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Barrel behaves

 
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  #1  
Old 01-15-2003, 06:22 PM
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Join Date: Nov 2001
Location: Canada
Posts: 268
Barrel behaves

I "believe" I was reading Dan Lilji website or I downloaded his new barrel software called "Barrel Weight Calc and stiffness.

If the barrel is 40" long and you have 9 inch barrel block, the barrel will behave like 31". (40" - 9" = 31")

I believe the barrel block wrapped around the barrel and it doesn't vibrate much.

Do you think the 31" barrel behaves like 40" with 9" barrel block? Just asking ya... I know a few of you guys are using barrel block and what was your experience on this?

I prefer untapered barrel if possible.

-Denny
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  #2  
Old 01-15-2003, 06:36 PM
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Re: Barrel behaves

Denny

Had and have guns with barrel blocks. Once you cross that 32" threshold, pretty much only way to go unless you have a big custom action. Most of the guys who played with barrel blocks have pretty much decided based on lot of testing that the 9" block is the best.

As for straight or tapered, mine and other shooters experience is that tapered barrels are easier and quicker to tune. Seem to have larger tuning nodes (sweet spots) versus straight barrels. But everyone has an opinion.

BH
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  #3  
Old 01-15-2003, 10:05 PM
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Join Date: May 2001
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Re: Barrel behaves

Denny,
With the long barrels the block is the way to go. I don't think you'll get much arguement on that. Unless you are the 'smith that has to turn the handles on the Bridgeport to make it or the man paying the bill for the lots of extra hours it takes to make one. [img]images/icons/smile.gif[/img]
I have/had glued sleeves and split blocks both. But don't kid yourself into thinking the block does away with the vibrations. They are still there. Now you simply have a stiffer cantilever (shorter barrel as you pointed out) and the harmonics are a different pitch now. So you still have to deal with them.
You can tune a load up and down using a in/# torque wrench on the screws of a split block gun. I've seen and had rifles that shot best at 4in/# on each screw all the way to tightened them as hard as you can. Rifles vary in that department. All you are doing is changing the harmonics in the barrel to match your given load by changing the torque on these screws.
But don't use the torque on the block screws to compensate for a so-so load. There is no compensation for good load developement. So develope a good load first and foremost. THEN you fine tune it with the torque wrench.
Think of these blocks kind've like the BOSS system and the rimfire barrel tuners. They all really work on the same principle. They are just applied to different areas of the barreled action system.
The other added benefit is it gives you a place to mount a scope without touching your action or barrel. And the action is now 100% free floated behind the barrel block also. It turns your action into a place to lock the bolt down and hang the trigger from and that's all the action has to do. That's why a lot of 1000yd guns have Rem 700 actions on them. There is no stress on them at all because nothing is touching them so it doesn't take a huge custom action in this scenerio.
The disadvantage of a block is weight and bulk of the block normally doesn't make a comfortable carry gun. Normally a block gun is strictly shot off a bench. But I've seen some lighter weight blocked carry guns also.

Steve

[ 01-15-2003: Message edited by: Steve Shelp ]
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  #4  
Old 01-17-2003, 05:17 PM
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Re: Barrel behaves

Steve,

The barrel block is the best choice if the barrel is over 32". I agree w/ you.

I would like to get more info from you about the in/# torque wrench.
At first I wanted to have split block, but now I'm leaning torward to get one piece block. I'll not switch the barrels.

Can you tune up the screws on one piece block? I was looking at the pictures I took at Williamsport and it seemed that the screws are very small on top of the block. I don't think it can be tune up with it, huh?

Estimate weight on 9" aluminum one piece block? (I'd probably let Baer make one for me)

-Denny
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  #5  
Old 01-17-2003, 06:38 PM
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Join Date: May 2001
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Re: Barrel behaves

Denny,

I would like to get more info from you about the in/# torque wrench.
You need one that starts at 0in/# and goes up. You'll find cheap ones that start at 25in/# but that doesn't go down far enough. Any ft/# torque wrench is too course to do anything with. And chances are you'll end up putting to much torque on those screws in the aluminum and stripping the threads. My blocks are made of brass(not really a big deal) but I installed threaded inserts (heli-coils) to stop galling and possiblity stripping the threads in mine. They are sold at your local auto-parts store to dig out the 250# backyard mechanic that can't lay-off using is 1/2" breaker bar on all bolts threaded into aluminum engine blocks. [img]images/icons/grin.gif[/img]

At first I wanted to have split block, but now I'm leaning torward to get one piece block.
Are you referring to a glued sleeve? or simply a block with a slit in one side of it? The one piece split blocks don't seem to influence the barrel as much as a 2 pcs split block IMO. You can still tune them but to a different degree. I'll have to defer some in this department. I have limited experience with a block with only one slit in it. BUT.. that isn't a bad thing either. That was always the headache in the past of keeping a 2 pcs block gun tuned up. It was easier to get tuned but you had one more variable to give you variations with to keep it tuned.
This was one reason a lot of shooters went to the glued sleeve method. But you loose the ability to tune via a torque wrench altogether. The glue sleeve doesn't impart any stress whats-so-ever (if done correctly). The disadvantage is that it is more work to install and remove when rebarreling. But I think you using your rifle primarily for a hunting gun correct? If so this may not be a big deal as you won't have to rebarrel after every match season. So not a big deal.

Can you tune up the screws on one piece block?
see my comments above about a 1 pcs block with a slit down the top or one side.

[I] I was looking at the pictures I took at Williamsport and it seemed that the screws are very small on top of the block. I don't think it can be tune up with it, huh? [/I}
Most (if not all) blocks guns I've seem used 1/4-20 caphead machine screws. Plenty of torque there. You'll strip out the threads in the aluminum before the screw fractures. I was told by one top long range smith that they air-gauged a barrel before and after clamping with a barrel block and could measure a difference.... a very, very,very small difference. That was a 1.250 barrel if I remember correctly.

Estimate weight on 9" aluminum one piece block? (I'd probably let Baer make one for me)
can't answer that one Denny. My brass block gun has the bottom half of the block permanantly glued into the stock. So I can't weigh it and covert it to aluminum density. Bruce has a lot of experience with this stuff obviously. I would tell him what your want as the end product and let him tell you how to do it. That is part of the price you pay when dealing with a smith with his LR experience. He's done enough split blocks and glued sleeves he could probably do them in his sleep and tell you what they would weigh from memory.

Steve

[ 01-17-2003: Message edited by: Steve Shelp ]
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  #6  
Old 01-17-2003, 10:20 PM
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Join Date: Dec 2002
Posts: 4
Re: Barrel behaves

Use 0.10 pound per cubic inch density for aluminum to calculate the weight of your barrel block.

[ Titanium alloys are about 0.16 lbf per cubic inch, and

Steel alloys are about 0.30 lbf pre cubic inch. ]
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