cure for dot dip?

[Will Abrahams]

i have been having alot of problems with the dot tracking well on my Dawson full length open gun (stroker). the dot seems to be going well below the start point as the slide goes back into battery. also the dot is not very consistent when it dips down, which makes follow up shoots much more unpredictable than i would like.

here is my theory on this...please correct me if i am thinking about this wrong.

i used to use very slow powders like VV N105. the dot would dip significantly with this load (9.5 grains, 124 gr MG JHP 1.240 OAL). so then i tried going with a powder that was a bit quicker VV 3N38. with this i noticed that the dot would dip less, but it was still doing it and making follow ups less predictable. my thinking is that with these relatively slow powders with lots of gas volume keep the gun very flat. and by doing so when the slide cycles back into battery (with the gun fairly flat still) it pushes the gun down and thats what is causing the dot dip???

are these possible solutions?

1)use a lighter recoil spring that way the slide doesnt close with so much force? when i first got the gun in i used an 8lb, but switched to the 9lb because i was getting failures to feed. the 9lb seemed to cure this...but with the 9 came the dot trouble.

2)switch to a steel guide rod vs the tungsten i have now...maybe by taking some of the weight off the front, it will help with the dip?

3)does the slide need to be lightened?

4)switch to a faster powder?

or does any body have any better idea of whats going on before i spend time and money trying to fix this.

thanks for any help!

Edited June 27, 2007 by W.Abrahams

[wide45]

If the gun is running right, you just need to groove yourself to shoot it better.

also the dot is not very consistent when it dips down

Most likely you not being consistant.

[BritinUSA]

My suggestions, cheapest first...

1. Get someone else to shoot your gun and see if they see the same problem. If they do not then it's down to your grip/stance.

2. Failing that, have you tried variable strength recoil springs? Wolff makes them... Try a 8lb and a 9lb to start with.

[JThompson]

I started a thread about this very issue. Most likely, it's an issue with your grip, and or a push from you to counter recoil. I use 3n37, but just switched to 7625. I'll check the dot again tomorrow to see if it's still happening. I'll post again and let ya know.

JT

Edited June 27, 2007 by JThompson

[G-ManBart]

Sounds like some slide lightening might be in order if you're not getting what you want with load/spring changes. Swapping out the guide rod to one that's lighter is worth trying, but I'm not so sure it would make that big a difference...only one way to find out and it's cheap.

Did you ever try a lighter mainspring with the 8lb recoil spring to see if it would feed properly that way? If the mainspring was too heavy for the recoil spring, the slide might not have been compressing the recoil spring completely...which would prevent it from going forward as it should. It's another easy thing to try before spending a lot on slide work.

[Crusher]

Grip tension need tweeking and stop anticipating the recoil (if there is any) you are more than likely "pushing" the gun on follow-up shots.

Some timing drills (oh......say....... about 5000 rounds worth) into a berm with nothing to watch but the "dot" should get you on your way.

which makes follow up shoots much more unpredictable than i would like.

The ONLY way to predict a shot is to see where the dot is when the shot breaks, you ain't calling the "dot"

[Will Abrahams]

thanks for the suggestions. alot of you mentioned altering my grip. i will be out at the range tomorrow, i'll experiment with some grip changes...any suggestions though about what i might be doing wrong with my grip (assuming its not any kind of a flinch)???

britianUSA-good suggestion about having someone else shoot it, never thought of that!

G-manbart-the mainspring is a 15lb, at least thats what Dave told me it was? does that set up sound right (15 lb, with a 8 or 9lb recoil spring)?

[rvb]

I'm new to open also.... Have about 3500 rounds through my gun and maybe 4 matches. I'm still battling the dipping dot. I'm running a box-stock STI Trubor except I did some extractor tuning and put in an 8-lb recoil spring. I would suggest focusing on grip change before you mess with springs and milling the slide. Those things are good and I will eventually get some metal removed from my slide, but not until I can control the dot in stock form.

I asked some of the experienced open guys at my local matches, and what I've learned is you can't carry a super firm limited/production gun grip to open division. Shooting a "normal" gun your muscles are timed to push the front sight back down and you are trying to tame the recoil. My timing was causing me to push the gun back down under the target, which sounds like what you are struggling with, also.

