What would be a minimum (safe) barrel contour for this big bore? Is #5 contour big enough? Where can I find barrel contour dimensions? Any info will be appreciated. Thanks. Ming

I am not sure what the minimum would be but my 500 A2 has a #5 contour that is .875 at the muzzle. I think .800 at the muzzle would be a good minimum.

Sir Mitch, Knight of the Realm, Lord of the Big Bores:

I am grateful for your instruction in T. rex technique, and the great favor of firing your 577 Tyrannosaur 43 times. Many thanks.

I do not presume to contradict you sir, but what maker's contour scheme are you going by?

I do agree whole heartedly with your muzzle diameter choice for the 500 A-2, as I chose the same for my 510 JAB/500 A2.

The Douglas contours are pretty standard, and agree with Krieger and Shilen as follows, last time I checked:

#1 0.560"
#2 0.600"
#3 0.625"
#4 0.650"
#5 0.700"
#6 0.750"
#7 0.875"
#8 1.000"
#9 1.125"
And the B Rester/Basic: 1.250", straight cylinder

I think the minimum for caliber with any barrel should be the caliber plus 0.250".

For the .510" bullet pusher it should be .510" + .250" = 0.760".

More weight and stiffness help with the bigger bore, so I would agree that the 0.800" would be the minimum barrel I would consider for the 500 A2.

The old fat barreled Ruger Magnum 416 Rigby had a .810" muzzle. A rebore of that would make a sporty 500 A2 if another recoil lug were added to the action and a real second lug on the barrel instead of the recoil plate contraption. Comes with integral quarter rib as a plus however. I might rebore my fat girl some day to 500 A2/510 JAB.

Thanks guys for the info. I just created a drawing of a possible profile for my 500 A-Square. Is this profile acceptable? There seems to be two types of profile. One is called Straight Taper contour which is my is based upon while the other one is called Sporter contour. Which one is better for this big bore?

I like a shorter barrel so I think I will make it about 23 in. It will probably have an intergal lug and rear sight base. Anyway, I am try researching at this point. Any input will be greatly appreciated. Thanks. Ming

ming,
You have exactly drawn the barrel that is on my BRNO 602 ZKK in 510 JAB/500 A2, assuming the overall 23" length includes the threaded portion of the shank.

The straight taper you have shown is a target taper, beyond the cylinder portion of the shank. I liked this best, being a little heavier and stiffer than the sporter contour.

My rifle in a McMillan stock weighs 10 pounds and 10 ounces empty and iron sighted.

I used a McGowen stainless 1 in 10" twist. I have a muzzle brake that screws on for load development, and screws off for hunting.

If I am pushing 750 grain bullets at 2050 to 2100 fps for target precision, I use the brake too.

The 570 grain bullet at 2300 to 2400 fps is the preferred hunting load.

I have a 27" barreled Ruger No. 1 with a 1.000" muzzle that will add 100 fps to the above velocities with the same loads. These are mild loads, but very accurate. I could easily raise the velocities, but don't need the recoil gain. More than enough is enough.

Thanks Ron for the info. How did you get the McMillan Express stock to fit since it is only good for a "#5 contour". I would love to have a McMillan fiber glass stock but they told me it would not fit a bigger barrel contour. However, I did not ask them what is their #5 contour. Anyway, I am looking around for a good stock for this big bore. Cheers! Ming

Ming,
It will fit, with thin side walls at the edges and a barrel recoil lug and hidden cross bolt buried in the forearm underneath.

The barrel channel from the factory will only go up to #5 by the scheme above, in a sporter contour.

The barrel channel just has to be enlarged by scraping and sanding. There is enough forearm material to allow it. Glass bedded throughout, it looks perfect when done right.

I have chosen a double taper for my .585 barrel, it will be reciever diiameter (602 action) for the first couple of inches, then it 1.2" for the next bit tapering to 1" at the muzzle.

I reckon for the big bangers a little bit of meat in the barrel does not hurt.

PC,
This is similar to my Ruger No.1 in 510 JAB 500 A2.

It too is a McGowen stainless 1 in 10" twist, but has that tiny .510" bore so will weigh quite a bit more than your .585" bore.

I left the shank end of the barrel full thickness for 6 inches beyond the threads, then tapered down to 1.00" at the muzzle. Total barrel length is 27" including the threads but excluding the screw on muzzle brake.

