Ruger SFAR small frame 308, 6.8 pounds

[doubloon]

So far you haven't addressed gas volume in your calculations

#1 That's because I really haven't been doing any calculations, just comparing like to like in system length and port diameter because the postulation was made that bigger brass requires a bigger gas port. I do not believe there is a direct correlation between gas port size and brass size.

#B I *think* I mentioned in one of those previous posts that I don't believe it's necessary to increase the size of the port to get more gas on the BCG ... supers vs subs prove this every day. I *think* I also mentioned something about "available gas" in one of the previous posts

#𑜳 Internal ballistics and pressures at gas ports change every time you seat a bullet. Powder, COAL, primer, brass, boolit ... the amount of shit that affects port pressure and volume boggles a computer simulation. i was trying to avoid this because gas port requirements can change based on internal ballistics within the same caliber or rifle or gas system length ... 300BLK subs vs 300BLK supers for example and one reason we have AGBs.

#四 if you want to banter about internal ballistics Constructor looks like an adequate foe

300 also uses faster burning powders than a 308
...
It's a piston gun ...

Si. Although I don't own a piston gun and don't know anything about them so I appreciate the lesson.

 

[TonyTheTiger]

#四 if you want to banter about internal ballistics Constructor looks like an adequate foe

Not looking for a foe, just didn't remember it being mentioned and if I was guessing I'd say it plays a greater role in port size than case surface area/chamber friction does.

 

[GreenGO Juan]

Not looking for a foe

Yep just trying to add to the think. Hopefully learn from it.

I'm not leaning into it needs a bigger gas port because it shoots a bigger boolit.

It's not the bigger bullet, it's the bigger case still under press when it's being extracted, grabbing the chamber walls.

I have hand loaded and shot over 8,000 rounds though a Small frame "AR308" with a ar15 sized bolt carrier, and played with many different powder and bullet types. It is more sensitive to powder type and charge than any other ar10(a real one) and AR 308 I have loaded for. It starts to show signs of early/aggressive extraction before it's heavier BC brethren.

You might not want to lean into it too hard, but I think there is a definite reason the light bolt carrier( less mass in motion) need more gas to reliably extract a fatter cases and fully cycle. Again this is a direct 5.56 to .308 comparison. As they use similar burn rate powders. Haveing a .308 with that light of mass make a much more sensitive system and needs to be recognized as such. Especially when you have hot loads with slow powder and a can.

My personal favorite load for run around pewing with a small frame, 15 sized BC .308 is a 110 vmax, IMR4198(fast powder, low port pressure). Muzzle velocity out of a 16 is mid 2900fps and shoots flatter than a 150 out to 600. After 600 it completely goes to shit, but inside of that is straight fire. Low recoil, Flat shooting, smooth cycling.

 

[doubloon]

Not looking for a foe, just didn't remember it being mentioned and if I was guessing I'd say it plays a greater role in port size than case surface area/chamber friction does.

Agreed. The sticktion factor can't be denied especially if one subscribes to the lore of lacquered steel cases.

But mass and spring tension seem like the biggest factors to be overcome and both gas pressure and volume need to be considered to balance the system. I tend to believe the difference in volume/pressure between 308 and 5.56 is one of the reasons a LR-308 can cycle reliably and smoothly with a port size nearly identical to the AR-15. This is also why I believe the SFAR is horrendously over-gassed with a 0.114"+ gas port.

 

[doubloon]

It's not the bigger bullet, it's the bigger case still under press when it's being extracted

Sure, I called it bigger brass a couple times, sorry if I confused you with the "boolit" word.

As mentioned before, 308 brass is bigger in every dimension, except maybe neck diameter, than 300BLK brass but 300BLK has a huge gas port in comparison to 308 in the same gas system length. There's a lot more at play than brass sticktion in determining gas port size.

As I have said multiple times, I believe an AR-308 needs more gas to cycle but that does not mean it needs a bigger port than AR-15. I also believe the sticktion thing is not as big a deal as superstition wants to make it. I believe it takes more force for 'primary extraction" in a AR-308 than a AR-15 but I do not believe this requires a bigger port. When somebody creates a rig that can measure case sticktion between different loads and calibers then I'll treat it with more significance than anecdotal observation. Everyone is, of course, allowed to put as much significance as they want on whatever they want but as long as there is documentation that speaks to AR-308 cycling reliably with a nearly identical port size to AR-15 then I'm going to stick by the idea that AR-308 does not need a bigger port than AR-15 to cycle reliably unless something is out of balance and then you'd be better off fixing the balance than just hitting it with a bigger hammer (gas port).

Again this is a direct 5.56 to .308 comparison

Again, in a direct comparison, the LR-308 with a bigger BCG, bigger brass, maybe a bigger buffer?, maybe a bigger spring? has a gas port nearly identical in size to the AR-15 for the same length gas system and both are slightly over-gassed from the factory which is why discerning shooters tend to install aftermarket AGBs.

Hand loads are always dicey when people start pushing the envelope of performance or when they just don't fully understand what they're doing. I'm perfectly willing to accept the fact that hot hand loads can cause any firearm to become unreliable or unsafe. But I expect every firearm I buy to handle factory ammunition safely and reliably. Some people look at my brass picture and want to say "dur, that's the way all my AR-308s work". But none of mine do and none that belong to anyone else I know "work" that way. I'm OK with people being happy with shit firearms that function poorly or dangerously, they're just not going to sell me on the idea that this is how things should be.

Somebody on another forum had a 16" SFAR before Ruger said "DOH! We overgassed it bad. We have a new regulator for anybody with a 16" SFAR who wants one.". But only after his FCG was blasted down into the trigger guard of his lower. He sent the 16" back to Ruger, they said there's nothing we can do to repair this it is destroyed, we can give you a new rifle. He got them to send him a 20" as a replacement which he sent off to a smith to have the barrel chopped and reduce the dwell time before he attempts any other tweaks.

Another guy here at SH, either on this thread or another one, I *think* replaced the Ruger AGB with an aftermarket AGB, maybe some other parts as well, so he could further reduce the adjusted port size even smaller than the min ~0.06x" on the Ruger factory AGB. He says his rifle runs fine now, even with bigger brass.

