Poppa Bear Posted May 15, 2012 Share Posted May 15, 2012 Read through Competition Mag Tuning Tutorial and understand all the steps. My question is what do the parts get me? Going with a stock tube and sanding the insides, how many full and even fractional rounds do I gain with the Grams followers and spring? How many do I gain with the Dawson +1 base pad? What do I gain with the re-dimensioning? I just picked up an STI and got two stock mags with it. I ordered a set of tuned mags so that part will be fine, but I am a tinkerer by trade so I JUST have to tune up the two stock mags. My brain is also wired to want to understand how the parts all come together. That way I get a better understanding of what changing from say a Dawson to a Bolen to Grams base pad will have, or changing followers and springs. This is especially true if I am sitting at say 19.75 rounds in the mag or even at 20 but so tight that I cannot seat the mag unless the slide is locked back. Some parts like the base pads cannot be modified to increase capacity, some like the springs and followers can be tweaked. Which brings up a thought. What is the effect of sanding up just a bit higher on the tube so that the internal capacity is increased slightly? Will it cause feeding problems if the area sanded in Bobby's tutorial is 1/2" or 3/4" higher than shown? Link to comment Share on other sites More sharing options...
feederic Posted May 15, 2012 Share Posted May 15, 2012 Grams spring and follower gets you +1 and maybe a little more. Bolen pads get me around +1, but I can't speak for Dawsons. Redimensioning the tube helps ensure the tube drops free, while also widening it for extra capacity. I am not sure sanding up on the tube a little higher will net you anything really beneficial. Sanding there is to help prevent the follower from rolling over by providing a smooth transition point since they will make their way further down the tube below the support ribs. Link to comment Share on other sites More sharing options...
Poppa Bear Posted May 15, 2012 Author Share Posted May 15, 2012 (edited) Unless someone has already tried it and had problems, if so speak up so that I do not screw one up also, I am going to experiment with the amount of material removed from the side of the body to see if it screws up feeding. I am also going to see what effect it has on overall capacity. I imagine a couple of extra thousandths could add up. It might be why some people can get 19 reloadable and others 20 or even 21. Edited May 15, 2012 by Poppa Bear Link to comment Share on other sites More sharing options...
a matt Posted May 16, 2012 Share Posted May 16, 2012 I have a set of SV tubes Bolen pads and springs. Two I can get 21 tight two I can get 20 1/2 in.. All are easy to reload. Link to comment Share on other sites More sharing options...
Pat Miles Posted May 16, 2012 Share Posted May 16, 2012 Unless someone has already tried it and had problems, if so speak up so that I do not screw one up also, I am going to experiment with the amount of material removed from the side of the body to see if it screws up feeding. I am also going to see what effect it has on overall capacity. I imagine a couple of extra thousandths could add up. It might be why some people can get 19 reloadable and others 20 or even 21. Just exactly where are you going to remove material from the side of the body? How are you going to remove it? Pat Link to comment Share on other sites More sharing options...
Poppa Bear Posted May 16, 2012 Author Share Posted May 16, 2012 Dimensioned the tubes tonight and realized the the one tube is actually a 38 tube because the feed lips were set to .366. The other tube was already dimensional correct so I just needed to sand down the base of the rib. Now both tubes hold an easy 17 with all stock parts. Once the new internals get here I will see what each of them does. Hopefully each will give me 1 1/2 bullets so that I get an easy 20 reloadable for both mags. Link to comment Share on other sites More sharing options...
Poppa Bear Posted May 16, 2012 Author Share Posted May 16, 2012 Unless someone has already tried it and had problems, if so speak up so that I do not screw one up also, I am going to experiment with the amount of material removed from the side of the body to see if it screws up feeding. I am also going to see what effect it has on overall capacity. I imagine a couple of extra thousandths could add up. It might be why some people can get 19 reloadable and others 20 or even 21. Just exactly where are you going to remove material from the side of the body? How are you going to remove it? Pat The ribs that keep the tube rigid take up about .06" of each side of the tube. Combined they reduce the internal capacity by .12" or about 1/8". I am going to try a flat file and see if I can get the bottom 2/3 of the tube so that the ribs are down to .045 to .050, and then polish it up with some 1200 grit paper. This still leaves plenty for structural strength but that extra 1/32 of an inch could allow an extra round or at least 1/2 of a round. If it helps great, if it does not really do anything then at least I tried. If it turns a stiff 20 rounder into an easy 20 rounder then others that are border line will now know something to try. Link to comment Share on other sites More sharing options...
