A real puzle for someone...I can't figure it out...yet.

[jakfrost1]

Big match coming up so as per usual I went to the range to confirm the zero on both guns...and well, for the life of me I can't figure out what the problem is. I guess I could buy 2 new RTS-2's to eliminate the scopes as the culprit but I can't afford the luxury of owning 5 of the little buggers. I can't imagine what the gun's themselves could be doing to cause this, but anything is possible.

The primary gun is a 3 yr old, 8-10K round, STI DVC with the usual mods, Aftec, grips, magwell, ambi shielded safeties, pinned beavertail, etc. The secondary is EXACTLY the same, mods and all, except it has less than 2K rounds thru it. They are both wearing a fairly new Mk 4 6 MOA C-MORE RTS-2 scope. 

 

I went back to the range today to confirm yesterdays confusing effort to zero both guns. It seemed that the first shot from EITHER GUN, firing both my match ammo ( only difference is the OAL, mine is 1.170" and hers is 1.150" ) and a friends 9 major match ammo, producing almost exactly the same result. 

 

Shooting seated, off a bagged table rest, the first round is about 7-8" low at the 5 o'clock position from the primary gun, and 4-5" low at 5 o'clock from the secondary gun. The rest of the string of 10rds are all pretty well grouped at the centre. I pulled down the first target and put up a clean one and tried again. Same result just not quite as dramatic. The secondary groups really well, but has the most dramatic excursion on the first shot. Shooting the second string on the new target has the same result, 1st shot low to the right, just not nearly as far out. 

 

Something to do with a cold/cool barrel? It certainly wasn't 'cold' out at 27c. The only thing that I can think of is maybe the lens/dot alignment 'settles' or 'self-adjusts' after the first shot? Not sure how that technology works...? but both scopes at the same time? Weird. 

 

Anyone seen this phenomenon before? 

 

Going to be a challenge at the match if I have to 'Crockett' the first shot, and ONLY the first shot, on every stage, haha...

 

Jim

 

 

 

Edited July 28, 2018 by jakfrost1
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[echotango]

Try letting the slide slam fwd when racking vs following it thru. If that makes sense. 

 

If you are racking with a full mag and let it load slowly, I've seen this happen(but that that off). 

Edited July 28, 2018 by echotango

[jakfrost1]

Hmmm...I changed out the slide return springs in both guns very recently, putting in brand new Wolff 9lb springs. BUT, I noticed that both guns often need a little ‘encouragement’ to go into breech lock for the first round. All subsequent shots are without issue. I have been using some ‘older’ brass lately for practice sessions and blamed the brass...but maybe the spring isn’t up to snuff and my ‘helping’ with the slide racker is causing/confusing the issue? 

 

I would think 9lb springs should put good clean ammo into breech lock no problem...? 

Edited July 28, 2018 by jakfrost1

[ltdmstr]

Cold bore shift is a factor with rifles, but usually amounts to a fraction of an inch at 100+ yards.  It's not going to be a factor in a handgun at that distance.  At least not anywhere near several inches at 15 yards.  And the odds of having nearly the same identical mechanical issues in two different guns is very slim.  So i would say it probably has to do with optics or something you're doing. 

[Sarge]

52 minutes ago, echotango said:

Try letting the slide slam fwd when racking vs following it thru. If that makes sense. 

 

If you are racking with a full mag and let it load slowly, I've seen this happen(but that that off). 

That’s what I’m thinking. Rack it hard and fast, slingshot it, whatever. Try to get the barrel lockup closer to gun running. To test this just launch one into the berm and then shoot your group. At least that would tell if we are on the right track with a lock up issue.

[AWLAZS]

How does loading the chamber slowly influence the accuracy of the first shot?

[Sarge]

Just now, AWLAZS said:

How does loading the chamber slowly influence the accuracy of the first shot?

In my guns it doesn’t seem to matter enough for me to tell. By from what I understand tight fitting guns can have a different POI on first rounds fired.

[ltdmstr]

45 minutes ago, Sarge said:

In my guns it doesn’t seem to matter enough for me to tell. By from what I understand tight fitting guns can have a different POI on first rounds fired.

 

Not sure how tight fit would cause accuracy problems.  Maybe excessive headspace.   

[caspian guy]

I have seen issues in some guns (tight/lightly sprung) where the barrel lockup difference between a hand cycled round and a round fired when the gun functions can cause the first shot not to group with the rest.

 

Something you might try in addition to sages's suggestion is once you have fired a shot and the gun has cycled, gently pull the slide out of battery (without ejecting the round) and then gently ease it back into battery and fire the shot.  See if the shot shows the same dispersion.