I sent my rifle back to give Ruger a chance to fix this issue and I'm trying to raise awareness that the SFAR may be unsafe with some factory ammo and some hand loads. If all you ever shoot in it is NATO ammo or cheap range blaster stuff you may never have a problem.

If Ruger can't or won't fix the rifle then I'll try to fix it myself and publish the results. If I can't fix it I'll sell it cheap with all the original parts to anyone who thinks this is the way AR-308s are supposed to work.

 

[GreenGO Juan]

Sure, I called it bigger brass a couple times, sorry if I confused you with the "boolit" word.

As I have said multiple times, I believe an AR-308 needs more gas to cycle but that does not mean it needs a bigger port than AR-15. I also believe the sticktion thing is not as big a deal as superstition wants to make it. I believe it takes more force for 'primary extraction" in a AR-308 than a AR-15 but I do not believe this requires a bigger port. When somebody creates a rig that can measure case sticktion between different loads and calibers then I'll treat it with more significance than anecdotal observation. Everyone is, of course, allowed to put as much significance as they want on whatever they want but as long as there is documentation that speaks to AR-308 cycling reliably with a nearly identical port size to AR-15 then I'm going to stick by the idea that AR-308 does not need a bigger port than AR-15 to cycle reliably unless something is out of balance and then you'd be better off fixing the balance than just hitting it with a bigger hammer (gas port).



Again, in a direct comparison, the LR-308 with a bigger BCG, bigger brass, maybe a bigger buffer?, maybe a bigger spring? has a gas port nearly identical in size to the AR-15 for the same length gas system and both are slightly over-gassed from the factory which is why discerning shooters tend to install aftermarket AGBs.

Hand loads are always dicey when people start pushing the envelope of performance or when they just don't fully understand what they're doing. I'm perfectly willing to accept the fact that hot hand loads can cause any firearm to become unreliable or unsafe. But I expect every firearm I buy to handle factory ammunition safely and reliably. Some people look at my brass picture and want to say "dur, that's the way all my AR-308s work". But none of mine do and none that belong to anyone else I know "work" that way. I'm OK with people being happy with shit firearms that function poorly or dangerously, they're just not going to sell me on the idea that this is how things should be.

Somebody on another forum had a 16" SFAR before Ruger said "DOH! We overgassed it bad. We have a new regulator for anybody with a 16" SFAR who wants one.". But only after his FCG was blasted down into the trigger guard of his lower. He sent the 16" back to Ruger, they said there's nothing we can do to repair this it is destroyed, we can give you a new rifle. He got them to send him a 20" as a replacement which he sent off to a smith to have the barrel chopped and reduce the dwell time before he attempts any other tweaks.

Another guy here at SH, either on this thread or another one, I *think* replaced the Ruger AGB with an aftermarket AGB, maybe some other parts as well, so he could further reduce the adjusted port size even smaller than the min ~0.06x" on the Ruger factory AGB. He says his rifle runs fine now, even with bigger brass.

I sent my rifle back to give Ruger a chance to fix this issue and I'm trying to raise awareness that the SFAR may be unsafe with some factory ammo and some hand loads. If all you ever shoot in it is NATO ammo or cheap range blaster stuff you may never have a problem.

If Ruger can't or won't fix the rifle then I'll try to fix it myself and publish the results. If I can't fix it I'll sell it cheap with all the original parts to anyone who thinks this is the way AR-308s are supposed to work.

And the reason I have not bitten to hard on relationship to a normal Ar-308 is because this is not an ar 308. Infact was trying to highlight how different they are.

Yes a cartridge with a slower burning ball powder, like remmington soft point 180’s with an unknown suppressor, is going to be dicey and difficult to tune and possibly show signs of early extraction. Like you are seeing. The popped primers raises an eyebrow. That is weird. But that was also with an un crimped primer with an unknown suppressor.

I think the expectation that its going to operate to your expectations, exactly like an ar-308, with all types of ammo and suppressor combs is asking too much and a bit unrealistic.

Its going to take some tuning. As mentioned a different gas block is a potential answer if you plan on a wide variety of ammo or with/without a can, Different buffers and what not.

The way i see it is. You can tune the gun to work with the ammo, or find/tune the ammo to work with the gun.

Good luck with it.

 

[doubloon]

And the reason I have not bitten to hard on relationship to a normal Ar-308 is because this is not an ar 308. Infact was trying to highlight how different they are.

Agreed. It is a breed on it's own but not entirely unlike a POF Revolution which I think has a similar sized BCG at least visually as referenced in a video posted by a member here ... video link at the bottom. The BCG between the two is similar in size/weight but the SFAR recoil spring is huge byu comparison. I have no experience with the POF Revolution so I don't know the size of the gas port and I don't know if the POF chews up brass and pops primers. But I think the POF is a piston gun as well? So it may not be good data to compare to a SFAR.

I think the expectation that its going to operate to your expectations, exactly like an ar-308, with all types of ammo and suppressor combs is asking too much and a bit unrealistic.

This may be true and I have acknowledge this possibility. But I don't think it's too much to expect a commercial rifle to provide proper support for primers. I also think it's odd/weird/problem that in the 5 cases posted in my picture 3 have loose primers, 4 have chewed bases but 1 looks relatively unmolested ... all 5 round shot within seconds of each other on the same settings with the same suppressor. I think in addition to being over gassed it's unlocking early when there's still too much pressure in the case. But I don't know how to prove it's unlocking early.

The way i see it is. You can tune the gun to work with the ammo, or find/tune the ammo to work with the gun.

100%. Even with my current AR-308 and my poodle shooter I have the gas set to cycle the weakest ammo I shoot regularly. The really cheap 5.56 stuff that comes in clips (I forget what it is) doesn't cycle reliably but PMC "bronze?" works fine and Hornady Black and more. The AR-10ish is set up the same way, cycles PPU and CoreLokt alike with no drams but there is some weaker stuff that gives it hearburn.

But on both my rifles I feel safe shooting the hottest OTS ammo available ... right now not so much with the SFAR.

