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Posted: 8/12/2016 7:26:07 PM EDT
[#1]
I forget where it was posted or on which forums, but recently the U.S. Army did a test between several drop-in piston kits (different kinds and manufacturers) vs DI and for the most part they were about the same in terms of reliability, accuracy, etc.
I wish I had the link. I've been looking for it too. |
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Posted: 8/12/2016 9:17:09 PM EDT
[#2]
Some claim that the added mass and moving parts of a piston system make it less accurate than a DI, which sounds logical.
Yet, my LWRC is about the most accurate AR that I own. I think that a properly made piston system is just as accurate as a DI system, even if it was harder for it to get there (more QC needed for the same accuracy level as a DI system. |
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Posted: 8/13/2016 1:08:23 AM EDT
[#3]
Quote HistoryQuoted:
Some claim that the added mass and moving parts of a piston system make it less accurate than a DI, which sounds logical. Yet, my LWRC is about the most accurate AR that I own. I think that a properly made piston system is just as accurate as a DI system, even if it was harder for it to get there (more QC needed for the same accuracy level as a DI system. i'd agree with that. i have a 18" DMR upper at its a 1 moa shooter. even my new IC SPR 14.7 upper shoots pretty damn well. i thought i recall piston uppers suffering from vertical stringing but not mine. |
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Posted: 8/13/2016 2:06:58 PM EDT
[#4]
All things being equal, there is no difference in inherit precision between a GP and DI platform.
Accuracy is your responsibility. If one is interested in achieving the most precision possible, nether GP or DI are considered suitable. Bolt action reigns in this area. |
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Posted: 8/13/2016 2:57:39 PM EDT
[#5]
With the same quality barrel there would be no advantage either way . I would expect a good quality piston AR to be as accurate as a D I AR , and in fact mine are .
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Posted: 8/15/2016 9:55:09 AM EDT
[#6]
Quote HistoryQuoted:
Some claim that the added mass and moving parts of a piston system make it less accurate than a DI, which sounds logical. Yet, my LWRC is about the most accurate AR that I own. I think that a properly made piston system is just as accurate as a DI system, even if it was harder for it to get there (more QC needed for the same accuracy level as a DI system. That's what I always thought and while I don't have a super high end Di my ic spr 14.7 beats my aero precision, Ruger, and bcm. |
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Posted: 8/15/2016 10:55:06 AM EDT
[#7]
Quote HistoryQuoted:
That's what I always thought and while I don't have a super high end Di my ic spr 14.7 beats my aero precision, Ruger, and bcm. Quote HistoryQuoted:
Quoted:
Some claim that the added mass and moving parts of a piston system make it less accurate than a DI, which sounds logical. Yet, my LWRC is about the most accurate AR that I own. I think that a properly made piston system is just as accurate as a DI system, even if it was harder for it to get there (more QC needed for the same accuracy level as a DI system. That's what I always thought and while I don't have a super high end Di my ic spr 14.7 beats my aero precision, Ruger, and bcm. are your aero and rugar barrels chrome lined? seems like most of us with LW uppers that are more accurate than our DI stuff are comparing them to chrome lined DI barrels. LW barrels are nitrided and i think its been established that nitrided is more accurate than chrome line right? my only other nitrided barrel is a BA 16" pencil that isnt following that pattern. its less accurate than my FN, noveske and BCM chromelined. i dis motice my LWRC 18" DMR was not that accurate out of he box. seems like it got better over time or maybe i got better? not sure. |
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Posted: 8/15/2016 8:30:54 PM EDT
[#8]
Quote HistoryQuoted:
are your aero and rugar barrels chrome lined? seems like most of us with LW uppers that are more accurate than our DI stuff are comparing them to chrome lined DI barrels. LW barrels are nitrided and i think its been established that nitrided is more accurate than chrome line right? my only other nitrided barrel is a BA 16" pencil that isnt following that pattern. its less accurate than my FN, noveske and BCM chromelined. i dis motice my LWRC 18" DMR was not that accurate out of he box. seems like it got better over time or maybe i got better? not sure. Quote HistoryQuoted:
Quoted:
Quoted:
Some claim that the added mass and moving parts of a piston system make it less accurate than a DI, which sounds logical. Yet, my LWRC is about the most accurate AR that I own. I think that a properly made piston system is just as accurate as a DI system, even if it was harder for it to get there (more QC needed for the same accuracy level as a DI system. That's what I always thought and while I don't have a super high end Di my ic spr 14.7 beats my aero precision, Ruger, and bcm. are your aero and rugar barrels chrome lined? seems like most of us with LW uppers that are more accurate than our DI stuff are comparing them to chrome lined DI barrels. LW barrels are nitrided and i think its been established that nitrided is more accurate than chrome line right? my only other nitrided barrel is a BA 16" pencil that isnt following that pattern. its less accurate than my FN, noveske and BCM chromelined. i dis motice my LWRC 18" DMR was not that accurate out of he box. seems like it got better over time or maybe i got better? not sure. very true, not a true comparison. They are both chrome moly. I would like to see a lwrci Di go up against a piston. Might be a better measuring stick. |
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Posted: 8/21/2016 8:53:20 AM EDT
[#9]
Quote HistoryQuoted:
Some claim that the added mass and moving parts of a piston system make it less accurate than a DI, which sounds logical. |
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Posted: 8/21/2016 2:34:40 PM EDT
[#10]
Quote HistoryQuoted:
If that were true, the SCAR, ACR, G36, etc. would all have worse accuracy than the AR. Their carriers are massive in weight compared to AR carriers. In fact, if that were true, why would people add more reciprocating mass, in the form of heavier buffers and David Tubbs' carrier weights, in an attempt to improve accuracy? Quote HistoryQuoted:
Quoted:
Some claim that the added mass and moving parts of a piston system make it less accurate than a DI, which sounds logical. yep. i had a scar16 and once i got a geisele trigger in it, it was a tack driver... for that skinny ass barrel. |
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Posted: 8/22/2016 4:06:47 PM EDT
[#11]
Ah yes the old "Piston guns vertical stringing." Exists only on the internet.
Seriously if that were true wouldn't rifles such as the M1 Garand suffer from this also since it has a piston and op rod? |
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Posted: 8/22/2016 5:59:13 PM EDT
[#12]
I wonder if the old wife's tales of piston rigs stringing comes from a time when most of the piston guns were conversions or franken guns piecied together by small outfits.?
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Posted: 8/22/2016 6:21:26 PM EDT
[#13]
Quote HistoryQuoted:
I wonder if the old wife's tales of piston rigs stringing comes from a time when most of the piston guns were conversions or franken guns piecied together by small outfits.? That seems like a logical point but...........my experience: On the military side of the house I got to test the HK416 when the idea first hit to use it in the Army. Aside from excessive felt recoil due to it being over gassed for "reliability" no issues. At the same time I became involved with Adams Arms when they only made piston kits. I still have two of their original systems installed on Sabre Defense uppers they shoot very accurate for their age. AA kit on 10.5 Sabre Upper 
Red Dot? ........Why Yes that is a still working 1990's Israeli Elbit Falcon (if you google it a majority of the pics that come up are from me.) |
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Posted: 8/22/2016 10:11:40 PM EDT
[#14]
Piston systems have advantages and disadvantages. The disadvantage is that they are susceptible to carrier tilt when the piston strikes the carrier - there's a difference between gas impinging on the bolt carrier gas key and a solid rod slamming into the carrier key that is offset from it's center of mass. This can cause accuracy issues (as measured by CONSISTENT POI for consecutive shots) and excessive wear - especially near the buffer tube. Short stroke piston systems may be more susceptible as opposed to long stroke systems - depending on how they are configured. Long stroke systems such as PWS' have a long solid rod connected to the carrier so the "impacting" occurs much closer to the gas block.
