Range Report - Chupacabra
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Old 01-14-2013, 07:09 PM   #1
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Default Range Report - Chupacabra, an AR style carbine

I assembled an AR pattern carbine, using parts from various manufacturers. I named it Chupacabra. I took it to the range. Here is my story.





I began with 5.56 upper and lower receivers from J D Machine Tech for two reasons. I have used JD receivers before. They fit tightly with no play or rattles, and the finish is smooth and uniform. I was painfully unemployed and underemployed during the mid- to late ‘70’s, and I wanted to buy from a local business.

I selected a Bravo Company “recce” style barrel, machined from 410 stainless steel, with a 1-in-8” twist, medium profile, and mid-length gas port. I completed the upper with a BCM bolt carrier group, Samson Evolution hand guard, Benny Hill Rolling Thunder compensator, Badger Ordnance ambidextrous charging handle, and a J P Enterprises low profile adjustable gas block.

The lower receiver assembly sports a Timney 4 lb. trigger, Magpul ACS stock, enhanced butt pad, and enhanced trigger guard, B.A.D. ambidextrous safety with a hybrid lever on the off side, DoubleStar lower parts kit, Brownell’s carbine stock completion kit, Assault Planet bullet button, Falcon Industries Ergo Suregrip, and a superfluous set of KNS non-rotating pins.

Chupacabra weighs 7 pounds 8 ounces with no sights, optics, or magazine. Overall length is 39”, and the length of pull is 14 ¾” with the stock fully extended, which is how I leave it.

On December 21, I took the carbine to a local range with three objectives: function testing, adjustment of the gas block, and preliminary accuracy testing. I wanted to keep the round count low until I saw how it shot and cleaned up, so I could assess the need for break-in or fire-lapping procedures. I mounted a Burris Fullfield II 3-9x40 scope with a Leupold mount for the test.

On the 25 yard range I fired ten handloads consisting of Winchester 64 grain Power Points over 24.3 grains of Winchester 748 and Small Rifle Primers in Remington brass to adjust the gas block, zero the scope, and qualify the carbine for the 100 yard range. On the 100 yard range these handloads yielded an 8 shot group and a 5 shot group, both of which measured 1.90”! I wasn’t too concerned about the size of these groups because I haven’t gotten much better accuracy from these bullets in other firearms, because my eyesight is not good, and because I am just getting used to the idiosyncrasies of shooting the AR platform.

Ten handloads consisting of Sierra 69 grain MatchKing Hollow Point Boat Tails over 24.9 grains of Reloder 15 and Winchester Small Rifle Primers in Remington cases yielded five-shot groups measuring 0.95” and 1.50”.

The barrel cleaned up pretty easily, with no indication of copper fouling to speak of. I then mounted a huge Nikon Monarch 5-20x44 scope with a Nikon M-223XR mount for the next test.

On January 11 I returned to the range. A total of 34 rounds were fired at 100 yards during this session.

Four handloads consisting of Winchester 64 grain Power Points over 24.3 grains of Winchester 748 and Winchester Small Rifle Primers in Remington cases were fired to zero the scope. Five more rounds yielded a group measuring 1.10” (four rounds into 0.85”).

Fifteen handloads consisting of Sierra 69 grain MatchKings over 23.3 grains of IMR 4895 and Winchester Small Rifle Primers in Remington cases (range pickup) at about 2,550 fps yielded three groups measuring 1.10”, 1.00”, and 0.75”, for an average of 0.95”.

Ten handloads consisting of Hornady 75 grain Match BTHP’s over 21.7 grains of Reloder 15 and Winchester Small Rifle Primers in Remington cases (range pickup) at about 2,400 fps yielded groups measuring 0.85” (0.50”) and 1.00” (0.60”), for an average of 0.93”, or 0.55” without two fliers.

The average for the day (six groups) was 0.97”. Discounting the 64 grain Power Point group the average was 0.94”. Discounting the 64 grain Power Point group and two fliers the average was 0.79”. I will call the gun a 0.95” shooter without feeling like too much of a liar.

I will do further testing with the Sierra 69 grain MatchKings, Hornady 75 grain Match BTHP’s, and some Sierra 65 grain GameKings. I think with a little practice and load development I can get Chupacabra knocking down 0.70” 5 shot groups at 100 yards, consistently.

