SPR mid length gas systems

[Lapuapalooza]

Do any of you guys with SPR type rifles run mid length gas systems with 18” barrels? How is it working for you? What BCG are you running with them?

I have a Yankee Hill upper that I thought about putting an 18” 1-8 twist match barrel on, but I’m thinking I’ll need to replace the BCG as well. The rifle is a mid-length gas system, so if I have to buy a Handguard to convert to a rifle length gas system too I may just contemplate a complete upper.

Thanks for your input.

 

[MontanaMan]

Yes, I've run mid-length gas on 18" barrels. Works fine, more flexible / forgiving (as far as functioning goes) than rifle gas, IMO. I run adjustable gas blocks to fine tune as well.

Both WOA & Compass Lake recommended mid-length gas to me when I bought my 1st 18" barrels.

MM

 

[Lapuapalooza]

What type of bolt carrier and bolt do you run? (M16, AR15, etc...) what do you shoot out of it? I bought some Hornady 75gr eld’s to push with 8208xbr in hopes of hitting 800yds... How far have you been able to push yours?

 

[TonyTheTiger]

Hope you're planning on single loading those 75's.
Rifle length gas gives you a much bigger operational window when you're pushing handloads hard.

 

[Primus]

Old theory was a mid gas system was better for running in cold weather. I have built a few dozen sprs over the years and much preffer a rifle length system with an adjustable gb ( years I know not a clone). It just opens up options for running suppressed and different loads. The jp SCS system is also a big factor.

 

[Lapuapalooza]

Tony,

I wasn’t planning on that! I knew the A Max runs long, but I thought I could do mag length loads with these...

If a rifle length gas systems is best, then I’ll probably just buy another upper. I wanted to stay in .223 Remington to keep my cartridge inventory down, but if I buy an upper then the .224 Valkerye would actually fit the intended use better.

 

[MontanaMan]

Tony,

I wasn’t planning on that! I knew the A Max runs long, but I thought I could do mag length loads with these...

If a rifle length gas systems is best, then I’ll probably just buy another upper. I wanted to stay in .223 Remington to keep my cartridge inventory down, but if I buy an upper then the .224 Valkerye would actually fit the intended use better.

The 73's will fit the mag; 75's won't.

Rifle gas is not best or better, just different. Mid-gas set up correctly is every bit as good..............however you want to define "good / better / best".

Mid-gas with the right buffer, spring & adjustable gas block, & BCG is every bit as soft as a rifle gas on an 18" barrel & actually offers at least as much, if not more, flexibility on the range of ammo that can be used in any kind of temperature range.

There's a reason that both WOA & Compass Lake will tell you that they prefer mid-gas over rifle gas on an 18" barrel.

MM

 

[TonyTheTiger]

Tony,

I wasn’t planning on that! I knew the A Max runs long, but I thought I could do mag length loads with these...

I run the 75's out of a mag but it takes some modifications to magazines and the barrel extension to do so. Its not for everyone.

 

[TonyTheTiger]

Mid-gas with the right buffer, spring & adjustable gas block, & BCG is every bit as soft as a rifle gas on an 18" barrel & actually offers at least as much, if not more, flexibility on the range of ammo that can be used in any kind of temperature range.

Thats simply not true. Average port pressure at a mid port is around 27k psi verses a rifle port around 20k psi. You can mask some of the symptoms of 7k psi with buffer/spring/AGB tuning but you can't beat physics and make them equal.

In theory they both have the same flexibility range, just with mid gas biased towards lower pressure ammo and rifle gas losing some of its weak ammo compatibility in favor of tearing up brass and parts a lot less with hot ammo.

In practice I've not found the rifle gas to be more finicky at the bottom end though. I have a rifle gas 16" thats tuned to just barely lock back on empty with 55gr bullets at 2500ish fps in 60-80 degree temps. Turns out it does the same with the same brass ejection patterns at 100 degrees all the way down to 0.

[/QUOTE]There's a reason that both WOA & Compass Lake will tell you that they prefer mid-gas over rifle gas on an 18" barrel.

