lvjeffro 30 Posted July 12, 2014 Report Share Posted July 12, 2014 OK, since my S12 runs well, I want to cut down the barrel, rethread it and install a GK-01 for a total length of 18.1". Will this combo require any gas system mods? I have read you could cut the barrel down to about 12" before having to shorten the system, but also read that shortening the barrel and adding a brake will mess with dwell timing? What is the consensus? Just cut and weld, or major gas system overhaul? Thanks Quote Link to post Share on other sites
gunfun 3,931 Posted July 12, 2014 Report Share Posted July 12, 2014 Probably not. If yours is borderline right now, a couple inches of chop could possibly make the difference for the need for some minor friction tuning as I've described numerous times here. Maybe bump the ports up a couple thousandths. But you don't need to pre-emptively cross that bridge. People who chop down to 12" definitely need port size to go up, but the difference between a 19" barrel and a 15" or whatever is not so great. I wouldn't worry about dwell time issues at all. But this is just my opinion. Quote Link to post Share on other sites
Maxwelhse 1,285 Posted July 12, 2014 Report Share Posted July 12, 2014 I'm not a total expert all things "legal firearms", but I believe if you THREAD a GK-01 on there for a total length of 18.1" you'll have an illegal SBS. Your GK-01 would have to be permanently mounted. I know that's not what you asked, but... Quote Link to post Share on other sites
evlblkwpnz 3,418 Posted July 12, 2014 Report Share Posted July 12, 2014 I chopped one of mine to 13.5" and permed a GK-01 on it and it ran great, but I moved the gas system back 2.25". I was able to get by with just 4 ports at .080". There was a lot of action work and it had factory springs, puck, and gas regulator. If you leave the gas system as-is, you will have to run a much larger combined port surface area, refine the action well, and possibly use a weaker forward recoil spring, assuming you want to run bulk pack ammo in it.. In regards to a Saiga 12 shotgun..... Dwell = The period during the cycle when nothing is happening except powder burning and the load is traveling through the bore before it passes the gas ports. Post dwell = The portion of the cycle when the load is traveling from past the gas ports to the end of the bore or choke and gas is interacting with the action causing the unlocking of the bolt and the ejection stroke. Quote Link to post Share on other sites
BobAsh 582 Posted July 13, 2014 Report Share Posted July 13, 2014 I put a lot of information in the SBS thread, NFA section of this forum. 2 Quote Link to post Share on other sites
saltydecimator 482 Posted July 13, 2014 Report Share Posted July 13, 2014 i shall trod what has been trodden before.... i shall trod what has been trodden before.... hahah oh hell i quoted myself. try it. just dont drive your cross pins into your gb all the until after you see if it cycles what you want it too Quote Link to post Share on other sites
VladTepes 160 Posted July 13, 2014 Report Share Posted July 13, 2014 I run a 14in barrel with a 4in muzzle device with factory gas system.. it will basically run all heavy ammo... and it will basically not run any light ammo.. but since I really only desire to run heavier ammo in the gun it was a non issue for me.. Quote Link to post Share on other sites
jdtravers 637 Posted July 13, 2014 Report Share Posted July 13, 2014 I chopped one of mine to 13.5" and permed a GK-01 on it and it ran great, but I moved the gas system back 2.25". I was able to get by with just 4 ports at .080". There was a lot of action work and it had factory springs, puck, and gas regulator. If you leave the gas system as-is, you will have to run a much larger combined port surface area, refine the action well, and possibly use a weaker forward recoil spring, assuming you want to run bulk pack ammo in it.. In regards to a Saiga 12 shotgun..... Dwell = The period during the cycle when nothing is happening except powder burning and the load is traveling through the bore before it passes the gas ports. Post dwell = The portion of the cycle when the load is traveling from past the gas ports to the end of the bore or choke and gas is interacting with the action causing the unlocking of the bolt and the ejection stroke. Here is the definition of "Dwell Time" which has been used in the firearms industry for a long, long time: In a gas-operated automatic or semi-automatic firearm, the dwell time is the amount of time that the gas system is charged with high pressure. It is determined by the amount of barrel after the gas port; once the bullet passes the gas port, the amount of time it takes to get from the gas port to the muzzle is the amount of time the gas system is charged with high enough pressure to cycle the weapon. Here is one of the links that has this definition, there are many more: http://guns.wikia.com/wiki/Dwell_time This definition is used by all the major shotgun manufactures and the big boys like Briley, Nu-Line, etc. It is based on a curve very similar to electronic Dwell Time graphs. I have never heard of the terminology "Post Dwell" time in reference to firearms. Not to say it isn't used in some backroom, but the industry does not recognize it. Jack 1 Quote Link to post Share on other sites
BobAsh 582 Posted July 14, 2014 Report Share Posted July 14, 2014 I agree with Jack regarding the terminology. 1 Quote Link to post Share on other sites
cvhanh20 1,052 Posted July 14, 2014 Report Share Posted July 14, 2014 Hi Bob! Great to see you back in here posting. 1 Quote Link to post Share on other sites
james lambert 3,059 Posted July 14, 2014 Report Share Posted July 14, 2014 if you wait, usually the guys that know what they are talking about chime in Quote Link to post Share on other sites