 

[GreenGO Juan]

Agreed. It is a breed on it's own but not entirely unlike a POF Revolution which I think has a similar sized BCG at least visually as referenced in a video posted by a member here ... video link at the bottom. The BCG between the two is similar in size/weight but the SFAR recoil spring is huge byu comparison. I have no experience with the POF Revolution so I don't know the size of the gas port and I don't know if the POF chews up brass and pops primers. But I think the POF is a piston gun as well? So it may not be good data to compare to a SFAR.


This may be true and I have acknowledge this possibility. But I don't think it's too much to expect a commercial rifle to provide proper support for primers. I also think it's odd/weird/problem that in the 5 cases posted in my picture 3 have loose primers, 4 have chewed bases but 1 looks relatively unmolested ... all 5 round shot within seconds of each other on the same settings with the same suppressor. I think in addition to being over gassed it's unlocking early when there's still too much pressure in the case. But I don't know how to prove it's unlocking early.


100%. Even with my current AR-308 and my poodle shooter I have the gas set to cycle the weakest ammo I shoot regularly. The really cheap 5.56 stuff that comes in clips (I forget what it is) doesn't cycle reliably but PMC "bronze?" works fine and Hornady Black and more. The AR-10ish is set up the same way, cycles PPU and CoreLokt alike with no drams but there is some weaker stuff that gives it hearburn.

But on both my rifles I feel safe shooting the hottest OTS ammo available ... right now not so much with the SFAR.

Yeah the popped primer thing is very odd.

It was factory ammo right? Not someones reloads in a factory box.

Did gas escape and cut into the the bolt face?

 

[doubloon]

Si, factory ammo. I haven't reloaded 308 in quite a while because I'm protesting primer prices. The left over primers I have I use for 45-70 subs.

Among other things I neglected to inspect in detail before sending it back was the bolt, didn't even take a picture. Not a real gunsmith so I don't think like one. Just a tinkerer who hasn't lost any fingers yet.

Tracking says it will be back here on the 18th so I should be able to see if Ruger put any details on the work order other than "works for me". I did take measurements of the old regulator valve so I'll be able to figure out on my own if that changed and I should be able to tell if they replaced the barrel based on how dinged up the muzzle face was when I got it.

 

[doubloon]

SFAR came home early.

Work order says

ITEMS REPLACED: BOLT
ITEMS REPAIRED: GAS REGULATOR AND GAS PORT

I'm not sure how they "repaired" the gas port. They say they fired 20 rounds of Federal and Aguila without malfunction but that doesn't mean it still isn't chewing brass.

The muzzle is too covered in crud for me to know for sure if it's the same barrel but I'll scope it later to see if the port changed size and take the regulator apart to put some calipers on it.

After I clean it, scope it and measure some parts I'll take it to the range as "repaired" so see if anything is different. I don't expect it to be.

Feels like the same recoil spring. I think the "engineers" who developed this gun drilled a hole in the barrel big enough for it to double as a snorkel then kept putting bigger springs in it until the brass started flying between 3-4 o'clock because THAT's the mark of a truly quality rifle, brass that flies to the right and a little back ... even if it's in multiple pieces.

 

[wvfarrier]

I wonder if Ruger has the name and staying power to make this stick. DPMS Gii didn’t stick. The POF revolution is cool, but who’s got one? A small frame, light weight, semi auto 308 checks a lot of boxes. But, there’s still a lot of questions…

I have had two of the Revs and got rid of both

 

[Charmingmander]

SFAR came home early.

Work order says

ITEMS REPLACED: BOLT
ITEMS REPAIRED: GAS REGULATOR AND GAS PORT

I'm not sure how they "repaired" the gas port. They say they fired 20 rounds of Federal and Aguila without malfunction but that doesn't mean it still isn't chewing brass.

The muzzle is too covered in crud for me to know for sure if it's the same barrel but I'll scope it later to see if the port changed size and take the regulator apart to put some calipers on it.

After I clean it, scope it and measure some parts I'll take it to the range as "repaired" so see if anything is different. I don't expect it to be.

Feels like the same recoil spring. I think the "engineers" who developed this gun drilled a hole in the barrel big enough for it to double as a snorkel then kept putting bigger springs in it until the brass started flying between 3-4 o'clock because THAT's the mark of a truly quality rifle, brass that flies to the right and a little back ... even if it's in multiple pieces.

This has been my worry since the gun came out. Some people questioned the bolt but given Ruger's presence in aerospace manufacturing that wasn't my concern. Gassing was.

Glad I held off on purchasing after reading this thread. I'll be waiting on your range report.

 

[doubloon]

LIARS!

Pulled some of the gunk off the muzzle and the dings present are the same as the dings on it when it came from the factory so same barrel.

Put a scope down the bore and the port, at least from the inside, is unchanged. Same size, same scab on the edge.

*MAYBE* they changed or "repaired" the regulator but if they did the made it worse. The #3 aperture still measures 0.114", the #1 aperture still measures 0.068" BUT either I measured the #2 aperture wrong the first time or it's bigger now at 0.103" ... #%#% ... if anything now it's even MORE over-gassed on setting #2. Need to find someone with a new SFAR 20" to get some comparative measurements.

I can't tell for sure whether or not they replaced the bolt but let's just say they did. The bolt face on the new one is still smeared with brass on every surface and there are brass chips everywhere in the bolt face and in the lugs in the barrel extension.

They did fuck all to address any issues. They just ran maybe a half a box each of lightweight range blaster ammo through it and sent it back dirty.

The amount of gas coming down that tube is still spinning that unlock cam hard enough and fast enough for the ejectors to shear brass off the base of those cases.

I don't see any point in taking it back to the range as it is. I'll be buying a new adjustable block and one or two recoil springs for playing with at the range to see if this rifle is even salvageable.

 

[doubloon]

I have had two of the Revs and got rid of both

This is saddening as well.

After the experience with the SFAR I was starting wonder if maybe the Rev is worth the money and the hype.

DPMS is still king of the hill as far as I can tell.

 

[Charmingmander]

Distressing to be sure. I handled a SFAR at my LGS Sunday and noticed the bolt on that one had brass smearing even though it was brand new.

