Cut rifled. $450. Fits ops / ocm cans. Ordered will report back
Geisselles new SPR barrel with special gas system
- Thread starter BurtG
- Start date
It's a different concept than what I envisioned when it was first talked about. I initially thought that it would take a proprietary gas block, but it is compatible with any 0.750" block. The radial groove would seem to make locating the ports in the grooves of the rifling easier, and precise rotational alignment with a proprietary gas block would not be required. I'm not sure where the ports are located, but if one of the ports was located furthest away from the normal top port and at BDC, which I don't think it is, that gas impulse would be the equivalent of around rifle+1.18", not taking into account the depth of the groove.
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Yeah those gas ports aren't at all what I had pictured in my head when I first heard about this.
@BurtG Hopefully you can get some details before you build it out, like clocking locations of the gas ports, each gas port diameter and whether they are bored straight or at an angle.
Also, what's the time lag between a rifle length gas port and a rifle+1.18" port? I get around 40μs, or 40/1,000,000 of a second, using 2500 FPS at ~13.5" (port location).
Also, what's the time lag between a rifle length gas port and a rifle+1.18" port? I get around 40μs, or 40/1,000,000 of a second, using 2500 FPS at ~13.5" (port location).
it must not be very good, they didn’t include “super” in the name like everything else they sell…
Sorry for the derail, it’s very interesting concept hopefully it pans out.
Sorry for the derail, it’s very interesting concept hopefully it pans out.
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It will leak with gas blocks that have lightning cuts in them, and maybe clamp-on blocks.
That multi-port circumferential gas path trench will do best with a tight seal over it.
I would want an indexed block with tab and cut into the barrel shoulder, with either a press-fit or KAC Mod 2 style set-up with a lock ring that presses the block against the barrel shoulder. They also put a lock nut around the gas tube that presses the gas tube against a ferrule on the block. Really eliminates leakage and allows you to dial in the gas port size. No more roll pins and taper pins.
Ok. Barrel gets here today. What gas block should I order. Prefer adjustable. Already have my rd15 for a function or die rifleIt will leak with gas blocks that have lightning cuts in them, and maybe clamp-on blocks.
That multi-port circumferential gas path trench will do best with a tight seal over it.
I would want an indexed block with tab and cut into the barrel shoulder, with either a press-fit or KAC Mod 2 style set-up with a lock ring that presses the block against the barrel shoulder. They also put a lock nut around the gas tube that presses the gas tube against a ferrule on the block. Really eliminates leakage and allows you to dial in the gas port size. No more roll pins and taper pins.
SLR gas blocks I’ve used have fit tight, but the adjustment screw can seize up if not regularly played with. The RifleSpeed blocks are my preference for adjustment but fit fairly loose on all barrels I had on hand. This might be a case for not running an adjustable block since the barrel has a
I’d probably seal the gas block bore/journal with some green loctite whatever you end up using.
I had wondered how they were gonna fit three gas tubes under there. Question answered!
It's not as complicated as you guys think, its just spreading the gas part pressure out of three ports instead of one... simple math, take the average PSI that thier standard single gas port barrels produce and divide by three. The end result will be the ability to run multiple small gas ports the will significantly reduce Port erosion and dampen recoil impulse.
They've just machined a channel 360° around the gas block Journal, when the gas block is installed that channel now becomes a sealed unit allowing the evenly dispersed gases up and back through the gas tube like a traditional design but significantly reducing gas port pressure at the barrel.
They've just machined a channel 360° around the gas block Journal, when the gas block is installed that channel now becomes a sealed unit allowing the evenly dispersed gases up and back through the gas tube like a traditional design but significantly reducing gas port pressure at the barrel.
lol no I’m more of an enhanced upper kind of shooter myself. Why G doesn’t embrace the gospel is beyond me
Still have those 2 G uppers NIB if anyone is looking for 1 or 2
It’s smart, for sure. I don’t think anyone’s saying there’s inherently more chance of a gas leak, it’s that a gas leak is that much worse until it fouls up and seals with carbon from use. There are some good designs for gas system optimization that could certainly used ICW this system as a min/max wet dream.
I believe the claim there is the recoil impulse is softer. Like a muzzle brake helps you spot trace.
Please explain how the gas port pressure changes alter the bone crushing recoil impulse of the 5.56 cartridge
I'm reasonably acquainted with physics.