jdtravers 637 Posted July 14, 2014 Report Share Posted July 14, 2014 Yeah, but we tend to get slammed by the guys who just built their first Saiga and now they consider themselves Master Gunsmiths and know it all:) Jack Quote Link to post Share on other sites
james lambert 3,059 Posted July 14, 2014 Report Share Posted July 14, 2014 Yeah, but we tend to get slammed by the guys who just built their first Saiga and now they consider themselves Master Gunsmiths and know it all:) Jack See it every day Quote Link to post Share on other sites
gunfun 3,931 Posted July 15, 2014 Report Share Posted July 15, 2014 Yeah, but we tend to get slammed by the guys who just built their first Saiga and now they consider themselves Master Gunsmiths and know it all:) Jack See it every day So was any bad advice given, or did anyone claim to be a master gunsmith? If something was wrong above, point out what was wrong, rather than talking down to the other people in the thread. This was done with the definition of dwell I am not sure if the remarks in the quote were aimed at me, but it does seem most likely, since I was the first reply on this thread. All I did was essentially recap the info that guys like you have made available here, I also made a point not to claim any expertise. I make a genuine effort to learn as much as possible and not claim knowledge I don't have. I responded because often others don't. If people get serious, I send them to the experts. I haven't built hundreds, but I've done a few conversions. Most of the normal stuff has been done right and wrong with the results where everyone can see them that we can all see what works and what doesn't. Even if it wasn't aimed at me, the tone is pretty condescending. You guys are the experts in the field, and I respect your work, particularly the info Bob Ash has been kind enough to share. I've certainly plugged each of your services to people who were asking about that kind of thing in the past. I own or have used a few of JTE products and recommend them. I've enjoyed talking with both of you on several occasions. However, the whole attitude of looking down on the amateurs looks bad on you. It also has an element of 'emperor's new clothes' about it. Sure there are some things you guys do that most of us can't or haven't,\. Other things are worthwhile but would be more cost effective for even skilled hobbyists to hire out to a specialst. On the other hand, something like 90% of what comes up here is easily something the average guy can do well, and questions about them are usually something that you guys won't take the time to respond to. I don't blame you for that. I appreciate it when people step in to correct bad advice, and especially when they fill in information that is not commonly available. For most things that go on here, these are simple machines and most of the problems and solutions are simple too. You don't have to build a thousand restaurants to figure out that the secret sauce is mayo and ketchup. The topic of this particular thread is information that is publicly available and all but common knowledge. He was asking pretty general introductory questions, and I think got answers that fit. It is more or less recapping things you guys have said yourselves a few times: Specifically, a moderate chop and perm probably won't need serious gas work. If he had asked about a more extreme modification, I would have said that more chop probably will require a shortened gas system, and is something most people should have done by a specialist. I think you both would still agree with that. I wouldn't touch a few tasks or advise others to do them, i.e. anything that requires special tooling or which might affect headspace or timing. If people ask about that I suggest that is probably a service better to have the pros do. But if we are talking about a non-chopped conversion that is reliable and smooth, we can all do that. Are the tuned competition guns nicer? Sure, but by how much? A few percent better if we're honest. That's worth it to those who can afford it and need it. However, the rest of us are no less legitimate for it. Competition is not nobler than other uses. It is just one of many good uses. Not everyone is up to a basic conversion either, and I know I have told a lot of people that Jack's basic package is reasonably priced... Quote Link to post Share on other sites
jdtravers 637 Posted July 15, 2014 Report Share Posted July 15, 2014 (edited) I am sorry if we hurt your feelings, maybe you need a big forum hug?? Jack Edited July 15, 2014 by JTE Quote Link to post Share on other sites
gunfun 3,931 Posted July 15, 2014 Report Share Posted July 15, 2014 Nah, but it would be nice if you'd not be needlessly condescending to people who buy your stuff. You do good work, but most of it isn't rocket science. I don't know why- but every professional builder I know seems to think he is the only one on the planet capable of building a decent gun, and no other smith's work is good enough for him. They all seem to act as if even the easy stuff can only be done by their exalted hands. It gets hard to put up with that kind of talk for years without calling B.S. on it now and then. When you have the nerve to mock us/me in front of us, that's a bit rich. You know I don't claim more expertise than I have. I just try and help people out who wouldn't be helped otherwise, and correct misinformation that would cost people. If that is something to look down on, well go ahead. Quote Link to post Share on other sites
