Barrel Dampener for harmonics

[Gibbs]

Gibbs, you've shown that you can shoot well enough to test something like this out.  Have at it.  Pick up something to tune a barrel, test that thing out, makes your groups, and let us know how it does or doesn't. 

 

For you, with the way you shoot, that's easy. 

Tom, I'll have to give it a try.  Nothing but fun and games, some time.  I often forget that not everyone has access to a range within 1 minute of their back door.  I'm lucky that I have enough range to test 100 to about 400 yards on my property.  I also forget that not everyone handloads.  I handload and think it's the normal thing to do, but there are many that never have done it.  One of the tnings mentioned by David Tubb in his video as well as what I have recently read elesewhere is the key word  "Factory Ammo".  People that buy factory and can't get their rifle to shoot "that" particular load they want to shoot, and get frustrated at the group size.  However, handloaders like you and my self and plenty on here have the ability to find the bullet we want and vary the powder, charge, seating depth, crimps, etc etc  to change the pressure that changes the frequency (barrel harmonics and nodes) that match well wtih that particular barrel.  You change the pressure in the brass and you change how the bullet travels down the barrel and how the harmonics affect the bullet the instant it leaves the muzzle.  Factory is sort of a "catch all"  Rounds are built to be safe, fairly stiff loads, and for some they have really worked out the bugs in making them pretty excellent for a lot of barrels, such as those Match Ammo put out by some well known ammunition manufacturers.

 

One thing I have kept in my head all these years is to never let anything touch the barrel ahead of where it is supported by the stock, or in this case, the gas block.  I've known that it makes a difference on where the bullets hit and grouped downrange, but never quite understood exactly why something as simple as resting the barrel on a box, a tree branch, or a sandbag can change how it performs.

[Microgunner]

I use a Fudd tuner with bloop tube on a 22lr target rifle.

It does indeed tighten groups, but with every range or load charge the barrel must be retuned.

The tuner has graduation marks that allows you to keep a log of settings for these changes.

This tuner is heavy enough to seriously unbalance the rifle making this set up good for bench shooting only.

[DNP]

That's 3 more....drink!

[StainTrain]

 That's 3 more....drink!

Im hammered.  :happydrunks:

 

I will add with my booz soaked fingers that quality barrels+quality ammo+quality shooter=quality results.  When a shooter gets to the point he is analyzing barrel harmonics to milk that last bit of accuracy out of his uber custom barrel, he will be on here teaching us.

Edited August 26, 2014 by StainTrain

[98Z5V]

I'm with him ^^^   I can't keep up...  :happydrunks:

[StainTrain]

It's either the Port or the Cigar.....

Edited August 26, 2014 by StainTrain

[washguy]

Im hammered.  :happydrunks:

 

I will add with my booz soaked fingers that quality barrels+quality ammo+quality shooter=quality results.  When a shooter gets to the point he is analyzing barrel harmonics to milk that last bit of accuracy out of his uber custom barrel, he will be on here teaching us.

im toasted       :whip2:     Wash

[Gibbs]

You should see my single shot groups!! :lol:

 

Perhaps I'm chasing a ghost.  Back in the 1980's I had a bolt action .223 that when I first got it would not keep 5 bullets on the paper at 100 yards.  Boat tails were the best, but even those were inches apart and some even hit the target sideways.   Then, I started looking more closely at the end of the muzzle and there was some rifling damage done at the factory.  LONG before internet, emails and the like I merely showed it to a gun smithing friend who lived just north of Crawford (NE).  Barrel was badly damaged in the crown from the rifling so he chucked it in his lathe, trimmed of about 7/8 inch or so of the barrel and put a target crown on it.  After that, using Hornady .223 SP flat bottom bullets 3 bullets hit the same hole.  It could repeat time and again and I lost that target some time ago.  But I remember a rifle that had had groups that you could not measure center to center as it was one hole.  .223 was the minimum for deer hunting and I killed a nice buck the fastest with it next deer season with a shot right at the base of the skull.  Dropped like lighting hit him.

 

So now I chase that elusive ghost, a single hole shooter....  But the barrel harmonics were an interesting read and learning piece.  I wonder if the actual trimming of that rifle barrel had changed it's nodes and vibration to the point it was such a good shooter?  I find the study and information about barrel vibrations, nodes and barrel harmonics very interesting, and wonder if, like that old .223 I had with the cut off barrel, that some of these devices, whether by Browning (BOSS) or what David Tubb has something to do with "tricking" the barrel to think it's loner or shorter than it actually is?  The quest to find something that can change how a rifle shoots with different loads and do it consistently was my original thought and idea, but I don't think it really can be done now as each batch of ammo (commercial or home made) will not create the same pressures, and harmonics, nor will a "device" average them out to where they shoot the same groups on paper.  Adjustments with scope will have to be made, as well as determine the sweet spot for bullet grain any particular rifle likes and work within those parameters.

