Stock Rigidity

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Albow
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Stock Rigidity

#1 Postby Albow » Wed Mar 14, 2018 6:25 am

Hi

Looking for others thoughts around stock rigidity. I am in the process of condisering a new stock design for my LG though the design / construction method should see it be rather stiff.

The question is, can you make a stock too stiff or rigid to the extent that it actually affects accuracy due to vibrations and resonance that is retained in the stock when a shot is fired?

I am interested to know peoples ideas, thoughts, experiences or theories.
Thanks Al

Gyro
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Location: New Zealand

Re: Stock Rigidity

#2 Postby Gyro » Wed Mar 14, 2018 6:50 am

Morning Al. My feeling is go as stiff as u can get ! I have not proven that and it's probably near Impossible to as there's so many things happening when a rifle is fired.

I think the likes of Speedy Gonzalez is totally on the right track with the stocks he is involved with with Shurley Brothers ( ? ) where the stocks mid section is left beefed up to avoid a 'hinge point '. So many 'pretty ' stocks are to my mind badly designed and too flexible !! And people pay a whole lotta money for them.

When a stock flexes it loads up. That stored energy WILL go feral during recoil. The cross hairs may be on the targets center when the shot is released but the bullet will not necessarily go there.

Tim L
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Re: Stock Rigidity

#3 Postby Tim L » Wed Mar 14, 2018 8:45 am

I think it's quite possible to go too stiff, the torque and recoil forces are going to go somewhere, all 'stiffness' or 'ridgidity' do is get them there quicker. That's not necessarily a good thing. I have a very flexible stock that came about simply by trying to get the weight down. It bounces around thike a frog in a sock. But, if I do my bit it can still be a very accurate platform, it's probably the best training aid i have for refining technique.

Gyro
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Re: Stock Rigidity

#4 Postby Gyro » Wed Mar 14, 2018 8:56 am

A flexible wooden stock is not so bad i reckon Tim because at least it will keep u warm on a cold night when ya burn it !

Tim L
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Re: Stock Rigidity

#5 Postby Tim L » Wed Mar 14, 2018 11:33 am

Gyro wrote:A flexible wooden stock is not so bad i reckon Tim because at least it will keep u warm on a cold night when ya burn it !

The flexible one is an alloy one that got shaved until it got to weight. :cry:
My wooden stocks ( made by Bob Eager) will not become firewood even to prevent hell itself freezing over.
They are just the right mix of stiflex to absorb all those nasty forces and keep my shoulder in tip top condition while launching projectiles at the required velocity. :D

Albow
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Joined: Wed Jan 30, 2008 9:59 pm

Re: Stock Rigidity

#6 Postby Albow » Wed Mar 14, 2018 7:19 pm

Gyro

I think i read something about speedy putting in some carbon to strengthen up the stocks around the area where they were cutting the slot for recoil lugs. Is that what you are talking about?

Tim

Unfortunately I shoot BR and a stock that jumps all over the place is no good. You need it to track. I do realise that the recoil needs to go somewhere though if it is a flexible stock loading up and reacting later which is possibly changing every time the shot is fired I think just adds another element to try and manage. I think a rigid stock would react and track more consistently with the right design features to handle the recoil. The concern I have is with the vibrations created and how long they remain.
Thanks Al

Tim L
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Location: Townsville

Re: Stock Rigidity

#7 Postby Tim L » Wed Mar 14, 2018 8:10 pm

I hear you Al. I won't be using the bouncy stock for comp, but it's a good tool to test my set up and release. Shooting FTR i have to deal with rifle movement but bouncing 3 targets was a bit excessive :? . Bob ran carbon rods down some internal side chanels in the most recent stock he made for me. He also laminates the area of the action and forestock with carbon fibre matting. Sounds similar to what you are describing with Speedys stock.

Gyro
Posts: 349
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Location: New Zealand

Re: Stock Rigidity

#8 Postby Gyro » Thu Mar 15, 2018 3:15 am

It's actually a hugely complicated subject Al and as I've built all my stocks I'm very interested and curious about this topic. There was a thread on here a few years back beffore i became a member here called I think " Recoil and Stock Design " which I read and studied at length.

The likes of Tony Boyer in his book says stock stiffness doesn't matter but then he's talking about the PPC guns ?

I shall add more soon when I get time.

Gyro
Posts: 349
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Location: New Zealand

Re: Stock Rigidity

#9 Postby Gyro » Thu Mar 15, 2018 4:09 am

Can a stock be too stiff ? Can it be too hard or too soft ? I don't know.

My current F Open stock is 90% carbon fiber and is extremely stiff. Plus with a 30" Full diameter barrel I still have over a kilo to spare which is cool as that kilo can be added strategically. Which I did i.e. i used it in such a way that it helped with limiting torque. But then the gun comes back much harder during recoil.

All this experimentation brings up as many questions as answers for me which is good.