Here's hoping PSA's DPMS Gen 2 revival goes well I suppose.

 

[doubloon]

brass smearing even though it was brand new

Probably test firing as part of production.

According to the WO they used "Federal and Aguila" to test fire my rifle before sending it back. No specifics provided but I assume cheap/weak blaster ammo because their goal is to make it cycle with basically anything off the shelf no matter how crappy. Probably because most of the people who complain something is wrong with their rifle are shooting the cheapest stuff they can get shipped.

The barrel had white-ish residue the whole length of the barrel, maybe ash, maybe salts ... who knows.

It's going to be a week or so before I make the changes and get back to the range but I'll post results then and maybe have a rifle for sale cheap.

 

[doubloon]

Just pulled the gas block off in prep for ordering parts and measured the port in the barrel.

1/8" diameter tunnel (0.126x")

ETA:

It has plenty of wiggle room ... what's the ID of a 1/8" roll pin? can I buy/make a sleeve for it like an engine cylinder?

 

[hlee]

Ought to have plenty of gas , and a lot of room to play once you get an appropriate adjustable gas block...

 

[LRRPF52]

7.62 NATO/.308 Winchester are the types of cartridges that push into a space where the body mass of the person firing them in a semi-automatic carbine or rifle comes into consideration, especially when you start stepping into lighter weight rifles. For big dudes with lots of upper body mass, it isn’t as much of a problem. For people with smaller upper body mass, like manlets, smaller females, and adolescents who aren’t overweight/obese, it’s a tall order to expect reliable function.

I’ve never had a problem shooting the legacy battle rifles of the 1950s (FAL, G3, M-14, AR-10) if they are built right, but I think once we start dropping the firearm weight with a 7.62 NATO carbine, things can get out-of-hand.

One of the rules of thumb they used at ArmaLite in the 1950s was a ratio of carrier mass to bolt mass. Carrier momentum with that mass ratio proved to be sufficient to support extraction and full cycling distance to facilitate reliable self-loading function of the reciprocating mass relative to the magazine and bolt hold-open (if present).

So I looked at my DPMS LR-308 BCG from my .260 Rem:

Carrier: 432g
Bolt: 78g

5.54 ratio

Then my Savage MSR-10 Small Frame (Mid-Sized between SR-25 and AR-15)

Carrier: 346g
Bolt: 78g

4.44 ratio

We know that the POF Rogue and Ruger SFAR use AR-15 carriers.

If you can weigh those 2 components from the SFAR, you’ll see an even lower ratio, though the bolt mass is a lot lower than on the larger AR-10s.

I think it’s asking a lot of the Small Frame .308 BCGs to extract and cycle reliably across a wide range of body mass shooters from such a lightweight frame and overall firearm weight. When you go really lightweight with .308, things get outside of the optimum window of masses and recoil.

 

[doubloon]

That makes some sense even though I hadn't considered it. Kinda like hold sensitivity in springer air guns or limp wristing?

I *think* the SFAR bolt has some titanium parts, I'll have to try to weigh it all out. Is that carrier weight the "bare" carrier or does it include the firing pin, etc.?

Fortunately, I'm the primary shooter so mass behind the stock shouldn't be an issue.

 

[LRRPF52]

SFAR bolt and barrel extension are made from exotic aerospace alloys, likely AerMet if I were to guess.

Titanium would not work.

The weights are stripped of cam pins, firing pins, and firing pin retaining pins. The Savage MSR-10 has a sprung firing pin with a triangular shaft, like the old Alexander Arms firing pins we used to see in 6.5 Grendel factory rifles.

 

[doubloon]

You're probably right, it's probably the firing pin that's made of titanium.

 

[Constructor]

Agreed. The sticktion factor can't be denied especially if one subscribes to the lore of lacquered steel cases.

But mass and spring tension seem like the biggest factors to be overcome and both gas pressure and volume need to be considered to balance the system. I tend to believe the difference in volume/pressure between 308 and 5.56 is one of the reasons a LR-308 can cycle reliably and smoothly with a port size nearly identical to the AR-15. This is also why I believe the SFAR is horrendously over-gassed with a 0.114"+ gas port.

The piston inside the AR10 carrier is larger than the one inside a small frame 308 AR. larger area =more force even at a lower pressure.

 

[doubloon]

The piston inside the AR10 carrier is larger than the one inside a small frame 308 AR. larger area =more force even at a lower pressure.

Agreed. Physics is going to do what physics does.

I assume, without any proof other than the testimony of Tactical Machining, that more force will be delivered at the key between 7.62 and 5.56 if the gas systems are as identical as they can be (same port size, same tube diameter/length, same dwell time, same gas block).

FWIW, the bolt in my SFAR weighs ~44.4g and the bolt from my AR-15 weighs ~43.2g

The actual gas rings on the SFAR bolt are right at 0.50" diameter and the main body of the bolt is right at 0.51" diameter, I *think* this is pretty close to AR-15 dimensions so very close to the same surface area.

I *think* the primary reason for the gas in the tube that hits the key is for the unlock? And residual chamber pressure is the primary driver of extraction/ejection? ETA: There's a lot of focus on the bolt weight/dimensions and I could be wrong but I think the gas entering the key pushes the carrier away from the bolt to accomplish but unlock. The force to move the weight of the bolt seems to be more a function of just getting dragged along with the carrier by the residual chamber pressure once it's unlocked?

On sheer mass and dimensions alone the numbers would seem to point to the idea that the SFAR would need about the same amount of gas/pressure on the key to unlock as an AR-15 but that doesn't take into account residual chamber pressure.

 

[CRT2]

Observations from owning and shooting an SFAR Model 5611, 20” barrel. Ammunition used: Hornady TAP 80965 the 168 gr A-MAX. Shooting distance of 106 yards measured using SIG Kilo 2400 ABS range finder. Scope is Vortex PST2 3-15, FFP MOA and scope base is a Vortex one piece mount. Rifle, scope and mount weigh 9.2 lbs. Weather was sunny, 89 degrees, humidity 70%, and pressure 30.12.