A steel picatinny rail sits on the full thickness portion of the barrel for scope mounting.

Both the 27" Ruger and the 23" BRNO are the same length overall.

RAB. Great hearing from you. I wish all of my students of 577 T.rex. 101 shot as great as you(LOL). I have a McGowen Barrel on my 500 A2, at the time I had Harry make the barrel he told me he was going to use a #5 contour and I told him I wanted it .875 at the muzzle. Whether it is actually a #5 contour I am not sure but that is what Harry told me.

[ 06-30-2002, 19:53: Message edited by: Mitch ]

DaggaRon,
The thickness at the muzzle depends on the barrel length chosen. If a #5 contour is .750 at the muzzle of a 26" barrel, the muzzle diameter will be larger for a shorter barrel due to taper.
Ming,
Krieger can tell you what the muzzle diameter will be for the length that you want. Ask for the weight also.
Todd

Mitch,
Is your barrel a straight taper or does it contour down such as a sporter barrel?

Could you also give some contact info for McGown rifle barrels? I have not been able to find a website for them.
Thanks,
Todd

Thanks Ron for the info about the McMillan stock. I am also looking at MPI stock. They seem to be able to customize a stock for any barrel contour. I will give them a call next week.

PC, You got one heavy 585 rifle there my man. I hope it will turn out good. Please keep us posted.

Todd,
It is not nessesary that the muzzle diameter is driven the the barrel lenght. You could hold the muzzle diameter and shank diameter constant and let the barrel lenght drive the amount of taper. It all depends how you define your profile.

I don't think Harry has a website yet but here is his contact info. Cheers! Ming

McGowen Rifle Barrels
5961 Spruce Lane
St. Anne, IL 60964-5332
(815) 937-9816

Mitch,
It is my honor to say hello, and thanks again for letting me have a blast with your T.rex. I had never experienced that amount of torque in a rifle before, and the muzzle blast in that indoor range rivaled a braked 50 BMG. Wow! Your brake and Answer recoil pad with a total scoped weight of 14 pounds (IIRC) made it tolerable for a dozen rounds or so, after that I started getting a little fuzzy in the head, but felt very anti-depressed by the shock therapy. I remember it as a very pleasant learning experience, as you were so kind and helpful with your pupil.

We were at least trying out some new loads for accuracy, and I think we verified the accuracy of your rifle with a few of those loads.

If anybody ever makes you an offer on the T.rex that you consider fair, please check with me to see if I can beat it, if I don't have my tit in a wringer over something else.

Boltgun, yep,
So let me list some barrel lengths this time with the contour information supplied by Harry McGowen:

"BARREL SHAPES

"Our shapes are about the same as Douglas, all sizes approx. Barrel lengths are available any length up to listed size at no extra charge.

#1--22"--Lt.Wt.Sporter--.550" Muzzle--2.25 lbs. Weight approx.
#2--24"--Reg.Sporter--.660"--3 lbs.
#3--24"--Reg.Sporter--.625"--3.25 lbs
#4--26"--Med.Hvy.Sporter--.650"--4 lbs.
#5--26"--Magnum Sporter--.700"--4.5 lbs.
#6--26"--Lt.Target--.750"--5 lbs.
#7--26"--Med.Target--.875"--6 lbs.
#8--28"--Heavy Target--1.000"--8 lbs.
#9--28"--Magnum Target--1.200"--9 lbs.

"We also make various shapes for 22s, M92, M94, 336, Mini 14, 10/22, etc, or we can copy your pattern." ...

Harry also offered octagon barrels, tapered octagon, half round, integral ribs, etc. ... and lo and behold, REBORING! All at reasonable prices. Lots of gunsmithing services too!

(Got me thinking about a rebore now ... )

McGowen Rifle Barrels
5961 Spruce Lane
St. Anne, IL 60964

Phone: 815-937-9816
Fax: 815-937-4024
FFL # 36-8651

ming,
We posted at the same time above. Thanks for the explanation to Boltgun. Fact is, Harry will make a barrel however you want it, chrome moly or stainless, in all kinds of twists. He is an unsung hero of barrel making in my opinion. Been doing it since 1959.

I haven't verified that he is still reboring, but I intend to.

Dagga Ron, your set up sounds excellent, I am just hanging to get mine, I am resisiting the tempation to e-mail my gun smith every day " Is it done yet"

I might piss him off and then he might take longer.

