As an update, no trigger group yet, things running behind and I cannot eve strip out my old AR15 group because of pin size so have to sit and wait, and such is life!
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What have I done wrong now?
- Thread starter copemech
- Start date
As an update, no trigger group yet, things running behind and I cannot eve strip out my old AR15 group because of pin size so have to sit and wait, and such is life!
Update!
Range update as of today was a bit mixed! After setting trigger back from Bill Springfield, it works better, but the gun was still iffy with the H2 buffer.
Took 4 types of ammo and intentionally picked up a pack of the original offender Monarch 145gr(steel) which would not cycle. Ran 20rds.
It actually worked pretty well with occasional failure to lock back last round.
I bought TULA steel 150, it SUCKED! Out of 20 rds, 4 dead primers, two bolt overrides, 2 failures to feed(no pick-up). Found cases next to me. at times. That is the **** because I have another 4 boxes of this stuff at ten bucks each!
Monarch 150 Brass soft point ran well, no issues using two at a time, only used ten within the group test. Saved the rest for later.
Remington 150 core lock works as well as before, with no issues.
Grouping still an issue, seems some of it shoots high and some low, with the Rem being most consistent thus far, yet I cannot dial it in because of a 2" spread at 50 yds. I have not bothered going to 100. The Rem seems to perform within 1" or so at this range, so a 2" at 100 may be workable with it, time will tell.
But for now, and given results, I am wondering if I should try the H3 buffer, or just try and stick with brass, which seems to work.
Btw, casings seemed to fall in a 6-8 ft range today, with exception of the suspect shortstrokes and FTF which were nearby. I consider this more normal but input from others appreciated.
Range update as of today was a bit mixed! After setting trigger back from Bill Springfield, it works better, but the gun was still iffy with the H2 buffer.
Took 4 types of ammo and intentionally picked up a pack of the original offender Monarch 145gr(steel) which would not cycle. Ran 20rds.
It actually worked pretty well with occasional failure to lock back last round.
I bought TULA steel 150, it SUCKED! Out of 20 rds, 4 dead primers, two bolt overrides, 2 failures to feed(no pick-up). Found cases next to me. at times. That is the **** because I have another 4 boxes of this stuff at ten bucks each!
Monarch 150 Brass soft point ran well, no issues using two at a time, only used ten within the group test. Saved the rest for later.
Remington 150 core lock works as well as before, with no issues.
Grouping still an issue, seems some of it shoots high and some low, with the Rem being most consistent thus far, yet I cannot dial it in because of a 2" spread at 50 yds. I have not bothered going to 100. The Rem seems to perform within 1" or so at this range, so a 2" at 100 may be workable with it, time will tell.
But for now, and given results, I am wondering if I should try the H3 buffer, or just try and stick with brass, which seems to work.
Btw, casings seemed to fall in a 6-8 ft range today, with exception of the suspect shortstrokes and FTF which were nearby. I consider this more normal but input from others appreciated.
Im sorry your having trouble. That sucks no doubt, I've been there too. I shot some .308 Tula this month and was blow away by the accuracy at 200 yards, but I'm shooting another brand of ar-10 platform. Hope you get it figured out, if not, sell it and get something else. I became so frustrated I did. My only regret is not doing it sooner. The .308 i ended up with will cycle any .308 or 7.62x51 i put in it. Even the CBC NATO stuff my M&P hated.
My guess is your buffer is too heavy. I tried German milsurp in mine and needed to run a carbine buffer. Even the H buffer gave me short stroking. I haven't had the chance to try commercial ammo yet
Well you see there within lies the issue. People want to run whatever they want through these high strung guns! And you admit you have not even tried any standard US made ammo!
I get back to what the fellow a S&W told me, if you send it in and we run it fine on standard US ammo, we are sending it back!
OK, fair enough, no hiccups as yet with standard brass, US or otherwise. I have to run race gas in my bike too! Just a given.
Yes , I am still cheap! But not that cheap.
Time will tell what the racehorse will feed upon and what it will not. Biggest issue with the Tula was the primers, sorry but they sucked!
Im sorry your having trouble. That sucks no doubt, I've been there too. I shot some .308 Tula this month and was blow away by the accuracy at 200 yards, but I'm shooting another brand of ar-10 platform. Hope you get it figured out, if not, sell it and get something else. I became so frustrated I did. My only regret is not doing it sooner. The .308 i ended up with will cycle any .308 or 7.62x51 i put in it. Even the CBC NATO stuff my M&P hated.
So, funny you are still here in this thread, what magic combo is in your gun?
The Enidine buffer I am using weighs 6oz. I had to increase the gas port diameter slightly to eliminate the short cycling.