Fired 60 rounds to zero, determine accuracy and as part of the 200 round break-in. Gas left on setting 3. Average velocity was 2630 using LabRadar. Accuracy was MOA or better. I am limiting factor on accuracy (76 and onset of essential tremors).

I experienced 3 failures to eject. When they occurred I believe I was not firmly holding the rifle - similar to cycling problems with a 1911 with a weak grip (limp wristing). Didn’t see damage to brass, however, I didn’t inspect every piece of brass.

I am happy with this rifle but will install a LimbSaver recoil pad and replace the charging handle with an Aero Precision Ambidextrous Handle.

 

[Charmingmander]

Just pulled the gas block off in prep for ordering parts and measured the port in the barrel.

1/8" diameter tunnel (0.126x")

ETA:

It has plenty of wiggle room ... what's the ID of a 1/8" roll pin? can I buy/make a sleeve for it like an engine cylinder?

View attachment 8186918

That's fucking clown shoes

 

[EzGoingKev]

Just pulled the gas block off in prep for ordering parts and measured the port in the barrel.

1/8" diameter tunnel (0.126x")

ETA:

It has plenty of wiggle room ... what's the ID of a 1/8" roll pin? can I buy/make a sleeve for it like an engine cylinder?

View attachment 8186918

Is that a 16" or 20" barrel?

 

[doubloon]

Gas left on setting 3

Cool, glad you like it.

Do you ever plan to shoot it on any setting other than 3?

 

[doubloon]

Is that a 16" or 20" barrel?

Mine, the one in the picture with the 1/8" punch wiggling in the gas port is a 20" model 5611

 

[CRT2]

Cool, glad you like it.

Do you ever plan to shoot it on any setting other than 3?

Yes, after the 200 rounds.

 

[MadDuner]

Just pulled the gas block off in prep for ordering parts and measured the port in the barrel.

1/8" diameter tunnel (0.126x")

ETA:

It has plenty of wiggle room ... what's the ID of a 1/8" roll pin? can I buy/make a sleeve for it like an engine cylinder?

View attachment 8186918

I don't claim to know a single thing about gun design or any of the finer details of gas gun operation, so those of you who do understand the mechanics of the design - help me understand.

So here's my question:
Since the barrel diameter is larger on a 30 cal vs 22 cal barrel - which allows the gas to escape easier.... isn't the larger gas port required then to get enough volume in the gas tube to compensate for the less pressure in the barrel?

 

[doubloon]

Since the barrel diameter is larger on a 30 cal vs 22 cal barrel ... isn't the larger gas port required then to get enough volume in the gas tube to compensate for the less pressure in the barrel

No.

Differences in pressure, BCG weight, buffer weight, spring weight, dwell time, yada yada all have to be accounted for to properly balance the system

Barrel diameter plays a role but it is not the only factor or the deciding factor.

The barrel diameter for a 7.62x39 is the same as the barrel diameter for a 7.62x51, the port for a rifle length gas system for a 7.62x39 runs about the same as what they installed in the SFAR. The port in the 7.62x39 needs to be larger because there is less gas/pressure available to move the BCG and force the bolt unlock.

Counter to that ...

The barrel diameter for a 7.62x51 (AR-308) is larger than the barrel diameter for 5.56 but the port for a (successful) rifle length gas system in both is nearly identical even though the AR-308 has a heavier BCG, heavier buffer and heavier spring. There would seem to simply be more gas/pressure available in the AR-308 so you don't *need* a bigger port to deliver more gas/pressure than 5.56 for the unlock.

What Ruger did, in all their wisdom, is put a BCG and buffer nearly identical to a 5.56 BCG and buffer in their rifle with a maybe 20% heavier than 5.56 spring and then drilled a 30%+ larger hole than normally required by anyone else (I know of) in AR-308 or AR-15 business.

AR-15 Gas Port Sizes

Information to help you decide which gas port size may be suitable for your build

tacticalmachining.com

 

[EzGoingKev]

What Ruger did, in all their wisdom, is put a BCG and buffer nearly identical to a 5.56 BCG and buffer in their rifle with a maybe 20% heavier spring and then drilled a 30%+ larger hole than normally required by anyone else (I know of) in AR-308 or AR-15 business.

Yes but they also put on an adjustable gas block that restricts the gas flow. While Ruger went huge on the port size and blew it in execution I would think having a larger gas port would be something you would want with this type of configuration.

 

[doubloon]

they also put on an adjustable gas block that restricts the gas flow

The port in the SFAR barrel is ~0.126" ... HUGE ... bigger than anything else

The #3 valve in the SFAR AGB is ~0.114" ... HUGE

The #2 valve in the SFAR AGB as returned to my by Ruger CS is ~0.103" ... HUGE

The #1 valve in the SFAR AGB is 0.068" and still over gassed

The port in my LR-308 would seem to be ~0.096" as reported by Tactical Machining (I've never measured it myself) even with a heavier BCG and a heavier buffer than the SFAR and the LR-308 was over gassed to the point of denting cases upon ejection before I installed a JPE AGB and adjusted it ... no more dents

The SFAR AGB restricts the gas flow insufficiently ... Ruger failed

But some people are OK with mutilated brass and everything that goes along with over gassing and they are entitled to be happy with a less than optimally functioning firearm.

 

[45-90]

Yep just trying to add to the think. Hopefully learn from it.

It's not the bigger bullet, it's the bigger case still under press when it's being extracted, grabbing the chamber walls.

I have hand loaded and shot over 8,000 rounds though a Small frame "AR308" with a ar15 sized bolt carrier, and played with many different powder and bullet types. It is more sensitive to powder type and charge than any other ar10(a real one) and AR 308 I have loaded for. It starts to show signs of early/aggressive extraction before it's heavier BC brethren.

You might not want to lean into it too hard, but I think there is a definite reason the light bolt carrier( less mass in motion) need more gas to reliably extract a fatter cases and fully cycle. Again this is a direct 5.56 to .308 comparison. As they use similar burn rate powders. Haveing a .308 with that light of mass make a much more sensitive system and needs to be recognized as such. Especially when you have hot loads with slow powder and a can.

