thing to do on a rifle who's bolt floats...but it has been done.

Finally, it should be made 100% certain all other normal procedures like gas tube alignment and float, and barrel nut torque are followed.

Feed this thing a diet of good brass, prepped as it can be, with NO quarter given to the mentality that "it's just an AR". Use Berger or Sierra bullets, premium powders, and BR primers.

You won't be disappointed.

-Nate

I think the OP wants an accurate varmint rifle, not a competition bench gas gun

 

[NyleRN]

More clarification. I can reliably hit black at 500 yards with irons. I want something that will hit sub MOA out past 500 with glass if I do my job. I am sure I would use it on varmits but for now only paper. The rifle is going to be my version of a DMR. From the sounds of it this is probably out of my skill level right now, might have to farm this one out.

Sub moa on a consistent basis can be achieved at 500 but you'll need to be an excellent wind caller using the .223 round. Be easier with the heavy Bergers but you'd have to hand feed the gun. Then that defeats the purpose of a gasser

 

[raptrbreth]

Plan on hand loading for this weapon. Didn't get deep enough into the research to see the OAL was going to be a problem.

 

[Woobie]

Sub moa on a consistent basis can be achieved at 500 but you'll need to be an excellent wind caller using the .223 round. Be easier with the heavy Bergers but you'd have to hand feed the gun. Then that defeats the purpose of a gasser

77 grain Sierra TMK's will feed, and they have a B.C. Of .420. Not saying that eliminates wind, but it definitely helps.

 

[padawan]

Sub moa on a consistent basis can be achieved at 500 but you'll need to be an excellent wind caller using the .223 round. Be easier with the heavy Bergers but you'd have to hand feed the gun. Then that defeats the purpose of a gasser

Hand feed due to COAL- correct?

 

[padawan]

77 grain Sierra TMK's will feed, and they have a B.C. Of .420. Not saying that eliminates wind, but it definitely helps.

We've had good luck with 69g TMK's but not out that far yet. Also like Noslers.

 

[NyleRN]

Hand feed due to COAL- correct?

Correct. When I say the heavy Bergers I mean the the 80 and 90gr pills. In order for the 77s to say supersonic at that range you need to start going up the ladder on charges. Then the load becomes compressed just trying to keep them mag length. I love the .223 round but it gets tough trying to go downtown with such lightweight bulllet

 

[AllenM]

Snap this upper on a lower and be done. I had one, you would not be disappointed.

6mmAR Turbo

 

[natdscott]

I think the OP wants an accurate varmint rifle, not a competition bench gas gun

NyleRN, I have read your feedback on my post. That having been said, as the Original Post said this:

I have built a few uppers now but am wondering what a gunsmith might do 'extra' that makes the upper better.

...and then he said this...

I want something that will hit sub MOA out past 500 with glass if I do my job. ...The rifle is going to be my version of a DMR.

...I gave credit that the Poster already knew a fair amount about AR rifles, and needed more information about what CAN be done. I provided that additional information to the best of my knowledge and ability; that happens not to be insignificant in regards to this particular rifle platform where accuracy and function are concerned.

Hey, I don't claim to know everything about anything.

But since you have challenged my position, I will defend it: My personal long-range AR is a true 1/2 Minute gun with irons, and barring a bad-batch of anti-sieze used on the paddle that caused it to hang up once, I have never had a stoppage in a match or in practice that was due to the rifle itself. I have yet to see the FIRST stoppage due to loads.

My matches are conducted in open fields under no cover, lying, sitting, or standing in the dirt (or mud), shooting in about any weather condition except tornadoes and lightning. It's been fired in -8 degrees through 101 degrees, and has continued to fire 10's and X's at 600 yards in so much rain that it was running out the magwell, then out the chamber when I got the rifle taken down to clean it. It has also served me as a field rifle quite well, albeit with the weights taken out of the guards and stock.

It's never seen a shooting bench in it's life, since my ranges don't even have benches.

If anybody thinks you can't have both extreme accuracy AND a fully functioning AR, then you don't know a great deal about the platform.

When I say the heavy Bergers I mean the the 80 and 90gr pills. In order for the 77s to say supersonic at that range you need to start going up the ladder on charges. Then the load becomes compressed just trying to keep them mag length. I love the .223 round but it gets tough trying to go downtown with such lightweight bulllet

OP: Nyle is correct here, inasmuch as stating that the 75-82 grain dedicated LR bullets are typically easier to shoot well at 5-600 yards. That having been said, even the elite Army Marksmanship Unit--at least until a few years ago--still gave the CHOICE to their shooters as to whether they used the 77 Sierra all the way through from 200-600 yards, or whether the shooter wanted to go to a dedicated 600 yard load using single-fed cartridges.

The 77 SMK is fine at 600, and the cannelured version of the same has been proven combat effective to 800+ yards in the near-nuclear Mk 262 Mod X loads employed in the Mark 12, and similar rifles. From magazine, the 77 SMK would be one of my first choices, unless I got some spectacular deal on the Berger version of the same, and it shot better in my rifle.

Personally, I do not like feeding autoloading rifles plastic-tipped bullets. It's been awhile since I heard of one, but the tips HAVE become dislodged. It a tip ends up RE-lodged in the wrong place, pretty bad things can happen; as I said, ARs do not blow up well.

As far as the loads are concerned, they are not really nuclear. Most guys end up running 23.5-24.5 grain RE-15 loads behind the 77 SMK, or an equivalent powder; while the load starts to lightly compress at 24.0 grains in most brass, with Wylde or similar chambers, it's not of great concern, and barrel life still runs 3,000-4,500 rounds, depending mostly on the pedigree of the barrel blank.

-Nate

 

[natdscott]

Plan on hand loading for this weapon. Didn't get deep enough into the research to see the OAL was going to be a problem.

If you get into the loading ideas, and need to bounce ideas around, feel free to PM me. IndyJohn is a good resource as well.

-Nate

 

[Jerryboy]

Does varmit=accuracy for your goals? Our rule of thumb is barrel+loads to match, trigger, glass. Then its up to the person pulling the bang switch.

I totally agree.