MM[/QUOTE]

I would venture a guess that its because both companies are ran by geezers that don't like pushing the envelope on anything, and because any fucktard can assemble an overgassed rifle and have it work acceptably without calling the barrel manufacturer ten times to troubleshoot.
I've even been told this exact same thing about 18" rifle gas barrels by another old man piloted barrel company.

 

[Primus]

Awesome Post Tony, you hit the nail on the head.

 

[TonyTheTiger]

Awesome Post Tony, you hit the nail on the head.

See, we can agree on something...

 

[MontanaMan]

Well, I don't agree at all. I've got 18" guns with both mid & rifle gas.

Shooting the 2 versions shows no discernible difference in any respect, both are tuned such that they both shoot the same ammo, with the same ejection patterns & neither gas system shows any difference on the extraction or ejection damage to the brass.

Sure, the mid-gas has higher port pressure, but tuning accounts for the difference via an adjustable GB.

Both work just fine. There's no "better"; there may be personal preference but that's not the same as "better" in the end result sense. "Better" how? What's your definition of "better"?

If there is a "better", it might be an intermediate length system on an 18" barrel; & yes, rifle gas is the "better" (preferred?) gas length for a 20" barrel, that surely does not necessarily translate to "better" on an 18" barrel.

Obviously you have your view, I have mine. End of the discussion for me, but it's interesting to learn that you know more than either John Holiger or Frank White.

MM

 

[Primus]

You may be able to control the gas that goes into the tube, but it effects the dwell and the higher pressure is going to erode your gas port way faster.

 

[TonyTheTiger]

Obviously you have your view, I have mine. End of the discussion for me, but it's interesting to learn that you know more than either John Holiger or Frank White.

MM

I have no doubt they know more about barrel making and all things purely accuracy related than I do.
But did you ask them about port pressures? Port erosion? Brass and parts wear and tear at max loads? Recoil impulse? I'm guessing you didn't ask about that and I don't think they could disagree with me on these points, considering its physics based not just my opinion.

BTW, an adjustable gas block limits gas volume, not pressure.

PS.
We haven't even mentioned suppressed use yet, then it gets even harder to argue.

 

[Lapuapalooza]

Tony,

Do you know what your COL is on your loads? When you say modify your mags & barrel extension, how so? Is it a PIA?

Haha. I was just looking to get a gun up into shape enough I might like to shoot some matches with it. It seems I have created a conundrum...

 

[TonyTheTiger]

Tony,

Do you know what your COL is on your loads? When you say modify your mags & barrel extension, how so? Is it a PIA?

Haha. I was just looking to get a gun up into shape enough I might like to shoot some matches with it. It seems I have created a conundrum...

COAL is somewhere around 2.41" off the top of my head. You can get 2.31" in ASC mags but its not enough to get the ogive out of the case neck. Cutting the mags gets you to about 2.36" or so, and then the 75 ELD's fit better but they still wouldn't shoot for me with that much jump. Next I filed out a channel in the front of the magwell with a corresponding notch in the barrel extension to get a 2.42" max COAL.
It's worked great for me, no malfunctions, no mag problems, 75 ELD's at around 2900fps puts the ballistics well above anything people expect from a 223 gas gun. But it's certainly not going to help resale on a gun and I wouldn't want to drop the mags in the mud.

What kind of matches are you looking at? 223 in a gas gun needs all the help it can get in a long range match, a longer barrel might be what you're really after, and it negates your original question.

 

[Lapuapalooza]

There is a local long range match here I want to get involved in. Targets range from 75 to 1200 yards. I know the .223 wouldn’t reach to 1200, but I didn’t expect to do much more than show up and gain knowledge and experience anyway. I didn’t really want to get a Valkyrie upper and another long range scope, so I thought I could piece some kit together to see if I wanted to jump in all the way. I do have a Bergara bolt gun in 6.5CM, maybe I should just use it. My thought was with an AR I could use the advantages of that platform.

Thanks to all you guys that responded to my original question. I certainly received more depth of knowledge that I thought the original question would bring to the surface.