At our recent Nationals no way was my rifle the most accurate one there !! It was the most interesting one, plus I get to learn lots of things along the way that others have mostly very little understanding of.

Anyway, right now I still reckon go as stiff as u can get. Cheers Rob Kerridge

Rebel105
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Re: Stock Rigidity

#10 Postby Rebel105 » Thu Mar 15, 2018 10:02 am

I'm not an expert but I can add something to this subject. As apposed to Rigidity, a stock should not be flexible. My recent experience with a Carbon Fibre skin stock does not have a happy ending. It was too flexible producing vertical shots while testing at 140yds. This is confirmed after 3 sets of testing the rifle in a more rigid timber stock producing one hole groups then fitting the same barreled action into the carbon fibre skin stock using the same ammo that produced one hole groups. Result a vertical string 1.5 inches high each time with an SD of 6.
Now equate that vertical to 1000yds. So yes it matters.
Geoff

Wal86
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Location: Kilmore, VIC

Re: Stock Rigidity

#11 Postby Wal86 » Thu Mar 15, 2018 10:18 am

Changing stocks can change harmonics / loads.. Especially when the two stocks like above have completely different characteristics/materials..
What works with one stock might not necessarily work in others...
You couldn't give me a carbon fibre skin stock.. But that's just me...
Cheers
Alan

Rebel105
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Joined: Fri Jun 13, 2008 12:22 am

Re: Stock Rigidity

#12 Postby Rebel105 » Thu Mar 15, 2018 10:50 am

Alan, I wouldn't have another one either. Just clarify, no amount of testing in the carbon fibre stock of over 200 rounds did I find anything without huge vertical. We only changed stocks to see if it was barrel related. Williada will agree on this one as we were working together.

Gyro
Posts: 349
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Location: New Zealand

Re: Stock Rigidity

#13 Postby Gyro » Thu Mar 15, 2018 12:02 pm

The problem lads is it sounds like a bad stock is being referenced here. What's wrong with a good carbon fiber stock ? Look at all the winning that's been done with the Bob Scoville stock.

I have no vested interest in carbon. I just know if it's used right it is very stiff. My current stock has 'Hi Modulus ' carbon fiber tube in parts and uni-directional panel in others. The tube I had made by C-tech here and the zero-degree layup panel I got from Dragonplate in the USA. Easy as.

My stock still isn't right I'm sure, so I continue to develop it. I'm sure it's too low at the back for example, which seems to allow it to torque more than is desirable ? Many stock builders have tried many different ideas going back many years. Innovation is fun but it does NOT always work.

DaveMc
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Joined: Mon Aug 22, 2011 6:33 pm

Re: Stock Rigidity

#14 Postby DaveMc » Thu Mar 15, 2018 12:49 pm

My thoughts are - there is no right and wrong here and it really depends on how the whole package acts together with the shooter.
Light stiff stocks can work very well if they are on the right platform and allowed to move backward/track correctly and consistently without imparting a significant recoil "reaction" on the action and barrel (like a rail gun). The downside is more felt recoil if you aren't free recoiling. Of course your shoulder force can then impart a recoil impulse back through the stock and action. Whether or not this impulse affects the muzzle before the bullet leaves is very much dependent on the whole interaction, barrel time and recoil speed etc. Bench rest rifles (esp 6ppc) with short barrels and higher speed, lighter projectiles are a different kettle of fish to a larger, heavier calibre, slower, longer barrel etc.

The long and short of it is we see many very accurate, heavy wooden stocks but you can also build very accurate rifles with light stocks and more weight in barrel and action. All of the above are interesting to experiment with.

What is hard to control and will definitely throw in a lot of vertical barrel whip is a heavy stiff stock and no room to move in rest.

Rebel105
Posts: 623
Joined: Fri Jun 13, 2008 12:22 am

Re: Stock Rigidity

#15 Postby Rebel105 » Thu Mar 15, 2018 1:27 pm

Gyro wrote:The problem lads is it sounds like a bad stock is being referenced here. What's wrong with a good carbon fiber stock ? Look at all the winning that's been done with the Bob Scoville stock.

I have no vested interest in carbon. I just know if it's used right it is very stiff. My current stock has 'Hi Modulus ' carbon fiber tube in parts and uni-directional panel in others. The tube I had made by C-tech here and the zero-degree layup panel I got from Dragonplate in the USA. Easy as.

My stock still isn't right I'm sure, so I continue to develop it. I'm sure it's too low at the back for example, which seems to allow it to torque more than is desirable ? Many stock builders have tried many different ideas going back many years. Innovation is fun but it does NOT always work.

Gyro,
I'm not mentioning brand of stock on this forum but I can say it's of composite manufacture, A lot of styrene foam is used in the butt and forend i've since found out to keep the weight down. It has a carbon fibre skin and not much carbon internally only where it's bedded. Had I known of the composite nature before I would not have purchased it.
Geoff


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