AR Sponsor
Posted: 5/30/2010 7:29:51 PM EDT
| Any one try it with an AR, chrome lined or not, what type of results did you get? |
|
Fire lapping has its place, especially in hand-made, high precision barrels. These are the kind of barrels that someone pays an awful lot of money for, like $1,000 or more just for the barrel. On the other hand, an AR barrel of any kind will be a lot less expensive, and even the top of the line will be thoroughly finished and smooth-within reason.
There is a lot of lore about "chrome lined barrels aren't as accurate as unlined barrels," but these stories come from WAY back when Ordnance Corps first started playing with chromed chambers and then later chambers and bores. That was coming up on 50 (that is FIVE ZERO) years ago, and the science and techniques of the chrome lining process have improved a lot since then. Unless you compare a given chrome lined barrel with an otherwise identical unlined barrel in the most exacting test stands, I don't think anyone will be able to conclusively show that either is more or less accurate than the other. When they first started producing chrome lined AR barrels for the Army, the state of the art was not nearly as advanced as it is today-back then the integrated circuit was just a concept, and it was decades before more than a few transistors could be fitted onto a chip, yet today we have devices that have billions of transistors...this miniaturization trend also applies to hard chroming processes, as the plating/coating processes are closely related. In short, today's chrome lined barrels are for all practical purposes just as accurate as today's unlined chrome/moly barrels. |
|
It's a great theory and is possibly even corrent with regard to what the state of the art can achieve.
But then there is reality. The devil is in the details and not everyone wil pay te same atention to detail. Cost and prdouction time are also factors. If the original 50 year old chroming process meets mil spec and it is less expensive than the more exotic process needed to produce an uber smooth and accurate chrome bore - but one that "excessively" smooth for the usual AR purposes and accuracy required, the more exotic process is just not going to be used. Or you could look at it the other way, I just don't see the folks who make uber accurate barrels using any hard chrome processes as even with the best chroming technology available, you are just adding another variable and another area for inconsistency that won't help accuracy. So in the real world what we are talking about is the potential that hard chroming does not hurt accuracy as much as it used to. I will give you credit in terms that the average chrome lined AR barrel will still shoot way better than the average AR owner pulling the trigger, espcially in the current leaning toward tactical (and often just tacticool) shooting. But when real long range accuracy is required in a civilian application, chrome bores tend to be absent. When accuracy matters, fire lappingis also not in the picture. If you are spending $600-$1000 on a precision barrel, the last thing you are goping to want to do to it is fire lap it as the process is way to aggressive and on a barrel that has already been hand lapped, it is totally unneccesary and usually detrimental to accuracy, Fire lapping does have a place on a mid range production barrel on a rifle where accuracy is desired and excessive copper fouling is a problem due to an overly rough production grade bore. |
|
Quoted:
Good points here, really good ones. My post assumes we're not talking about barrels from "Joe's Storm Door and Rifle Barrels," but from a high quality producer, and that we're not talking about bargain bin or "factory seconds" barrels either.
It's a great theory and is possibly even corrent with regard to what the state of the art can achieve. Out beyond 300 yards or so, precision accuracy isn't the strong suit of any mass produced barrel; "acceptable" accuracy for a new, GI rifle at 300 yards is hardly "precise." Saving the $50 or so premium on chrome lined barrels because "they just aren't as accurate" is a false economy, particularly if the barrels in question come from reputable barrel makers. But almost any brand new barrel that wasn't made in a shed by someone with hand tools will shoot "better than most shooters." The question is how long it will keep that accuracy and how far beyond the shooter's skills the barrel is capable of. Fire lapping "may be" useful in tuning a fancy barrel to a specific diameter of bullet for pet loads, but as you say the $600-$1,000 range of barrels that are built to be precise won't need it. Their hand-lapped bores are as smooth as they're going to get-that's what you paid all that money for. This is also the reason that "barrel break in" is hooey; why would a maker spend all that time smoothing the bore if the leade is still rough? Lots of studies, formal and informal, have shown that barrels have particular preferences, and that it's possible that most barrels shoot more consistently when "somewhat dirty." But that's not what the "barrel break in" camp says... Anyway, when I buy a new barrel, I get it from someone who I trust to make a high quality, smooth and consistent barrel, and I won't even pause to consider that the bore could be "less accurate" because I choose a chrome lined barrel. But if I want long range precision, I'll go for something that's made to be more than "better than my skills" and is already as smooth and finished as it can be. Thought I misspelled a word, but I was wrong. |
| i have fire-lapped two AR's,, a colt H-bar and a B/M 20''. it makes cleaning LOTS easier, as a patch will glide right down the bore smoothly, and clean quicker. i really can't speculate on any accuracy gain, as i did not scope them before and after. however, i did not follow the ''full-deal-meal'' fire-lapping, i used about 1/2 the recommended number of shots, and started with 400 grit. the idea to me is to smooth the leade and throat, as hand-lapping will hardly address this. besides, hand-lapping is done back and forth, but fire-lapping sends the lapping the same way the bullet travels––––just something to mess with––-and,, i bought one of the NECO fire-lapping kits years ago when i was shooting heavy barrel varmit rifles a lot [ i swear it improved the accuracy of a savage 112 and rem 700 SSHB, also had both cryo'ed] |
| The problem with the CL bore is the bore has to be completely finished a little too big, then the CL added to make it the right diameter. Like the man said, depending on who's doing this there's a lot of room for inconsistencies in the thickness of the CL which has been ID'd as the cause of any accuracy difference from a decent non-CL barrel. These accuracy differences are minor for a combat carbine or rifle but could be apparent in high-accuracy shooting. There's really no valid reason to have a CL barrel in a semi-auto that uses non-corrosive ammo. However, both of mine are CL! To the question, you would not ordinarily use fire-lapping in a CL barrel - just shoot and clean. Also take it easy with the steel brushes and ultra-strong bore cleaners. A phosphor-bronze brush is adequate along with your regular CLP. I've only had one AR barrel that was unlined, and it is an Olympic 16" fluted HBAR 1:9. I never really gave it much of a test, but it certainly was accurate at the sight-in distance. My son has that AR now and he says it's 'pinpoint' at the distances he's tried - no long range shots. In fact, this is the only AR I've had where the rear sight was still centered after the sight-in. Maybe that has more to do with front sight installation than the barrel, but I think that barrel is a good one. |
AR Sponsor