Longevity, Accuracy Tips for the AR15

[bwaites]

IMHO don't waste your money on a torque screw driver. Buy a 1/4 torque wrench. You can use a 1/4 socket with a phillips bit in it or an allan socket to torque the screws in your mount. You'll get more use out of a good torque wrench than a torque screw driver, outside of your rifles.

Hard to find them calibrated in inch/pounds though in most hardware stores. And if they are, they are generally more oriented towards the automobile scales, 120 inch/pounds vs the 10-40 inch/pounds you use for scopes rings and such.

[Whelenon]

It's threads like this one that makes the price of admission worth being here. Thanks guys for all the advise.

Lacking an Upper Rec. Lapping Tool what is a good way measure or visually inspect to verify if the Receiver's face is true?

[cory]

Hard to find them calibrated in inch/pounds though in most hardware stores. And if they are, they are generally more oriented towards the automobile scales, 120 inch/pounds vs the 10-40 inch/pounds you use for scopes rings and such.

Amazon is your friend. It is mine.

http://www.amazon.com/gp/product/B000I7ZDN4/ref=wms_ohs_product?ie=UTF8&psc=1

[bwaites]

Amazon is your friend. It is mine.
5
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

Cory, that's an automotive tool. Torque wrenches become increasingly unreliable the closer you get to their limits, either up or down. The are most accurate right in the middle of their range. I throw out the bottom and top 10-20% of the range to avoid those inaccuracies. That wrench is probably reliable from 40-180 inch/lbs or so. Some specialists tell me I am generous, and they only use them within the middle 50% of range, throwing out the top and bottom 25%. That means its reasonably accurate from 60-160 inch/lbs. There are lots of things on rifles that need less than 20 inch pounds or about 20 inch pounds.

Rings are typically 13-25 inch/lbs, for instance.

[JohnOD]

I've been using a Borka Tool for rings, mounts etc. Its not inexpensive but good tools seldom are.

http://www.borkatools.com/

[Klem]

Apart from the dicussion over the accuracy of wrenches I like how the torque screwdriver is small, compact, and fits in a range bag. If you take it with you, you tend to use it. Unless you Loktite your ring and base screws/nuts you will find they will loosen, and at differing rates. To the feel it is done up but one will always be looser than the other. Going over all the screws before you shoot every time is as important as preparing the barrel and only takes a minute. Regardless of what the actual torque is the important thing is that all screws and bolts in an interface system are at exactly the same torque.

In answer to your question about how can you know if your receiver is exactly square to the barrel extension without buying a lapping tool. I'm thinking you could use a marker pen on the surface that is to mate and then (if your receiver lets you) gently rotate the barrel in the receiver while applying a little binding pressure. Then pull them apart and see if it has rubbed off evenly.

I agree with 52's take on the difference between bulk manufacturing, core competencies and 'OCD machinists' (made me laugh but it is true). The 45 minutes it takes to centre the barrel in the barreling fixture varies depending on how good the gunsmith is, but also how much run-out they are aiming for on the gauges. Do they care? Is it a Friday afternoon or a Monday morning? Do they like you? This is the part that always gets me... when you shell-out the dollars as they smile at you, you will never know.





This one is a Wheeler called the FAT ('Firearm Accurizing Tool'... the Marketing Department on fire!)

[LRRPF52]

The problem with trying to check receiver face true with a barrel is the indexing pin, and the angle of a sloppy barrel extension.

The lapping tool is the only practical answer I can come up with, but I'm sure a tool or die maker has $100's in tools that could probably pull it off as well.

The $22-$27 lapping tool seems like a much better option to me.

+1 for the torque drivers.

[Klem]

Yes, ignore my earlier suggestion about marker pen...the pin will prevent you rotating. It's held in the extension bash-fit and getting it out will be nigh on impossible.

[customcutter]

It's threads like this one that makes the price of admission worth being here. Thanks guys for all the advise.

Lacking an Upper Rec. Lapping Tool what is a good way measure or visually inspect to verify if the Receiver's face is true?

I agree it's worth twice the price of admission.

FYI, I did see one thread on AR accuracy where the builder used a surface plate and machinist square to check the top of the upper for squareness to the face of the threads. I really don't consider that an accurate way of measurement, what about the other 359* of the circle? Only way I can think of would be to use the lapping tool and lap it in.

[dave102269]

The lapping tool is the only practical answer I can come up with, but I'm sure a tool or die maker has $100's in tools that could probably pull it off as well.

The $22-$27 lapping tool seems like a much better option to me.

I have the lapping tool and have used it on a couple Spike's forged uppers with what I consider success. I'm about to assemble an upper on a Mega billet receiver and am concerned about using the lapping tool to check that it is true. If I spin the tool, it will remove the anodizing and open up the possibility of corrosion. Can I assume the Mega billet upper is true? Is corrosion an issue?