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Posted: 8/22/2016 10:18:14 PM EDT
[#15]
Quote HistoryQuoted:
Piston systems have advantages and disadvantages. The disadvantage is that they are susceptible to carrier tilt when the piston strikes the carrier - there's a difference between gas impinging on the bolt carrier gas key and a solid rod slamming into the carrier key that is offset from it's center of mass. This can cause accuracy issues (as measured by CONSISTENT POI for consecutive shots) and excessive wear - especially near the buffer tube. Short stroke piston systems may be more susceptible as opposed to long stroke systems - depending on how they are configured. Long stroke systems such as PWS' have a long solid rod connected to the carrier so the "impacting" occurs much closer to the gas block. Was Carrier tilt a issue at one time yes but was that solved a few years back......... with everything from redesigning the back of bolt carriers to changing the angle of the gas key (strike plate on bolt carrier). |
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Posted: 8/23/2016 5:22:48 PM EDT
[#16]
Quote HistoryQuoted:
I forget where it was posted or on which forums, but recently the U.S. Army did a test between several drop-in piston kits (different kinds and manufacturers) vs DI and for the most part they were about the same in terms of reliability, accuracy, etc. I wish I had the link. I've been looking for it too. Over on M4C... Link Reliability was nowhere near the same, exact reverse on common internet wisdom. |
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Posted: 8/23/2016 6:08:30 PM EDT
[#17]
Quote HistoryQuoted:
Over on M4C... Link Reliability was nowhere near the same, exact reverse on common internet wisdom. Quote HistoryQuoted:
Quoted:
I forget where it was posted or on which forums, but recently the U.S. Army did a test between several drop-in piston kits (different kinds and manufacturers) vs DI and for the most part they were about the same in terms of reliability, accuracy, etc. I wish I had the link. I've been looking for it too. Over on M4C... Link Reliability was nowhere near the same, exact reverse on common internet wisdom. All of the failure modes can be attributed to excessive cyclic rate (but, there can be other reasons), and note that most that had problems, also had very high, or excessive cyclic rates That's not what the tests said if you read it all the way through. It was about the same. However...all issues, which were reported to be cyclic related, could have been remedied by adjustable gas blocks, springs, buffers, or carriers. |
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Posted: 8/23/2016 7:01:43 PM EDT
[#18]
Quote HistoryQuoted:
. That's not what the tests said if you read it all the way through. It was about the same. However...all issues, which were reported to be cyclic related, could have been remedied by adjustable gas blocks, springs, buffers, or carriers. Quote HistoryQuoted:
Quoted:
Quoted:
I forget where it was posted or on which forums, but recently the U.S. Army did a test between several drop-in piston kits (different kinds and manufacturers) vs DI and for the most part they were about the same in terms of reliability, accuracy, etc. I wish I had the link. I've been looking for it too. Over on M4C... Link Reliability was nowhere near the same, exact reverse on common internet wisdom. All of the failure modes can be attributed to excessive cyclic rate (but, there can be other reasons), and note that most that had problems, also had very high, or excessive cyclic rates That's not what the tests said if you read it all the way through. It was about the same. However...all issues, which were reported to be cyclic related, could have been remedied by adjustable gas blocks, springs, buffers, or carriers. The tests showed the following: 
EDIT: "A12" should read "A1" EDIT: Blank entries should read "0" I said that all of the failure modes could be attributed to high cyclic rates. And, that was based on the assumption that there was excessive bolt bounce (high numbers of light strikes and failures to fire, which accounted for 110 of A1 and A2's malfunctions). Since they never attempted to address the high cyclic rate, we don't know what the actual results would be. And, I am not ready to go so far out on a limb to say that they will be "just as reliable". But, I am willing to say they will not be "less accurate". EDIT: Re-reading it, I see how it can be confusing... Reports like this always end with recommendations. The last line under "GENERAL ISSUES AND OBSERVATIONS:" is my comment, it is not part of the report. My apologies. It has been edited to be more clear. |
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Posted: 8/23/2016 7:48:57 PM EDT
[#19]
double tap
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Posted: 8/23/2016 9:57:18 PM EDT
[#20]
My piston LWRC and PWS are more accurate then my DI. Sold off pretty much all my DI except for 1.
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Posted: 8/25/2016 12:48:43 PM EDT
[#21]
I haven't noticed much of a difference.
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Posted: 8/25/2016 1:28:32 PM EDT
[#22]
IIRC hk had to add a bunch of meat back to the barrel to get barrel whip and vertical stringing under control. I know the new marine IAR is heavy as shit.
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Posted: 8/25/2016 4:34:44 PM EDT
[#23]
Quote HistoryQuoted:
IIRC hk had to add a bunch of meat back to the barrel to get barrel whip and vertical stringing under control. I know the new marine IAR is heavy as shit. could be something to that cuz my LWRC m6a3 and newer m6 IC are not GI under the hand guards..... AND...i recall seeing a post from a guy with the m6 SL version that was having accuracy issues. the SL version uses a lighter profile too, i think. |
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Posted: 8/26/2016 10:20:08 AM EDT
[#24]
Thicker barrel to cut barrel whip...false
The military has very thick barrel thickness requirements. They believe the thicker the barrel longer barrel life. Even though you could say a thinner barrel cools down quicker (less hot metal) and thus leading to longer life. And barrels erode fro the inside out so once you lose rifling you lose accuracy regardless of barrel thickness. I'm no barrel expert but I do know military rifles like the M4A1 barrels are very thick. Compare it to this Adams Arms VDI Tactical Elite barrel which is pretty average compared with most DI barrels 
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Posted: 8/26/2016 11:31:09 AM EDT
[#25]
Quote HistoryQuoted:
Thicker barrel to cut barrel whip...false The military has very thick barrel thickness requirements. They believe the thicker the barrel longer barrel life. Even though you could say a thinner barrel cools down quicker (less hot metal) and thus leading to longer life. And barrels erode fro the inside out so once you lose rifling you lose accuracy regardless of barrel thickness. I'm no barrel expert but I do know military rifles like the M4A1 barrels are very thick. Compare it to this Adams Arms VDI Tactical Elite barrel which is pretty average compared with most DI barrels http://i83.photobucket.com/albums/j292/stukas87/20160826_101258_zpspqawna73.jpg Are you saying thicker barrels are not stiffer and thus less prone to whip? You theory on a thinner barrel cooling faster seems to forget that they also heat considerably faster. A lot of the damage we here about is done when the barrel is hot and the throat erosion is accelerated. You seem to really go against the grain when it comes to barrel and wear ideas. |
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Posted: 8/26/2016 12:09:30 PM EDT
[#26]
I have never seen a piston AR at Camp Perry.
