Advanced Marksmanship Differences shooting gas versus bolt guns?

[Sig685]

Re: Differences shooting gas versus bolt guns?

Thanks for the link. It's quite a long read. I was not aware the gas in the gas tube and then the key actualy holds the bolt forward against the pressure in the chamber. I thought that was the job of the bolt lugs. I love that graph, btw.

Obturation is a fundamental phenomenon for virtually every firearm in existence and it works the same way every time. What people seem to forget is that obturation works at both ends; the bullet and the cartridge and that's why the bolt of a properly functioning AR does not open before the bullet leaves the barrel.

 

[ssgp2]

Re: Differences shooting gas versus bolt guns?

I have seen many times the last round out of the group on a semi.
To confirm that the bolt locking open was the problem, I simply remove the mag on the last round and observed the group without flyers.

On the other hand, I did not have this problem with my AR15 CLE 24".
But I did some modification that might explain why.
Tubb's recoil spring + Tubb' weight system in the carrier.

It might slow down the action and allow the last bullet to hit on the POA.

 

[Graham]

Re: Differences shooting gas versus bolt guns?

It would seem to me that an additional 13" of suppressor ahead of the muzzle would have the effect of adding to barrel length for the sake of timing the bullet travel.

Years ago, circa 1983, Tommy Campbell, on behalf of Smith & Wesson, did a very high frame-per-second slow motion video of a rapid-fire string from an auto pistol. The goal was to dissect the forces present in recoil and to parse the elements of recoil in a semi-auto: slide unlocking; gasses leaving the barrel; slide hitting the stop in its most rearward position; feeding the next round; slide re-locking into its forward position.

The video showed the importance of trigger control, the disconnect and reset, and the unusually large recoil force generated by the slide hitting the frame as it stops its rearward travel.

Frank, do you have the capability of filming a high speed slow motion video of a suppressed piston-action rifle? A video like that would be helpful, as was the S&W video.

 

[our gang]

Re: Differences shooting gas versus bolt guns?

Well, I don't what a Mark Eleven is so I cannot comment on the last shot.
IME many semi autos have a "first shot flyer" problem due to the different seating impact of a gentle manual bolt release vs the seating force of actual operation.
The only reason a carbine would wear out faster than a rifle is differences in engineering, materials or maintenance. I don't hear anyone yelling about the Springfield armory short barreled 308 semi autos having any more or less problems than the long barrel versions. That tells me that a PROPERLY engineered carbine will work just as well, If this were not true all the experts would be shooting 30" barrels.
I know a lot of folks love to hate the AR gas system but I have found that in my three DPMS gas guns that minimal upkeep keeps em' running w/o a hitch AND one is 16", one 20" and one 24". If the first shot is loaded from the magazine using the bolt release, it and all the rest go into the same group.

 

[Graham]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: our gang</div><div class="ubbcode-body">I don't hear anyone yelling about the Springfield armory short barreled 308 semi autos having any more or less problems than the long barrel versions. </div></div> They all have the same problem: neither will consistently shoot 1 MOA without a great deal of work.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: our gang</div><div class="ubbcode-body">I know a lot of folks love to hate the AR gas system but I have found that in my three DPMS gas guns that minimal upkeep keeps em' running w/o a hitch AND one is 16", one 20" and one 24".
</div></div> Not in the desert.

 

[Lowlight]

Re: Differences shooting gas versus bolt guns?

I don't have high speed video capabilities, but this image shows the gases leaving the muzzle, the spent casing is already ejected and the gun is reloading, all pretty close together. The casing is about 6 or more inches from the ejection port, so it was out for a bit.

http://www.snipershide.com/modules/galle...cc27b12ee4d7c47

 

[Graham]

Re: Differences shooting gas versus bolt guns?

Hhmmmmm.

 

[j-huskey]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">So if they are saying gas moves 5X faster than the bullet, the bullet has 7 inches in front of the gas key, and 13 inches of suppressor, the gas is moving about 13" back to the bolt on a Mk11 , 5X faster means the bullet hasn't left the muzzle before the unlocking operations has started. </div></div>

And best I can tell, this is why we have some of the trouble with the AR-10's showing excess pressure signs on the brass when the load is not over pressure at all. The bolt IS opening when the bullet is still in the barrel and the chamber is overpressure and the case has not begun to release it's grip on the chamber walls.