jdtravers 637 Posted July 15, 2014 Report Share Posted July 15, 2014 (edited) I was supporting your definition of "Dwell Time". The evlblkwpnz guy was putting out erroneous information. So now I am going to hurt his feelings and he can write a nasty post to me:) Jack Edited July 15, 2014 by JTE Quote Link to post Share on other sites
evlblkwpnz 3,418 Posted July 15, 2014 Report Share Posted July 15, 2014 I was supporting your definition of "Dwell Time". The evlblkwpnz guy was putting out erroneous information. So now I am going to hurt his feelings and he can write a nasty post to me:) Jack Please do not take this in the wrong tone, I do not mean it that way. Anyone who really knows me knows that I don't go around acting nasty. It doesn't help people. It takes a lot of digging to get to what I was talking about and I have to admit I did dumb it way down, but you are right. Still, there are nuances and widespread misnomers according to the context which some terms are used in. This subject is not absent them. Still, you are right, so I am not trying to get into a debate about it in a general sense. I never claimed to know it all or be a master gunsmith, not once anywhere, not even in a backroom, and certainly not every day, lol. That is a stretch and I would appreciate it if you would simply stick to fact if you are going to relay things that I say, that's all. Anyone who knows me will tell you that I have no problem stating the limits of what I am capable of. What I do is very narrow and focused, but I do ok with it. Have a great day, no need to get ruffled. I still haven't seen an SBS in that length from anyone else that runs like the first one I did with nearly nothing.... for fun, lol. You have to admit that was pretty good for a first one. That thing has been beat to hell and still runs great. Quote Link to post Share on other sites
jdtravers 637 Posted July 15, 2014 Report Share Posted July 15, 2014 We're good man!!! My "Back Room" comment is in regards to how the dis-information is passed from one person to another like at a range, gun shop or a bar. It really doesn't matter how we try and help, it seems like someone always gets their feelings hurt, like "Gun Fun" because he thought we were taking about him. What J. Lambert and I were referring to was not even on this particular topic. But it is true. Gun Fun proved that!!! There was nothing condescending about my post, unless you think it is directed at you (Gun Fun). And it doesn't matter how nice or professional we try and make a post, someone will always get their panties twisted and get pissed off because they take it all so seriously! Jack Quote Link to post Share on other sites
james lambert 3,059 Posted July 15, 2014 Report Share Posted July 15, 2014 Nah, but it would be nice if you'd not be needlessly condescending to people who buy your stuff. You do good work, but most of it isn't rocket science. I don't know why- but every professional builder I know seems to think he is the only one on the planet capable of building a decent gun, and no other smith's work is good enough for him. They all seem to act as if even the easy stuff can only be done by their exalted hands. It gets hard to put up with that kind of talk for years without calling B.S. on it now and then. When you have the nerve to mock us/me in front of us, that's a bit rich. You know I don't claim more expertise than I have. I just try and help people out who wouldn't be helped otherwise, and correct misinformation that would cost people. If that is something to look down on, well go ahead. I call BS here The real gunsmiths and PRO builders have a lot of respect for each other. The wannabees never see the skill level of those people, never see the value of their decades of experience. Many think building a dozen guns can some how make them equivalent. Well they are not. You wont see the skilled arguing with the skilled, those people are on the same page. People who know exactly what they are talking about, are often overridden by idiots spewing bull in an attempt to bolster their egos. Or in some cases, to cover their own inferior work. There are a lot of pretenders here. The best builders/ manufacturers/gunsmiths here post all the time trying to help the home builder and the DIY guys. They dont feel they have (EXALTED) hands, and are genuinely interested helping out. But some jackasses always take offence and push crap back at them. So much BS advise goes unchecked or ignored simply because the people who know better, are sick of taking the crap. Quote Link to post Share on other sites
VladTepes 160 Posted July 15, 2014 Report Share Posted July 15, 2014 no idea if anything was directed at me.. nor do I really care.. but I was simply relaying my personal experience with one gun.. Quote Link to post Share on other sites
pedal2alloy 206 Posted July 16, 2014 Report Share Posted July 16, 2014 Imagine how much shorter these threads could be if they stayed on topic Quote Link to post Share on other sites
Machinist 150 Posted July 16, 2014 Report Share Posted July 16, 2014 We're good man!!! My "Back Room" comment is in regards to how the dis-information is passed from one person to another like at a range, gun shop or a bar. It really doesn't matter how we try and help, it seems like someone always gets their feelings hurt, like "Gun Fun" because he thought we were taking about him. What J. Lambert and I were referring to was not even on this particular topic. But it is true. Gun Fun proved that!!! There was nothing condescending about my post, unless you think it is directed at you (Gun Fun). And it doesn't matter how nice or professional we try and make a post, someone will always get their panties twisted and get pissed off because they take it all so seriously! Jack PRODIGY....Hmmmm Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.