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Posted: 8/26/2016 12:34:00 PM EDT
[#27]
Quote HistoryQuoted: there's a difference between gas impinging on the bolt carrier gas key and a solid rod slamming into the carrier key that is offset from it's center of mass. |
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Posted: 8/26/2016 12:46:40 PM EDT
[#28]
Quote HistoryQuoted:
Are you saying thicker barrels are not stiffer and thus less prone to whip? You theory on a thinner barrel cooling faster seems to forget that they also heat considerably faster. A lot of the damage we here about is done when the barrel is hot and the throat erosion is accelerated. You seem to really go against the grain when it comes to barrel and wear ideas. Quote HistoryQuoted:
Quoted:
Thicker barrel to cut barrel whip...false The military has very thick barrel thickness requirements. They believe the thicker the barrel longer barrel life. Even though you could say a thinner barrel cools down quicker (less hot metal) and thus leading to longer life. And barrels erode fro the inside out so once you lose rifling you lose accuracy regardless of barrel thickness. I'm no barrel expert but I do know military rifles like the M4A1 barrels are very thick. Compare it to this Adams Arms VDI Tactical Elite barrel which is pretty average compared with most DI barrels http://i83.photobucket.com/albums/j292/stukas87/20160826_101258_zpspqawna73.jpg Are you saying thicker barrels are not stiffer and thus less prone to whip? You theory on a thinner barrel cooling faster seems to forget that they also heat considerably faster. A lot of the damage we here about is done when the barrel is hot and the throat erosion is accelerated. You seem to really go against the grain when it comes to barrel and wear ideas. Good points .. (I think lighter barrels don't heat up faster, they just transfer the heat to the outside faster being thinner) A thicker barrel will take longer to warp (bend) and catastrophic damage (bullet out the side) under prolong high rate of fire hence the thicker barrels on machine guns, the M4A1 and other military weapons. I am sure a barrel maker could come on here and really explain what makes a good barrel..What Im saying accuracy based on barrel harmonics/quality not thickness. Are their plus qualities to a thicker barrel yes, but... The point Im going after is to dispel the vertical stringing of piston guns myth. I own several pencil thin AA Evo Ultralite barrels they shoot great. Now once they heat up does the group open up some yes. But no vertical stringing. For some reason the issue of vertical stringing only comes up with piston ARs. Never comes up with any other piston gun or any gun with a OP rod AK, FN FAL on and on. It seems the issue has been made up as a excuse to say Piston ARs are a worthless concept . Now is going Piston gun worth it? If you shoot a ass ton I would say yes I love the fact that I can go the life of the barrel and never take piston apart and only need to wipe off bolt carrier every 2000-3000rds Shoot every once in a while then plenty of Damn fine DI guns out there. |
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Posted: 8/26/2016 1:48:52 PM EDT
[#29]
Quote HistoryQuoted:
I have never seen a piston AR at Camp Perry. Quote HistoryQuoted:
I have never seen a piston AR at Camp Perry. Ha!! That's my line 
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Thicker barrel to cut barrel whip...false The military has very thick barrel thickness requirements. They believe the thicker the barrel longer barrel life. Even though you could say a thinner barrel cools down quicker (less hot metal) and thus leading to longer life. And barrels erode fro the inside out so once you lose rifling you lose accuracy regardless of barrel thickness. I'm no barrel expert but I do know military rifles like the M4A1 barrels are very thick. Compare it to this Adams Arms VDI Tactical Elite barrel which is pretty average compared with most DI barrels http://i83.photobucket.com/albums/j292/stukas87/20160826_101258_zpspqawna73.jpg Are you saying thicker barrels are not stiffer and thus less prone to whip? You theory on a thinner barrel cooling faster seems to forget that they also heat considerably faster. A lot of the damage we here about is done when the barrel is hot and the throat erosion is accelerated. You seem to really go against the grain when it comes to barrel and wear ideas. Good points .. (I think lighter barrels don't heat up faster, they just transfer the heat to the outside faster being thinner) A thicker barrel will take longer to warp (bend) and catastrophic damage (bullet out the side) under prolong high rate of fire hence the thicker barrels on machine guns, the M4A1 and other military weapons. I am sure a barrel maker could come on here and really explain what makes a good barrel..What Im saying accuracy based on barrel harmonics/quality not thickness. Are their plus qualities to a thicker barrel yes, but... The point Im going after is to dispel the vertical stringing of piston guns myth. I own several pencil thin AA Evo Ultralite barrels they shoot great. Now once they heat up does the group open up some yes. But no vertical stringing. For some reason the issue of vertical stringing only comes up with piston ARs. Never comes up with any other piston gun or any gun with a OP rod AK, FN FAL on and on. It seems the issue has been made up as a excuse to say Piston ARs are a worthless concept . Now is going Piston gun worth it? If you shoot a ass ton I would say yes I love the fact that I can go the life of the barrel and never take piston apart and only need to wipe off bolt carrier every 2000-3000rds Shoot every once in a while then plenty of Damn fine DI guns out there. I would guess that's because there aren't many precision rifles built on those platforms certainly not to the extent that they are with the AR platforms. |