I can get my dot to go straight up and come straight back and stop at dead center, but only if I am neither over-gripping or under-gripping the gun. The key is to let the comp work. I put 300 rounds down range tonight working on just that... training the proper grip into the subconscious and getting that dot to come right back on target. Splits are much faster and accuracy much better when I can manage the right grip and don't have to wait on my brain to track the dot and bring it back up on target.

Hope that helps..... I'm only passing along my similar recent experience and the words of wisdom that were passed on to me.

rvb

[G-ManBart]

thanks for the suggestions. alot of you mentioned altering my grip. i will be out at the range tomorrow, i'll experiment with some grip changes...any suggestions though about what i might be doing wrong with my grip (assuming its not any kind of a flinch)???

britianUSA-good suggestion about having someone else shoot it, never thought of that!

G-manbart-the mainspring is a 15lb, at least thats what Dave told me it was? does that set up sound right (15 lb, with a 8 or 9lb recoil spring)?

A 15lb mainspring sounds reasonable for that setup. I'm far from an expert on springs, so someone else might give you a more exact answer, but it doesn't sound like that should be causing a problem.

[R.Elliott]

are these possible solutions?

1)use a lighter recoil spring that way the slide doesnt close with so much force? when i first got the gun in i used an 8lb, but switched to the 9lb because i was getting failures to feed. the 9lb seemed to cure this...but with the 9 came the dot trouble.

2)switch to a steel guide rod vs the tungsten i have now...maybe by taking some of the weight off the front, it will help with the dip?

3)does the slide need to be lightened?

4)switch to a faster powder?

or does any body have any better idea of whats going on before i spend time and money trying to fix this.

thanks for any help!

It's going to be a trial and error process to discover the right "tune" for your gun. In order I would do the following, one step at a time.

1. Switch out the Tungsten guide rod for steel, and try a polymer one as well. Either one should reduce the dot dip; up to you which one gives the best result. If this doesn't completely fix it then,

2. Try a variable spring with new new guide rod in place.

3. Try a faster powder. 3N37 worked very nicely for me.

4. Consider slide lightening. Go slow and do a little at a time. Note after the first cuts if any positive change is achieved.

My guess is that the tungsten guide rod isn't helping you, and the variable spring might soften the transition back into battery just enough.

Good luck.

[Front Man]

Come to the Dark Side and try 115 Grain bullets.

FM

[Dream]

have you tried a springco. this is what they do reduce dip when the slide closes...

[TONY BARONE]

have you tried a springco. this is what they do reduce dip when the slide closes...

I would return that gun to its original configuration and just shoot it. Dave did all the R&D on that Mini Gun and it runs fine for every one that I know that has one. As TGO says let the gun do what it has to just pull the trigger when the dot is where you want it.

[shred]

3N28 and N105 are both still in the 'slow' category. Try some loads with 7625 or N350 to compare. 7625 works for our national Open champion, so it's worth a shot, so to speak.

Does it do it strong-hand-only or weak-hand-only?

[Will Abrahams]

3N28 and N105 are both still in the 'slow' category. Try some loads with 7625 or N350 to compare. 7625 works for our national Open champion, so it's worth a shot, so to speak.

Does it do it strong-hand-only or weak-hand-only?

thanks Roy, i will give them a try. i just get a little nervous about using the fast burning, high pressure powders. i know there is alot of complaints about the inconsistency of IMR 4756, does this hold true for the 7625 as well?

no noticable dip with weak or strong hand only.

[JThompson]

I get no dip now with 7625 and MG 124s. I was using 3n37 and Zero 115s. No grip change to speak of....

JT

[shred]

3N28 and N105 are both still in the 'slow' category. Try some loads with 7625 or N350 to compare. 7625 works for our national Open champion, so it's worth a shot, so to speak.

Does it do it strong-hand-only or weak-hand-only?

no noticable dip with weak or strong hand only.

With no dip SHO or WHO, it would sort of imply that the dip is grip/timing-related and not ammo-related, right? Have you tried Burkett's timing drills with the different grip pressures and elbow angles and so on? Matt's site appears to be down right now, but Saul has a bunch of Matt's tips on his site: http://www.doublealpha.biz/tip_burkett.htm#Timing%20Drills

[ipscbob]

thanks Roy, i will give them a try. i just get a little nervous about using the fast burning, high pressure powders. i know there is alot of complaints about the inconsistency of IMR 4756, does this hold true for the 7625 as well?

7625 is still extremely inconsistent for this application Lot to Lot. Alot of folks I know who have experienced this won't use it for this reason. It also generates relatively high pressures at major PFs in super.