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A forum to talk about Olympic style shooting, rifle or pistol, 10 meters to 50 meters, and whatever is in between. Hosted by Pilkguns.com
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PostPosted: Wed May 03, 2017 8:13 pm 
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Joined: Sun Nov 13, 2016 7:26 pm
Posts: 11
Fellows. Its my understanding that some of the 40x smallbore stocks featured 2 adjusting screws that were/are located near the foretip of the stock that were set against the barrel and used to mitigate barrel vibrations.

Long run on sentence I know. I'm I correct about these "damping screws"?

Reason I ask is that my previous question to the board about noticing my front sight aperture "wiggling/vibrating" and not really coming up with a sure bet answer got me looking at the m12 rifle.

I had it on my work bench and gave the barrel a "flick" with my finger.... the barrel sort of "buzzed". I used my other hand to lightly touch the barrel and I could feel this.... "buzz". The buzz seemed more noticeable near to the muzzle.

This got my thinking about the 40x smallbore stocks and those "damping screws"....Were they used to damping this buzz I'm feeling? If so how were they adjusted?


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PostPosted: Wed May 03, 2017 10:28 pm 
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Joined: Fri Jan 18, 2013 11:59 pm
Posts: 272
Tuning screws (up pressure) for timing the exit of the bullet with the barrel vibration for positive compensation. Some folks measured electronic resistance to synchronize the adjustment across the two. There is no unusual vibration with them backed out on the 40x. Do you have a bedding issue?

Mark


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PostPosted: Sun May 07, 2017 7:48 pm 
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Joined: Thu Feb 02, 2012 3:37 pm
Posts: 66
Location: Colorado
The Remington gadgets were generically referred to as "barrel bedding screws". Freeland and others sold aftermarket barrel bedding devices as well. They predate glass bedding of receivers and follow-on the practice of adjusting the receiver and barrel channel wood to metal fit to achieve some upwards force on the bottom of the barrel. This was the case with the M1903 Springfield, early Winchester 52s and the Remington Model 37. Upwards pressure on the barrel could improve shot consistency. The technique has been all but abandoned in favor of bedding the receiver and (mostly) free floating the barrel.

All barrels vibrate like a guitar string as soon as the cartridge ignites. I believe the term is a 'standing wave pattern' having nodes and antinodes. I could hear the sound from a Walther UIT Match I had. When fired the barrel would hum until I grasped the bolt handle.

I do not think that anyone could see barrel vibrations - the amplitude is too small.


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PostPosted: Sun May 07, 2017 8:10 pm 
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Joined: Fri Jan 18, 2013 11:59 pm
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Sometimes shooting prone the 1913 will ring after the shot, and when it does the groups at 100 are outstanding. My low mileage 37 has a Freeland tuner in a custom Freeland stock with an Eric Johnson barrel Al hung; hope to experiment with it this summer. Initial tests without the tuner showed promise.


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PostPosted: Sun May 07, 2017 11:07 pm 
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Joined: Thu Feb 02, 2012 3:37 pm
Posts: 66
Location: Colorado
My Remington Model 37 has an aftermarket barrel bedder installed in the factory stock. It has a band around the barrel, a stud with tension screw thru the forend. The tension screw torques thru a compression spring.

The forend barrel support pad was sanded out, apparently as part of the bedder install.


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PostPosted: Wed May 31, 2017 1:06 am 
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Joined: Sat Aug 24, 2013 11:26 pm
Posts: 112
Location: Seabeck, Washington
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While today we free-float barrels and pillar bed actions to achieve perfectly consistent harmonics, that isn't the only solution.

There are a number of rifle designs that do better with up to 14lbs of upward pressure on the barrel, notably the M14 and the K31, and in unbedded smallbore rifles like the 513, stuffing a matchbook cover between the barrel and the tip of the fore end has tightened groups noticeably since the 1940's when someone first tried it.

Hence the 40X design pictured above. Did it work back in the day? Yes. Is it better today to pillar bed and freefloat? Also yes.
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Bob


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