Pat Miles Posted May 16, 2012 Share Posted May 16, 2012 (edited) I assume that you are going to take the material off of the inside of the tube. You will gain inside real estate but what will happen is the rounds will be able to get side by side and jam against each other and the tube sides. This is what is happening if you can get 12 -16 rounds in the tube while loading it up and have to bang the mag down on something to finish loading. The rounds will get stuck in the same fashion as you are unloading the mag (shooting) and either stop pushing the bullet column upward or feed sluggishly causing a failure to feed. The majority of the time STI mags have to be squeezed to lessen the side to side dimension while NOT letting it grow larger front to back. If the front to back dimension is allowed to grow the mag will not drop free. I use a 5" Kurt milling vise to squeeze while I have a 1" steel bar clamped downward to stop the front to back growth. The change is made up in the radius where the front of the tube rolls over to the sides. IF you decide to try squeezing the tube go very slowly. Trying to do it all at once will sometimes cause the weld on the front or back to crack. Good luck with your grinding. Pat Edited May 16, 2012 by Pat Miles Link to comment Share on other sites More sharing options...
Poppa Bear Posted May 16, 2012 Author Share Posted May 16, 2012 Haven't taken anything extra off the sides and probably won't. Pat's post made me think about how the rounds stack in there when you reach 16+ rounds so I removed the base pad and then loaded the mag up allowing the spring to slide out of the bottom every couple of rounds. At 18 rounds I held the tube with the bottom up and the feed lips down and one finger at the nose to stop any from just sliding out the feed lips. The rounds in the base of the tube where the ribs were already ground down were pretty close to two wide. Increasing the internal width over a greater portion of the tube seems to have a lot of potential for causing the rounds to jam in the tube because of how the follower applies its pressure. All I am going to do now is polish the area already ground down where the transition takes place with some 1200 paper followed by some Flitz. It is easy to see why S_I tubes need to be kept so clean internally. Even a little grit can stop a round from sliding up the side jamming all the rounds below it. The ribs provide a channel for that grit to make it past the rounds and the bearing surface of those ribs is small enough that it reduces the friction between the case and the tube. Sanding down those ribs will just increase the bearing surface and increase the potential for a jam. Link to comment Share on other sites More sharing options...
CenTX Posted February 25, 2013 Share Posted February 25, 2013 Dimensioned the tubes tonight and realized the the one tube is actually a 38 tube because the feed lips were set to .366. The other tube was already dimensional correct so I just needed to sand down the base of the rib. Now both tubes hold an easy 17 with all stock parts. Once the new internals get here I will see what each of them does. Hopefully each will give me 1 1/2 bullets so that I get an easy 20 reloadable for both mags. The way to tell if you have a 38/40 or 45 tube is the ribs on the side of the mag. A 38 has 4 deep ribs, a 40 has 2 deepand 2 shallow and a 45 has 4 shallow ribs. Link to comment Share on other sites More sharing options...
CocoBolo Posted February 25, 2013 Share Posted February 25, 2013 How about 22 in a mag. Can you say Rescomp? Manny Bragg was selling them on his site. Link to comment Share on other sites More sharing options...
cbmax Posted February 28, 2013 Share Posted February 28, 2013 Hi, I "tuned" my stock STI 140mm tubes. All I did was polish the feed lips and made sure the feed lips were at the correct measurement. I don't remember the measurement off hand, but if you look at Brazos Custom magazine article they provide the correct dimension. I used Dawson SNL plus 1 base pads and Grams followers. I polished the entire outside of the mag tube. I trimmed the follower to ensure no slide lock. I wouldn't personally take any material out of the inside of the magazine. Just stick with making the mag lips perfectly smooth. I get 20 rounds, easily reloadable. If you really feel the need to try and get 21 rounds, I would leave that job to the pros. Just my 2 cents! CB Link to comment Share on other sites More sharing options...
Ranger6 Posted February 28, 2013 Share Posted February 28, 2013 Grams Engineering! Send them to Blevin. Send some $. Great guy. Great Service. My mags never fail. Ranger6 Link to comment Share on other sites More sharing options...
Biloxi23 Posted March 1, 2013 Share Posted March 1, 2013 I tuned mine by buying tuned magazines from Brazos. STI mag tubes cost too much to be worked on by me. I have this history with Dremels, files, sandpaper, etc. I ususally end up ruining something and it cost twice as much as if I would have bought it in the first place. Link to comment Share on other sites More sharing options...