 

[TonyTheTiger]

I do have a Bergara bolt gun in 6.5CM, maybe I should just use it. My thought was with an AR I could use the advantages of that platform.

This is going to be the path of least frustration.

 

[dms416]

@TonyTheTiger and @Primus,

Curious to hear your thoughts on the "Intermediate" system in 18 and 16...specifically 16"

 

[TonyTheTiger]

I love intermediate gas 16" barrels. It's the perfect gas/barrel length combo. I tested against 18" and 16" rifle gas barrels with identical components and the difference in recoil was almost imperceptible, but they are a plug and play type system without all the tuning a 16" rifle gas takes to get working great.

 

[dms416]

I love intermediate gas 16" barrels. It's the perfect gas/barrel length combo. I tested against 18" and 16" rifle gas barrels with identical components and the difference in recoil was almost imperceptible, but they are a plug and play type system without all the tuning a 16" rifle gas takes to get working great.

How wide open do you have the gas port? Near as I can tell, most are drilling 'em way out to like .091-.093.

 

[TonyTheTiger]

Both the int. 16" barrels I've messed with I never even checked gas port size, whatever the manufacturer drilled them at had plenty of headroom. With full mass components and springs they still had plenty of gas to operate without being overgassed. With low mass components you can turn the gas down a ways to really find the sweet spot.
Rifle length 16" definitely takes some gas port vs. spring vs. reciprocating weight vs. ammo balancing though. I wouldn't recommend it for a general purpose gun.

 

[Jsp556]

The 73's will fit the mag; 75's won't.

Rifle gas is not best or better, just different. Mid-gas set up correctly is every bit as good..............however you want to define "good / better / best".

Mid-gas with the right buffer, spring & adjustable gas block, & BCG is every bit as soft as a rifle gas on an 18" barrel & actually offers at least as much, if not more, flexibility on the range of ammo that can be used in any kind of temperature range.

There's a reason that both WOA & Compass Lake will tell you that they prefer mid-gas over rifle gas on an 18" barrel.

MM

Frank suggests mid length gas due to burrs developing at the gas ports in Kreiger and Bartlein 18” rifle gassed barrels. Notice he offers that set up in Criterion and Douglas.

 

[MSTN]

Do any of you guys with SPR type rifles run mid length gas systems with 18” barrels?

I've got some ancient history on the mid vs. intermediate length gas system story for you, if interested.

My association with Noveske Rifleworks goes back to their beginnings. Pat Rogers told me in I think it was 2005 that there was this new guy in Oregon turning out killer accurate AR' barrels. I've been using Noveske barrels in one form or another ever since.

Noveske built for me, among other custom barrels, 18" SS barrels (1x8 three groove) with rifle length gas in a proprietary profile (jokingly referred to as my "SPR Mk 12 Mod 2" profile) for many years. John really never liked the idea of rifle gas on an 18" barrel. Obsessed with the quest for reliability above all, and knowing how much weak and underpowered ammo there is out there, Noveske, like many other manufacturers, opt for shorter gas systems and big gas ports to ensure guns with Noveske barrels always would cycle.

When John Noveske first started building 18" barrels for resale, he started out using a mid-length gas system. We both built uppers with these barrels and agreed that we were not satisfied with the accuracy results we were getting.

We both knew his barrels were capable of doing much, much better in the accuracy department. Noveske got together with Eric Kincel of Vltor (now with BCM) and developed what they called the intermediate length gas system. To this day, that's all Noveske Rifleworks offers commercially in an 18" barrel.

There was another lesser known, so-called gas system of "intermediate" length - longer than mid-length but shorter than rifle length - out there, unknown to most, since the mid-nineties. Eugene Stoner, in developing a 16" variant of the SR-25 for Knight's Armament, originally came up with this format. Knight's wisely chose to use this gas system in later models of their 16" SR-15, rather than the at the time in vogue mid-length gas system.

