Deep in The Weeds- Barrel Edition

[BoydAllen]

Sdean

The same amount as the chamber end.

Hal

Have you ever seen a graph of the pressure in a barrel as the bullet moves forward in it? If I have read your statement correctly, you are saying that the pressure on the barrel at the muzzle is the same as it is at the breach, and that is not even remotely true. Here is a very well done article on the subject.

https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2010/armament/WednesdayCumberlandPhilipDater.pdf

 

[BoydAllen]

Diving deep into the subject of barrels the thing that neither shooters nor gunsmiths can measure that definitely affects accuracy is residual stress in the steel. It is my understanding that cut rifle barrel makers rely on the mill that makes the steel that they use for stress relief. There is a non destructive test for stress, but I know of no barrel maker that is equipped to test steel in this way. It is called X-ray diffraction.
If you really want deep in the weeds, here you go.

https://www.lambdatechs.com/wp-content/uploads/200.pdf

 

[Hal]

Boyd
Thanks for correcting me and posting the link to some great info.
I haven't read all the info on that link yet but I'lll work on it.
I would like to know why/how velocity goes up yet the pressure drops in longer barrels.

Hal

 

[CharlieNC]

Boyd
Thanks for correcting me and posting the link to some great info.
I haven't read all the info on that link yet but I'lll work on it.
I would like to know why/how velocity goes up yet the pressure drops in longer barrels.

Hal

The pressure is BEHIND the bullet, between it and the charge, as the front of the bullet in the barrel is open to the atmosphere. Powder burns progressively, not all at once, so with more time as in longer barrels there is less remaining powder to burn with time.

 

[tom]

We try things rather often, up to and including purchasing tooling, so I know others had to have in the past or so I would think. The latest "fight club" barrels are in the mail


Tom

 

[Jud96]

We try things rather often, up to and including purchasing tooling, so I know others had to have in the past or so I would think. The latest "fight club" barrels are in the mail


Tom

I know you guys are always testing and up to something. That’s the stuff that’s interesting!

 

[tom]

I know you guys are always testing and up to something. That’s the stuff that’s interesting!

Most of it ends up backwards, and no one ever hears about it! Lol

Tom

 

[Jud96]

BTT. I’d like to see some more discussion on this topic

 

[6MMsteve]

in a cut rifling barrel does the barrel seem better when a new tool cutter is used or better with a cutter that has maybe seen a couple barrels, or is one cutter used per barrel or multiple cutters for one barrel. kinda 2 questions but I always wondered on the cuts per tool per barrel I know the cutter isn't cutting but a small amount I don't know anything bout it, just curious

 

[Acyr]

in a cut rifling barrel does the barrel seem better when a new tool cutter is used or better with a cutter that has maybe seen a couple barrels, or is one cutter used per barrel or multiple cutters for one barrel. kinda 2 questions but I always wondered on the cuts per tool per barrel I know the cutter isn't cutting but a small amount I don't know anything bout it, just curious

In my experience the first cut after sharpening the cutter is a touch rough. Not bad but a little rough. It will lap out fine. I will cut 10-15 barrels before touching up the cutter. It will go longer but i choose to do it before it gets too dull.

 

[AckleymanII]

in a cut rifling barrel does the barrel seem better when a new tool cutter is used or better with a cutter that has maybe seen a couple barrels, or is one cutter used per barrel or multiple cutters for one barrel. kinda 2 questions but I always wondered on the cuts per tool per barrel I know the cutter isn't cutting but a small amount I don't know anything bout it, just curious

I have seen some darn UGLY cut rifle barrels the last three years from one maker, and service after the sale is no better, which was NOT a barrel Krieger(their customer service is second to none).

 

[gunsandgunsmithing]

How much pressure would you think for the last few inches?

Lots of variables to that question. Barrel length and powder burn rate both are way bigger factors that one might think. I deal in BR stuff and I've done pressure testing with a Pressure trace. At the higher end, 5,000-8,000psi at the muzzle is not far off. Where a rf, might only have a few hundred psi at the muzzle. That's the main reason that I believe a taper lapped bbl is of far more significance to a rf than a cf. Pressure alone creates a "natural" choke in a cf, due to bore expansion at those pressures, as they get lower toward the muzzle, rapidly. For reference, a Pressure trace system uses strain gauges that convert stretch to current and graphs it out on a computer screen for you. You can faintly see primer ignition and that's not even close to what you still have when the bullet reaches the muzzle. To faint to really read primer pressure unless the newer systems were better. But just a tiny blip on the graph.

 

[Bc'z]

It’s a PPC but I’ll keep the maker to myself so I don’t start a shit storm. I just shot this group 15 minutes ago. 5 at 200 yards

Thank you...
For a minute there...
Oh never mind
How's blue?

 

[Bc'z]

Just something to think about.

What do you think happens, size wise, when the chamber end of the barrel is hit with 50,000+ psi of internal pressure,

Probably swells up like a dead deer in the Texas heat instantly unlike the the deer tak24-48 hours

 

[jimmymac]

try f

Thank you...
For a minute there...
Oh never mind
How's blue?

I am picking it up tomorrow.

 

[Bc'z]

try f


I am picking it up tomorrow.