Frankl03 Posted March 3, 2013 Share Posted March 3, 2013 I didn't tune my STI mags but I did polish the tubes and added grams springs, followers and Dawson plus 1 bases. They will all hold 20 but they don't all easily seat in the gun with 20. I also filed the followers so the gun doesn't lock back. Maybe after a bit of use they seat with 20! Link to comment Share on other sites More sharing options...
jimbullet Posted April 17, 2013 Share Posted April 17, 2013 I didn't tune my STI mags but I did polish the tubes and added grams springs, followers and Dawson plus 1 bases. They will all hold 20 but they don't all easily seat in the gun with 20. I also filed the followers so the gun doesn't lock back. Maybe after a bit of use they seat with 20! Is this for a 40cal? What internals did you use to achieve 20 rounds? Link to comment Share on other sites More sharing options...
wgj3 Posted April 17, 2013 Share Posted April 17, 2013 (edited) Grams are the guts to use if you dont want to have to worry with it too much. They just work. Edited April 17, 2013 by wgj3 Link to comment Share on other sites More sharing options...
jimbullet Posted April 22, 2013 Share Posted April 22, 2013 the problem I have is that the rounds are getting crimped when I load up 17 rounds on 40cal. Im wanting to avoid this. Link to comment Share on other sites More sharing options...
thegunnerd Posted April 22, 2013 Share Posted April 22, 2013 I have a tuned mag that can certainly hold 20 , grams spring and follower , dawson tooless etc . Loads and drops super smooth, BUT I'm having a hard time getting my mag to catch when reloading if i have it fully loaded with 20. No doubt it's butting up against the extractor and the added spring tension of the mag is making it hard to seat. Is there a way to give the round enough clearance underneath the extractor so it doesn't require so much force to seat? Should i be looking at the mag, the mag catch , the extractor ? Link to comment Share on other sites More sharing options...
Zoomy Posted April 24, 2013 Share Posted April 24, 2013 I have STI tubes, Grams springs and followers and Bolen 4mm base pads. Stock I get 20 .40 S&W but tight, not reloadable and will not fit gauge. Now the fun begins. I first macined off the base pad .015 and ground off .015 from the back of the feed lips so it fit in the gauge. Next I noticed my reloads where not resized all the way down to the extractor groove and where .003 larger diameter at the bottom. I roll sized the cases so they are the same size full length. By doing this I will not gain the full .063 room since vthis is not a single stack magazine but I do gain 1/32". And last I machined the top of the Grams follower using tooling that gave the same profile as origional. After all this I have 20 round capacity that is reloadable. If I did not have the machine resources to modify the origional equipment I would probably still have 19 rounds reloadable. I did the same using Rescomp 138mm tubes and have 21 rounds reloadable. Link to comment Share on other sites More sharing options...
jimbullet Posted April 24, 2013 Share Posted April 24, 2013 I realize that most of those that are able to achieve 20 rounds refer to USPSA rules. Not wanting to hijack this thread but just wanting to know if those that are using the wedge base pads for IPSC standard division which needs to fit the IPSC box - how many rounds do you get? I have used the wedge base pad, bolen followers and springs on an STI 126mm tube, and could only put in 17 rounds and while it appears to be reloadable, it is very hard to put into the gun. Is 17 rounds then normal? I had to compare, that my Para p16-40 is able to get in 18 rounds with ease. Link to comment Share on other sites More sharing options...
Mick Posted May 16, 2013 Share Posted May 16, 2013 Anyone know what the feedlips on the STI .45 mags are suppossed to measure? Link to comment Share on other sites More sharing options...
Pat Miles Posted May 16, 2013 Share Posted May 16, 2013 Anyone know what the feedlips on the STI .45 mags are suppossed to measure? STI says .435"-.445" lip width. Benny Hill once told me he likes .415". I would suggest .415". Pat Link to comment Share on other sites More sharing options...
Mick Posted May 19, 2013 Share Posted May 19, 2013 Anyone know what the feedlips on the STI .45 mags are suppossed to measure? STI says .435"-.445" lip width. Benny Hill once told me he likes .415". I would suggest .415". Pat Thanks, I'll do the .415 first. All 8 .45 mags were right on .390" and fed terribly. I borrowed a couple that were at .430 and they were smooth but I'll bet Benny went a little tigher for a reason.....;-) Link to comment Share on other sites More sharing options...
DirtDiver Posted May 22, 2013 Share Posted May 22, 2013 Bolen basepads, followers.....to clean and polish the mag tube put them in the tumbler for 8 hours or so.....nicely polished inside and out. Link to comment Share on other sites More sharing options...
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