You are fighting one end against the other it sounds to me!
Where is Rojo when you need him!
You are fighting one end against the other it sounds to me!
Where is Rojo when you need him!
Well, knock on wood, the rifle is in check and has run great for just over 1200 rounds since the last gas system mods in early December.
Factory spring rate, bcg weight, and port diameter are never perfect. Instead they are averaged not matched. You should only attempt to mess with one variable at a time to fix these issues. the spring is the easiest to change/modify without serious cost or serious consequences to the gun.
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So, funny you are still here in this thread, what magic combo is in your gun?
While i no longer have a M&P 10 i have other S&W guns. I post and lurk in those sections. For this section, I subscribed to several threads where folks had similiar problems as mine hoping to find answers. I was sincere in saying I'm sorry your having troubles. I'll leave your thread alone as you seem to be upset i posted. For the record i bought a PWS MK220 and couldnt be happier! I still hope you get yours sorted out.
Factory spring rate, bcg weight, and port diameter are never perfect. Instead they are averaged not matched. You should only attempt to mess with one variable at a time to fix these issues. the spring is the easiest to change/modify without serious cost or serious consequences to the gun.
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What would you recommend for a low-cost replacement of the M&P 10 factory spring based on the symptoms and conditions discussed in this thread?
Reading your original post, I actually disagree with some posts. Lets start with the muzzle brake...what it does- helps minimize recoil. HOW- it changes the direction of the air being compressed in front of the bullet from straight forward to the direction of the ports on the brake. This allows the bullet to move forward with reduced resistance. Therefore more of the explosive force is transfered to the bullet and less to the bcg. In simple terms reduced muzzle resistance equals less bcg rearward movement which requires a lighter spring. (This is also the reason a muzzle brake will give you extended range). Hope this helps.
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Reading your original post, I actually disagree with some posts. Lets start with the muzzle brake...what it does- helps minimize recoil. HOW- it changes the direction of the air being compressed in front of the bullet from straight forward to the direction of the ports on the brake. This allows the bullet to move forward with reduced resistance. Therefore more of the explosive force is transfered to the bullet and less to the bcg. In simple terms reduced muzzle resistance equals less bcg rearward movement which requires a lighter spring. (This is also the reason a muzzle brake will give you extended range). Hope this helps.
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I believe the "explosive" force itself is a constant and not affected by the muzzle brake. Because of the dynamic of the gas port as an orifice or venturi, the gas tube pressurizes consistently in ratio of the diameter of the gas port to the barrel diameter in any case (on the basis of the Bernoulli Equation). The muzzle brake's ability to reduce turbidity in front of the bullet allows for an increase in the bullet's velocity, which reduces the length of time that the pressure from the "explosion" (the "pulse") exists in the barrel because the bullet leaves the barrel faster.
The expansion is constant.....the force is determined by resitance of the bullet to leave the chamber. And btw I find it funny you chose to use bernoulli's equation ( I use at work) an increase in speed is due to the drop in back pressure....thanks for pointing that out
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Duggie76, if you read my posts, my rifle is running just fine.
Anyhow, the force or energy applied to the bullet is a constant (your tank of gas). The amount of transferred energy the bullet uses (from its "tank of gas" to leave the barrel is proportionate to the resistance it meets in the path of travel. Hence, the bullet retains more energy (gas) when it leaves the barrel and can use that energy to travel a little farther, due to the energy-robbing resistance that the muzzle device may have mitigated. It's like driving a big truck with a full tank of gas against the wind ... it consumes more gas than driving with no wind resistance and can therefore travel farther on the same tank of gas when it isn't driving against the wind.
That having been said, we now observe that the bullet is moving faster under this condition ... and getting to the gas port sooner. This means that the bolt carrier group is receiving the energy sooner (albeit the same constant of energy that is determined by the proportion of the gas port diameter to the barrel diameter). This energy is made available to the bolt carrier group on the basis of a) however long it takes the bullet to pass the gas port and reach the end of the barrel and b) however long it takes the gas key to lose its connection to the gas tube.