 

 

 

Edited August 26, 2014 by Gibbs

[Magwa]

you can tune a piano but you can't tuna fish....... :)

[Microgunner]

Your right. Target barrels used to be tuned by recrowning a few thousandths at a time while test firing the chosen load in between.

This was repeated as long as the groups continued to tighten.

The first time the groups failed to tighten the barrel trimming ceased. Barrel tuned.

The adjustable tuners attempt to mimic these results without permanent alterations.

[Gibbs]

Got an email back from David Tubb (really nice guy) about their muzzle brake and if it would work for the .308 AR series of rifles.  What he said "

Yes you can tune the AR10 barrel like you can with a bolt action. When using our muzzle break and break nut you want a ¾” x 28 TPI muzzle end and will have to drill the hole for the .308 as they are made for the .243 bullet. If there is anything else we can do for you please let us know."

 

Big thing is I really don't want to thread the end of a barrel 3/4 - 28.  REALLY fine threads.  Looks to me it would make more sense to buy the muzzle break unfinished, with no threads at all and just a pilot hole in the end.  I can thread it 5/8-24 then drill out the hole to clear .308 bullets.  (I used to be a machinist at Boeing in Seattle)  Just makes more sense to tap that end piece to what you want and then you don't even need the special nut as you can buy 5/8-24 jam nut http://www.joeboboutfitters.com/JP_Jam_Nut_5_8x24_925_p/jp-jn.58.925.htm  In fact one might find such a jam nut quite handy rather than the crush washer.  Nice at times to take off the end of the flash hider just to clean.  Local gun store in Kalamazoo, MI  (On Target) sell these all the time for that purpose and are currently out of stock on them.

[StainTrain]

Which brand barrel are you running on your 308ar?

[DNP]

Think there's any reasoning behind the 3/4-28 threads? I'm gonna go with 98 on this one and say go for it...record the hell out of the data...come back and teach us about it between tests. It's all interesting stuff. Waaaay beyond me or my abilities, but interesting.

[98Z5V]

You should see my single shot groups!! :lol:

 

 I wonder if the actual trimming of that rifle barrel had changed it's nodes and vibration to the point it was such a good shooter?  I find the study and information about barrel vibrations, nodes and barrel harmonics very interesting, and wonder if, like that old .223 I had with the cut off barrel, that some of these devices, whether by Browning (BOSS) or what David Tubb has something to do with "tricking" the barrel to think it's loner or shorter than it actually is?

 

We've talked about that extensively here.  There are two separate threads directly about this topic you mention.

 

 (I used to be a machinist at Boeing in Seattle) 

 

Now you did it.  As a machinist at Boeing in Seattle, you have all the skills anyone would need to buy the Tubb brake, mic it all out in excruciating detail, and make your own brake just like it - with the thread pitch and diameters that you'll need for the 308 AR.

 

Am I right?

[Microgunner]

The 28 threads would make it easier to fine tune.

[Gibbs]

It would be more logical to talk to David Tubb and see if I can get one without any threading.  I worked at Boeing back in the later 1970's early 1980s.  They had macines.  I now work as a wine maker but only have a wood lathe and drill press in my shop (along with band saw) but even that 5/8 - 24  tranlates to 0.625" x 24 pitch thread and David Tubb's brake is 3/4 - 28  or 0.750 x 28 pitch.  If it were smaller I could drill, ream, then tap the larger size thread, but don't work going the other way. 

 

Not much room on the end of the barrel anyway.  Just for fun last night I shot a 3 shot group of one of my hanloads with the flash hider off the end.  About a 1.7"  inch group.  Put the flash hider back on, snug, and the same batch of reloads shot about a 0.543 in group.  So even that little bit on the end of the barrel seems to matter.

[Microgunner]

Time for a drink.

[Gibbs]

Which brand barrel are you running on your 308ar?

 

It's just a DPMS LR308 Oracle I bought at Cabela's in Grandville, MI.  Traded in one of my 6.8 SPC rifles I built for it and thought it was not a bad deal for a new rifle, but also odd that I didn't get any owners manual, box, etc.. just the .308 and a magazine.  Found out later it was actually used.  VERY little used, but still used.  I can only imagine that someone bought it, shot it, found out it kicked, and traded it back into Cabela's (original FFL who owned it).  So, nothing special barrel, 1:10 twist 6 groove 16" barrel.

[98Z5V]

It would be more logical to talk to David Tubb and see if I can get one without any threading.  I worked at Boeing back in the later 1970's early 1980s.  They had macines.  I now work as a wine maker but only have a wood lathe and drill press in my shop (along with band saw) but even that 5/8 - 24  tranlates to 0.625" x 24 pitch thread and David Tubb's brake is 3/4 - 28  or 0.750 x 28 pitch.  If it were smaller I could drill, ream, then tap the larger size thread, but don't work going the other way. 

