View Full Version : Help decide how to upgrade this old FSB Sabre Defence upper
I have this old upper that I still like, it had one of the early Sabre Defence 1:7 CL mid-length barrels. For those who've been around long enough to recall, Sabre made good barrels back in the day. This one will spew lead downrange in vast quantities without overheating and without drifting beyond about 1.5 - 2.0 MOA, depending on ammo. It's still a great shooter. As pictured it has: BCM MK2 lower, Geissele SSA-E trigger, the Sabre Defence barreled upper, the Troy quad rail, LMT fixed rear sight, T2.
Trying to decide whether, or how, to upgrade this upper to bring it into the 21st century. ;) The role it plays for me is it's my one remaining "KISS" rifle: fixed irons, with or without RDS. As shown with mounted T2, RVG, light, and rail covers, it weighs 8.2 lbs.
What I'd like to do ideally is...
* Go on a diet, get the weight down another half a pound or so if possible with this heavier barrel, while keeping a VG of some type.
* Upgrade the cheese grater Troy rail. Prefer an Mlok, and something that extends beyond the FSB to get any VG I use out a little farther.
What are good options to pull this off?
What I'm considering:
* Centurion C4 Mlok rail mid cut ( https://centurionarms.com/c4-m-lok-rail-mid-cut/ ). This should get the weight down since I can lose the rail covers, plus the rail itself is light and extends about 2.25" beyond the current Troy rail.
70764
I have Centurion rails on a couple 14.5 guns.
Probably close to favorites. One is a LW/minimalist carbine that I seem to grab frequently due to light weight.
Midwest Industries has a cutout M-LOK midlength handguard.
Moving to either a Daniel Defense or Scalarworks fixed rear sight should save a bit more.
You’d be hard pressed to find a nicer rail that uses the standard barrel nut made by anybody but Centurion.
Man. I have this sabre defense 14.5 middy that will spin apart 55 gr Hornady soft point for some reason. I never did figure out why. My first SBR used an 11.5 Sabre that was MASSIVELY over-gassed. This was back before "we" understood port sizes. The bolt would outrun the mag follower it was going so fast. Off topic Sabre chat. ;)
Man. I have this sabre defense 14.5 middy that will spin apart 55 gr Hornady soft point for some reason. I never did figure out why. I think I remember you posting about that before. Did you ever check what the actual twist rate is?
My Sabre barrel has been an absolute champ and has put up with a lot of abuse over the years, but it's getting pretty long in the tooth. Wish I could have bought another.
Not going to lie, I love the way it's set up right now and wouldn't change a thing. But if you DO the Centurion rails, like others have said, are outstanding. I have two of their MLOK rails and two of their quad rails and honestly I would get the quad with the middy cut out. Not sure that meets your weight goals. Or, and here's a thought, send the barrel out for a chop to 11.5 and Form 1 it?
Not going to lie, I love the way it's set up right now and wouldn't change a thing. But if you DO the Centurion rails, like others have said, are outstanding. I have two of their MLOK rails and two of their quad rails and honestly I would get the quad with the middy cut out. Not sure that meets your weight goals. Or, and here's a thought, send the barrel out for a chop to 11.5 and Form 1 it?
If that's a midlength, I think the shortest you're going to be able to go is probably 12.5. The gas port will need to be drilled to 0.075-0.078 too if it isn't already there.
If that's a midlength, I think the shortest you're going to be able to go is probably 12.5. The gas port will need to be drilled to 0.075-0.078 too if it isn't already there.
Good point on the length. Wasn't thinking about that. 12.5 would still be cool and he won't give up all that much over the 14.5 IIRC.
SuperOmega
08-28-23, 12:59
I have a 24" heavy fluted SS Sabre Defense 1:8" that also would spin apart bullets of 50gr and less. Fiocchi Extrema 40gr V-Max you would see the lead powder.
I think I remember you posting about that before. Did you ever check what the actual twist rate is?
I've never been able to do that Jag thing to check twist rate. That would actually be a good way to see if the barrel had any tight spots too.
I have a 24" heavy fluted SS Sabre Defense 1:8" that also would spin apart bullets of 50gr and less. Fiocchi Extrema 40gr V-Max you would see the lead powder.Makes me wonder what the actual twist rate is. Have you ever checked it to verify? I'd be surprised if it wasn't faster than 1:8.
I've never been able to do that Jag thing to check twist rate. That would actually be a good way to see if the barrel had any tight spots too. Do it. I'm curious.
SuperOmega
08-28-23, 14:22
I used a rotating cleaning rod a piece of tape (like depth flag for drill bit) and measured approx 7.7" per rotation.
Good ideas in the thread for shedding some weight.
After seeing some of the comments and running some numbers after changing to certain rails, swapping rear sight, etc, it's probably going to be difficult to significantly lighten up this upper; it's an uphill battle with that beefy barrel. Changing rail and maybe rear sight would shed a few ounces but not a lot. Now I'm toying with the idea of keeping it as-is, shoot it until accuracy degrades. And instead of investing approx $300 to upgrade a rail on an old upper that's probably 2/3 thru its useful barrel life, I'll put the $$$ into a new Centurion upper with a lighter barrel and the rail that I want.
