Marine Cpl
.577 Tyrannosaur.
Will a KAK Flashcan affect a pencil barrel as far as barrel whip and harmonics go? I know a thicker barrel would be ideal but I'm looking to make the lightest rifle possible. It'll be a 200 yard and below rifle.
Pencil Barrel Whip
- Thread starter Marine Cpl
- Start date
S
stuck in ny
Guest
As long as it's symetrically round, then how would it affect anything?
Marine Cpl
.577 Tyrannosaur.
I'm guessing weight at the end of it maybe?
ManrisFrack
6.5 Creedmoor
Everything on a barrel will effect the harmonics. It's one of the biggest reasons different rifles prefer different ammo. From what I've read point of impact shifts are common when adding a suppressor, for example.
Even bull barrels oscillate when a round is fired. They're "more accurate" because the barrel is stronger and this makes the oscillations smaller.
Put whatever you want on the end of your barrel. Try different ammo until you get the accuracy you want.
Even bull barrels oscillate when a round is fired. They're "more accurate" because the barrel is stronger and this makes the oscillations smaller.
Put whatever you want on the end of your barrel. Try different ammo until you get the accuracy you want.
If you are worried about it why not leave the barrel naked? Also have you considered the "non tapered: profiles like the Gunner profile from Faxon or the Hanson profile from Ballistic Adavntage? There are others that are similar I'm sure. Its basically a medium light profile, I got the Hanson one for my NYGF build.
Marine Cpl
.577 Tyrannosaur.
I'm looking into doing a lightweight build. It'll be a SHTF gun so ear plugs won't be used. A flash can that projects the concussion forward would be ideal.
I'll let you know what mine weighs in at.
I'm just running an extended birdcage on mine, pinned to a 14.5" middy.
S
stuck in ny
Guest
It's because of whip? If the thing is floated, then where's the direction of the whip coming from? I though hbars were just more accuate because they could absorb more heat without losing their rigidity.
ManrisFrack
6.5 Creedmoor
Take a look at this video at about 2:20. That is also a floated barrel.
The whip comes from the rapid pressure increase of the round going off. Take a long thin steel rod and put it in a vise. Then hit it with a hammer and you'll see vibration of the free end. A similar thing is happening when a round goes off. To achieve repeatable accuracy, you want to find a round that exits the barrel when the tip of the barrel is coming to a stop and reversing direction. Even better, would be to find a load that makes a vibration node coincide with the end of the barrel (google "vibration node" if you want to learn the basics of vibration). This is a video that does a decent job with the basics. Don't worry that he focuses on bolt actions - the basic physics are the same for an AR.
Heat does all sorts of weird stuff to metal, especially if you heat the metal unevenly. All metals have some level of impurity and stresses from manufacturing. When you get it hot enough, these stresses and impurities can actually change the shape of the barrel. This should change the harmonics as well. Heavy barrels heat more slowly due to higher mass. As I said above, their added strength results in smaller oscillations. That means that even if you get the barrel hot enough to change the harmonics, the changes should be noticeably smaller than the changes seen in a hot, thin barrel.
This is my understanding currently but I haven't done scientific study specifically on this subject. It does, however, agree with what I know regarding metallurgy, vibration and thermodynamics.
Marine Cpl
.577 Tyrannosaur.
I'll watch the videos when I get home. Do you guys think one 20 round magazine will heat it up to the point where accuracy is affected?
20 rounds of rapid fire will heat the barrel to the point of burning skin but would it affect the barrel? Depends on the barrel I suppose. According to the vid I posted modern manufacturing methods, materials and treatments can mitigate the affect of heat soak. I am interested in seeing how my new AR will perform in this regard. My current AR has a cold hammer forged, chrome lined gov't profile and is little affected by heat. No change in POI and group size increases only a small amount. The new barrel is button rifled, nitrided and with the med. light profile I described earlier. A comparison will be interesting. Perhaps I should do a thread on it?
ManrisFrack
6.5 Creedmoor
I was very impressed with that video and the Faxon barrels. My only complaint with them is that they don't make 6.8 barrels.
Test the BA barrel and do a thread on it. The more gun threads, the better!
I see Faxon and Ballistic Advantage as offering identical products at an identical quality level.
I will do the comparison thread of the BA equipped NYGF carbine, it uses a 14.5" barrel, and the Daniel Defense with the 16" barrel.
@Bullet Guy speaks very highly of the BA product and I put great stock in his opinion, however the DD has proven itself an outstanding performer in my service. I have purchased a large quantity of 55gr 5.56 for testing, again from a manufacturer that Bullet Guy highly recommended. I only wish I had better than red dots to exploit the potential of the above.
meketrefe
.450/400 Nitro Ex
Anything you attach to a barrel has the potential to change the harmonics and POI and/or accuracy.
There is nothing wrong with a light barrel but the problem with most pencil barrels is that they are cut wrong where
the minor diameter in critical areas is going to compromise both accuracy and durability.
