Marvel accuracy decline

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Post by 10sandxs on Fri Mar 15, 2019 9:37 pm

I've had a marvel for well over a decade, close to two I think. When I was younger, I would ransom rest ut every year or two, just to make sure it was ok. I hadn't done it in probably four or fie. But it didn't seem like shots were going where they used to, so I thought it would be wise to test ammo. I was supprise to see average 10 shot groups (at 50 FEET) of .75 and larger with several different types and lots of ammo. I used to see those types of groups T 50 YARDS.  Ive only got arround 35k rounds through it and rarely truely clean the barrel. Chamber yes, barrel no, so it might be time. 

Any other thoughts on what would cause a decline in accuracy?

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Post by Allen Barnett on Fri Mar 15, 2019 9:48 pm

What does the crown look like?  It might have a ding in it, doesn't take much.

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Post by Jon Eulette on Fri Mar 15, 2019 11:04 pm

Recrown it! I doubt the barrels worn out. A fresh crown most likely will solve the issue. Been there done that a few times.
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Post by 10sandxs on Sat Mar 16, 2019 6:10 am

Well, that's easy enough... I'll give it a try... thanks

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Post by CR10X on Sat Mar 16, 2019 6:21 am

Crown and carbon ring in the chamber are the first two areas to look for.  But when testing, be sure to clean (chamber brush and pull though patch) between ammo types, it will make a big difference with some .22 ammo. 

If it is a early model, be sure to closely examine the lower lug the guide rod screws into.   There can sometimes be a stress crack or fracture that can cause some issues.  Saturate the block with kroil or very light oil, wipe everything you can off, and set aside for a few minutes.  If you come back and see a line of oil, then you will know. 

CR

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Post by mikemyers on Sat Mar 16, 2019 6:48 am

Ignoring the first part of this video, and going right to crowning the barrel, is this what we need to do to crown a barrel?   How can someone visually observe a barrel and find out if it's needed?  
https://www.youtube.com/watch?v=b43odFm0mrI

Sorry if I'm not asking this right - until just now, I didn't even understand what crowning a barrel meant.
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Post by jglenn21 on Sat Mar 16, 2019 9:03 am

The ptg or manson hand crowning tools work reasonably well but the right way is to center the barrel bore in a lathe and then cut the crown.

The manson tooling is superior to ptg IMHO

Even cutting a new crown on a new or fairly new barrel can have benefits in these days of CNC.
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Post by Aprilian on Sat Mar 16, 2019 11:05 am

CR10X wrote:Crown and carbon ring in the chamber are the first two areas to look for.  But when testing, be sure to clean (chamber brush and pull though patch) between ammo types, it will make a big difference with some .22 ammo. 

If it is a early model, be sure to closely examine the lower lug the guide rod screws into.   There can sometimes be a stress crack or fracture that can cause some issues.  Saturate the block with kroil or very light oil, wipe everything you can off, and set aside for a few minutes.  If you come back and see a line of oil, then you will know. 

CR
Another way is to clean of the oil and then lightly dust with any spray powder product, if there is a crack, that will show dark and wet against the bright white surrounding.   I use this technique to find out where oil is leaking in engines when other visual methods are insufficient.
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Post by fc60 on Sat Mar 16, 2019 11:50 am

Greetings,

I was asked to re-barrel a Pardini 22lr a while back.

With a bore scope, the original barrel showed little rifling in the throat area.

The pistol was rather new, so I set up an Outer's Foul Out electronic cleaner to it.

The cleaning lights came on. After three hours of cleaning, the rifling reappeared!!!

Testing in my barrel fixture, the barrel shot sub X-ring at 50 yards.

Sorry to dispel a common myth, 22lr barrels can foul with Lead.

Cheers,

Dave
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Post by jglenn21 on Sat Mar 16, 2019 12:50 pm

love those Foul Outs...  shame they discontinued them.
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Post by mikemyers on Sat Mar 16, 2019 12:56 pm

jglenn21 wrote:love those Foul Outs...  shame they discontinued them.
Maybe one of these would do the same?
http://castboolits.gunloads.com/showthread.php?306630-Outers-Foul-out-kits-discontinued-Someone-on-here-make-their-our-or-similar
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