Is the barrel a "government profile" or something else?
Do you use a hammer grip on the VFG? If you grip with part of your hand on the rail and part on the VFG don't you need some rail in front of it?
I used a rotating cleaning rod a piece of tape (like depth flag for drill bit) and measured approx 7.7" per rotation.I'm not surprised about the 40 grain stuff coming apart, but I am about the 50 grain.
Good ideas in the thread for shedding some weight.
After seeing some of the comments and running some numbers after changing to certain rails, swapping rear sight, etc, it's probably going to be difficult to significantly lighten up this upper; it's an uphill battle with that beefy barrel. Changing rail and maybe rear sight would shed a few ounces but not a lot. Now I'm toying with the idea of keeping it as-is, shoot it until accuracy degrades. And instead of investing approx $300 to upgrade a rail on an old upper that's probably 2/3 thru its useful barrel life, I'll put the $$$ into a new Centurion upper with a lighter barrel and the rail that I want. Probably the way to go. I will tell you though that those Sabre barrels have a lot of life in them, if reputation and my sample of one is any indication. You might consider getting the upper you want before things get weirder coming up to the election and just save your Sabre upper as a spare. 2 is 1 and 1 is none, and all that.
SuperOmega
08-28-23, 15:19
They do! My 16" carbine gas has around 12k rounds and chuggin.
Hammer_Man
08-29-23, 13:06
That setup looks like a battle tank as is. Looks like it could take a beating and keep chugging along without issue.
^Yeah it *is* kind of a tank, super tough, super reliable. But it kind of weighs like a tank too. :cool:
One related question about rail strength, since I considered moving away from the shorter quad to a longer Mlok (and also looking at the same type of rail change on an older SS410 BCM upper I have):
* Assuming a quality brand/model rail is used, does there tend to be a noticeable difference in precision/accuracy when you change out from a quad rail to an Mlok? I've read about issues like "deflection", and some argue that a quality-made quad rail is inherently stronger than an Mlok thus better for accuracy. I've not seen this firsthand on any rifles I've shot, but have heard it discussed often enough that you wonder if it's a real issue.
Hammer_Man
08-31-23, 10:29
^Yeah it *is* kind of a tank, super tough, super reliable. But it kind of weighs like a tank too. :cool:
One related question about rail strength, since I considered moving away from the shorter quad to a longer Mlok (and also looking at the same type of rail change on an older SS410 BCM upper I have):
* Assuming a quality brand/model rail is used, does there tend to be a noticeable difference in precision/accuracy when you change out from a quad rail to an Mlok? I've read about issues like "deflection", and some argue that a quality-made quad rail is inherently stronger than an Mlok thus better for accuracy. I've not seen this firsthand on any rifles I've shot, but have heard it discussed often enough that you wonder if it's a real issue.
Are you referring to the urban legend that says slim hand guards flex, therefore allowing the zero of your designator (PEQ-15, Dbal) to shift? Or are you referring to your weapon’s zero/POI shift?
Mainly thinking of the scenario of bipod use, and the potential impact of shifting POA/POI if a given type of rail has a tendency to be more 'flexy'. Again I haven't experienced that with my two Mlok rifles so far, but see the issue discussed a lot.
Mainly thinking of the scenario of bipod use, and the potential impact of shifting POA/POI if a given type of rail has a tendency to be more 'flexy'. Again I haven't experienced that with my two Mlok rifles so far, but see the issue discussed a lot.
Doesn't having the front sight affixed to the barrel avoid that problem? :confused:
If it's not broken, and you're only able to drop a few ounces, then it's completely not worth the effort or cost.
I'd keep it as is, shoot it like I stole it, and replace it when necessary. Another option is to get an upper assembly you want now, and keep the Sabre upper as a spare, or EOTWAWKI upper.
I plan to pick up a Centurion Carbine Cut-Out rail for a Colt upper. I almost never hear bad things about Centurion rails. I've got 3 of them, and have never had a complaint.
If it's not broken, and you're only able to drop a few ounces, then it's completely not worth the effort or cost.
I'd keep it as is, shoot it like I stole it, and replace it when necessary. Another option is to get an upper assembly you want now, and keep the Sabre upper as a spare, or EOTWAWKI upper.
Yep, makes the most sense after looking at all the options, small-ish impact on weight, and cost. Ordered a Centurion CM4/LW upper with the Mlok rail, that's what I really wanted anyway. :p Gonna keep this upper as-is for backup and occasional KISS training with irons.
Yep, makes the most sense after looking at all the options, small-ish impact on weight, and cost. Ordered a Centurion CM4/LW upper with the Mlok rail, that's what I really wanted anyway. :p Gonna keep this upper as-is for backup and occasional KISS training with irons.
This is the way.
Yep, makes the most sense after looking at all the options, small-ish impact on weight, and cost. Ordered a Centurion CM4/LW upper with the Mlok rail, that's what I really wanted anyway. :p Gonna keep this upper as-is for backup and occasional KISS training with irons.
I have an upper built with a Centurion SOCOM profile carbine 14.5 barrel and their carbine cut out quad rail. I've never weighed it but it feels heavy even without optics. Currently all it wears is a Scalarworks rear iron. I do prefer a lighter set up so it waits as a back up.
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