We took the same rifles and closed off the gas system making them a single shot rifle and shot the same ammunition in them. Zero pressure signs. We did this more than once in two places, one I can discuss and one I cannot. The results were the same.
It didn't matter whether we did it with or without a suppressor. There was also no difference when we measured the fired brass from the AR-10 and the bolt guns. Both measures what the chamber dimension was supposed to be based on the chamber castings.

It's a AR-10 thing. Some work much better than others.

Sig, you are welcome to the link, it's the best one I've found so far.

Ourgang, the MK 11 is the Knights Armament SR 25 military version, aka the SASS. And the M1A versions with any length barrel are a controlled gas driven piston system, rather than an impingement system, two very different animals, and where the military wants to go with the AR family aka POF piston systems and such.

 

[sinister]

Re: Differences shooting gas versus bolt guns?

"So if they are saying gas moves 5X faster than the bullet, the bullet has 7 inches in front of the gas key, and 13 inches of suppressor, the gas is moving about 13" back to the bolt on a Mk11 , 5X faster means the bullet hasn't left the muzzle before the unlocking operations has started."

"And best I can tell, this is why we have some of the trouble with the AR-10's showing excess pressure signs on the brass when the load is not over pressure at all. The bolt IS opening when the bullet is still in the barrel and the chamber is overpressure and the case has not begun to release it's grip on the chamber walls."

Cases are still obturated to the chamber walls in both 24-inch and 22-inch AR-10Ts when the extraction cycle begins (when gas pressure begins to overcome the standing-still inertia of the bolt carrier group, buffer, and operating spring). In a standard gun or suppressed rifle you can see this on the cases by the "High pressure" indications on the case (flattened primer and possibly some case head flow into the extractor hole, some extractor rim peeling, and smoke-smeared cases).

On my rifle I found I could help slightly delay unlocking and extracting by using a Tubb Carrier Weight System (using the heavy tungsten insert). I'm sure you can probably use a heavy "Slash" tungsten carrier to do the same thing.

Steve Thompson at ADCO Firearms in Ohio modifies the AR-10T the same way Dave Tubb did when he was shooting the SR-25 at Camp Perry, namely by using a slightly longer gas tube (maybe two inches longer), tapping the gas from the barrel slightly farther from the present gas port position (pressure behind the bullet will drop slightly as it has slightly more distance and volume to fill in the barrel before it's tapped, and a little farther to go to the carrier once it IS tapped).

Unlocking starts as soon as the gas starts to build up pressure in the gas carrier key. The bolt still remains locked, but on an AR as the carrier starts moving to the rear the bolt cam pin starts to turn the bolt to clear the locking lugs in the barrel extension. On a bolt action the rearward force of the case on the bolt face stops as the bolt lugs stop on the receiver lug faces.

Follow-through is way more important for an AR than a bolt gun as lock time is longer (a striker-fired 700 beats a hammer any day).

I think what folks are going to find with 7.62 piston-drive systems (HK, POF, LWRC) is the same problem -- that piston is going to smack the op-rod and get the carrier going back as soon as gas is tapped.

 

[j-huskey]

Re: Differences shooting gas versus bolt guns?

Brother Dave Sir,

It is so good to hear from you. Rio Rancho NM? You retire and not tell us?

jw

PS, I fixed my AR-10 by reducing the amount of gas that could get back there. I fixed the AR-15 stuff by going to a rifle length gas system on the 18" guns and going to mid length gas systems on the 16" guns. I thank you for your help back then, much much much, and for setting me up with our friend Gene in the shop. I owe you.

 

[James H. Graham]

Re: Differences shooting gas versus bolt guns?

In the old days- there was a difference in accuracy, but these days the only difference is the Bolt gun works as fast as you can operate it while you have to wait on the gas gun for it's parts to function.

Peopel will argue accuracy - it depends on your preforming purpose.

 

[Turk]

Re: Differences shooting gas versus bolt guns?

On paper there is a difference; in the field the difference is minimal. I would imagine working for your parts to function isn't too time consuming! Then again....