In the perfect combustion cycle, the charged round will fire, and as the bullet is set in motion down the barrel toward the gas port, at the same time the spent casing expands against the chamber walls and then cools and contracts(releasing its grip on the walls) by the time the bullet reaches the gas port. When the bullet passes the gas port, the gas tube is pressurized and energy is transferred to the bolt carrier. At this point the amount of energy available is still a constant in proportion to the length of the gas pulse. Once enough energy is transferred, the bolt carrier is set in motion, and it begins extracting the spent casing from the chamber. At this point, you have to wonder, if the bullet is moving faster, and it reaches the gas port sooner ... and same constant of energy is transferred to the bolt carrier sooner ... what if the bolt carrier is set in motion while the casing is still expanded in the chamber? Well, this means that the bolt carrier has to expend more of its available energy breaking the grip of the casing on the chamber walls. In many cases, so much of the bolt Carrier's energy is spent at this point that it is able to extract the casing, but doesn't have enough energy left to travel back far enough to draw the next round out of the magazine. This circumstance is known as fast-cycling (the bolt carrier is set in motion too soon). The cure for this is to increase the weight of the bolt carrier or buffer in order to increase the energy required to set the bolt carrier in motion (which still consumes some of the bolt carrier's available energy), but gives the spent casing an extra milisecond or two (dwell time) to release its grip on the chamber wall.
Rojo Diablo hinted that this cure is somewhat a catch 22 ... possibly because the available energy transferred to the bolt carrier may not be enough to carry the weight added to the bolt carrier to cure the fast cycling issue ... and then, if you increase the available energy to the bolt carrier by increasing the gas port size too much, you are back to fast cycling.
I am sorry if I offended you previously. It was not my intent to seem like I was attacking you. I realize that I could have injected my comment in a much better and more constructive way.
Anyhow, the force or energy applied to the bullet is a constant (your tank of gas). The amount of transferred energy the bullet uses (from its "tank of gas" to leave the barrel is proportionate to the resistance it meets in the path of travel. Hence, the bullet retains more energy (gas) when it leaves the barrel and can use that energy to travel a little farther, due to the energy-robbing resistance that the muzzle device may have mitigated. It's like driving a big truck with a full tank of gas against the wind ... it consumes more gas than driving with no wind resistance and can therefore travel farther on the same tank of gas when it isn't driving against the wind.
That having been said, we now observe that the bullet is moving faster under this condition ... and getting to the gas port sooner. This means that the bolt carrier group is receiving the energy sooner (albeit the same constant of energy that is determined by the proportion of the gas port diameter to the barrel diameter). This energy is made available to the bolt carrier group on the basis of a) however long it takes the bullet to pass the gas port and reach the end of the barrel and b) however long it takes the gas key to lose its connection to the gas tube.
In the perfect combustion cycle, the charged round will fire, and as the bullet is set in motion down the barrel toward the gas port, at the same time the spent casing expands against the chamber walls and then cools and contracts(releasing its grip on the walls) by the time the bullet reaches the gas port. When the bullet passes the gas port, the gas tube is pressurized and energy is transferred to the bolt carrier. At this point the amount of energy available is still a constant in proportion to the length of the gas pulse. Once enough energy is transferred, the bolt carrier is set in motion, and it begins extracting the spent casing from the chamber. At this point, you have to wonder, if the bullet is moving faster, and it reaches the gas port sooner ... and same constant of energy is transferred to the bolt carrier sooner ... what if the bolt carrier is set in motion while the casing is still expanded in the chamber? Well, this means that the bolt carrier has to expend more of its available energy breaking the grip of the casing on the chamber walls. In many cases, so much of the bolt Carrier's energy is spent at this point that it is able to extract the casing, but doesn't have enough energy left to travel back far enough to draw the next round out of the magazine. This circumstance is known as fast-cycling (the bolt carrier is set in motion too soon). The cure for this is to increase the weight of the bolt carrier or buffer in order to increase the energy required to set the bolt carrier in motion (which still consumes some of the bolt carrier's available energy), but gives the spent casing an extra milisecond or two (dwell time) to release its grip on the chamber wall.
Rojo Diablo hinted that this cure is somewhat a catch 22 ... possibly because the available energy transferred to the bolt carrier may not be enough to carry the weight added to the bolt carrier to cure the fast cycling issue ... and then, if you increase the available energy to the bolt carrier by increasing the gas port size too much, you are back to fast cycling.
I am sorry if I offended you previously. It was not my intent to seem like I was attacking you. I realize that I could have injected my comment in a much better and more constructive way.
While i no longer have a M&P 10 i have other S&W guns. I post and lurk in those sections. For this section, I subscribed to several threads where folks had similiar problems as mine hoping to find answers. I was sincere in saying I'm sorry your having troubles. I'll leave your thread alone as you seem to be upset i posted. For the record i bought a PWS MK220 and couldnt be happier! I still hope you get yours sorted out.
No, not upset or trying to run you out! However as you well know, sometimes folke as in your situation do offer nothing bet negative comments.
I did indeed ask if you knew the "magic" combo in your new gun. Yes one gets into a lot of specs here that you may not know or care as long as it works.
No offense intended if it was not due!
