BARREL PRESSURE MANAGER

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  • Last Post 23 March 2019
joeb33050 posted this 14 February 2019

Since I found that CBA shooters haven't made any substantial improvement in rifle accuracy in over 20 years, I've been experimenting and reading about jacketed bullet and rimfire shooting, looking for a secret.

My experience with a chronograph and both jacketed and cast bullets suggests that MV variation does NOT correspond to accuracy variation, at least at 100 yards.

The rimfire community DOES seem to agree that MV variation DOES correspond to accuracy variation at 100 yards; and take actions to reduce that variation by, for example, weighing/sorting cartridges.

It occurred to me that MV variation could be reduced with an adjustable, spring-loaded, pressure relief valve; a barrel pressure manager.

A hole drilled in front of the chamber and threaded, a needle valve, and a spring loaded adjustable force arrangement are easily imagined and easily constructed.

Perhaps MV / pressure variation by the shooter is A way to improve cast bullet accuracy.

I have a Savage .22 barrel as the test bed, who will volunteer to do the machine work?  

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mashburn posted this 23 March 2019

I'm going to stay out of this one. My pay grade is a way too low to respond to this. If you think; Since the invention of a firearms: nearly every patent for firearms is an improvement over something that already exists. I'll stick to making everything mechanical as perfect as I can make it, including ammunition and rifles. Someone mentioned that they thought  that varying pressure at the muzzle was detrimental to accuracy. I definitely agree with this. Being a old Hot Rodder  and knowing a valve will flow more air with a three angle seat I have crowned some muzzles with a 3 angle crown ending up with an 11 degree angle on the outside one and sometimes on the inside. They were all accurate but I never did do a experiment on the same rifles with different crowns. One of the attractions to me for shooting cast lead is the nostalgia.But of course I want to have all the accuracy that is possible Good luck and success with your  ideas.

Mashburn

David a. Cogburn

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muley posted this 23 March 2019

Joe , why have the guage on top of the barrel in line with the sights? it could be placed at 2 o,clock and still get the same pressures and still fit in the stock.

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M3 Mitch posted this 22 March 2019

I would be wearing serious eye protection for sure.  I might want to do the old "tie it to an old tire" trick and fire the first shot with a string.  That thing may, possibly, come off the barrel on the first shot or it may take several shots.  Or it may work great.  But just don't get hurt!

Don't take that as me being negative about this, far from that.  It's just when you do something that has not been done before, at least IMHO one should take all reasonable precautions.

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joeb33050 posted this 22 March 2019

On the barrel-barrel is on an action, ready to shoot tomorrow

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joeb33050 posted this 22 March 2019

Assembled with pressure relief valve

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joeb33050 posted this 22 March 2019

Transition, hollow 10-32 rod one end, IPS (1/2?) other end

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joeb33050 posted this 22 March 2019

Barrel hole; .050" through to bore, ~ 2.5" from bre3ech end. 10-32 threaded above.

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Squid Boy posted this 24 February 2019

 This is an interesting discussion but I do think that if such a device were possible that it would have already been done. I know Mann tested barrel venting near the muzzle without finding any advantage. I think the issue is the pressures and times involved prevent anything mechanical from working as desired. My load program shows a 30-06, 180 grain cast bullet loaded in front of 53 grains of H-4895 reaching Pmax (57,120 psi) at just .6 milliseconds at a velocity of 1,008 fps when the bullet has traveled 1.95". This is a lot happening in a very short period of time and I don't know many mechanical devices that can react that quickly or accurately especially at the pressures and volumes we are discussing. I have been focusing on lowering the SD on my loads with careful powder selection and other techniques. I have a load for a cast bullet in the 32-20 that shows an average SD of only 1.6 fps. The real trick is finding the ideal velocity and still keeping the very low SD. This loading is quite accurate but I need to get a good scope on the rifle to really realize what it can really do. That's just my opinion for what it is worth. Thanks, Squid

"Squid Pro Quo"

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joeb33050 posted this 24 February 2019

Picture

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joeb33050 posted this 23 February 2019

The CR25 pressure relief valve, 0-100 psi micrometer adjustable, arrived yesterday. Now to see Mike. 