[lacivilian]

Yeah I just had this happen to me out of my new Atlas Chaos. It all has to do with how hard you rack the first one in like others have stated above. I would fire the first shot and it would be no where close to the next 4. Ended up figuring it out after too many rounds. Really slingshotting the slide back into battery solved the issue for me. Try that out and let us know if it solved your issue. 

[ltdmstr]

I'm having a hard time understanding how a tight fit could result in inconsistent lockup.  In fact, the exact opposite would be true.  Unless there's excess headspace or something else going on with chamber, how hard you rack the slide isn't going to make a bit of difference as long as it goes into battery.  There has to be a loose tolerance or some other issue to give that result.

[Hi-Power Jack]

The gun writer, Massad Ayoob, has long professed that the first shot from a semi-auto

will hit in a different spot than the rest of the mag.

 

I usually fire my first shot into the berm if I'm testing for accuracy     

[jakfrost1]

8 hours ago, Sarge said:

That’s what I’m thinking. Rack it hard and fast, slingshot it, whatever. Try to get the barrel lockup closer to gun running. To test this just launch one into the berm and then shoot your group. At least that would tell if we are on the right track with a lock up issue.

 

OK...first, thanks for all the replies! 

 

‘Itdmstr’  I agree, not sure how loading slowly vs hard rack can affect the accuracy, after all the gun is either ‘in battery’ or not...? How does the breach know if the bullet was inserted slowly or quickly. 

 

‘Sarge’  I’m going to make the 1 hour round trip again this morning after chores to do the ‘fire one into the berm’ test, but again, unless the gun has an adversion to ‘white paper’ the result should be predictable...all remaining shots, after the ‘berm shot’ should be well grouped, as per the targets, no? 

But you do raise an interesting question about the ‘first round chambering’ procedure. I have been doing the ‘load and make ready’ procedure ‘on autopilot’ for so long that upon closer examination I realize that I have been ‘assisting’ the gun into battery with the slide racker, since when I slowed all my actions down for a closer examination of the actual procedure, I realized the gun (either one...) wouldn’t go quite all the way into battery on the first round without a slight nudge from me. After the first round the slide goes fully forward for every following round. So there is a difference there I suppose...

Anyway that is a different question, that in reality shouldn’t have any bearing on the the accuracy of the round, ‘pushed into battery’ or not, the question is, is the 9lb slide return spring too light if simply releasing the slide doesn’t result in the gun going fully into battery. The gun runs fine after one loaded, just not accurate on the first round. Its a puzzle! 

Just now, Hi-Power Jack said:

The gun writer, Massad Ayoob, has long professed that the first shot from a semi-auto

will hit in a different spot than the rest of the mag.

 

I usually fire my first shot into the berm if I'm testing for accuracy     

 

And Hi-Power Jack, did Massad have any explanation for his theory? Or is it ‘just one of those things’...

[jakfrost1]

‘Light bulb’ moment...rather than do a ‘berm check’ why not just shoot the ‘first round flyer’, then clear out the gun, top up the mag, re-rack and fire another...should go into the same spot as the ‘first round flyer’ did, no? 

Would this not confirm or eliminate the first round ‘racked to slowly’ theory? 

[echotango]

You could do that.  I would do both and play around with it. 

[9146gt]

Same thing happens with the first shot from a new mag when shooting from a Ransom Rest first shot almost always low. Yes it does seem to be slide speed related. I have seen many first shots 5" or lower.

When I asked Brian Zins about this he smiled and said my first shot is always on call

 

Tom

 

[ltdmstr]

1 hour ago, Hi-Power Jack said:

The gun writer, Massad Ayoob, has long professed that the first shot from a semi-auto

will hit in a different spot than the rest of the mag.

 

I usually fire my first shot into the berm if I'm testing for accuracy     

 

1.  Gun writers say a lot of stupid things that have no basis in reality. 

 

2.  If this is happening, it’s the shooter not the gun.

 

I’ve built a lot of 1911/2011s and tested them in a ransom test and can tell you that most any that is correctly built with decent parts will shoot under a half inch group at 25 yards.  In the rare instance there is a significant first round variance it has been due to setup or operator error and not a mechanical issue with the firearm.    

[zzt]

10 hours ago, jakfrost1 said:

Hmmm...I changed out the slide return springs in both guns very recently, putting in brand new Wolff 9lb springs. BUT, I noticed that both guns often need a little ‘encouragement’ to go into breech lock for the first round. All subsequent shots are without issue. I have been using some ‘older’ brass lately for practice sessions and blamed the brass...but maybe the spring isn’t up to snuff and my ‘helping’ with the slide racker is causing/confusing the issue? 