Duggie76, if you read my posts, my rifle is running just fine.
Anyhow, the force or energy applied to the bullet is a constant (your tank of gas). The amount of transferred energy the bullet uses (from its "tank of gas" to leave the barrel is proportionate to the resistance it meets in the path of travel. Hence, the bullet retains more energy (gas) when it leaves the barrel and can use that energy to travel a little farther, due to the energy-robbing resistance that the muzzle device may have mitigated. It's like driving a big truck with a full tank of gas against the wind ... it consumes more gas than driving with no wind resistance and can therefore travel farther on the same tank of gas when it isn't driving against the wind.
That having been said, we now observe that the bullet is moving faster under this condition ... and getting to the gas port sooner. This means that the bolt carrier group is receiving the energy sooner (albeit the same constant of energy that is determined by the proportion of the gas port diameter to the barrel diameter). This energy is made available to the bolt carrier group on the basis of a) however long it takes the bullet to pass the gas port and reach the end of the barrel and b) however long it takes the gas key to lose its connection to the gas tube.
In the perfect combustion cycle, the charged round will fire, and as the bullet is set in motion down the barrel toward the gas port, at the same time the spent casing expands against the chamber walls and then cools and contracts(releasing its grip on the walls) by the time the bullet reaches the gas port. When the bullet passes the gas port, the gas tube is pressurized and energy is transferred to the bolt carrier. At this point the amount of energy available is still a constant in proportion to the length of the gas pulse. Once enough energy is transferred, the bolt carrier is set in motion, and it begins extracting the spent casing from the chamber. At this point, you have to wonder, if the bullet is moving faster, and it reaches the gas port sooner ... and same constant of energy is transferred to the bolt carrier sooner ... what if the bolt carrier is set in motion while the casing is still expanded in the chamber? Well, this means that the bolt carrier has to expend more of its available energy breaking the grip of the casing on the chamber walls. In many cases, so much of the bolt Carrier's energy is spent at this point that it is able to extract the casing, but doesn't have enough energy left to travel back far enough to draw the next round out of the magazine. This circumstance is known as fast-cycling (the bolt carrier is set in motion too soon). The cure for this is to increase the weight of the bolt carrier or buffer in order to increase the energy required to set the bolt carrier in motion (which still consumes some of the bolt carrier's available energy), but gives the spent casing an extra milisecond or two (dwell time) to release its grip on the chamber wall.
Rojo Diablo hinted that this cure is somewhat a catch 22 ... possibly because the available energy transferred to the bolt carrier may not be enough to carry the weight added to the bolt carrier to cure the fast cycling issue ... and then, if you increase the available energy to the bolt carrier by increasing the gas port size too much, you are back to fast cycling.
I am sorry if I offended you previously. It was not my intent to seem like I was attacking you. I realize that I could have injected my comment in a much better and more constructive way.
App, you are making my old head hurt with posts like this!
All this operational theory and debate. I understand the operational theory and the variables, what I still do not completely have my head around is what range of ammo I need to find that works consistently with a given setup.
All tests thus far have been with cheap ammo thus far, with exception of the standard Rem 150 corelock SP.
So I changed buffer, now the main offender of the 145 steel Monarch worked, then the cheap steel 150 Tula did not fare well, and all brass has ran ok thus far, even Monarch.
All in 150! Which brings me to another point that you geeks may debate.
I doubt the gun knows much about what that case is made of, bullet weight the same, what is different? THE POWDER!
I am no expert, but I know enough about reloading to know different powders burn at different rates and have different pressures and rates.
Then on a gas gun, it is these pressures within the limited range of gas port opening and bullet exit that makes things work.
And there within, one must find sufficient pressure to work a given action.
Just how wide this window is would be the question as we are running more mass on the 308 the window seems to narrow it seems.... I really need to go try to push some 168 or even 180 out the end of it and hopefully find more consistency, cause the light stuff is jumping around too much it seems, with some running high and others running low, two inch groups at 50 is not where I want to be. Same thing happens with my 10/22 with different ammo put in, but if I dial in to a good standard round, no matter the brand for the most, it is drilling !
Copemech, I went to the range this morning and shot 80 rounds of American Eagle 168 grain OTM and 20 rounds of CorBon 185 grain subsonic FMJ ... talk about a huge difference in powder charge.
I think I've posted this before, but here is my gas system specification (which is based on the DPMS LAR308 I had previously and gave to my niece ... and is still working):
1) A2 type buffer extension tube (not the original tube)
2) Enidine 308 Full Stock Buffer (this is the longer size rifle type buffer that weighs 6 ounces)
3) DPMS 308 rifle length spring (this spring is actually 3/4" longer than the original, with roughly the same coil spacing, but the coil thickness looks to be slightly thicker than the original ... the original looks like a longer version of a AR15 spring)
4) Gas port diameter enlarged to .078ish" (I didn't have any pin gauges when I did the porting, but I perceived the original port size to be between .070" and .072" ... maybe .076ish" is the target).