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Posted: 8/26/2016 2:31:55 PM EDT
[#30]
Quote HistoryQuoted:
I have never seen a piston AR at Camp Perry. Yes but you have seen M1 Garands.............piston |
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Posted: 8/26/2016 3:43:30 PM EDT
[#31]
My CMMG piston is pretty accurate w m193gets me 1.5 groups at 100 yards the accuracy plus the advantage of it being better for suppressors is why I will choose my piston ARs over myDI
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Posted: 8/26/2016 4:24:24 PM EDT
[#32]
Quote HistoryQuoted:
Yes but you have seen M1 Garands.............piston Quote HistoryQuoted:
Quoted:
I have never seen a piston AR at Camp Perry. Yes but you have seen M1 Garands.............piston The garands and M1As can't keep up with the ARs. |
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Posted: 8/27/2016 3:45:42 PM EDT
[#33]
Quote HistoryQuoted:
Good points .. (I think lighter barrels don't heat up faster, they just transfer the heat to the outside faster being thinner) A thicker barrel will take longer to warp (bend) and catastrophic damage (bullet out the side) under prolong high rate of fire hence the thicker barrels on machine guns, the M4A1 and other military weapons. I am sure a barrel maker could come on here and really explain what makes a good barrel..What Im saying accuracy based on barrel harmonics/quality not thickness. Are their plus qualities to a thicker barrel yes, but... The point Im going after is to dispel the vertical stringing of piston guns myth. I own several pencil thin AA Evo Ultralite barrels they shoot great. Now once they heat up does the group open up some yes. But no vertical stringing. For some reason the issue of vertical stringing only comes up with piston ARs. Never comes up with any other piston gun or any gun with a OP rod AK, FN FAL on and on. It seems the issue has been made up as a excuse to say Piston ARs are a worthless concept . Now is going Piston gun worth it? If you shoot a ass ton I would say yes I love the fact that I can go the life of the barrel and never take piston apart and only need to wipe off bolt carrier every 2000-3000rds Shoot every once in a while then plenty of Damn fine DI guns out there. Quote HistoryQuoted:
Quoted:
Quoted:
Thicker barrel to cut barrel whip...false The military has very thick barrel thickness requirements. They believe the thicker the barrel longer barrel life. Even though you could say a thinner barrel cools down quicker (less hot metal) and thus leading to longer life. And barrels erode fro the inside out so once you lose rifling you lose accuracy regardless of barrel thickness. I'm no barrel expert but I do know military rifles like the M4A1 barrels are very thick. Compare it to this Adams Arms VDI Tactical Elite barrel which is pretty average compared with most DI barrels http://i83.photobucket.com/albums/j292/stukas87/20160826_101258_zpspqawna73.jpg Are you saying thicker barrels are not stiffer and thus less prone to whip? You theory on a thinner barrel cooling faster seems to forget that they also heat considerably faster. A lot of the damage we here about is done when the barrel is hot and the throat erosion is accelerated. You seem to really go against the grain when it comes to barrel and wear ideas. Good points .. (I think lighter barrels don't heat up faster, they just transfer the heat to the outside faster being thinner) A thicker barrel will take longer to warp (bend) and catastrophic damage (bullet out the side) under prolong high rate of fire hence the thicker barrels on machine guns, the M4A1 and other military weapons. I am sure a barrel maker could come on here and really explain what makes a good barrel..What Im saying accuracy based on barrel harmonics/quality not thickness. Are their plus qualities to a thicker barrel yes, but... The point Im going after is to dispel the vertical stringing of piston guns myth. I own several pencil thin AA Evo Ultralite barrels they shoot great. Now once they heat up does the group open up some yes. But no vertical stringing. For some reason the issue of vertical stringing only comes up with piston ARs. Never comes up with any other piston gun or any gun with a OP rod AK, FN FAL on and on. It seems the issue has been made up as a excuse to say Piston ARs are a worthless concept . Now is going Piston gun worth it? If you shoot a ass ton I would