 

[our gang]

Re: Differences shooting gas versus bolt guns?

Like your story. I used to win a lot of bets as a youth that I could fire 6 shots faster with an ejector side by side 12 bore than the other guy with a waterfowl legal
(3 shot) pump or semi-auto 12 bore.
That said, I doubt anyone with a conventional bolt gun can put fire downrange quicker than M-14 or black rifle.
As to functioning, I don't live in true desert, rather "high desert" arid, but not Iraq. However, I doubt we would be kicking the ragheads asses, as many troops who were/are there have told me, were are weapons so dramatically inferior to the enemy as some would have us believe. The same experts BTW that said the M1 Abrams would fail in the desert, ditto Apache and so on.
As for accuracy I note that the Brits and us are both using a 50 BMG semi-auto for putting down targets at extreme range and we are going to convert to a semi-auto 308 sniper rifle. A rifle that will, day in and out, put the first shot in a 1 MOA group will kill or disable any human out to 1000 yards. While .25 5 shot groups are neat but even a little raghead is a lot bigger than a gopher and if he is on the move rapid repeat shots w/o losing the target is a big plus. There was a neat video floating around the net last year of, as I recall, an Army sniper team shooting from a concrete balcony at ragheads running around some city. The sniper had a modified AR 10 and the spotter live dialogue was wonderful although not PG rated. "You hit the f---er in the leg, take another, that's good the f---er is done flopping around." and so on for 5 minutes. Several would have escaped were it not for rapid followup shots.... a lot more rapid than an M 40!
IMO our biggest error in Iraq was using troops with rifles to clear out rooms rather than B-52s with 750 pound bombs. We lost how many troops in Fallujah? when were it given the Bremen treatment those boys would still be alive. George Patton is spinning in his grave. Enough said.

 

[Turk]

Re: Differences shooting gas versus bolt guns?

It's too bad you weren't around when they collected all the great military minds together!

 

[our gang]

Re: Differences shooting gas versus bolt guns?

I fail to see where I qualified myself as "a great military mind" nor what that has to do with gas vs bolt guns.
Or when Caeser, The Khan, Fredrick the Great, Wellington, George Washington, Mac, Ike and Norman were ever assembled in one room? Keep it simple for this poor old man who only knows the history he has read and the 66 years he has lived through it. You were where in 1965-70?

Victory is only achieved when you kill so many of the enemy that they no longer have the resources to resist. I'd much rather have my son do that from 50,000 feet with bombs than in some dark house in some back street one on one with some doped up raghead. My Dad, CO company K 109th 28th division felt the same way after chasing the Krauts for almost 3 years. Funny how real experience tempers the "thrill of combat".

 

[Turk]

Re: Differences shooting gas versus bolt guns?

I was here in 65-70. Judging by your statement above you have no "real experience" nor do I!

 

[ssgp2]

Re: Differences shooting gas versus bolt guns?

Do you think that changing the bullet weight would have an effect on the timing of the rifle?

If so, heavier or lighter bullet?

 

[Turk]

Re: Differences shooting gas versus bolt guns?

As long as the amount of powder was the same it should be about the same; I think!

 

[Greg Langelius *]

Re: Differences shooting gas versus bolt guns?

This is interesting stuff.

I heard that a friend recently needed to send an AR10 back to the builder because it was opening early and damaging the cartridge rims.

I recently got to actually see the rifle and at first I mistook it for an M4gery, it was so short.

This reinforces my take on the above comments about minimum barrel lengths beyound the gas port.

I wonder how gas port size weighs in with this issue, and whether the minimum lengths would be affect by that, and by the differences between the 5.56, 7.62, and maybe even the .260?

This is why I like the short-stroke piston system on the M14/M1A. It is essentially a self regulating system with the key factors of the timing being built into the piston and cylinder.

I have owned an AR, an M1A,and still own my Garand, each of which takes a very different approach to gas driven operating systems.

If I had my druthers, I'd have an M14 style shortstroke piston system on an AR type action.

The AR depends too much on ammunition configuration to establish its timing. IMHO, this imposes extra, maybe excessive, demands on the load development process.

