Krom 36 Posted April 6, 2008 Report Share Posted April 6, 2008 I got the kit and threaded my barrel successfully! But I'm having a problem.. when I install the ak74 style brake I got from dinzag the rifle shoots terribly (extreme down and right). I thought it I might have damaged the crown on the barrel, nope I took the brake off and shoots as well as ever. Any ideas what could cause this? The rifle I'm working on is a 762x39 20" barrel. I have a few ideas about what could be causing it. 1. When I started to thread the barrel I had the dye backwards, so the outside of the barrel on the tip is unthreaded and slightly smaller (see attatched pic). And this is some how f*ckin up the physics on the inside of the brake. 2. Since a 20" barrel flexes more than a 16" and the ak74 brake is alittle heavy maybe this flexing is causing it to throw rounds weird. 3. The brake is deflective somehow. Please lemme know if you know any ideas of how to fix/troubleshoot this problem. thx Quote Link to post Share on other sites
1liter 20 Posted April 6, 2008 Report Share Posted April 6, 2008 Check the internals of the break for any damage. If the threading was F'ed up, your break might be sitting at an angle and deflecting the round. Quote Link to post Share on other sites
oldandslow 3 Posted April 6, 2008 Report Share Posted April 6, 2008 Stick the cleaning rod into the bore. Is the rod centered in the brake? Quote Link to post Share on other sites
IndyArms 10,186 Posted April 7, 2008 Report Share Posted April 7, 2008 a couple things to ponder... How far is "Extreme down and right", and are the rounds GROUPING? Even though they are not going where they would when the brake is off, If they group, just re-sight in with the brake attached... Do you have the proper brake installed? This may sound silly... but I bought a Tantal brake and wanted to put it on my 7.62 X 39... *OOPS!!!* That brake was for a 5.45mm round and although the bullets would fit through it... they were zinging all over hell... I put it on a .223 Saiga and it shot beautifully... Make sure you have a 30 cal. brake on a 30 cal. rifle, etc... I have never heard of a defective brake... I dont know how one could be... other than as mentioned... it is not true to the bore, and is crooked on the barrel. Either your threading is crooked, and the bullets are hitting the brake and they are being deflected, or the brake is threaded crooked and the same thing is happening. Good luck... Quote Link to post Share on other sites
Krom 36 Posted April 7, 2008 Author Report Share Posted April 7, 2008 (edited) K, thanks for the replies btw. I think I found the problem, first the threads are a tiny bit off (not enough to cause the symptom though). So since I'm working with a 20" barrel I went ahead and chopped it down to 16+"ish and re-threaded it and double checked the threads for damage. Threads are good, but I'm pretty sure that the brake is defective, when I and screwing it on it consistently moves in an oval pattern all the way till the end (and it's still not all the way aligned w/ the muzzle. Any advice on crowning? I mean I cleaned it up pretty well with a file then I used the flexible paper sanding circles in my dremel to crown the barrel (basically when I press the circle sander into the barrel it partially conforms to the muzzle and makes a crown sorta. I know that it would not be concave enough to protect the muzzle if it was open, but since I'm putting a brake on then I'm hoping it won't matter. Anyone have experience with this? Can I expect good accuracy from my bubba crown job or a significant loss of accuracy? I just ordered a J-Tac and as long as it fits and fires good, I'll prob weild it on. Edited April 7, 2008 by Krom Quote Link to post Share on other sites
BobAsh 582 Posted April 7, 2008 Report Share Posted April 7, 2008 Muzzle devices have 2 different alignment issues. Concentricity- the alignment of the different bored diameters of the device itself; for instance if the threaded bore is not centered on the bullet bore. Angular- this is more common. The 2 mating faces must be square to the bore. Since you cut your own barrel I would be looking at this. Quote Link to post Share on other sites
jamesavery22 54 Posted April 7, 2008 Report Share Posted April 7, 2008 He didn't cut the barrel did he? Looks like he just cut off the FSB sleeve, threaded it, then grinded down the front ~1/4" of threads. Quote Link to post Share on other sites
BobAsh 582 Posted April 7, 2008 Report Share Posted April 7, 2008 Unless I'm misunderstanding this: So since I'm working with a 20" barrel I went ahead and chopped it down to 16+"ish and re-threaded it and double checked the threads for damage. Quote Link to post Share on other sites
jamesavery22 54 Posted April 7, 2008 Report Share Posted April 7, 2008 ah didnt read that post sorry! Quote Link to post Share on other sites
Krom 36 Posted April 7, 2008 Author Report Share Posted April 7, 2008 Muzzle devices have 2 different alignment issues. Concentricity- the alignment of the different bored diameters of the device itself; for instance if the threaded bore is not centered on the bullet bore. Angular- this is more common. The 2 mating faces must be square to the bore. Since you cut your own barrel I would be looking at this. Well I'll have to wait and see how it shoots when my jtac brake gets here since I have not fired it w/ the shortened barrel yet. I'm not sure what you mean by angular, I used the TAT and it will thread straight from the TAT to the muzzle so I'm pretty sure the threads on the muzzle are very straight and aligned correctly. Could you elaborate a little more on the angular possible problem? Quote Link to post Share on other sites
grimper 0 Posted April 7, 2008 Report Share Posted April 7, 2008 I got the kit and threaded my barrel successfully! But I'm having a problem.. when I install the ak74 style brake I got from dinzag the rifle shoots terribly (extreme down and right). I thought it I might have damaged the crown on the barrel, nope I took the brake off and shoots as well as ever. Any ideas what could cause this? The rifle I'm working on is a 762x39 20" barrel. I have a few ideas about what could be causing it. 1. When I started to thread the barrel I had the dye backwards, so the outside of the barrel on the tip is unthreaded and slightly smaller (see attatched pic). And this is some how f*ckin up the physics on the inside of the brake. 2. Since a 20" barrel flexes more than a 16" and the ak74 brake is alittle heavy maybe this flexing is causing it to throw rounds weird. 3. The brake is deflective somehow. Please lemme know if you know any ideas of how to fix/troubleshoot this problem. thx I have the same problem on one of my saigas. I love dinzag and think he gives really good service and have used his 74 brakes before with no probs (other than me killing one of his dies -srry D) But I feel like the chasing that he does to the brake was off on this particular order? Is that even possible?. i contacted him and he offered me to send it back for him to review, but being lazy and in Kali i didnt, I just left it off and the rifle shoots fine, with it on though I am down and to the right. Wonder if there is a connection? Quote Link to post Share on other sites
BobAsh 582 Posted April 7, 2008 Report Share Posted April 7, 2008 Could you elaborate a little more on the angular possible problem? Sure. There is a little play inherent in any threaded connection. The main thing that aligns the centerline of the brake to the centerline of the barrel is the mating surface at the muzzle. The muzzle end must be square to the bore and the recess in the brake must be square to it's bore. If either of these is off, when the brake screws down tight it will be off at that angle. The misalignment may be small over the diameter of the barrel, but it will be magnified by the length of the brake. Quote Link to post Share on other sites
Krom 36 Posted April 9, 2008 Author Report Share Posted April 9, 2008 Good news! After I was able to remove then reinstall the fsb and I borrowed a jtac brake from a friend then test fired.. Worked great the threads I cut after I shortened the barrel are fine and my fsb install is almost dead on w/o adjusting the sight post. I like the jtac too, don't have much experience with brakes but I can double tap @ 25yrds almost in the same holes. Thanks for all the input and help (if wasn't for the wealth of knowledge on this board I'd def my f'ed in the A when it comes to gunsmithing) Quote Link to post Share on other sites
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