While I'm here...This is my first high end billet upper assembly. Will I need to use a torch to get the extension to mate with the receiver? Could one of you experienced guys elaborate on this process?

[NugginFutz]

The area where the lapping tool contacts your upper's interior is already subject to reciprocating friction from the BCG, as well as contact with the barrel extension. Also, the application of a good light oil on the lapping tool should go far in mitigating any incidental wear you might incur when using it. In the grand scheme of things, though, any wear from the lapping tool is in the noise, compared to what happens under normal operation. Further, don't overlook the fact that the anodized component of the upper is being deliberately removed at the mating surface. I've never seen any signs of corrosion with any of my lapped uppers, whenever they have been torn down for any reason. I invite the metallurgists in the Horde to comment further, and perhaps add insights on assembly greases.

I personally don't like making any assumptions about how straight anything is. If you wish to verify, a very few rotations with the tool will quickly reveal how square your upper is. (Refer to LRRPF52's photo, in post #1, as an example.)

As far as fitting your barrel to the Mega Billet upper goes, I seem to remember someone mentioning that they had to put their barrel in the freezer and, just before installing it, they put the upper in an oven. I further remember the OP had called the mfgr, who told them to do this. Anecdotal, to be sure, but that's how I remember it.

[customcutter]

I have the lapping tool and have used it on a couple Spike's forged uppers with what I consider success. I'm about to assemble an upper on a Mega billet receiver and am concerned about using the lapping tool to check that it is true. If I spin the tool, it will remove the anodizing and open up the possibility of corrosion. Can I assume the Mega billet upper is true? Is corrosion an issue?

While I'm here...This is my first high end billet upper assembly. Will I need to use a torch to get the extension to mate with the receiver? Could one of you experienced guys elaborate on this process?

The only area that the lapping tool should be removing the anodizing is where the shoulder on the tool contacts the front of the threaded section. As stated earlier see LRRPF52's pic. I would not put a torch of any type on the upper to expand it to fit over the extension, (unless you are from Great Britain, they call a flashlight a torch). I don't know the temperature at which aluminum starts changing it's heat treat characteristics, but I would recommend contacting the mfg before heating over anything that needs gloves to handle.

I'm working on my first AR build also, so don't take my word on it. I used to make custom knives and I know a quick pass with a torch to straighten a knife blade just out of heat treat will affect the heat treat and edge holding ability.

[Klem]

Fair enough, bearing in mind that part of the gun gets pretty hot during sustained fire anyway, so I suppose mild heating within reason is not completely out of the question.

[NugginFutz]

The only area that the lapping tool should be removing the anodizing is where the shoulder on the tool contacts the front of the threaded section. As stated earlier see LRRPF52's pic.

True story - it bears emphasizing that you are ONLY lapping the RIM of the threaded portion of your upper, not the interior. My somewhat wordy previous response was intended to help dave set aside his concerns about the tool doing any damage, elsewhere in the upper.

Lastly, I'm going out on a limb here to suggest you might consider not using a muzzle device at all. Pay particular attention to the crown and protect it religiously from damage and crud. If you screw on a muzzle device it tends to build crud quicker than not and this will affect accuracy. Consider having the barrel re-crowned if at all in doubt down the track, it's not a big job. You can even buy a hand crown reamer from Pacific Tool and Gauge with it's own pilot guide and do it yourself.

I hope there's room on that limb for more than one. I have brakes or flash hiders on all but one of my AR's. Guess which one I've never had to de-crud the muzzle on? While the brakes make for less recoil, I seriously doubt the 6.5 would be much more fatiguing to shoot without it, if at all.

I am seriously considering having my 22" threaded barrel cut down to 20 or 21, and putting a target crown on it My only regret is I won't be able to cut it to 21 3/4".

[LRRPF52]

There is no discernible wear from the lapping tool on the raceway inside the upper where the Bolt Carrier rides.

Do not use a torch on a heat-treated aluminum or steel part on the AR15 would be my advice. I have been able to do all the heating necessary with a hot air gun, which is used to loosen up Loc-tite and things of that nature. 7075 aluminum is about as hard as you want for a receiver.

The optimum answer would be to have a receiver that was trued before it is anodized, but I can't think of anything that would degrade the part with a trued face where the anodizing has been lightly skimmed. I've seen military guns where Marines had green-padded their M16A2's to make them "clean" for Command Inspections, and these guns had more exposure so salt and beach sand than the guys carrying them would ever see. Bare aluminum was visible on the upper & lower receivers.

You do have to be mindful of what greases you choose when assembling the upper, as some chemical elements may react with the aluminum. There is the account of the Ranger School student whose barrel fell off in Florida Phase, but they were doing a lot of waterborne patrols and something fishy was particular about his M4.