I can verify this. I have two uppers with 24” .936 1:7 twist Krieger barrel same brand upper & lower receivers and BCM BCGs ( one is FDE). The one that has the +2” gas system shoots noticeably softer than the other, BTW thanks @TonyTheTiger for that, this is with the same projectile (73 ELDX) same powder (ARCOMP) and the same type of brass (new LC). The one with the +2 gas system is also easier on components.
@BurtG are you putting a + rifle gas system on the new barrel you mentioned in the OP?
The same volume volume and pressure is still required to flow through the gas tube regardless of how many holes in
the barrel.
Don’t know. Prolly the geisselle contour.
thought the heavy barrels were only available separate but I don’t keep up
They're selling complete Uppers with the heavy barrels as well.
I see they have a heavy barrel & standard here:
But I can’t find the Geissele contour for the life of me.
Unless it’s this?
Not a barfcom member BTW.
What year did you win the uppers?
Your uppers have the chrome lined barrels?
Damn, already sold out before I even knew about these. Bummer. They don’t appear to be available anywhere else besides the Geissele website.
Hopefully they make a 16” version next.
Hopefully they make a 16” version next.
If they do, I hope it has the 5/8x24 muzzle and an intermediate gas system.
I'm intrigued by this system, but I can't quite wrap my brain around how 3 small ports delivering the same gas volume and pressure as one bigger port can be reducing recoil.
It looks like the groove with the gas ports is cut at an angle which I’m guessing means that the gas hits the ports in a 1,2, 3 sequence. Slightly spacing out the timing of the gas hitting the ports potentially smooths out the recoil impulse. That’s my guess.
This is what I could find in the patent so far
The respective axial positions of the barrel gas ports 110 can be different , and the groove 108b can have a shape other than curvilinear in variants of the barrel 16b . In the depicted embodiment , the propellant gas enters the lower , rearmost two barrel gas ports 110 simultaneously and the top , frontmost gas port 110 after the other two . In some embodiments , axially offsetting two or more of the gas ports produces a softer push of the action , which is believed to be caused by the offset timing of the gas passing through the ports . This softer push may improve operation of at least some firearms
I would ask Geissele since they have the most experience with what makes those guns run.
They’re going to say to use their gas block, since they can’t control anyone else’s dims.
For me, I would want something press-fit, so I would spec the block to be sized to the journal.
Most of the after-market gas blocks have to be sized to slip-fit, otherwise they’ll be dealing with a high return rate on a low-cost part, which will make that particular SKU not generate revenue to justify it.
Measure the journal when you get it to see if it’s actually .750”, vs .7492” or something under-sized.
With 3 ports and the volume of the trench, any leakage will likely short-stroke the BCG.
You’ll want an efficient BCG too, not a sloppy nitrided cheap parts BCG that are all so common today.
Alright, I hadn't looked that far into it. I could see how spreading the impulse out longer by having the ports timed differently could make some difference.
My tracking information has the barrels arriving on the 6th, I'll post pics with full details when they arrive.
I have everything needed to assemble them into complete Uppers.
I went with the following parts.
Vltor Mur FDE upper receiver for increased rigidity over the standard Geissele upper receivers.
Geissele FDE 15" MK16 Handguards.
Standard low profile Plain Jane Gas blocks, I would normally go with SA Set screw AGB but I'm sure as their standard Barrels are gassesd perfectly it won't be needed.
I'll try the Geissele Gas Blocks but the pre drilled pinning hole gives me pause for potential gas leaks, I won't know my options until I have the barrels but I'll demonstrate on here what will be best suited for this application in full detail.
( When I do a finally assembly I always seal my Gas Systems with Loctite 620, the gas tube is sealed in the Gas block and the Gas block is fully sealed around the gas block journal.)
Geissele Ambi FDE Charging Handle.
For BCGs I pick up to different types.
(1) BCM in FDE
(2) Superlative Arms FDE Carrier and JP bolt kit with Springco Gas rings.
Let me know if you have any specific questions or concerns and I'll do my best to address them.
Also one of these complete Uppers will go to the PX.
Jake
I'll just be curious to hear your thoughts on the recoil reduction aspect when you get to that point.
G has officially jumped the shark.
I’ve seen where this leads to
I’ve seen where this leads to
Gas holes are. Special.
Contour seems perfect. AI barrel for comparison
Contour seems perfect. AI barrel for comparison
Thanks for the pics, this whole thing makes way more sense now. I didn't realize that the port manifold cut was helical and that it didn't go all the way around. Maybe everyone else already understood this and I'm just way behind.
The hatefest between Bill Geissele and Mark Larue continues to be one of the silliest and most entertaining bits of AR mfg lore. I hope they never get over it.