Greg

 

[Sig685]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ssgp2</div><div class="ubbcode-body">Do you think that changing the bullet weight would have an effect on the timing of the rifle?

If so, heavier or lighter bullet? </div></div>

Definitely. A lighter bullet will exist the bore earlier and faster than a heavier bullet.

 

[Sig685]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">This is interesting stuff.

I heard that a friend recently needed to send an AR10 back to the builder because it was opening early and damaging the cartridge rims.

I recently got to actually see the rifle and at first I mistook it for an M4gery, it was so short.

This reinforces my take on the above comments about minimum barrel lengths beyound the gas port.

I wonder how gas port size weighs in with this issue, and whether the minimum lengths would be affect by that, and by the differences between the 5.56, 7.62, and maybe even the .260?

This is why I like the short-stroke piston system on the M14/M1A. It is essentially a self regulating system with the key factors of the timing being built into the piston and cylinder.

I have owned an AR, an M1A,and still own my Garand, each of which takes a very different approach to gas driven operating systems.

If I had my druthers, I'd have an M14 style shortstroke piston system on an AR type action.

The AR depends too much on ammunition configuration to establish its timing. IMHO, this imposes extra, maybe excessive, demands on the load development process.

Greg </div></div>

IIRC, the M-14 system is somewhat fragile and extremely sensitive to the type of ammo being used in it. If too stout a load is used, you run the risk of breaking the op-rod or at least bending it. This will be a problem encountered by the piston-engined ARs. The only good thing is that they are starting to appear at a time when bullets have attained their maximum weights in the .223. With a jet-powered AR, I can easily tune the rifle to compensate for heavy bullets and hot loads. I have been using a CWS for some years now to good effect. I would not dream of shooting my LR load in my AR without it. I currently use the heavy tungsten carbide insert and my brass piles up next to me on the line and is not mangled at all; it is emminently reloadable. If I were to reduce the load or the bullet weight, I could use the lighter insert, or no insert at all, or enevn remove the CWS altogether. This way in my rifles, I can shoot anything from 35grs to 82gr bullets, which is an extremely wide range and I can assure you that my 80gr LR loads are not pussycats.

I have no idea how I could accomplish something similar in an M-14 without extensive mods. If you were to shoot a very heavy 190 gr load out of your M14, I suspect the op-rod would resemble a pretzel.

It is my contention that piston-driven ARs are going to bring a new set of problems to the fore, not the least of which is diminished accuracy. Make mine jet-powered.

 

[Lowlight]

Re: Differences shooting gas versus bolt guns?

just a little amendment to this, last night we shot the Mk11 in total darkness using the SIMRAD and ATPIALs, and while watching the students shoot, I was able to videotape the sparks that were coming out the ejection port.

these sparks flew about a foot (plus) out of the ejection port about the same time the rifle was fired, it could have been a timing issue as noted above, but it was pretty well across the board. More rifles shot the sparks out the ejection port more times than not, and they varied in direction from straight out to angled back towards the shooter. This was definitely not the brass, but a series of sparks.

I can't post the video because I don't have the connection capabilities here, but I can get when I get home. As well, we also note that guys shooting the Mk11 end up with black cheeks, over people who shoot AR style 5.56 stuff. I have some pictures but unfortunately they are on my home computer.

As far as bullet weight, you are talking a 175gr SMK going a tick under 2600fps, so there is a big difference there over a 5.56.

 

[Lindy]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I have no idea how I could accomplish something similar in an M-14 without extensive mods. If you were to shoot a very heavy 190 gr load out of your M14, I suspect the op-rod would resemble a pretzel.</div></div>

There are adjustable gas plugs for the M1 Garand, so I expect someone has or could adapt those to the M14.

 

[Sig685]

Re: Differences shooting gas versus bolt guns?

The judicious application of a CWS in the carrier of the MK11 could prevent the premature opening of the bolt. (I'm fairly confident that you no longer think the bolt retracts completely and rechambers a round while the bullet is still in the bore.) Are we using suppressors here?

My point about bullet weights was to highlight the RANGE of weights used in a .223 AR-15.

For a .308 this would go from 100gr to 220gr; the 175gr is like a 69gr in a .223 (again, using the respective ranges.)

