On a plain old 5.56 chambered, Chrome lined, standard combat barrel... is there a bad or unsafe amount of leade?
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On a plain old 5.56 chambered, Chrome lined, standard combat barrel... is there a bad or unsafe amount of leade?
I don’t think it will become unsafe but the accuracy can drop off severely.
On a GI 5.56 barrel, no. Colt and FN barrels are throated long. As they wear the throat gets longer. Not necessarily unsafe but as you start getting gas blow-by and bullet free-jump (the space between the case neck and where the bullet ogive starts engraving on the leade on each land) you're not going to get the best accuracy out of that weapon.
Even with single-loaded 80-grain Sierra Match Kings the bullet ogive ain't going to touch unless that sucker's loaded WAAAAAAY long.
Off the top of my head a short-throated National Match rapid-fire barrel will mic cartridge overall length about 2.445 - 2.450 long. A USAMU Match throat is 2.500. A Colt or FN MILSPEC M16 or M4 is 2.500 to 2.550.''
If you borescope your weapon you'll see the throat show gas cracking and chrome wear advancing from the start of each leade along the top of each land about .001" per thousand rounds.
Load it up and shoot it.
OK. So I was looking at the 5.56 chamber drawing. It shows .146 leade.
I have pretty old bushy barrel that has a bullet jump of .177". Now that thing probably didn't start out with a mil spec leade. I'm just trying to get an idea if the barrel has a lot of life left in it.
If working with 5.56mm NATO layout, you could try to dredge up a barrel erosion gauge and just measure instead of guestimating.
Pull the BCG, drop the tool through the receiver into the bore and if it's a go, then all if fine, if it's beyond the limit line on the tool, its basically shot out.
http://pics.gunbroker.com/GB/2201120...x550880306.jpg
You could ask IG if he has a barrel erosion gage and check it for you.
A barrel erosion or throat gage is quick (it really doesn't tell you much).
A Stoney Point gage is better (you can gage the throat with the actual bullets you shoot instead of just a nominal gage diameter).
Borescoping gives you a visual.
Best performance standard is to actually shoot the weapon and determine if it meets your expectations.
Most folks who will NEVER shoot past 100 yards/meters it ain't going to matter. An IPSC or E-type is very forgiving.
If you plan on shooting further than 100 then you have to look at group size. Is a 2-8 inch circle at 200 OK for you? Is just hitting ANYWHERE on the target OK?
For me and a rifle or carbine if I'm not hitting on-call at 200, 300, and further then I need a new barrel. I can't stand shots off-call where I have no idea why the rounds or groups went there, or the groups are unexplainably big.
Barrels are a consumable. With a vise, action blocks, a wrench, and a headspace gage I can change one out in just a few minutes.
Scrub it clean. Shoot it until accuracy goes away, by whatever measure you use. Replace it.
I've seen barrels lose accuracy at 5K, and some still hold acceptable (minute of bad guy) past 15k.
If you're worried that it might go away any time soon, and you don't want to be caught short, then it is a simple calculation for you: balance the peace of mind of a new barrel, against the cost for same.
Only you can tell you how much cost is too much.
Hey, Patrick.
Good to see you post on here. I enjoy your handguns episodes with Aaron Rogers.
How is .177" guestimating? :confused:
The barrel seems to shoot good still. And yes, I do shoot it out to 400 plus yards on occasion... but usually on gongs... so I don't know what the groups are looking like.
I'm kind of wondering if the .177" is an alarming amount or just a small piece of the whole picture.
For comparison, I measured my brand new FNMI M16 barrel, and it was in the 140s. That's why I checked the diagram... I didn't know a 5.56 chambered barrel had that much leade from the get go.