What a hit that SR-15 was, too. (And it still is, IMO. One of the best AR-15 variants out there, still.) That the SR-15's with the KAC "intermediate length" ran so much more smoothly than any 16" with a conventional mid-length gas system really impressed me. Since the Noveske/Vltor intermediate length was only 0.4" longer than the KAC intermediate length, I immediately asked John Noveske to build a run of custom 16" barrels with his intermediate length gas system.

These have worked out well for the better part of a decade. In addition to barrels with the Noveske/Vltor intermediate length gas ssytemI've done about a hundred custom 16" SS Noveske barrels with the KAC length intermediate, as well. Why? I ran into 100 custom gas tubes, thanks to Marvin Pitts, and they would fit under the KAC URX of the day, but the Noveske/Vltor length would not.

Of course, the next month, I think, KAC came out with yet another URX that did not require the KAC intermediate length ...

There was no difference in the performance of the two intermediate length gas systems that I could see.

I'll never use a mid-length on anything longer than a 14.5" 5.56 barrel, if I have a choice. I even like a mid-length on a 12.5" barrel. I'll go no shorter than intermediate length on a 16" and rifle length on an 18".

 

[MontanaMan]

I've got some ancient history on the mid vs. intermediate length gas system story for you, if interested.

My association with Noveske Rifleworks goes back to their beginnings. Pat Rogers told me in I think it was 2005 that there was this new guy in Oregon turning out killer accurate AR' barrels. I've been using Noveske barrels in one form or another ever since.

Noveske built for me, among other custom barrels, 18" SS barrels (1x8 three groove) with rifle length gas in a proprietary profile (jokingly referred to as my "SPR Mk 12 Mod 2" profile) for many years. John really never liked the idea of rifle gas on an 18" barrel. Obsessed with the quest for reliability above all, and knowing how much weak and underpowered ammo there is out there, Noveske, like many other manufacturers, opt for shorter gas systems and big gas ports to ensure guns with Noveske barrels always would cycle.

When John Noveske first started building 18" barrels for resale, he started out using a mid-length gas system. We both built uppers with these barrels and agreed that we were not satisfied with the accuracy results we were getting.

We both knew his barrels were capable of doing much, much better in the accuracy department. Noveske got together with Eric Kincel of Vltor (now with BCM) and developed what they called the intermediate length gas system. To this day, that's all Noveske Rifleworks offers commercially in an 18" barrel.

There was another lesser known, so-called gas system of "intermediate" length - longer than mid-length but shorter than rifle length - out there, unknown to most, since the mid-nineties. Eugene Stoner, in developing a 16" variant of the SR-25 for Knight's Armament, originally came up with this format. Knight's wisely chose to use this gas system in later models of their 16" SR-15, rather than the at the time in vogue mid-length gas system.

What a hit that SR-15 was, too. (And it still is, IMO. One of the best AR-15 variants out there, still.) That the SR-15's with the KAC "intermediate length" ran so much more smoothly than any 16" with a conventional mid-length gas system really impressed me. Since the Noveske/Vltor intermediate length was only 0.4" longer than the KAC intermediate length, I immediately asked John Noveske to build a run of custom 16" barrels with his intermediate length gas system.

These have worked out well for the better part of a decade. In addition to barrels with the Noveske/Vltor intermediate length gas ssytemI've done about a hundred custom 16" SS Noveske barrels with the KAC length intermediate, as well. Why? I ran into 100 custom gas tubes, thanks to Marvin Pitts, and they would fit under the KAC URX of the day, but the Noveske/Vltor length would not.

Of course, the next month, I think, KAC came out with yet another URX that did not require the KAC intermediate length ...

There was no difference in the performance of the two intermediate length gas systems that I could see.

I'll never use a mid-length on anything longer than a 14.5" 5.56 barrel, if I have a choice. I even like a mid-length on a 12.5" barrel. I'll go no shorter than intermediate length on a 16" and rifle length on an 18".

That's interesting history to hear.

Knight's uses a rifle length gas on their 18" barreled 5.56, even with Kreiger when they were using them, in spite of your comments as to Frank White's reasoning on the gas port burr..........I have one with a Kreiger barrel.

