I’ve got a Spike’s Tactical SL-15 that I built from the ground up. The gun has roughly 6k through it. 3k Tula 55 grain steel and 3k various 55-75 grain brass (XM193, M855, M856, 5.56 Winchester, .223 Federal, .223 TAP). The gun has a 14.5" lightweight chrome molly 1/9 barrel, carbine gas system w/DD low pro GB, Spike’s M16 BCG, ST-T2 buffer, Tubb flatwire buffer spring inside a MilSpec buffer tube. All parts are still stock factory with no replacements added and has been flawless since day one.
Up until last weekend all brass would eject around 2 o’clock and steel would eject around 4 o’clock with no issues related to the build. While at the range Saturday I noticed my steel was ejecting at 2 o’clock and the last 10-15 rounds started keyholing (400 fired) at 25 yards. The keyholing was after a 30 round mag dump as well.
The week before I did some hot/cold barrel testing on various brass to test grouping. 75 grain TAP would group very tight with a cold barrel and XM193 would spread. When the barrel got hot (2x 30 round mag dumps) the results were just the opposite. TAP was showing a larger group and XM193 produced a very tight group. Steel was spreading hot or cold regardless.
I have read that a worn out barrel will case keyholing, but with only 6k fired and the unusual 2 o’clock case ejections I wonder if it’s ammo related or if it’s something else in the gun. I am very concerned about this so by all means please post your experiences/opinions. You guys are the pros here and have always looked to ya’ll for advise.
I would give the gun a huge cleaning first to make sure its not grime related.
if it indeed is worn out, a hammer forge barrel might be worth changing to since it seems you do a lot of shooting. However tho theres been some midlengths that have shot over 30k in non hammer forge barrels with no keyholing.
It is indeed possible the barrel is toast…I did the same thing with my first AR,(bushmaster) lots of mag dumps…5000 rnds later accuracy is gone, keyholing, yup, just a few mag dumps too many. In my case, a new barrel and I was back in business…Now, to the OP…you said in your post the barrel in question was a chrome moly barrel. If it’s not chrome lined, you may be able to save it…you’d have to pull the barrel and have it rechambered…very probably the throat is toast,Usually the rifling itself is in good shape, If the throat it self is gone, rechambering/rebarreling are your only options. I don’t know how much this would cost, But if it was me,I’d use this opportunity to upgrade to a higher quality barrel if possible. I’d consider either a CHF barrel from DD, BCM, or a Noveske barrel, and maybe back off the mag dumps…
If you’ve been doing magazine dumps your barrel’s probably toast by 6,000.
Any keyholing at all at 25 meters means the barrel’s gone. If you shoot at 200 and 300 yards you’ll either see bigger patterns or groups, or have un-called flyers and misses.
The are two ways to check – one cheap, the other requires some work.
Clean the barrel well – barrels wear at the throat where the bullet ogive first meets rifling grooves. You can find a throat erosion gage which drops in from the rear or has an angled handle and fits in from the ejection port. It’ll go in a certain distance depending on how it was originally chambered. You won’t know what it gaged as new, but it’ll give an idea of how far the bullet jumps smoothbore from the case mouth until it touches or engages the first rifling land.
The most effective way is to get a gunsmith to borescope your barrel so you can see with your own eye (if it’s a good borescope record it on tape or CD/DVD) how the heat from gases pushing the bullets out of the case mouths have eaten away your rifle’s throat, smoothed the beginning of the land, and if GI how much chrome has been worn away from both lands and grooves.
Stick the borescope in from the muzzle and you can see how much of the gas port hole has been worn away. Gas port erosion will give you an idea of how many rounds have been down your gun and does not affect weapon functioning – kind of like looking at tooth and gum wear on a dog, horse, or deer carcass.
I know your accuracy standards are probably different than mine and you don’t consider a barrel shot out until it keyholes, but I would have, for my target shooting purposes, considered it a tomato stake probably around 3,500 round when it probably wouldn’t have held a 3.5 MOA 10 ring.
If it were me I would just clean it and shoot it with new ammo and see if that fixes it.
If you are still getting keyholes, than I would buy a new barrel. I would not speed a lot of time and money trying to fix a chrome molly barrel with 6K down the tube.
Would I loose my grouping and noticed keyholing in a week or should it develope over time?
Last week I was grouping well out to 50 yards just pending hot/cold barrel and ammo used. The XM193 (hot barrel) and 75 grain TAP (cold barrel) grouped within a half dollar (no magnification as my AR has an Aimpoint H1).
ETA: Sorry for the half dollar comparision as I do not fully understand 1-3 MOA, sub MOA, etc.
In a nutshell 1 MOA (minute of angle) is basically a 1 inch pattern at 100 yards. That’s rounded off of course. For a more detailed explanation read here.
A gun that shoots greater than 3MOA is a failed gun that will not be accepted by gov’t, so 3MOA is what’s called the threshold (minimum performance level), with 1MOA being the objective (ideal performance level). Most fall well inside the spec, and the median for fielded gov’t guns is around 2MOA.
Quality of ammo will affect your print. If you’re testing, spend the money to use match grade ammo in the 55-62gr range.
Quality of the shooter affects it even more, so there’s that…
Your barrel still may or not be ganked. I’m sorta wondering if shooting ammo over 62gr in a 1-in-9 barrel may have contributed to what you’re seeing. I don’t know enough to say that shooting the heavier stuff will wear the barrel faster, but bullets longer/heavier than 62gr don’t stabilize well in your twist rate.