5) SLR-DA7C adjustable gas block (I basically adjusted it to lock the bolt catch on the last round of a magazine of the ammo I was having the worst problem with (subsonic) and then added 3 more clicks of adjustment ... the gas block is adjusted over 80% open, but doesn't shoot any different at 100% open).
As far as your gun "knowing" the difference between brass and steel, it just might ... the 2 metals have different friction and expansion coefficients [sorry for the technical terms]. Without knowing the exact specifications of the steel or brass used for ammo (and any impurities that may be found in the metals), I couldn't begin to tell you what the tolerances or rates are however ... the difference may not amount to anything, but then again, at peak expansion the difference may be as much as a carrot compared to a cucumber in the rifle's orifice depending on the powder charge and the thickness and type of coating used on the steel and headspace of the chamber. Rojo may have some insight on this, as I think he's had his hands on a wider range of ammo types and barrels over the years. He's a really good source for wisdom and practice on AR's.
If I recall correctly, you have the original stock, original recoil spring, but added a heavier buffer recently. Again, if I recall correctly, when you added the buffer weight, some of the dynamics changed with regard to certain ammo, but overall you still have the same symptoms occurring. In this case, before you try any porting, I would look for a gas leak or a gas restriction or an impingement that's sucking the energy out of your bolt carrier. My first suspect is usually the gas key mating with the gas tube or the gas rings on older guns, but whenever someone says they've changed the gas block, that becomes the primary suspect. Once you've checked these areas, and nothing obvious stands out, have a good look at the chamber. If you know someone with headspace gauges, check the headspace. If not, before any attempt on porting, I would send the rifle in for warranty repair and tell them the symptoms and that you suspect something like micro fractures or imperfections in the chamber or something to that extent (however crazy it may be) so they have to inspect it or at least comment on the condition of the chamber.
I think I've posted this before, but here is my gas system specification (which is based on the DPMS LAR308 I had previously and gave to my niece ... and is still working):
1) A2 type buffer extension tube (not the original tube)
2) Enidine 308 Full Stock Buffer (this is the longer size rifle type buffer that weighs 6 ounces)
3) DPMS 308 rifle length spring (this spring is actually 3/4" longer than the original, with roughly the same coil spacing, but the coil thickness looks to be slightly thicker than the original ... the original looks like a longer version of a AR15 spring)
4) Gas port diameter enlarged to .078ish" (I didn't have any pin gauges when I did the porting, but I perceived the original port size to be between .070" and .072" ... maybe .076ish" is the target).
5) SLR-DA7C adjustable gas block (I basically adjusted it to lock the bolt catch on the last round of a magazine of the ammo I was having the worst problem with (subsonic) and then added 3 more clicks of adjustment ... the gas block is adjusted over 80% open, but doesn't shoot any different at 100% open).
As far as your gun "knowing" the difference between brass and steel, it just might ... the 2 metals have different friction and expansion coefficients [sorry for the technical terms]. Without knowing the exact specifications of the steel or brass used for ammo (and any impurities that may be found in the metals), I couldn't begin to tell you what the tolerances or rates are however ... the difference may not amount to anything, but then again, at peak expansion the difference may be as much as a carrot compared to a cucumber in the rifle's orifice depending on the powder charge and the thickness and type of coating used on the steel and headspace of the chamber. Rojo may have some insight on this, as I think he's had his hands on a wider range of ammo types and barrels over the years. He's a really good source for wisdom and practice on AR's.
If I recall correctly, you have the original stock, original recoil spring, but added a heavier buffer recently. Again, if I recall correctly, when you added the buffer weight, some of the dynamics changed with regard to certain ammo, but overall you still have the same symptoms occurring. In this case, before you try any porting, I would look for a gas leak or a gas restriction or an impingement that's sucking the energy out of your bolt carrier. My first suspect is usually the gas key mating with the gas tube or the gas rings on older guns, but whenever someone says they've changed the gas block, that becomes the primary suspect. Once you've checked these areas, and nothing obvious stands out, have a good look at the chamber. If you know someone with headspace gauges, check the headspace. If not, before any attempt on porting, I would send the rifle in for warranty repair and tell them the symptoms and that you suspect something like micro fractures or imperfections in the chamber or something to that extent (however crazy it may be) so they have to inspect it or at least comment on the condition of the chamber.
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