 

[j-huskey]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I have no idea how I could accomplish something similar in an M-14 without extensive mods. If you were to shoot a very heavy 190 gr load out of your M14, I suspect the op-rod would resemble a pretzel.</div></div>

There are adjustable gas plugs for the M1 Garand, so I expect someone has or could adapt those to the M14.
</div></div>

Lindy and Sig,

Back when the AMU and USMC were shooting 14's with heavy loads, they had two separate rifles for M852 ammo and for heavy loads (for shooting 1000 yards).
The heavy load guns had the gas plug drilled out to reduce the pressure, to prevent battering damage to the rifle. Some of these rifles would not function with 852. They DID NOT last long before having to be re-built as they had the shit battered out of them with heavy bulets.
The 14 was designed for a 147 grain bullet. The 172 match bullet required some mods to keep the weapon functioning at peak accuracy. Thats not a lot of difference in weight, but it was enough to keep the AMU armorers busy as hell.
Today's rifles will shoot the 147, 168, and 175 kept to 2600fps reasonably well but not as well as LONG time wise as a well built AR-10 platform rifle. (I know that comment will annoy some people, but JSSAP, Battle Lab, and TECOM studies verify that statement.)

The adjustable gas plug for a 14 is workable, but a pure pain in the ass, because as the weapon carbon fouls the plug, the pressure goes up and problems begin.

Those of us who shot the 14 as a service rifle had a carbon scraper to clean out the inside of the plug and a drill bit in a hand tool to clean out the plug hole.

If I could post a pic with my less than computer capabilities, I'd show you the tube wrench that you used to hold the gas tube in place not to cause it to move, the wrench you used to remove the plug, the inside carbon reamer, and the drill for the hole. It's laying on my load bench at home as I write this. We also had a spare gas plug with us at all times on the line just in case.

Just a little history from somebody who shot these systems in competition, had two different set up rifles (600 and in, and another for 1000), and dealt with the mentioned problems.

Many forget the known history of these weapons systems as time removes the people who shot them both in combat and competition, and the technical knowledge gets lost in storage where we can't find the old studies or armorers manuals.

 

[Lindy]

Re: Differences shooting gas versus bolt guns?

Bill: yeah, I think an AR10 with an adjustable gas system is a far better solution to the .308 gas gun than the M14. However, I retain some fondness for the M14 from the Marine Corps.

 

[Turk]

Re: Differences shooting gas versus bolt guns?

Sig685, are you saying more,less,or equal pressure w/ the lighter bullet and the same charge?

 

[Lowlight]

Re: Differences shooting gas versus bolt guns?

Well you are almost right in characterizing what I said, I said there are 3 recoils the shooter has to contend with and that a "lot" is going on while the bullet is in the bore.... I never got specific but it is meant to convey that follow through is more important on a gas gun, how you take what I said is on you.

But I haven't had to change my position based on what was posted here, I don't think you can say the same. As you so tried to point out regarding the math and psi, the same could be said for gas speed vs bullet speed and neither one adds up to show what we are seeing isn't happening. but again, I'm not here to argue, we know what is being see, both at the shooter and downrange and the shear volume of our experience speaks beyond a single rifle.

 

[sinister]

Re: Differences shooting gas versus bolt guns?

Bill's right on with the Long Range M14s and M21s. They each had a 1/64th -inch hole drilled in the end of the gas nut to vent excess pressure generated by a 190 Match King driven over a huge amount of 4064. When you shot a 1,000-yard rifle the bolt would smash the inside of the receiver so hard it would often ring like an M1 "Ping." Do it enough and you'd often find cracks in the receiver. Although you could also weld a lug on to a cast Springfield Armory M1A receiver there's definitely a difference over a bolt gun. Some 4064 and Varget loads are so hot the rifle won't extract or eject the case until the case has cooled (usually just a second) -- the shooter has to reach forward and hand-cycle the action because the piston is smashing the end of the op rod but the case is still obturated in the chamber!

There's no violent smashing of piston against op-rod in the M1 or AR-10. The AR-10 is more forgiving and adjustable because you can add carrier or buffer weight, while the M1 op rod could be bent if the powder burn rate is too slow.