It's a little surprising that they didn't just use the intermediate gas that they use on the 16" which is, as you say, very soft & smooth, I have a MOD 1 & a MOD 2, & everything else I own takes a 2nd seat to them....................but they are also the only INT gas, 16" guns that I own.

It's a little curious that after you working closely with John Noveske, & you preferring rifle gas on an 18", that he chose to stay with the INT gas on 18"ers; guess he just preferred reliability & flexibility above anything else.

Also interesting to note that today, WOA offers ML, INT & rifle gas on various 18" barrels, in fact INT is the standard on their new(er) 18" 3-G barrels.

A few years ago when I discussed the situation with both WOA & Compass Lake, they both said they recommended ML gas on 18" barrels (with an AGB) for the reason of working more reliably across more variables, nothing to do with either accuracy or burrs on the gas port.

The evolution of the system over time, configurations & preferences is interesting as is hearing about everyone's experiences with them................never ending learning experience, at least for me.

MM

 

[MSTN]

Noveske insisted on absolute reliability with any ammo, in any conditions, for any and everybody. Accuracy was of course a close second. He managed to balance the two exceptionally well over a broad range of calibers in different barrel lengths.

My customers tend to be the "full power" ammo variety, more interested in maximizing performance. With many shooting suppressed, too, the longer gas systems make life so much better.

I see gas port erosion in all gas system lengths, with the shorter gas systems producing more of it, and sooner.

Gas port erosion is an interesting topic. Watching it progress with a borescope is enlightening.

Ever build a SS barrel AR' that shoots great right off the bat - and then the accuracy suddenly drops off - and then comes back maybe 200 rounds later? That's the first "chunk" of steel in front of the gas port breaking off, with the rough edge scoring all bullet jackets as they pass, and then finally eroding smooth again.

You don't need to have a borescope, really, to observe this jacket stripping by a rough gas port forward edge in a newer barrel. Just clean the carbon from your bore, and then check the muzzle under a bright light. If you see a very narrow band of copper, say 1/10" or less wide, you'll know what's causing it.

 

[Jsp556]

I’ve never had any reliability issues with an 18” rifle gas barrel. Granted, I’ve never shot at -40 degree temps, never shot steel case ammo through them, or anything of that nature but shot the snot out of them. I’ve had 3 of them and all were set up the same, carbine extension, HBuffer, standard carbine springs.

Regarding Frank White, he told me about the burrs developing over the phone when I asked why he didn’t offer 18” rifle gas options with Kreiger and Bartlein. I’ve looked at the gas port of my current 18” rifle gas barrel and haven’t seen any abnormal port erosion. The barrel is melonited 4150cmv though.

 

[MontanaMan]

I’ve looked at the gas port of my current 18” rifle gas barrel and haven’t seen any abnormal port erosion. The barrel is melonited 4150cmv though.

There's a HUGE difference in melonited 4150 vs bare 416R stainless................how many rounds?

Great comments & insights from MSTN...........Thank You.

MM

 

[Jsp556]

A little over 2k. The erosion was comparable to my friends stainless barrel with similar round count and firing schedule. It was just as deep but not quite as far forward of the port. Ports are drilled after meloniting so you still have gas eroding bare steel. The throat looked better though.

 

[Earnhardt]

This is way too informative of a thread to lie dormant....it needs to be read

Bumpski...

My question is in regards to gas port type/location (mid, intermediate, rifle, rifle+2...)

After reloading for (3) 6.5 CM barrels, a .358, and (2) 45 Raptor barrels, the biggest thing I've noticed in gas port location is this...
(and yes, I know I'm going tio sound like Captain Obvious to many of the experts here...)

Are custom barrel makers reluctant to change their standard gas port location/size, even if you tell them your barrel will be shot with reloads?

ie...I could NOT get my first 45 Raptor barrel to shoot with a mid-length gas system and reloads.
It absolutely destroyed brass, the accuracy was mediocre, and the relaibility was spotty at best.
Enter a 24", rifle length, 45 Raptor barrel...(it's a hunting barrel)
I had to sweet talk the barrel maker in to making it, and stated that I would take full responsiblility if it didn't work
After finding a load, and setting the SLR gas block, this thing hasn't jammed in nearly 250 shots (that is an eternity for a 45 Raptor to not jam.)

