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Author Topic: D48 Front Sight Fail  (Read 352 times))

Offline Ilimakko

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D48 Front Sight Fail
« on: May 15, 2021, 03:04:45 PM »
I have had no issues with the plastic parts on my Diana springers, until now.

I noticed how the front sight bead on my D48 sits at angle against the front sight base, instead of flush, as it obviously should be. It turned out the metal bead had deformed the plastic base rail.

As the first photo shows, the bead sits flush on the rail, when the grub screw that tightens the bead against the rail is loose. The second photo shows what happens when the grub screw is tightened: a forward tilt appears. The third, unfortunately unfocused pic shows how the plastic rail has simply given way to the tightening pressure created by the metal bead.

A front sight bead on a sliding ramp must be securely tightened against the base, if any kind of accuracy is to be expected. With this particular D48, early recoil and shaking were so severe that the stock screws needed substantial tightening after every shooting session. I would’ve lost the front sight into the woods if I hadn’t screwed the bead on tight. At any rate, I didn’t use excessive force, only enough to tighten the bead on the rail.

In retrospect, I should’ve removed the front sight entirely for the duration of the break in, to save the perishable plastic from deformation. One thing is certain: if the front sight rail was steel, none of this would’ve happened.

It would blow to buy a new entire muzzle piece for the new gun to fix the issue. Maybe a slight epoxy coating, strategically needle-filed, would work to fix the rail, if epoxy is compatible with the plastic Diana uses in their airguns. Other than that, I'm not sure how to undo the damage.

« Last Edit: May 15, 2021, 03:07:18 PM by Ilimakko »
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Offline ER00z

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Re: D48 Front Sight Fail
« Reply #1 on: May 15, 2021, 04:14:17 PM »
Hopefully you can get things fixed. Maybe a HPM (muzzle harmonic tuning device) could be ordered and installed. The new Diana 54's have them, I believe the 48 and 54 variants have the same barrel setup. Of course you will lose the front sight with it installed. I believe the actual barrel is 15mm, so you may find something that fits if you chose another route, many possible options, but I haven't explored. At one point, there was a globe sight base offered, don't know if currently available. Just keep the shroud/sleeve tight, as I understand if that gets loose accuracy will be affected. Best of luck to you.

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Offline longhunter

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Re: D48 Front Sight Fail
« Reply #2 on: May 16, 2021, 10:57:32 AM »
I have had no issues with the plastic parts on my Diana springers, until now.

I noticed how the front sight bead on my D48 sits at angle against the front sight base, instead of flush, as it obviously should be. It turned out the metal bead had deformed the plastic base rail.

As the first photo shows, the bead sits flush on the rail, when the grub screw that tightens the bead against the rail is loose. The second photo shows what happens when the grub screw is tightened: a forward tilt appears. The third, unfortunately unfocused pic shows how the plastic rail has simply given way to the tightening pressure created by the metal bead.

A front sight bead on a sliding ramp must be securely tightened against the base, if any kind of accuracy is to be expected. With this particular D48, early recoil and shaking were so severe that the stock screws needed substantial tightening after every shooting session. I would’ve lost the front sight into the woods if I hadn’t screwed the bead on tight. At any rate, I didn’t use excessive force, only enough to tighten the bead on the rail.

In retrospect, I should’ve removed the front sight entirely for the duration of the break in, to save the perishable plastic from deformation. One thing is certain: if the front sight rail was steel, none of this would’ve happened.

It would blow to buy a new entire muzzle piece for the new gun to fix the issue. Maybe a slight epoxy coating, strategically needle-filed, would work to fix the rail, if epoxy is compatible with the plastic Diana uses in their airguns. Other than that, I'm not sure how to undo the damage.

I believe I have a spare metal one, if you'd be interested.
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Offline Ilimakko

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Re: D48 Front Sight Fail
« Reply #3 on: May 16, 2021, 02:59:25 PM »
Zack,

Thank you for the kind words. I'm an iron sights guy, so a front sight is mandatory. I searched pretty hard for the globe sight base a couple months back, but concluded that it was a one-time offer and long since gone, save for a chance second-hand find.

Scott,

Thank you for the offer, but I'm not quite sure what you mean - as far as I know, every D48 has a plastic muzzle piece, with the integrated front sight rail, which in my gun is compromised. The bead or front sight blade is metal, and intact in my gun. Or do you mean the new HPM
that Zack mentioned? If you do have a spare metal muzzle piece with the sight rail for the 48, I'm definitely interested.
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Offline longhunter

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Re: D48 Front Sight Fail
« Reply #4 on: May 16, 2021, 05:27:34 PM »
This is the older version.  They were metal. They have the dovetail rail, to adjust the elevation, like yours does. Should be a direct fit.
If you want one, pm me your address. I'll send it out tomorrow.
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Offline Jeff Marshall

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Re: D48 Front Sight Fail
« Reply #5 on: May 16, 2021, 06:07:30 PM »
Sir, it is virtually unheard of for these post type front sights to slide on the ramp regardless of what the dovetail is made from.