If not, I spent an awful lot of money to build a plinker!

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Old 01-14-2013, 08:17 PM   #2
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She's a beauty you must be proud congrats on your handmade AR

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Old 01-14-2013, 10:46 PM   #3
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DAMN!! i thought you nailed a chupacabra!!

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Old 01-14-2013, 11:17 PM   #4
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Quote:
Originally Posted by JonM View Post
DAMN!! i thought you nailed a chupacabra!!
No, Jon, I would never hurt a Chupacabra! You see, I have a soft spot in my heart for the Chupa. Allow me to explain.

Back in the day when I had a job, I ran across one of the stupidest, most outrageously comical fools I've ever seen, heard, or read about. This character was good for at least one act or statement every day that would cause you to struggle to keep from peeing in your pants. I'm not even exaggerating, people were laughing so hard they were pulling muscles, breaking their jaw bones, rolling around on the ground like mental patients. This guy was like something out of the Bible, if the Bible had a section about humans who acted stupider than jackasses. No kidding, monkeys would laugh at this guy, and marvel at what a buffoon he was.

The guys who worked for him, and they suffered terribly, nicknamed him Chupacabra.

At the time the real Chupacabra, the mythical creature which is actually real, was running amok in the Imperial Valley, killing numerous farm animals and pets, sucking their blood, and mutilating the corpses, then leaving the corpses where they could be found, so people would witness the awful power of Chupacabra, which obviously is real, because there could be no other explanation for all those horribly mutilated animal corpses littering the otherwise gentle and scenic Imperial Valley.

For several years, I was regularly convulsed with laughter by stories of the human Chupacabra, who supervised and tortured some very good friends of mine. After a few years of that, I could never hear the name "Chupacabra" without a broad grin grin splitting my face to the breaking point, no matter how miserable I was for other reasons.

Chupacabra. You just gotta laugh. If you didn't work for him, I guess. A few of those guys suffered legitimate emotional disorders, which is not funny, but maybe you just had to be there.

So when I decided to give a name to this carbine, I decided to give it a name that would make me smile, every time I picked up the gun. I'm smiling now. Chupacabra!

If this sounds strange to you, try spending some time with the hot Imperial Valley sun beating down on the top of your head. You'll know it's real. The Chupacabra is real. It is real.
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Old 01-14-2013, 11:51 PM   #5
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Lolololol!!!

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Old 01-15-2013, 06:47 AM   #6
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That is a funny story there!

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I'm gonna stop you right there, you just said an AR-15 is a high-powered rifle. It is obvious you don't know anything about guns and I shall ignore anything you say from this point on.

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Old 01-25-2013, 01:56 AM   #7
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LOL,That is funny LOL, great story and that rifle is art!

Khromo.! That barrel , (410 stainless), is that like "Molly" or hardened stainless ? That's making me drool,Beautiful! Heavy gun,recoil should be quite tame,sweet!

2400fps.......!

I read your post three times and each time ,something more profound catches my full attention! In man hours not that,that matters but a curiosity !
A"Guess-timation" ? And no,I don't mean laboriously but passionately!

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Old 01-25-2013, 03:30 AM   #8
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I am 60 years old and been around firearms most of my life. I have owned many and tinkered.
I've been a tool and die maker , custom machinist and understand the potential
of these machines.
Wow,you've just blown me away with this post and work of art.
Should I ever "Dumb luck out" Lottery , we have got to talk.
Thank you for that post!

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Old 01-26-2013, 09:22 PM   #9
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Hi, Dango! Bravo Company says the 410 stainless is harder and more corrosion resistant than the 416 used in most barrels. I settled on that barrel since my priorities were a 1-8" twist, mid-length gas, mid weight profile, and stainless.

I am not humping that carbine any distance, and I am not clambering in and out of humvees with it, so weight and length were not too important to me. At 7 pounds 8 ounces with no sights or optics, it is not too heavy for my purposes. The balance point is about an inch or two behind the pivot pin, and the weight is largely distributed between my hands, so it handles pretty well, but less than perfect.