The M14s (and to a lesser extent the M1s) would give you great spark shows at dusk as the light starts to fail and you get gases and unburnt powder grains lighting off as they get exposed to oxygen in the atmosphere as cases extract and eject. Add a suppressor to an XM-110 and you'll see the same kind of show out the ejection port.

(Bill, New Mexico is a terminal assignment for me -- I'm supposed to start thinking about what I'm going to do when I grow up. I hit 30 years in January)

 

[Lindy]

Re: Differences shooting gas versus bolt guns?

Dave - a friend of mine said that if you can reach 50 years old without growing up, you don't have to.

I passed that mark 12 years ago - and still behaving badly.

 

[TiroFijo]

Re: Differences shooting gas versus bolt guns?

In the piston ARs the system is supposed to be more self adjusting to different loads, because the excess gas bleeds off after a certain distance and the impulse transmitted to the op rod is limited at the very beginnig of the cycle. Of course, with a heavy gas port pressure the initial impulse on the operating rod is stronger, but the difference in bolt thrust is smaller than with a direct impingement system.

All the gas actions are a relatively finely balanced system optimized for one load and pressure curve. The AR is supposed to start bolt opening after the bullet has left and pressure has dropped almost to zero, but as many have posted this is not always the case. For example, using 5.56 ammo in a 223 chambered AR can cause failure to extract and an extractor that rips the case rims. Or using a hot load can blow the primers, etc.

And I think that the 5.56 ARs are more forgiving than the 308 ones, and easier to shoot well.

 

[Sig685]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Turk</div><div class="ubbcode-body">Sig685, are you saying more,less,or equal pressure w/ the lighter bullet and the same charge? </div></div>

In my experience on the AR-15, I find that shooting heavy bullets (80gr JLK and SMK and 80-82gr Bergers) with stout loads puts a lot more pressure on the system and necessitate the use of the CWS with the heavy insert. This would probably manifest itself in the same way that Lowlight is describing is experiences with the Mk11 and the 175gr bullets. The higher inertia from heavier bullets and lower muzzle velocities cause the barrel time of the bullet to be longer than specified and will allow the pressure in the return gas tube to rise to functional pressure before the bullet it out the door, so to speak. This means that it certainly is possible to start unlocking the bolt before the pressure in the bore/gas tube has completely reduced to zero and it will cause a more violent ejection cycle and it would mess up my brass.

Since I have to buy my brass, with my money, I do try to get the most use out of each piece.

When shooting lighter bullets, the inertia of the bullet is lower and so it accelerates faster and exits the bore in the proper time so that the extraction cycle is gentler and within specs.

One must also use appropriate powder. I find that for heavy bullets Varget works really well for me. It's not too slow that the pressure curve would shift to the right (higher over time) and not too slow that I lose too much pressure because of a long barrel (left shift, lower over time). As the story goes, it's just right for me with heavy bullets in long barrels.

When I shot lighter bullets (such as the 52gr SMK,) I found that a faster powder line 2230, worked better than Varget. Since I hate using different powders in a match gun, I simply standardized on one powder, one bullet. It makes it simpler for my admittedly small brain. That way I leave the insert in all the time.

For the same charge lighter bullets will create lower pressures; they will exit said system faster than the heavier bullets. (Also, because the heavy bullets are in the barrel for a longer time, the throat erosion will be accelerated compared to using light bullets.)

 

[sinister]

Re: Differences shooting gas versus bolt guns?

Exactly right on the bore-time vice pressure curve -- which is why many National Match Course shooters get only 5 firings out of M14 7.62 brass before chucking it (given case stretch and the opportunity for case head separations). That same brass could go 10-20 firings from a bolt gun.

I chose the Tubb CWS to try to get a couple more firings out of Lake City cases from an AR-10.

 

[Sig685]

Re: Differences shooting gas versus bolt guns?

Case strecthing is not an issue for me. What I find to be a limiting factor is the expansion of the primer pocket. After a half-dozen LR loads, they are pretty loose.

 

[ssgp2]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Well you are almost right in characterizing what I said, I said there are 3 recoils the shooter has to contend with and that a "lot" is going on while the bullet is in the bore.... I never got specific but it is meant to convey that follow through is more important on a gas gun, how you take what I said is on you.