 

Not much room on the end of the barrel anyway.  Just for fun last night I shot a 3 shot group of one of my hanloads with the flash hider off the end.  About a 1.7"  inch group.  Put the flash hider back on, snug, and the same batch of reloads shot about a 0.543 in group.  So even that little bit on the end of the barrel seems to matter.

 

 

Okay, so winemaker now.  But Boeing Machinist back in the day.  You have machinist skills.  You worked that profession, for Boeing. 

 

You have the knowledge, experience, and training/work performance to accomplish this task.

 

Not asking you to modify a Tubb brake, not in the least. 

 

I'm saying, you have a quest to find out if this theory works, and you also have skills that most people don't.  Based upon those ASSumptions, you CAN buy a Tubb brake, and mic it all out - as a machinist, you know about precision measurement.  Externally, you could buy that brake, copy it's dimensions - externally - and MAKE that thing to fit your 308 AR at 5/8x24.

 

At that point, you could test the $hit out of it, and report back.

 

You may only have a wood lathe and drill press now - but as a machinist, don't you know other machinists that have the macines that will accomplish this task?

 

There's rules on this site.  Then, there's The Rule on this site.  You jump into something and start asking specific questions about a product, and no other member HAS that product...  then The Rule leaves it at this:  You wanted the info, You asked the questions, and no one has it.  At this point, You buy the product, test it, and You report back on it. 

 

You're in that category with this series of debate, right now.

 

Get busy.  You made the grade on this one...  <thumbsup>

 

Or, just make excuses...  <dontknow>

[StainTrain]

I only ask because you mentioned one hole groups and while the groups you have posted are pretty good, it is worth remembering that you can turn a Chevy Cruse into a Mclaren P1.  DPMS barrels can be shooters, that is for sure, especially for production barrels, but doing a lot of lathing, cutting, threading, tuning, etc may make your .3 inch group in that production barrel worse rather than better.  3 shot groups tells a tale, 5 shot groups tells a story, 10 shot groups tells the truth.  

[98Z5V]

  3 shot groups tells a tale, 5 shot groups tells a story, 10 shot groups tells the truth.  

 

That's the very reason most people won't shoot 10-shot groups, right there. 

 

I need to find my IPSC head target at 75 yards, with the 16" precision gun, fired from the sitting position braced on a knee, leaning back against a 35" truck tire....  I have a picture of that bastard somewhere.   Everything is right in the cross of the T-Zone.

Edited August 28, 2014 by 98Z5V

[washguy]

                  I aint  no  woosie      :)  Wash

 

 

[Gibbs]

Pretty nice, Wash! 

 

I agree about the 3 shot groups.  They are just indicators, the  real test is several bullets and then you get a pattern on what the group is really going to be.  Since I hand load, I tend to make up small batches and try them out and see.  If it shoots a 3 shot group and it's 2" across, there is no sense in trying to continue on that line, as it will probably always be at least 2" across.  3 shots near each other mean I'm getting close.  3 shots touching means load a bunch up and try them.

 

A couple of years back I had a Saiga  AK in .308.  One day I shot some factory 150 gr out of it to see what it would do.  5 rounds (so more a story) on it's capability.  The barrel had a 1:12.? something twist.  It was made in Russia, so they did not use standard inches, but something more in mm.  It was slightly more than 1 turn in 12 inches, but not by much.  Posted on Saiga forums about that one time.  Anyway, I was surprised at what it did with the 5 rounds.  I didn't have any more made up targets, but I had a Pizza Hut box destined for the trash.  Put a magic marker dot on it and set it out at 100 yards.  Getting low light near dusk, and when I shot I could not see that I even hit the box, but thought, oh well, keep shooting these 5 rounds and see if any hit the box.  Only when I walked up there did I see that it had grouped pretty well for a Kalashnikov action rifle with the 16" barrel.

 

 

 

 

Yesterday for the fun of it I had some rounds of the same batch of reloads.  Same bullet, powder, crimp, lenght, etc.  Shot 3 rounds slowly into the bank just to warm up the barrel and then shot 3 shots with no flash hider on the end.  left the bolt hold open while I changed targets, put the flash hider back on and shot 3 more.  Posting just what I observed from that trial.  I'll work on that idea with a muzzle brake like 98 had suggested, but I'm doing it so it's repeatable for anyone that might wish to try it themselves.  No sense in dancing around possible patent infringements.  2 more targets....

 

 

 

[washguy]

Thanks Gibbs....that was a 20 rd mag ... Well you best keep the flashider on!    :)  Wash

[Gibbs]

Send you to Iraq and you can take the heads off 20 of them sonsabitches ISIS bastards.  Just adjust your scope 2 inch left and 1 inch up and you can pop them out at 200 to 300 yards easy.