My personal favorite load for run around pewing with a small frame, 15 sized BC .308 is a 110 vmax, IMR4198(fast powder, low port pressure). Muzzle velocity out of a 16 is mid 2900fps and shoots flatter than a 150 out to 600. After 600 it completely goes to shit, but inside of that is straight fire. Low recoil, Flat shooting, smooth cycling.

So the small frame 308 is going 2900 fps with 110 gr bullet...the AR 15 300 hamr does 2876 with 110 Varmageddon with 29.3 gr of AA 1680, in 18" 300 Hamr barrel. The 150 gr at 2398 26.8 gr CFE Blk with 8.0 S/D and a .264" 5 shot group at 100 with a little 300 Hamr no issues, with feeding or ejecting. Light AR 15 with almost the same performance, up to 150 grains as this heavier malfunctioning 308...it would appear...interesting. What happened to the 30 Remington AR? Or neck down a 450 Bushmaster case a lot of capacity at moderate pressure 308 casehead AR 15 platform. A 16 in 450 Bushmaster is range limited but with the fast twist resized 502 gr bullets can be used...and over 3000 ft/ lbs of muzzle energy available in 16" Bushmaster, AR 15, with standard off the shelf parts to configure any way you want it...a firearms main goal is to go bang, and function 100%. This Ruger experiment seems prematurely dumped on the public, without much testing, like so many manufacturers these days. And lacking in quality with priority parts...needs improvement before I'm interested. I'll just carry an extra pound or 2 with the AR10 for now, or go to the AR 15 if I desire something lighter.

 

[bfoosh006]

Just pulled the gas block off in prep for ordering parts and measured the port in the barrel.

1/8" diameter tunnel (0.126x")

ETA:

It has plenty of wiggle room ... what's the ID of a 1/8" roll pin? can I buy/make a sleeve for it like an engine cylinder?

View attachment 8186918

That is huge.
No offense to anyone, but how long do various parts last given that size of a GP ?
As an example, I worked on a cheap ass no name AR15 upper that was breaking hammer pins in half, turned out the GP on that 16" CLGS was larger than my pin gauges could measure... so .100+

 

[GreenGO Juan]

So the small frame 308 is going 2900 fps with 110 gr bullet...the AR 15 300 hamr does 2876 with 110 Varmageddon with 29.3 gr of AA 1680, in 18" 300 Hamr barrel. The 150 gr at 2398 26.8 gr CFE Blk with 8.0 S/D and a .264" 5 shot group at 100 with a little 300 Hamr no issues, with feeding or ejecting. Light AR 15 with almost the same performance, up to 150 grains as this heavier malfunctioning 308...it would appear...interesting. What happened to the 30 Remington AR? Or neck down a 450 Bushmaster case a lot of capacity at moderate pressure 308 casehead AR 15 platform. A 16 in 450 Bushmaster is range limited but with the fast twist resized 502 gr bullets can be used...and over 3000 ft/ lbs of muzzle energy available in 16" Bushmaster, AR 15, with standard off the shelf parts to configure any way you want it...a firearms main goal is to go bang, and function 100%. This Ruger experiment seems prematurely dumped on the public, without much testing, like so many manufacturers these days. And lacking in quality with priority parts...needs improvement before I'm interested. I'll just carry an extra pound or 2 with the AR10 for now, or go to the AR 15 if I desire something lighter.

So you are running a stupid hot load and going to come on here and brag about how bad ass it is.

Most published data for 110 loads is in the 25-2600 range.

I could load some 110’s way over pressure then brag about some high velocity but you know, I’m not as cool as you are

But this thread is not about that and I’m not trying to derail this topic so if you want to cry and bitch and a PM me or something I’m out

 

[LRRPF52]

So the small frame 308 is going 2900 fps with 110 gr bullet...the AR 15 300 hamr does 2876 with 110 Varmageddon with 29.3 gr of AA 1680, in 18" 300 Hamr barrel. The 150 gr at 2398 26.8 gr CFE Blk with 8.0 S/D and a .264" 5 shot group at 100 with a little 300 Hamr no issues, with feeding or ejecting. Light AR 15 with almost the same performance, up to 150 grains as this heavier malfunctioning 308...it would appear...interesting. What happened to the 30 Remington AR? Or neck down a 450 Bushmaster case a lot of capacity at moderate pressure 308 casehead AR 15 platform. A 16 in 450 Bushmaster is range limited but with the fast twist resized 502 gr bullets can be used...and over 3000 ft/ lbs of muzzle energy available in 16" Bushmaster, AR 15, with standard off the shelf parts to configure any way you want it...a firearms main goal is to go bang, and function 100%. This Ruger experiment seems prematurely dumped on the public, without much testing, like so many manufacturers these days. And lacking in quality with priority parts...needs improvement before I'm interested. I'll just carry an extra pound or 2 with the AR10 for now, or go to the AR 15 if I desire something lighter.

That 300 HAMR with the new 125gr Extreme Chaos from Lehigh Defense looks pretty brutal for hogs.

In the 1980s, I had this idea that a 7.62 NATO “CAR-15” was the solution to all of my practical blaster problems, so I’ve been an AR-10 guy for a long time. Then the typical issues with the large frame guns just rubbed me the wrong way and I shot them less and less until I didn’t. I put my .260 Rem back together after raping it for its Geissele trigger for one of my Grendels 8 years ago. Will have to take it out just so my youngest can shoot it now that he’s getting big enough.

The 30 RAR is an interesting cartridge with high efficiency given its short, fat configuration. It would be great with a 40˚ shoulder and a pressure containment system that could handle it. Biggest limiting factors are brass/ammo availability, the enlarged bolt and extractor, unique barrel extension, and basically single-column mags with low capacity riding up one of the feed ramps. You really need to design a rifle around it, starting with a good magazine. It would be cool in .277”, 6.5mm, and .257”, especially the quarter bore.

The DPMS GII killed Freedom Group’s interest in 30 RAR, then Freedom Group proceeded to run every one of its big name brands into the dirt until bankrupt, almost as if it was on purpose.

 

[45-90]

So you are running a stupid hot load and going to come on here and brag about how bad ass it is.