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joeb33050 posted this 20 February 2019

Well, I've moaned a guy at the gun club to the point where he has agreed to drill and tap a hole in my Savage M110 22-250 barrel, about 2 1/2" from the chamber end. However, he does not have a lathe, and refuses to buy one for this project.

Thus, I'm still searching for a lathe guy, to make this relief valve/pressure manager. Imagine a screw with a 2 diameter hole bored through it. Large and small diameters. Imagine a threaded cap to fit the screw. That's it. I'll be happy to pay, or accept charity. There's a good chance that your name will go down in history. Next to Pope, Roberts, Horace Warner and Edmund Fitzgerald. Who will respond?

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joeb33050 posted this 19 February 2019

What round are you shooting, what load, what rifle?  Is this typical velocity variation? 

 

22-250, 7/Titegroup, Savage M12. The standard deviation for the 50 shots is 20.2 fps. The standard deviation for ~188 loads, 10 shots/test, is 19.6 fps. So, yes, the velocity variation is typical.

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M3 Mitch posted this 19 February 2019

What round are you shooting, what load, what rifle?  Is this typical velocity variation? 

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joeb33050 posted this 18 February 2019

When you get this whole thing assembled and working to suit you (assuming that it will) you won't have advanced cast bullet accuracy one iota.  You will only have made a cobbled together ad hoc pressure regulated gun.  Have Fun.

HERE ARE 50 SHOTS, 200 METERS, MV AND ELEVATION

IF WE CAN MANAGE BARREL PRESSURE AND ELIMINATE THE 5 HIGHEST VELOCITY SHOTS, WE GET

 

AND MAYBE 5 GROUPS GET MUCH SMALLER.

IT WORKS FOR CAST, JACKETED, AND RIMFIRE.

Do you get it now?

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M3 Mitch posted this 18 February 2019

Well, I don't have an M1-A, and I don't have a chronograph either.  Maybe someone who does will pick up the torch.

As to proving it can't be done - that proof is one of the few things that can't be done for sure.  All a guy ever knows, is that so far he has not come up with a way to do it.  "When you say it can't be done, be sure you are not interrupting the guy who has just done it"!

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joeb33050 posted this 17 February 2019

Joe.... if it is as simple as you make out, then it would seem you have the capability of managing it yourself.... without the need of a machinist. We will all be waiting for your results.

Unfortunately, I can't do much of any manual work. How about you, Will you do it?

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Brodie posted this 17 February 2019

When you get this whole thing assembled and working to suit you (assuming that it will) you won't have advanced cast bullet accuracy one iota.  You will only have made a cobbled together ad hoc pressure regulated gun.  Have Fun.

B.E.Brickey

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45 2.1 posted this 16 February 2019

Joe.... if it is as simple as you make out, then it would seem you have the capability of managing it yourself.... without the need of a machinist. We will all be waiting for your results.

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joeb33050 posted this 16 February 2019

A hacksaw blade would make a good spring. Hose clamp, shims, a screw with a point filed to a v, screw and nut to adjust pressure, and a hacksaw blade. Advanced equipment.

Must I contact MIT, or is there a machinist here willing to tackle this task?

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45 2.1 posted this 16 February 2019


Perhaps a simpler test would be to see if identical ammo fired in an M-1A, and in another '06 that has a manual action, if the M-1A gives statistically significant reductions in muzzle velocity variation, I'm assuming here that the M-1A bleeds more gas off the "hotter" rounds, so would be a half-step in the direction you are contemplating.

Let me know how it turns out.

 

M1A is a 7.62 Nato chamber, a ballistic match for an '06, but at a higher pressure..... therefore identical ammo and situation is a problem. It also has a bleeder hole so the piston travels a short distance before the gas is vented. Really, some advanced equipment is needed for this kind of testing.

 

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