 

I would think 9lb springs should put good clean ammo into breech lock no problem...? 

 

I think your problem is too many bullets in the mag.  The top round is under a lot of pressure and is held too tightly against the feed lips.  The slide does not come forward fast enough to strip the round and chamber properly.  The nose of the bullet strikes the feed ramp too low because of how tightly it was held in the mag.  You get some bullet setback from that impact.  That increases pressure, changes velocity and affects POI.  You can test this theory by loading one less round in the mag and see what happens.  I have eight semi auto pistols and every one of them puts the second round where the first one went, even from a cold gun.

[Shmella]

This same thing has been brought up here before with an Sti DVC open gun. I’ll try and find it. I don’t think much cane from that thread either 

[Shmella]

here it is 

[superdude]

The first shot going wild is not unusual for some guns. The idea is that the slide doesn't have the same speed when hand cycled compared to when it is fired, and this changes the position of the barrel slightly.

 

I see this, and have others, when shooting from a Ransom Rest with some guns. That's why many Ransom Rest shooters shoot the first round off target, and the remaining ones for the group.  I have one pistol that ALWAYS shoots the first (hand cycled) round several inches out of the main group from the Ransom Rest.

[Sarge]

2 hours ago, jakfrost1 said:

 

OK...first, thanks for all the replies! 

 

‘Itdmstr’  I agree, not sure how loading slowly vs hard rack can affect the accuracy, after all the gun is either ‘in battery’ or not...? How does the breach know if the bullet was inserted slowly or quickly. 

 

‘Sarge’  I’m going to make the 1 hour round trip again this morning after chores to do the ‘fire one into the berm’ test, but again, unless the gun has an adversion to ‘white paper’ the result should be predictable...all remaining shots, after the ‘berm shot’ should be well grouped, as per the targets, no? 

But you do raise an interesting question about the ‘first round chambering’ procedure. I have been doing the ‘load and make ready’ procedure ‘on autopilot’ for so long that upon closer examination I realize that I have been ‘assisting’ the gun into battery with the slide racker, since when I slowed all my actions down for a closer examination of the actual procedure, I realized the gun (either one...) wouldn’t go quite all the way into battery on the first round without a slight nudge from me. After the first round the slide goes fully forward for every following round. So there is a difference there I suppose...

Anyway that is a different question, that in reality shouldn’t have any bearing on the the accuracy of the round, ‘pushed into battery’ or not, the question is, is the 9lb slide return spring too light if simply releasing the slide doesn’t result in the gun going fully into battery. The gun runs fine after one loaded, just not accurate on the first round. Its a puzzle! 

 

And Hi-Power Jack, did Massad have any explanation for his theory? Or is it ‘just one of those things’...

OP, if you find the gun groups fine after firing the hand racked round in to the berm then at least you can rule out something YOU are doing to cause the stray. From there you can explore other ideas. 

[jakfrost1]

1 hour ago, zzt said:

 

I think your problem is too many bullets in the mag.  The top round is under a lot of pressure and is held too tightly against the feed lips.  The slide does not come forward fast enough to strip the round and chamber properly.  The nose of the bullet strikes the feed ramp too low because of how tightly it was held in the mag.  You get some bullet setback from that impact.  That increases pressure, changes velocity and affects POI.  You can test this theory by loading one less round in the mag and see what happens.  I have eight semi auto pistols and every one of them puts the second round where the first one went, even from a cold gun.

 

Well I might give that thought some consideration except for the fact that in this case, if anything, the opposite would be true. Because...I am using MBX 155mm mags which without being restricted to 10 + 1/2 rounds by a ‘follower stop’ would hold 27 rounds. So the 13 coil spring is not even half way compressed. 

But what the heck, at this point I’m quite happy to try any suggestions!! 

[Shmella]

I’m going to say it’s a gun issue. Not a mag issue. As pointed out by waco in the other thread probably something to do with the barrel lock up. He shoots a lot and tinkers a lot with open guns. I trust his word on a lot of issues. 

[jakfrost1]

2 hours ago, Sarge said:

OP, if you find the gun groups fine after firing the hand racked round in to the berm then at least you can rule out something YOU are doing to cause the stray. From there you can explore other ideas. 

 

Thanks Kevin, I’m definitely going to clear that up as a possibility, but after 8 yrs of service as part of a 2 man team in a grass suit, and 20yrs of ISU competition, shooting off a table bag from 15yds with a red dot while sitting on a comfortable chair....well its hard to imagine I’m pulling the 1st shot 6-8” down and right. In both guns...but hey, anything is possible and I’d be happy to have a answer no matter how depressing, haha.

Edited July 28, 2018 by jakfrost1
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