Most published data for 110 loads is in the 25-2600 range.

View attachment 8192413

I could load some 110’s way over pressure then brag about some high velocity but you know, I’m not as cool as you are

But this thread is not about that and I’m not trying to derail this topic so if you want to cry and bitch and a PM me or something I’m out

My load is .3 tenths gr under max of the one you posted, at 2700 fps, mine were chronographed maybe different bullet, and longer barrel but still 110 grs .... so there's that...Total LOL...
And even if it's 200 fps difference your still carrying around more weight with less fire power, with non commonly available components, found everywhere, magazines, bolts, even on a battlefield, used parts and mags everywhere.
And a big plus and no issues feeding, ejecting, tearing up brass, a long proven, reliable, light weight, system. Against a heavier, faulty, unreliable, specialized components system... for a few hundred feet per second, not even using my data of 3 tenths under max...but super hot loads according to you ...that you printed! LOL...
The point is, not much gain in performance for the extra weight, specialized one of a kind, unreliable system, and all its problems...the juice ain't worth the squeeze,.. for me. I'll just carry my regular heavy reliable AR 10...or 300 Hamr, reliable, common parts everywhere.

 

[45-90]

That 300 HAMR with the new 125gr Extreme Chaos from Lehigh Defense looks pretty brutal for hogs.

In the 1980s, I had this idea that a 7.62 NATO “CAR-15” was the solution to all of my practical blaster problems, so I’ve been an AR-10 guy for a long time. Then the typical issues with the large frame guns just rubbed me the wrong way and I shot them less and less until I didn’t. I put my .260 Rem back together after raping it for its Geissele trigger for one of my Grendels 8 years ago. Will have to take it out just so my youngest can shoot it now that he’s getting big enough.

The 30 RAR is an interesting cartridge with high efficiency given its short, fat configuration. It would be great with a 40˚ shoulder and a pressure containment system that could handle it. Biggest limiting factors are brass/ammo availability, the enlarged bolt and extractor, unique barrel extension, and basically single-column mags with low capacity riding up one of the feed ramps. You really need to design a rifle around it, starting with a good magazine. It would be cool in .277”, 6.5mm, and .257”, especially the quarter bore.

The DPMS GII killed Freedom Group’s interest in 30 RAR, then Freedom Group proceeded to run every one of its big name brands into the dirt until bankrupt, almost as if it was on purpose.

It would be nice to have seen the 30 Rem AR succeed, and multiply.
I thought about chambering a barrel for a similar cartridge based on the 450 bushmaster case, bushmaster bolt, at bushmaster pressure, necked down with 30 Rem AR dies, bushmaster mags...standard AR 15.

 

[GreenGO Juan]

The port in the SFAR barrel is ~0.126" ... HUGE ... bigger than anything else

The #3 valve in the SFAR AGB is ~0.114" ... HUGE

The #2 valve in the SFAR AGB as returned to my by Ruger CS is ~0.103" ... HUGE

The #1 valve in the SFAR AGB is 0.068" and still over gassed

The port in my LR-308 would seem to be ~0.096" as reported by Tactical Machining (I've never measured it myself) even with a heavier BCG and a heavier buffer than the SFAR and the LR-308 was over gassed to the point of denting cases upon ejection before I installed a JPE AGB and adjusted it ... no more dents

The SFAR AGB restricts the gas flow insufficiently ... Ruger failed

But some people are OK with mutilated brass and everything that goes along with over gassing and they are entitled to be happy with a less than optimally functioning firearm.

1. I call bullshit on your claimed velocity. 2876 my ass! Thats bullshit more like 2680 out of an 18”. I was more calling bullshit on your velocity you have to load hot as fuck to get that velocity.

2. The 110 load I mentioned is the slowest velocity powders. I have seen published data for. It’s leaving a lot on the table to have a fast burning powder. you could probably get a 16 up in the mid 3000 maybe even up to 3100 if you went hot. I’m also talking about out of a 16 inch barrel.. add another 2 inches and you’re easily into 3100, with a hot load.

3. So the reality is the velocity of your new wonder around that you seem to like marketing in this thread, is nowhere near a fucking 308.

I mean look at the factory offerings you’re like 400 ft./s off all comparable factory ammo.

4. I don’t know about what fucking reliability problems you’re talking about. There you go just making more shit up

5. All right now this is the last time I’m gonna reply I’m fucking out.

 

[45-90]

1. I call bullshit on your claimed velocity. 2876 my ass! Thats bullshit more like 2680 out of an 18”. I was more calling bullshit on your velocity you have to load hot as fuck to get that velocity.

2. The 110 load I mentioned is the slowest velocity powders. I have seen published data for. It’s leaving a lot on the table to have a fast burning powder. you could probably get a 16 up in the mid 3000 maybe even up to 3100 if you went hot. I’m also talking about out of a 16 inch barrel.. add another 2 inches and you’re easily into 3100, with a hot load.

3. So the reality is the velocity of your new wonder around that you seem to like marketing in this thread, is nowhere near a fucking 308.

I mean look at the factory offerings you’re like 400 ft./s off all comparable factory ammo.

4. I don’t know about what fucking reliabOKility problems you’re talking about. There you go just making more shit up

5. All right now this is the last time I’m gonna reply I’m fucking out.

 

[45-90]

Enjoy your bullshit sandwich...and I have 3 tenths more powder "to add" to get to maximum load..according to "your data."
Max velocity 2876 fps average velocity 2803 fps. Just as my notes said. It's really hard to be nice to "some people"....but again, they deserve what they earn.

 

[BCP]

Freedom Group proceeded to run every one of its big name brands into the dirt until bankrupt, almost as if it was on purpose.

I thought the same thing, they trashed a bunch of well known brands. Bushmaster, Remington/DPMS, Marlin, even TAPCO bit the dust and there's always a market for the cheap plastic crap they sell.