Today tomorrow, or tomorrow tomorrow?
East West thing..
2am west coast at posting
Valid question LMFAO

 

[FrankG]

in a cut rifling barrel does the barrel seem better when a new tool cutter is used or better with a cutter that has maybe seen a couple barrels, or is one cutter used per barrel or multiple cutters for one barrel. kinda 2 questions but I always wondered on the cuts per tool per barrel I know the cutter isn't cutting but a small amount I don't know anything bout it, just curious

No it doesn’t matter. Thru out the life of the tool it gets dressed/sharpened. So a tool that did the first barrel doesn’t mean that the last barrel the tool does is a bad barrel etc…

The groove width will slightly change that’s why there is a tolerance on groove width etc…

Look at it this way…. When we make ammunition test barrels and we could make say 70 test barrels in the same caliber and all at the same time for a single order. Never seen a difference in performance period!

 

[FrankG]

“What’s your thoughts on some barrels, like Broughton, being consistently “faster” than equally spec’d barrels from other makers.”

Above is from the OP’s original post. Not bashing the op the way I start my response so don’t take it that way OP.

This is a B.S. statement regardless of who makes it. I’ve beaten this to death on multiple forums and threads.

Why is it B.S.? Unless you know the bore and groove dimensions from barrel to barrel or maker to maker etc…you are NOT COMPARING APPLES TO APPLES!!!!!!! A barrel with a tighter or looser bore and groove sizes will produce pressure differently and in turn effect velocity differently!

Same goes for the chamber. Don’t say well my buddys gun is in 308w and my gun is in 308w but his is faster? Was the chambers cut to the same spec? Not that one has a tighter free bore and shorter throat length etc…

A good example…. Ammunition pressure test barrels. I’ve seen actual pressure and velocity data from 6 barrels we made at one time for an ammo maker. The pressure was within 1500psi and the velocity was with in 10fps. That shows consistency in bore dimensions etc…

Right now with the 7/6.5PRC testing going on at Hornady with the pressure barrel we made… velocity with the same loaded ammo shot thru my gun and the pressure barrel is within 15fps and I know of a gun manufacturer that we make barrels for stopped in and had his ammo tested earlier this week. We made his barrels that are on the team guns 4 years ago. His barrels are 2” shorter in length and the velocity was within 40fps. Again that shows consistency.

Now change one thing spec wise…. and your data will or can change. I won’t even get into the variables in lots of powder, bullet diameters etc…adding these in just opens the can of worms even more.

The barrel is nothing more than a pressure vessel. Dimensions and what’s being run thru it are the variables.

Don’t even start on cleaning and what that can do.

Later, Frank
Bartlein Barrels

 

[Jud96]

“What’s your thoughts on some barrels, like Broughton, being consistently “faster” than equally spec’d barrels from other makers.”

Above is from the OP’s original post. Not bashing the op the way I start my response so don’t take it that way OP.

This is a B.S. statement regardless of who makes it. I’ve beaten this to death on multiple forums and threads.

Why is it B.S.? Unless you know the bore and groove dimensions from barrel to barrel or maker to maker etc…you are NOT COMPARING APPLES TO APPLES!!!!!!! A barrel with a tighter or looser bore and groove sizes will produce pressure differently and in turn effect velocity differently!

Same goes for the chamber. Don’t say well my buddys gun is in 308w and my gun is in 308w but his is faster? Was the chambers cut to the same spec? Not that one has a tighter free bore and shorter throat length etc…

A good example…. Ammunition pressure test barrels. I’ve seen actual pressure and velocity data from 6 barrels we made at one time for ammo maker. The pressure was within 1500psi and the velocity was with in 10fps. That shows consistency in bore dimensions etc…

Right now with the 7/6.5PRC testing going on at Hornady with the pressure barrel we made… velocity with the same loaded ammo shot thru my gun and the pressure barrel is within 15fps and I know of a gun manufacturer that we make barrels for stopped in and has his ammo tested earlier this week. We made his barrels that are on the team guns 4 years ago. His barrels are 2” shorter in length and the velocity was within 40fps. Again that shows consistency.

Now change one thing spec wise…. and your data will or can change. I won’t even get into the variables in lots of powder, bullet diameters etc…adding these in opens the can of worms even more.

The barrel is nothing more than a pressure vessel. Dimensions and what’s being run thru it are the variables.

Don’t even start on cleaning and what that can do.

Later, Frank
Bartlein Barrels

Thanks Frank, I understand the dimensions used in some barrels are different than others. My question about the Broughton barrels was more to ask what made them "fast". Was it rifling shape and geometry, bore and groove dimensions?

 

[FrankG]

Thanks Frank, I understand the dimensions used in some barrels are different than others. My question about the Broughton barrels was more to ask what made them "fast". Was it rifling shape and geometry, bore and groove dimensions?

Bore and groove size.

For the most part twist and style of grooves or number of grooves has no bearing on pressure and velocities. I have yet to see any hard data to say otherwise. As long as the total surface area of the bore is the same. Look at some saami print spec’s. Not just the bore and groove and twist spec.. etc… there is also a dimension for total bore surface area on the prints.

Here are some hard numbers…. Make the bore and groove both just a .0005” undersize from min spec and that will drive up pressures 8k - 10k psi which in turn drove up velocities +150fps. That was testing done with the same lot of ammo.

A worker who worked at Broughton for a while told me if the barrel was a .001” undersize he was made to lap it up to size. Trying to take that much material out by lapping it will do nothing but make tight and loose spots in the barrel.