The "Benny Hill Rolling Thunder" compensator adds a lot of weight and length to the end of the barrel, and a lighter and shorter alternative might have been a better choice for optimal handling characteristics. It keeps the sights on target, for sure, but I am not Joe Experience and there may be shorter and lighter comps out there that do as well. I must confess that I was concerned about the appearance of the finished product, and I only considered stainless muzzle devices.

I am pretty sensitive to recoil, and it is negligible with this carbine. I put the ventilated recoil pad on it to increase length of pull, but I can't imagine anyone complaining about the recoil even without it.

2,400 fps was the figure from the Hornady Handbook for this load, which was third from the bottom of six charge weights listed. They used a 20", 1-9" barrel in their load testing, so realistically Chupacabra was probably closer to 2,300 fps.

Are you asking how many hours the whole project took? I would break that into two elements: gathering the parts, and assembling the parts. I had already assembled two AR's when I cobbled this one together, so assembling the parts took much less time than it did for the first two. I probably spent two to four hours selecting and ordering the parts. The assembly took about three to four hours, including stripping and lubing the parts, coffee breaks, and stepping back to admire my "work."

I don't call this "building." I call this assembling, because it does not, for me, rise to the level of "building" something. Good quality, mil-spec parts require no real fitting. A guy with your background will probably find the assembly to be anticlimactic, even disappointing. If you were in a hurry, and had an organized work area, the assembly could be done within two hours. Easy. If there is anything to be proud of in this process, it is probably choosing components that work well together and fit the user's intended purpose.

F'ing nice guns, though! I've assembled three now, and two group under an inch, for 5 to ten 5-shot groups at 100 yards, in front of witnesses. The third did 1.10", and with a little load development I think I can get it under an inch. These groups are shot with handloads.

How about the bad news? When I first visited this site, I got the impression that "building" an AR was the one and only stairway to heaven, and anyone who bought an AR off the rack was a person of bad character, probably a child molester, because you could "build" a high-end custom AR for some outrageous savings over available alternatives. That idea is nowhere near the truth. There is a lot to be said for personalizing the gun to fit you and your intended use, but I believe the economy is grossly overstated.

Here is the itemized price tag for Chupacabra. It is a little inflated because my left-handed persuasion necessitated an ambidextrous charging handle and safety, the KNS pins aren't necessary with that trigger, and the compensator, butt pad, gas block, and a few other items suggest I am a pimp at heart, but you can get a feel for the darker side of this activity that some folks on this board don't seem to want to talk about!

Bravo Company recce barrel $308
Bravo Company bolt/carrier assembly 164
Samson Evolution forearm assembly 146
JD Machine Tech Upper Receiver 129
Badger Ordnance left hand charging handle 92
Benny Hill Rolling Thunder Compensator 85
Magpul MBUS Gen II Sights 79
J P Enterprises Low Profile Adjustable Gas Block 67
Sling adapter, QD 36
Les Baer Custom SS mid-length gas tube 13
Harford Engraving Ejection Port Cover 13
High Standard barrel nut 9
M G I D-Fender D-Ring 8
TTI Int. gas tube pin 2
Total cost of the upper $1,151

Timney 4 pound trigger 190
J D Machine Tech 5.56 stripped lower receiver 164
Magpul ACS Stock 94
B.A.D. ambidextrous safety with hybrid lever 70
Double Star lower parts kit 59
Brownell’s Mil-spec carbine stock completion kit 56
Spike’s Tactical heavy weight buffer 30
Assault Planet lock AR-15 bullet button 20
Falcon Industries Ergo Grip, SureGrip, ambidextrous 20
Magpul enhanced trigger guard 18
Magpul Enhanced Buttpad 17
J P Enterprises Tuned Carbine buffer spring 17
Double Star Twang Buster 5
Total cost of the lower $760

Chupacabra cost about $1,911, including sales tax, DROS, and shipping charges. I already had the tools, so I didn't factor that in there.

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Old 01-26-2013, 09:42 PM   #10
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Metallurgy? The stainless Hardness,is it a quenching process or just a high carbon compound ?

Future usage,Prone with By-Pod ?

100 YDS.,1 inch groups,"OUT-STANDING".!

Pimp on.BEAUTIFUL !!

Let me dissect this thread more and think!

I'll Be Baaacccckk...!!

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