say yes I love the fact that I can go the life of the barrel and never take piston apart and only need to wipe off bolt carrier every 2000-3000rds Shoot every once in a while then plenty of Damn fine DI guns out there. So where did you get this information on the thicker barrel requirements. The m4a1 uses the SOCOM profile barrel. As it was a requirement that Socom came up with. The m4a1 upgrades and carry overs from stuff that Socom has been using for a long time. A thinner barrel may cool faster. But it looses it strength faster as it hearts up. Steel is steel. And as long as it's the same type of steel it shares the same heat transfer property's. And a heavy bull type barrel with more steel will require more heat for longer before the entire barrels heats up compared to a light profile. Now as a barrel heats up the structure of the steel will start to change and get softer. The hotter is gets the more barrel whip/ harmonics will take effect. And to add the that the more heat transfered to the cartridge in the chamber changes powder burn rates, standard deviations and the point in the barrel whip cycle the bullet leaves. I'm also inclined to beleive the a gas piston imparts forces on the barrel the gas impingement doesn't. Specifically vertical forces from the gas system parts moving and interacting. Also the Army tested some gas piston uppers. The DI system was found just as or more reliable. Contrary to the Internet. Scott |
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Posted: 8/27/2016 3:48:05 PM EDT
[#34]
The bolt in each system locks up exactly the same way.
And the bullet is gone long before the bolt unlocks. |
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Posted: 8/27/2016 3:52:26 PM EDT
[#35]
Quote HistoryQuoted:
The bolt in each system locks up exactly the same way. And the bullet is gone long before the bolt unlocks. True. But the bullet is still in the barrel when outside forces start imparting on the barrel. The gas hits the face of the piston not to long after the bullet is past the port but still in the barrel. |
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Posted: 8/27/2016 3:56:39 PM EDT
[#36]
Quote HistoryQuoted: True. But the bullet is still in the barrel when outside forces start imparting on the barrel. The gas hits the face of the piston not to long after the bullet is past the port but still in the barrel. Quote HistoryQuoted: Quoted: The bolt in each system locks up exactly the same way. And the bullet is gone long before the bolt unlocks. True. But the bullet is still in the barrel when outside forces start imparting on the barrel. The gas hits the face of the piston not to long after the bullet is past the port but still in the barrel. Isn't the same true for a DI system? The gas travels down the gas tube and hits the gas key. I assume that's happening while the bullet is in the barrel. Not something i know for sure. |
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Posted: 8/27/2016 4:06:02 PM EDT
[#37]
Quote HistoryQuoted:
Isn't the same true for a DI system? The gas travels down the gas tube and hits the gas key. I assume that's happening while the bullet is in the barrel. Not something i know for sure. Quote HistoryQuoted:
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The bolt in each system locks up exactly the same way. And the bullet is gone long before the bolt unlocks. True. But the bullet is still in the barrel when outside forces start imparting on the barrel. The gas hits the face of the piston not to long after the bullet is past the port but still in the barrel. Isn't the same true for a DI system? The gas travels down the gas tube and hits the gas key. I assume that's happening while the bullet is in the barrel. Not something i know for sure. Yes. But it's pushing on parts that are farther away from the bore. And when it "pushes" it's inline with the bore, up against the tail of the bolt and opposing direction in the carrier. Where a gas piston it's pushing a half inch above the bore. Both have the whole newton's laws (equal and opposite reaction) thing going on. Just one is inline with the bore and the other is imparting leverage on the bore. Scott |
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Posted: 8/27/2016 10:15:25 PM EDT
[#38]
Wouldn't the barrel shift be the same for every shot within the variability envelope of the factors that affect the force vector causing the off-axis barrel shift?
Variables like powder charge, bullet weight, even primer consistency all affect velocity, and thus, force vectors. So, in a piston system, the gas impinges on the piston the same way every time, and with a DI system it impinges on the gas key the same every time. Thus, the angular force on the barrel is the same (again, within the envelope of variability) for every shot, with each of the two gas systems. It's like finding the nodes for barrel harmonics. |
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Posted: 8/27/2016 10:18:48 PM EDT
[#39]
Where is documented vertical stringing of piston guns? I have been involved with piston rifles since 2007 both civilian and military. To include testing HK416, LWRC for Army.