The recon barrel Lilja made for the navy seals is a good compromise between weight an rigidity.
http://riflebarrels.com/shop/drop-in-barrels/223-8-m4-copy-fluted/
These barrels will last a long time (Accuracy live) so one other thing I would do is to thread them with a 5/8 threads
vs 1/2 threads that should have never existed in the first place. This will help maintain the accuracy life longer for
the average shooter who wants the barrel to last as loon as reasonably possible.
Most of the pencil barrels in the market are fine for sporting use and for a very light ranch rifle but will not hold
if put on a serious rate of fire and will provide poor accuracy and short life, if not worse.
Hard to know the harmonics impact of a can. It depends on many factors and that is why some flutes and keeping
the diameter tapering w/o going below the section ahead is important and where the flutes above this diameter
hellp with rigidity and cooling.
There is nothing wrong with a light barrel but the problem with most pencil barrels is that they are cut wrong where
the minor diameter in critical areas is going to compromise both accuracy and durability.
The recon barrel Lilja made for the navy seals is a good compromise between weight an rigidity.
http://riflebarrels.com/shop/drop-in-barrels/223-8-m4-copy-fluted/
These barrels will last a long time (Accuracy live) so one other thing I would do is to thread them with a 5/8 threads
vs 1/2 threads that should have never existed in the first place. This will help maintain the accuracy life longer for
the average shooter who wants the barrel to last as loon as reasonably possible.
Most of the pencil barrels in the market are fine for sporting use and for a very light ranch rifle but will not hold
if put on a serious rate of fire and will provide poor accuracy and short life, if not worse.
Hard to know the harmonics impact of a can. It depends on many factors and that is why some flutes and keeping
the diameter tapering w/o going below the section ahead is important and where the flutes above this diameter
hellp with rigidity and cooling.
That's so expensive Meke. Here, look at this:
That looks like a very good compromise profile to me. Not pencil thin, but not too heavy either.
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meketrefe
.450/400 Nitro Ex
Yes lilja are brutally expensive. Lothar walter will cut you the same profile for around $400. Xcaliber even cheaper.
That looks better but what are the dimensions? pictures are deceiving sometimes.
Dimensions as far as.......? I can only say that particular one is a .750 gas journal at 14.5" in length. The one I will have is similar but in 4150 carbon steel, nitrided.
Marine Cpl
.577 Tyrannosaur.
Sometimes you need a heavy hammer and sometimes you need a lighter one.
Infantryman would be ill served with pencils. LRRP Units wouldn't however.
Infantryman would be ill served with pencils. LRRP Units wouldn't however.
When I was shooting in a 22 rimfire benchrest league with my Ruger 22/22 factory contour barrel, 25 shots for score in 30 mins at a 1/2" 10 ring at 50 yards. I could start out aiming at the dot (X) in the center and as the barrel warmed I some times had to aim a bite higher each shot to drop the shot in on the X! And that was with SV 22 ammo 1080 fps.
That's why the compromise profile appealed to me. Now the even with the gov't profile that Daniel Defense of mine is still well under 6.5 lbs naked. I figure with the BA barrel in that profile and at 14.5" there would be a weight savings beyond that even. When I shoot out the barrel of the DD I won't replace it with another gov't profile though.
Was there ever any lateral deflection?
None that I noticed!
Thats kind of odd isn't it? For the barrel to only be affected in the vertical plane.
I think it was more of a droop when it got warm. Remember 5.56 is almost 3x's faster then SV 22lr ammo (subsonic)?
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meketrefe
.450/400 Nitro Ex
It can happen in any directuon. Barrels are round so whereever they land after chambering. This could be a stress stored in the alloy o the action or a combination of those.
meketrefe
.450/400 Nitro Ex
Imo those could use a little more meat ahead of the camber where more heat is concentrated. Not much more but taper smoothly and not less than 3/4 minor diameter. After the gas block 5/8 is fine. In pracrical terms a few more ounzea yet a stronger barrel. Nothing anyone is going to notice in terms of weight.
So, it seems @Bullet Guy has whipped me up a killer little carbine. With the barrel referenced above and a 13.5" CMR handguard the thing weighed in at just under 6lbs. That's with a standard collapsible buttstock though, once the Magpul CTR is on there it will proly creep just north of 6lbs, so still lighter than my DD.
From what I understand the idea with that profile was for any changes in the profile to be gently radiused with no sharp angles. It's claimed that this helps with the harmonics. I'll let you know.
meketrefe
.450/400 Nitro Ex
It makes no difference but anything without sharp angles Is cosmetically better and also grit and debris do not get stuck in corners. same way
we flare a bit the muzzle or brakes so nothing catches or cuts when going into bags or rifle cases.
The main concern I have is that the tenons are cut too short. The spot ahead of the chamber and also minor diamters right behind the gas block
are points with both lots of heat and stress. In torture tests even when we think the gas block or tube are going to give up first then many times
it has been the barrel that failed at those points when it really shouldn't. This is also a mistake made in M4 style barrels.
The M4 style barrels should have never existed. Very bad design.