But I haven't had to change my position based on what was posted here, I don't think you can say the same. As you so tried to point out regarding the math and psi, the same could be said for gas speed vs bullet speed and neither one adds up to show what we are seeing isn't happening. but again, I'm not here to argue, we know what is being see, both at the shooter and downrange and the shear volume of our experience speaks beyond a single rifle.
</div></div>

I don`t think anyone is questionning the technics you are using/teaching.
And I value the info you are providing from your observations.

I believe there is a quest to understand the AR plateform and to exploit all info available to acheive the best accuracy and smoother operation.

My AR 15 was put together by CLE and I used the info in Black Magic, I called it the boring rifle.
Whatever I fed it, it was accurate and easy to shoot.

I`m having a little more problems with the AR10, and find this post very interesting.

I am curious to know if others feel like I do, in regards of having a section dedicated to the AR on this forum.

 

[our gang]

Re: Differences shooting gas versus bolt guns?

Actually Turk i was in SEA during those years and have some "experience."
I gather you believe that door to door fighting and losing our young men and women is preferable to just flattening the whole town and everyone in it? In WW II, after Germany was defeated, my Dad's division was to be staged for the invasion of Japan but two bombs removed that necessity so I grew up with a father rather than a faded picture as so many of the families who sons, fathers etc were sacrificed in stupid street fighting tactics in Iraq so we could avoid killing all those" women and children". What BS to feed the dumb, never served, sheep of the USA.
What really cuts is your handle of Turk. You might want to read about what the real Turkish military is like:
http://www.korean-war.com/turkey.html
in a much nastier war than Iraq!

 

[Turk]

Re: Differences shooting gas versus bolt guns?

Thanks for the history lesson! Sorry if my handle bothers you! The fact remains is that at the end of the day a soldier has to plant the flag, not a pilot at 50k feet! I'd rather not comment on the Iraq war because this isn't the place. From your infinite wisdom you have somehow deduced the fact that you think carbines are affected the same as rifles and don't wear at a faster rate! You have furthermore deduced that I prefer more soldiers being killed, and that you know more about the Turkish Military than I do! I have respect for my elders and am at a disadvantage. All I have to say is if B52's are the answer; why did almost 60k soldiers die in Vietnam? "Shock and awe" didn't cut it either! I am pretty certain less have died in Iraq. Btw one is too many! Now if you would permit I'd like to see the facts that you have in regards to the "carbine" theory of yours?

 

[Sterling Shooter]

Re: Differences shooting gas versus bolt guns?

There is no difference when shooting a bolt gun or a gas gun. Any gun requires the shooter to complete the firing task in a manner which supports undisturbed aim.

Sure, lock times may be different, and recoil may be different. yet, all shooting is the same; sight alignment and trigger control.

What's interesting about this thread, however, is how the facts have been displaced by minutia and gobbledygook, distorting basic marksmanship knowledge into something esoteric, thus, precluding any inexperienced shooter from an understanding of how to get the job done with any gun.

 

[Greg Langelius *]

Re: Differences shooting gas versus bolt guns?

I appear to have started a thread hijack here, and that was not my plan.

Using the M14 as a referent may have been unfortunate. The fragility in the M14 is in the oprod, and not in the gas piston/cylinder system. The way the gas piston port and gas cylinder port line up acts as a regulating valve to cut off the gas infusion once the piston initiates movement was the point I was attempting to make. That was the relationship I was promoting, and my primary emphasis was on the timing aspect.

Perhaps a better referent would have been the AR18/AR180 system, of which I am a solid fan. I have never understood why it never caught on in any way even nearly as well as the AR15/M16 system. IMHO, it is clearly the better system.

Greg

 

[our gang]

Re: Differences shooting gas versus bolt guns?

Thanks for getting all back on track. If you can shoot well, then you can probably shoot any operating system well. Four position shooting with a sling is becoming a lost art and far too many people cannot operate without a bench rest and/or bi-pod.

 

[our gang]

Re: Differences shooting gas versus bolt guns?