That is huge.
No offense to anyone, but how long do various parts last given that size of a GP ?
As an example, I worked on a cheap ass no name AR15 upper that was breaking hammer pins in half, turned out the GP on that 16" CLGS was larger than my pin gauges could measure... so .100+

I'm thinking it vents pressure through the extra holes in the BCG. Maybe they needed that excess pressure to unlock the bolt. Going by a lot of the Youtubes I see of jamming SFARs the 3-position gas block seems to be a bridge too far for some people.

 

[doubloon]

Yes, it vents gas through the holes in the BCG, I *think* technically after the unlock. But it "vents" gas everywhere ... block, charging handle ...

Yeah, I think adjustable gas blocks may be a bit much for some people to figure out.

 

[LRRPF52]

My load is .3 tenths gr under max of the one you posted, at 2700 fps, mine were chronographed maybe different bullet, and longer barrel but still 110 grs .... so there's that...Total LOL...
And even if it's 200 fps difference your still carrying around more weight with less fire power, with non commonly available components, found everywhere, magazines, bolts, even on a battlefield, used parts and mags everywhere.
And a big plus and no issues feeding, ejecting, tearing up brass, a long proven, reliable, light weight, system. Against a heavier, faulty, unreliable, specialized components system... for a few hundred feet per second, not even using my data of 3 tenths under max...but super hot loads according to you ...that you printed! LOL...
The point is, not much gain in performance for the extra weight, specialized one of a kind, unreliable system, and all its problems...the juice ain't worth the squeeze,.. for me. I'll just carry my regular heavy reliable AR 10...or 300 Hamr, reliable, common parts everywhere.

The .30 RAR would do well to have a 2.500” COL allowable magazine and lower receiver, with a large OD barrel extension and bolt head like they did. They kept the bolt and barrel extension lug lengths at AR-15 length, which limited the MAP to 55ksi, but that doesn’t bother me because there is so much case capacity.

2.260” really handicaps it to short, low-BC .30 cal bullets that are great for whacking game within 300yds, but to really open it up, it would either need to be necked-down to 6.5mm or increase the action/magazine allowable COL.

 

[mtrmn]

... then Freedom Group proceeded to run every one of its big name brands into the dirt until bankrupt, almost as if it was on purpose.

Yes. This is what I have always suspected. I would not doubt they were financed by Soros (and others) to buy out and destroy the American gun industry.

 

[doubloon]

I find myself to be all at the same time puzzled, pleased and a little perturbed at the results of today's SFAR experiment.

Went to a nearby indoor range to do some tests because it was easier to work it in while running errands than packing for a day of accurizing at the club range.

I added a weird twist just for fun, don't know what it proves but it's numbers so there's that.

The SFAR is in the condition as returned from Ruger after service

There are still definitely some scrapes and some imprints in the bases but the lugs are virtually brass chip free. The brass itself also looks 90+% better than it did before the service. Annotated brass picture at the end of this lengthy and boring post.

I ran 4 rounds, one on each regulator setting, with a naked muzzle, the factory brake and suppressed with the old Liberty Freedom then most of the rest of the box suppressed with the regulator set on 1.

It ran flawlessly except for the two rounds shot unsuppressed on regulator setting 1, they did not eject but that was the expected result.

The #2 regulator port is bigger now than it was when I measured it new out the box but everything else is the same. And yet ... different results. I don't know if it was widened by Ruger or if it just eroded that quickly.

They did say they replaced the bolt and now I wish I'd spent more time taking measurements on the bolt because I believe this is the only known change to the original build but I don't know exactly what they changed. So what could they have changed on the bolt?

I still think it's overgassed but it seems obvious from the results today that there was something fundamentally wrong with the bolt ... I just don't know what.

I plan to run it as-is for a while and check for regulator erosion and brass chips for a while. I still plan to replace the gas block eventually and play with tuning the spring and the buffer but I'll give Ruger a nod today for working some kind of magic.

The weird twist, I installed an accelerometer on my phone and strapped it to the handguard using a MLOK mount meant for something else.

Using an entirely unscientific method of loosely cradling the stock on my shoulder I proceeded to take some readings on the axis that mattered ... to me.

At a scoped, unsuppressed and unbraked weight of ~ 8lb 8.5oz acceleration in a rearward direction at regulator settings 3, 2, 1 and 0 were measured to be 72.4, 74.9, 74.7 and 69.9 m/s respectively.

At as scoped, unsuppressed and braked weight of ~8lb 10oz acceleration in a rearward direction at regulator settings 3, 2, 1 and 0 were measured to be 64.1, 52.2, 64.8 and 71.2 m/s respectively.

At a scoped and suppressed weight of ~9lb 15oz acceleration in a rearward direction at regulator settings 3, 2, 1 and 0 were measured to be 49.3, 50.9, 56.6 and 58.9 m/s respectively.

The flaws in the "hold on loosely but don't let go" technique are clearly visible but the averages tell a story that seems plausible when comparing it to "felt" recoil.

The Brass ...

 

[45-90]

The .30 RAR would do well to have a 2.500” COL allowable magazine and lower receiver, with a large OD barrel extension and bolt head like they did. They kept the bolt and barrel extension lug lengths at AR-15 length, which limited the MAP to 55ksi, but that doesn’t bother me because there is so much case capacity.

2.260” really handicaps it to short, low-BC .30 cal bullets that are great for whacking game within 300yds, but to really open it up, it would either need to be necked-down to 6.5mm or increase the action/magazine allowable COL.

There is alot that can be overcome but 2.5 " would require different mags, and lowers...but it would make a world of difference in the AR 15.
I can use Areo enhanced AR 15 upper with the extra material to insert a 308 barrel extension, and cut and thread for a barrel nut, that would have to be made. Make an adapter for a handguard. Machine down the 308 bolt to fit into the 15 carrier, bush the bolt for ar 15 cam pin..if it has enough through to index the bolt completely. Thing like that have to be over come or just use available materials and see how far that goes...I can always turn case heads down to fit grendel bolt or even 223 bolt and recut extractor groove, easy to do...

 

[45-90]

If the Ruger SFAR is such a pain, why not just build a light AR 10, with light fluted barrel, titanium bolt carrier, ultra light or carbon fiber handguard, with minimal stock...they come in light, and reliable, when set up properly. Maybe I should build one, just for fun...maybe.