Your gun either has a defective piston seal or breech/transfer port seal which is causing it to slam.

If slamming if fixed, your front sight will stay put on an undamaged dovetail with the grub screw lightly torqued.

P. S. I am not certain, but I do not think that an earlier metal unit will fit onto your gun.

Good luck!
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Offline HectorMedina

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Re: D48 Front Sight Fail
« Reply #6 on: May 16, 2021, 06:41:52 PM »
Jeff is right.

The old metal front / muzzle pieces have INTERNAL dovetails to align the front sight, the new ones have a "Flat" molded inside for the same purpose, and the barrels of the old rifles have the dovetails, while the barrels of the more modern guns have the inclined flat.

They CAN be made to fit but it is just as complicated as cutting sight dovetails in an HPM and installing a front sight with level (Which I have done in the past). SO, not an inexpensive "fix", but an elegant one.

Keep well and shoot straight!






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Offline Ilimakko

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Re: D48 Front Sight Fail
« Reply #7 on: May 17, 2021, 07:29:40 AM »
Thanks for the valuable info, guys!

It figures that what now is plastic was once steel. Alas, there seems to be no fit between the 80's and the 2010's (my gun is a 2018)

My D48 has been really loud and aggressive through the break in, but I hear it's not entirely out of character with these sidelevers, having lots of extra moving parts. I've had zero experience with sidelevers before this, but plenty of experience with breakbarrels of every power and quality level, which is where my comparisons come from. Add the persistent dieseling of the 48, and I've long now suspected a leaky piston seal. But would a leaky gun shoot such steady numbers on the chrono (the other thread), with no more deviation shot by shot than what healthy springers shoot?

If my D48 has a damaged piston seal from the factory, that makes it a full 100 % of Diana springers in my arsenal. Given that the OEM piston seals I have are way oversized, I'm not exactly thrilled at the prospect of replacing the still-new seal, with attendant deburring, sizing etc. Long hours ahead before I have a shooter, after already long hours of breaking in.

On the subject of grub screw tightening forces: I have a bunch of springers with front sight dovetail attachements. None of these are plastic, outside the D48. As noted earlier, I have not used excessive force to tighten the front sight on the D48, but comparable to the other similar front sight attachments my guns have. None have failed, but the plastic Diana.
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HW95L .22 cal
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Offline longhunter

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Re: D48 Front Sight Fail
« Reply #8 on: May 17, 2021, 11:29:31 AM »
Jeff is right.

The old metal front / muzzle pieces have INTERNAL dovetails to align the front sight, the new ones have a "Flat" molded inside for the same purpose, and the barrels of the old rifles have the dovetails, while the barrels of the more modern guns have the inclined flat.

They CAN be made to fit but it is just as complicated as cutting sight dovetails in an HPM and installing a front sight with level (Which I have done in the past). SO, not an inexpensive "fix", but an elegant one.

Keep well and shoot straight!






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Offline photrod2000

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Re: D48 Front Sight Fail
« Reply #9 on: May 18, 2021, 11:34:45 AM »
Yep, I don't the exact years, but depending on what year a used one is purchased, it may have earlier metal parts, and then later, plastic parts.  I have some that are pretty much mixed.
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Offline HectorMedina

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Re: D48 Front Sight Fail
« Reply #10 on: May 18, 2021, 07:42:57 PM »

If my D48 has a damaged piston seal from the factory, that makes it a full 100 % of Diana springers in my arsenal. Given that the OEM piston seals I have are way oversized, I'm not exactly thrilled at the prospect of replacing the still-new seal, with attendant deburring, sizing etc. Long hours ahead before I have a shooter, after already long hours of breaking in.


It is extremely rare that the piston seal in a sliding compression chamber rifle gets damaged upon assembly.

There are no slots, and the piston is put into the chamber, then the chamber and piston are assembled into the gun. No slots/cutouts/holes to jump over, so no cuts/nicks/nor scratches on the piston seals.

IF the piston seal is damaged, then we should look into the real causes.






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Offline Ilimakko

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Re: D48 Front Sight Fail
« Reply #11 on: May 20, 2021, 10:47:18 AM »
Hector, that makes sense. It will be very interesting to open the 48 up and see what it has eaten, some time this summer.
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H135 .25 cal
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Offline HectorMedina

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Re: D48 Front Sight Fail
« Reply #12 on: May 21, 2021, 12:31:37 PM »
OK, Ilimakko!

Keep us posted.




HM
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