Boltgun, The barrel on my 500 A2 has a sporter contour.

RAB, It was my pleasure to watch you shoot my t.rex. with such great skill. It is true my t.rex. is extremely accurate but it takes a really great shooter to shoot it accurately. You will be one the first to know if I decide to sell the t.rex. BTW. It has not been fired since the last time you shot it.

[ 06-30-2002, 13:24: Message edited by: Mitch ]

Ming- The Mcmillan express stock will take a Pac-Nor #7 barrel profile and will fit just fine. They will inlet it that way for you on demand. As far as barrel profile goes the general rule is caliber plus .200. Thus a minimum would be .710. If you are planning to put in a removable muzzel break then this needs to take into account the depth of the threads. This is one reason to have a muzzel break machined into the barrel. My 500A2 uses a 1.3 inch barrel for four inches then tapers to 1.1 and from there to 1.0 at the muzzel. Remember you need a second recoil lug and as much weight as possible. I also suggest you go with a longer barrel for more velocity and weight. A 28 inch barrel will give you a 150 fps advantage over the 24.-Rob

My Hannibal has a 23 1/4" barrel made by McGowen. It tapers to 0.985" at the muzzle. Like Rob said and others have noted a little longer barrel will give better velocity and if you aren't after that you can get the velocity you want with slightly lower pressure with a longer barrel. What I belive you should think about is: what will happen when you pull the trigger in a hunting situation? The muzzle blast from a full on load is kinda stiff if you know what I mean. A few more inches can get it farther away from your face. Using an appripriate taper you'll be able to maintain the balance you want, the desired weight and still have a little longer barrel.
Why don't you try to set it up for a 25" finished length and if you don't like it cut it down? A cut and blue is what...$200? If you start with the short barrel you'll never know if you'd have preferred the longer one.
Don't you just HATE all these decisions?

Ming will you break this rifle ?, what will your overall barrel length be with a break on?

Rob & Ming my gunsmith was adamant I should have a 27" barrel includuding break (24" barrel 3" break). He said if I chose the 26" and 3" for an overall length of 29" it would be like a "bloody fishing pole" I do agree with him and have said that is what we will have them built with, my only worry is the velocity loss, but I suppose the game shoot will never know the difference between a 24" and a 26" and when creeping through lignum I suppose it will be handier. I want to hunt with my .585 It needs to be practically weighted and also have practical loads. I did not spend all this money to have a gun that was just a closet sitter.

PC,

Sorry for not being able to reply to your question sooner. I just got home from a fun vacation. Anyway, I do not plan on putting a break on any of my big bore rifles. I will probably need one especially for a "big" 50 caliber. I have been talking to Dennis Olson and Frank Wells about this project but I am still in the researching stage now. Well, I will keep you guys posted when I get this project started. Thanks. Ming

Thanks Roger and Rob for the suggestion. For some reason I just do not like a very long barrel on any of my guns. For the various reasons stated, I will probably need a longer barrel other than just to gain a "few" feet per second in velocity. Cheers! Ming

Ming honestly I do not think you will have any dramas with a 24" barrel. 500 gr also said that if you have a muzzle break on top of this that also facilitates to some degree burning of gasses, thus increased velocity. That is a test I would like someone to do actually, chronograph loads from a big bore such as .500 A2 and the .585 Nyatti with break on and break off to see the difference.

PC- Your gonna try and burn a whole lot of slow powder ( 135-150 grs) in a 24 inch tube. I suspect velocity losses on the order of 35- 50 fps/inch. That's another major reason why I would go for as long a barrel as possible. Besides the increase in weight is a very good thing when considering the NYATI. Mine has a 28 inch barrel 1 inch thick at the muzzel and looks more like a cannon than a fishing pole.-Rob

I agree with the sentiment that .800" at the muzzle is a prudent minimum. I had the barrel band front sight from a Ruger #1 458 to use on my 500 Jeffrey, so the barrel was contoured to match, which is either .825" or .850" @ 25", I don't recall. If you're planning on a barrel band front sight, you might want to see what is available, and plan the barrel contour to match.

If you're building an unbraked 50, and you want it to be shootable, then build it heavy enough to be shootable! I'd also much rather have my weight in the barrel then in lead added to the stock.