Is it possible yes, that maybe just maybe some early piston guns in testing may have had a issue but no production piston gun in the last 10 years. So aside from theories based on design alone, forces during locking unlocking during firing cycle and I read it on another forum or saw it posted online somewhere? Where is the data? I will say it is nothing more than internet lore. |
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Posted: 8/27/2016 11:52:09 PM EDT
[#40]
Quote HistoryQuoted:
Wouldn't the barrel shift be the same for every shot within the variability envelope of the factors that affect the force vector causing the off-axis barrel shift? Variables like powder charge, bullet weight, even primer consistency all affect velocity, and thus, force vectors. So, in a piston system, the gas impinges on the piston the same way every time, and with a DI system it impinges on the gas key the same every time. Thus, the angular force on the barrel is the same (again, within the envelope of variability) for every shot, with each of the two gas systems. It's like finding the nodes for barrel harmonics. It would. I've noticed even in traditional DI guns vertical stringing exists. And I'm almost positive the most of it has to do with barrel profile more than operating systems. A hot barrel will be subject to flex more then a cold barrel. I'm inclined to beleive that a DI has the potential to be more accurate than a piston gun. Again that's my opion. Less moving parts and mass slamming around will make it easier to shoot. Now let's jump into the perfect world. Assuming your ammo. Is exactly the same. Every shot every time. No pressure deviations nothing. As the barrel heats it becomes softer. The closers you get to the melting point the softer the steel will get. With the potential to induce more flex in the barrel it's self. But because everything is the same in the ammo flex will always be the same. Now back to the real world were ammo is no the same. Since your ammo has variations, you get variations in the flex of the barrel. Meaning the bullet exits in a different pointime in the whip. Harmonics have a lot to do with it. But even in the accuracy node. Differences between shot to shot still play a part. |
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Posted: 8/27/2016 11:55:37 PM EDT
[#41]
Quote HistoryQuoted:
Where is documented vertical stringing of piston guns? I have been involved with piston rifles since 2007 both civilian and military. To include testing HK416, LWRC for Army. Is it possible yes, that maybe just maybe some early piston guns in testing may have had a issue but no production piston gun in the last 10 years. So aside from theories based on design alone, forces during locking unlocking during firing cycle and I read it on another forum or saw it posted online somewhere? Where is the data? I will say it is nothing more than internet lore. And after the published test from the army. Piston guns being more reliable seem to be a Internet lore to. Does the malfunctions have to do with the increased cyclic rate of the piston guns maybe. But it's still causing issues. Pistons guns have the potential to be every bit accurate as DI guns. And probly are. But why haven't piston guns swept the market? And honestly hk did the piston gun right, along with everyone else tat redesigned the upper receiver to house the piston set up. Shrinking the piston to fit a upper that wasn't designed for it, was a bad move. Small fragile parts the are subject to being bent. |
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Posted: 8/28/2016 12:34:04 AM EDT
[#42]
so....if vertical stringing is present in DI and piston, then maybe it a function of the ammo velocity?
my LWRC 18" DMR upper doest seem to have any vertical stringing. |
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Posted: 8/28/2016 1:55:33 AM EDT
[#43]
Quote HistoryQuoted:
so....if vertical stringing is present in DI and piston, then maybe it a function of the ammo velocity? my LWRC 18" DMR upper doest seem to have any vertical stringing. Its a function of a couple of things. What's the highest round count group size you've shot? What caliber? The standard deviation of your ammo. Powder temp stability. Barrel profile. Rate In which group was shot. My mk12 mod 1 upper doesn't string to bad. Get the barrel hot. And stringing starts showing its face. Last time I had my wife out shooting with me she was shooting my mk12. Probly threw 40-50 rnds down range in a hurry. She's not a awesome shot but she can hold a solid 1.5 MOA group. Watching through spotting scope after probly 25 rnds you could see the impacts start walking up. As I'm assuming the hot barrel was helping the powder burn a little fast. But was was being held in the orange dot now was working it's way out the top side of the dot. Stringing is a mixture of conditions coming together at the right time.if I had my dad's 700 308 carbine with me, as was able to shoot, it shows stringing very well after about 5 rnds. The pencil barrel it has gets hot fast. And with start walking impacts up. |
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Posted: 8/28/2016 6:47:12 PM EDT
[#44]
Quote HistoryQuoted:
Its a function of a couple of things. What's the highest round count group size you've shot? What caliber? The standard deviation of your ammo. Powder temp stability. Barrel profile. Rate In which group was shot. My mk12 mod 1 upper doesn't string to bad. Get the barrel hot. And stringing starts showing its face. Last time I had my wife out shooting with me she was shooting my mk12. Probly threw 40-50 rnds down range in a hurry. She's not a awesome shot but she can hold a solid 1.5 MOA group. Watching through spotting scope after probly 25 rnds you could see the impacts start walking up. As I'm assuming the hot barrel was helping the powder burn a little fast. But was was being held in the orange dot now was working it's way out the top side of the dot. Stringing is a mixture of conditions coming together at the right time.if I had my dad's 700 308 carbine with me, as was able to shoot, it shows stringing very well after about 5 rnds. The pencil barrel it has gets hot fast. And with start walking impacts up. Quote HistoryQuoted:
Quoted:
so....if vertical stringing is present in DI and piston, then maybe it a function of the ammo velocity? my LWRC 18" DMR upper doest seem to have any vertical stringing. Its a function of a couple of things. What's the highest round count group size you've shot? What caliber? The standard deviation of your ammo. Powder temp stability. Barrel profile. Rate In which group was shot. My mk12 mod 1 upper doesn't string to bad. Get the barrel hot. And stringing starts showing its face. Last time I had my wife out shooting with me she was shooting my mk12. Probly threw 40-50 rnds down range in a hurry. She's not a awesome shot but she can hold a solid 1.5 MOA group. Watching through spotting scope after probly 25 rnds you could see the impacts start walking up. As I'm assuming the hot barrel was helping the powder burn a little fast. But was was being held in the orange dot now was working it's way out the top side of the dot. Stringing is a mixture of conditions coming together at the right time.if I had my dad's 700 308 carbine with me, as was able to shoot, it shows stringing very well after about 5 rnds. The pencil barrel it has gets hot fast. And with start walking impacts up. interesting observations. thanks for posting. i've never shot that many on paper at one time but will give it a try next time. most of the time i'm picking on melon sized rocks so i cant tell. |
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Posted: 8/30/2016 9:26:02 AM EDT
[#45]
Quote HistoryQuoted: It would. I've noticed even in traditional DI guns vertical stringing exists. And I'm almost positive the most of it has to do with barrel profile more than operating systems. A hot barrel will be subject to flex more then a cold barrel. I'm inclined to beleive that a DI has the potential to be more accurate than a piston gun. Again that's my opion. Less moving parts and mass slamming around will make it easier to shoot. Now let's jump into the perfect world. Assuming your ammo. Is exactly the same. Every shot every time. No pressure deviations nothing. As the barrel heats it becomes softer. The closers you get to the melting point the softer the steel will get. With the potential to induce more flex in the barrel it's self. But because everything is the same in the ammo flex will always be the same. Now back to the real world were ammo is no the same. Since your ammo has variations, you get variations in the flex of the barrel. Meaning the bullet exits in a different pointime in the whip. Harmonics have a lot to do with it. But even in the accuracy node. Differences between shot to shot still play a part. Quote HistoryQuoted: Quoted: Wouldn't the barrel shift be the same for every shot within the variability envelope of the factors that affect the force vector causing the off-axis barrel shift? Variables like powder charge, bullet weight, even primer consistency all affect velocity, and thus, force vectors. So, in a piston system, the gas impinges on the piston the same way every time, and with a DI system it impinges on the gas key the same every time. Thus, the angular force on the barrel is the same (again, within the envelope of variability) for every shot, with each of the two gas systems. It's like finding the nodes for barrel harmonics. It would. I've noticed even in traditional DI guns vertical stringing exists. And I'm almost positive the most of it has to do with barrel profile more than operating systems. A hot barrel will be subject to flex more then a cold barrel. I'm inclined to beleive that a DI has the potential to be more accurate than a piston gun. Again that's my opion. Less moving parts and mass slamming around will make it easier to shoot. Now let's jump into the perfect world. Assuming your ammo. Is exactly the same. Every shot every time. No pressure deviations nothing. As the barrel heats it becomes softer. The closers you get to the melting point the softer the steel will get. With the potential to induce more flex in the barrel it's self. But because everything is the same in the ammo flex will always be the same. Now back to the real world were ammo is no the same. Since your ammo has variations, you get variations in the flex of the barrel. Meaning the bullet exits in a different pointime in the whip. Harmonics have a lot to do with it. But even in the accuracy node. Differences between shot to shot still play a part. Certainly that same ammo variability affects the force vectors on the piston and the gas key respectively, but the overall mass of the gun is so much more than the mass of the barrel, that those forces are much less likely to cause a lack of accuracy. |
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