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kurtm

The answer to Benelli slugs and pattern off from point of aim

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Alright, I have done enough testing to say Benelli barrels are straight!! Had a bunch of them air guaged, had a bunch that folkes thought were bad air guaged and guess what, they were all straight! So what is causing my Benelli to shoot 8-10" hi/rt/lft,low....etc.???? Well it is a miss alignment of the magazine tube to the centerline of the bore! To make this simple where ever the mag tube points is where the pattern or slugs will be thrown, and that may not be where you think it is pointing.

The hard part was making a guage that could measure whether the center of the mag tube was centered to the receiver bore for the barrel, BUT I got that done!!! The guage works PERFECTLY!!! Once the mag tube is centered to the center of the barrel, all the guns I tested threw patterns to the center of the bead, and slugs to point of aim/point of impact.

You see there was never anything wrong with the barrels that were being bent, They never should have been "whacked" on anything! It was all in the miss alignment of the magazine tube!!! If you think about it the barrel fit,s in the receiver fairly loose(so you can assemble and disassemble, and the barrel ring is what is tightened down way out front of the reciever with the magazine tube nut and the collar on the magazine tube, so which ever way the tube points is where your shell is going to shoot.

I may "make" the guages way in the future, but a few select smiths will have them. This is NOT A SALES PITCH!!! this is for those of you who are about to WHACK a barrel....DONT!

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I have resisted the urge for several years. I guess I can wait a little longer! Just let me know where to send it!

I never really liked the idea of voodoo barrel doctors.

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Very interesting, makes sense to me. I'm a believer. Thanks for the write-up.

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Kurt, isn't it simple enough to use the old trick of not tightening the mag extension all the way into the nut before putting on the clamp? In other words, back off the extension a quarter to half turn from bottomed out so that the tube floats in the threads. When putting on the clamp, the mag tube should align to the barrel, not the other way around. Mick

Edited by MickB

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I've always attributed my not shooting straight problem to my "Misspent youth"

But I have used the barrel band clamp to "Tune" the POI with various slugs of different power factors.

this also probably explanes why my rear ghost ring sight is jammed all the way to the left side.

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Interesting, here's a question along those lines.

shooting birdshot at 15-25 yards, dead on , shooting slugs at 75 yards holding a 4" pattern, only 12" low 8" left. three brands similar results.

Which, should I set zero to , birdshot , slugs?

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MickB, you have missed the point. The mag tube we are talking about is the one that is screwed into the receiver, not the extension. I don't run a clamp at all because my extension isn't,t way past the end of my barrel.

Toothandnail, I would bet yours is miss aligned. What showes up farther out will only look like a little in closer..when you patterned your gun did you have a distinct aiming pointed did you figure out the percentage of hits high, low, left, and right? A thousandth miss alignment equals abut an inch at 50 yards

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This all makes perfect sense...we've fussed with rifle barrels for years, truing actions, floating barrels and forearms, adjusting or relieving fore end pressure to alleviate undue force on the barrel to get the optimum accuracy. We are shooting the shotgun more like a rifle in this game anyway.

Kurt is right about misalignment with the shot load being likely. 4-5 MOA off at 100 yards is going to be real noticeable with a slug. Back it up to 25 yards with a load of shot spreading 30” or so and I bet its still there...just harder to quantify.

Mag tube misalignment is not just a Benelli thing. It can happen with any brand. Dial in the receiver perfectly straight and then run an indicator down the mag tube ( and that still does not address whether the barrel is square in the receiver or not, sounds like Kurt's gauge take that into consideration also).

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Yes my gauge is squared to the receiver barrel bore, the receiver face, and the bolt races. It was darn hard to figure out what place was square to measure from, but we got that figured out. In a few weeks I'm sure that the high end Benelli shops will have one.

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Hey Kurt, does your gauge hold the mag tube square so it can be re-tightened? Just curious how the fix works.

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Cool. Actual good, pertinent, accurate, and sensible information about Benelli, or any shotguns really. Thank you, Mr. Miller. You friend. Forrest Gump.

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Kurt, I did indeed miss your point. Makes sense.

So I'm guessing that once you remove a mis-aligned factory mag tube from the receiver, there is enough free play in the tube to align it straight when you screw it back in and the Loctite hardens?

Mick

MickB, you have missed the point. The mag tube we are talking about is the one that is screwed into the receiver, not the extension. I don't run a clamp at all because my extension isn't,t way past the end of my barrel.
Toothandnail, I would bet yours is miss aligned. What showes up farther out will only look like a little in closer..when you patterned your gun did you have a distinct aiming pointed did you figure out the percentage of hits high, low, left, and right? A thousandth miss alignment equals abut an inch at 50 yards

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There are several ways to use the gauge. It will hold a tube in alignment while it is being re-loctited. It will show how much miss alignment and tell you when everything lines up while "tweeking" the tube. And it shows alignment while impact tuning the tube..

All of these ways are fairly "permanent" but if you really spike your gun into a barrel or smack the side of the barrel hard you can re bend/ misaligne the mag tube again, in which case you meerly recenter it.

Edited by kurtm

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Should I whack my tube?

Haven't you been?

Does that make it point left ? (for a right handed shooter)

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Should I whack my tube?

Haven't you been?

Does that make it point left ? (for a right handed shooter)

Wow this is taking a "turn" for the worse. I can't believe I'm going to respond to this but it has to be said...

I think it would depend on whether he is whacking his tube strong hand or weak hand.

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Wow this is taking a "turn" for the worse...

Doesn't take long around here....

Maybe Pat can do a "tube whacking" session on the next 3GN program?

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It being Sunday morning makes it that much worse.... :blush:

In all seriousness – I am interested in Kurt's mention of “ impact tuning the tube”...I'll wait for his definition.

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No Mark, it wont help for a bent barrel at all as the gauge centers the mag tube to the center of the hole bored in the receiver for the barrel.

Jesse it is a bad idea just to Whack the tube, as you can oval the tube, mess up the threads, dent it etc.. If the tube isn't,t too far off, you can tap it with a dead blow hammer as long as you use a mandrel in the tube And put an end cap on the threads. Anyone who has ever straightened a crank shaftwill know what I mean. It is easy to go too far as it is an aluminum part and it is a bit brittle.

The usual suspects will have a gauge in a few weeks and how their perspective shops decide to use it is up to them.

Mark if you want to see one, I can bring it ti FB3G.

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Kurt:

So everything Taran Butler has done for years (as probably the best multi-gun shotgunner in the history of the sport) with regards to straightening the M2 barrel (as opposed to the M1, which is apparently perfect POI) is bullpucky?

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I guess I don't know who this Taran guy is. Could you shed some light on how bending a perfectly straight barrel makes it straighter Jed? Guys who have been bending barrels to make up for a miss alignment in another part of The system have been laboring with a complete misunderstanding of the problem.

Now from your comment it is apparent that you don't think I know anything about shotguns and mainly Benelli and thats cool. To be honest all this is just trolling to get a rise out of guys such as yourself who really know, or at least know the name of a guy who should know. Know what I mean?

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