I agree the soldier has to plant the flag but it is far easier to do it on a pile of rubble than a city that is intact. The invasion of Japan would have cost up to 1,000,000 American casualities.... Two bombs took care of that concern.
As for B52s... well if you can't figure out the differences between the Vietnam "war" and war in the desert, Then you need to get more history lessons than I have time to provide.
I think I am done straying off the post's subject to try and illuminate the obvious.

 

[Sig685]

Re: Differences shooting gas versus bolt guns?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Phylodog</div><div class="ubbcode-body">Appreciated Sig685. I'll be back out with it tomorrow and I'll pay more attention to my follow through and see what happens. </div></div>

It's been three days since the above. How did it work out for you, Phylodog? Inquisitives minds want to know.

 

[Phylodog]

Re: Differences shooting gas versus bolt guns?

Sorry about the delay, had several days of training which have kept me busy and I forgot about and update.

I put another 60 rounds or so through the rifle on Wednesday. My best efforts were still right around 1MOA for 5 rounds. I appears that the first round out of a mag finds a slightly different POI than the rest in a magazine but I didn't notice the last round issue.

I am in the process of changing several things about the rifle which will bring it a bit closer in feel to my bolt gun which I'm hoping may help me to shoot this rifle more accurately. A higher magnification scope, a shorter bipod and an adjustable cheekrest stock will all make this rifle feel more familiar and similar to my bolt gun. I'm also having the barrel threaded for my suppressor and installing a JP adjustable gas block. It'll be a few weeks until it's back together but I'm sure I'll be posting about it again.

Thank you for all of the information here.

Here is the rifle as it sits now. It should look significantly different in the coming weeks.

 

[Greg Langelius *]

Re: Differences shooting gas versus bolt guns?

I've got to believe the first round from each mag is going to a different POI because for some reason the way in which the battery lockup occurs is different from lockups that are the result of the action cycle. Maybe the buffer is playing some part in the cycle that the manual engagement cannot duplicate.

I also note the rifle does not have a forward assist (that I can see, anyway), and I suspect that using a forward assist might have some benefit.

Greg

 

[Phylodog]

Re: Differences shooting gas versus bolt guns?

I suspect the same Greg. I ordered an upper receiver with the forward assist yesterday. Once it arrives I'll play around with giving it a tap on that first round and see if I get any improvement.

 

[Sig685]

Re: Differences shooting gas versus bolt guns?

If I may be so bold, the only thing I would change is the barrel. BTW, the AR-10 from ArmaLite does not have a forward assist. Also, in my match AR-15, I don't believe I have ever touched the forward assist button.

Also, what kind of ammo are you using?

 

[Phylodog]

Re: Differences shooting gas versus bolt guns?

I've been shooting Federal GMM 168's and I tried a few of the 175's that I roll for my bolt gun but they're too long to feed through the mag properly.

I'll be working up a load once everything is back together.

 

[Sig685]

Re: Differences shooting gas versus bolt guns?

The singlemost greatest boost in sccuracy occured when I swapped my 1:8 24 inch Wilson barrel with a 1:7.7 26 inch Krieger barrel. That took me from Sharpshooter to Master in a few months.

Tell us about your barrel? Do you have free float handguards?

 

[Phylodog]

Re: Differences shooting gas versus bolt guns?

It is a free floated, 24", 1-10 twist, fluted, factory DPMS barrel. I have a Daniel Defense free float rail which will be going on and a JP adjustable gas block. Once the new receiver shows I will see about having the face trued prior to installing the barrel.

I have read reports that these DPMS barrels are capable if sub MOA accuracy but I purchased this rifle used so I have no idea what it's been through prior to me getting it. It did not appear to have been fired much though.

 

[Greg Langelius *]

Re: Differences shooting gas versus bolt guns?

Since the gas system is adjustable, I would adjust it for less gas until it fails to cycle reliably, the readjust it back just enough to get reliable cycling. This should bring the battery lockup due to the cycling process more into line with that which can be achieved with a manual bolt release. I'd be really interested in whther the main group comes closer to the CCB shot.

My reasoning: We're stuck with the manual cycling, we can't do much to change that. But we <span style="font-style: italic">can</span> adjust the operating cycle. Maybe we can make that lockup more Similar to what a manual cycle provides.

Greg