Are there many "hi-volume" barrel manufacturers out there (of the mid range priced barrels) that will build a "custom" gas port length/size, if you tell them that it will be for reloads only? Wilson? Faxon?
Does that normally add a significant cost to the barrel, if it's not the same contour/gas system as the barrels they make in runs of 50-100 barrels?
I only know of a couple...
X-Caliber (they made my 45 Raptor barrel)
Deadshot Barrels

Any more (with a good reputation)?


Thanks

 

[Molon]

I wasn’t planning on that! I knew the A Max runs long, but I thought I could do mag length loads with these...

This is what happens when you load the 75 grain A-MAX to the magazine length of a standard AR-15 magazine . . .

...

 

[Earnhardt]

“I gotta turtle head pokin’ thru!”

 

[Molon]

If there is a "better", it might be an intermediate length system on an 18" barrel;

John Noveske preferred the intermediate length gas system for his 18" barrels and he certainly knew what he was doing with regard to reliability. My 18" Noveske barrel produced excellent accuracy/precision as well as being 100% reliable.




Noveske 18” SPR Barrel Accuracy Evaluation

Noveske’s 18” SPR barrel is a stainless-steel barrel that has a medium contour and a 0.750” diameter gas block journal. The gas block journal for this barrel is designed for Noveske’s low profile gas block and the journal is only one inch in length; standard length gas blocks will not work with this barrel. Fortunately, Noveske’s pinned and set-screwed low profile gas block is included with the barrel (as well as an intermediate length gas tube.)

The Noveske SPR barrel employs an intermediate length gas system which eliminates the short-stroke issues that are sometimes encountered in cold weather with some 18” barrels that utilize a rifle length gas system. The barrel extension has “M4” feed-ramps. The barrel has a 1:7” twist rate and polygonal rifling (not a polygonal bore.)

The chamber found in this barrel is Noveske’s proprietary Noveske Match mod 0 chamber that “was developed to fire MK262 Mod 1 on AUTO in hot environments." I installed the SPR barrel in a Colt M4 upper receiver and free-floated the barrel with a LaRue Tactical 12” handguard.

I conducted an accuracy (technically, precision) evaluation of the Noveske 18” SPR barrel from my bench-rest set-up following my usual protocol. This accuracy evaluation used statistically significant shot-group sizes and every single shot in a fired group was included in the measurements. There was absolutely no use of any group reduction techniques (e.g. fliers, target movement, Butterfly Shots).

The shooting set-up will be described in detail below. As many of the significant variables as was practicable were controlled for. Pictures of shot-groups are posted for documentation.

All shooting was conducted from a concrete bench-rest from a distance of 100 yards (confirmed with a laser rangefinder.) The free-float hand-guard of the rifle rested in a Sinclair Windage Benchrest, while the stock of the rifle rested in a Protektor bunny-ear rear bag. Sighting was accomplished via a Leupold VARI-X III set at 25X magnification and adjusted to be parallax-free at 100 yards. A mirage shade was attached to the objective-bell of the scope. Wind conditions on the shooting range were continuously monitored using a Wind Probe. The set-up was very similar to that pictured below.

For this evaluation, I used one of my standard match-grade hand-loads topped with Sierra 55 grain BlitzKings. When fired from my Krieger barreled AR-15s, this load has produced ½ MOA 10-shot groups at 100 yards.

Three, 10-shot groups were fired in a row from the Noveske SPR barrel from a distance of 100 yards with the resulting extreme spreads:

0.812”
0.732”
0.873”

for an average 10-shot group extreme spread of 0.81”. The three, 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius of the 30-shot composite group was 0.28”

The 30-shot composite group . . .

N.B. - - This barrel was purchased prior to the untimely death of John Noveske.





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