Hey.
I'm seriously thinking of upgrading my .460Wby (Brno 602) to .500 A-Square, and have a couple of questions I would like to hear what the expertise here or AR has to say about;

-what rifle-twist is the proper one for this caliber??
(I have access to a barrel from a .50 Browning Marchingun, not used. And wonder if this can be used.)I dont know the twist in that one yet.

- Can this round be loaded with cast-bullets, and some black powder.(Just for fun.)(I know this is'nt a real black powder- cartridge.)

460,
I did a 500 jeffery, not 500 a2, but I think the suggestions will still be valid...

1: i went with the 1/18 twist... I am too much of a sissy to shoot 700/750gr, and I knew I would be staying at m2 ball, 640, if I shot surplus bullets.

2: It's 22" long, number 7 contour pacnor

3: I shoot cast bullets in it, gas checked, for the most part.... i've tried woodliegh, bridger, hawk, and cast... the bridgers were, without a doubt, the most accurate. The casts cost 17� each, at either 535 FP or 600gr (pretty bullet) RN from www.customcastbullets.com

4: these MONSTERS comsume LOTS of powder, even at 500 jeffe ballistics. 100 grains + a time is a lot of powder... I switched to cast bullets and surplus wc-852 (from pat's reloading) and slowly worked up a load to just over 2200 in BB brass. Guess what? with cast bullets and surplus powder (500 bullets and 8# is like bisquits and gravy, you should run out about the same time.. if not, buy more)... cost about 36.5� each, including primer

5: Lead bullets at 2200-2300 are awesome... jacketed bullets can go faster, per our buddies on this forum.

have a ball.... if I had to do it again, i might have done the 500a/2 510 wells rather than the jeffe first... the brass is cheaper, easier to get, and you can get it in more quantity.

i don't know about the BP.. but sure wold be funny ..

the bmg barrel is chrome lined, and some people wont rent reamers for it, or use there's on one... some might.

I think the barrel from pacnor was all of 160 bucks

have a ball
jeffe

Use a 1:14 or 1:15 twist barrel for 535-570 gr bullets. 1:10 if you want to shoot .50BMG pulls ( 650 grs). This by the way is lots of fun with 65 grs of XMP5574. I would suggest you buy one from Pac-Nor and not bother with the .50 BMG barrel for too many reasons to list here. 22-26 inch long barrels will work fine. This is an easy conversion on the Bruno 602 action and will only require some ramp work to get to feed properly. Use a Vias muzzel brake and some good mercury recoil reducers in the butt and make sure your gun is properly steelbedded and cross bolted or kiss your stock goodbye in a hurry. I assume that you already know you need a barrel mounted recoil lug, so just make sure it's bedded in steelbed. Otherwise the 500A2 will be a significant step up in horsepower from your 460WBY. Kinda like going from a 350 Chevy to a 502 Chev.-Rob

[ 09-05-2003, 22:45: Message edited by: Robgunbuilder ]

Hey, Rob.
Whats the main-reason you woundt go for a BMG-barrel?(Convence me!)
The reason I really want to go for the BMG-barrel is that I already got that one on hand, and barrels in fiffty caliber is not very common here in Norway. I could import it, of course, but that will cost me a lot.
BTW: I'm really thinking of a short canon(22"), but no muzzlebrake.
And yes, I know what to do with the stock. It's already been done when it came out as a 460.

I would like to have some joy with some blackpowder if possible. Just to makes things hard for my buddies to see the target when we compete. And to add a little smell of "rotten eggs"!!

Gents,
I have had my own 500 A-Square now since early this May. I throughly enjoy shooting "The Pope" as I call it. I had mine built on a P-14 action also,used a Pac-Nor barrel in a 1-14 twist also,put it in a Bell&Carlson stock and put a Timney trigger in. I still need to fix the mag box and follower problems,find a set of bases for I will have confidence in and polish it and have it rust-blued. But I do get to shoot it.
This is a current pic...................


45nut

Notes on .50 BMG barrel while we wait for RGB to return from the fried rattlesnake buffet line in the kitchen:

1) If you want to lift it, you have to turn that .50 BMG barrel down. Dang thing starts out at 33 lbs or more, which is somewhat heavy for a sporter....by the time you are done paying to turn the barrel down, you may have paid for a whole barrel blank or more, depending on what the barrel you have cost you. Better off buying a blank from somebody if you live in the good old USA...budget this out before you get started.

2)The twist is 1:15 (?). Others have said this twist is a little slow for best performance with .50 BMG pulls at the velocities available with sporting cartridges.

3) Bob Forker (Guns and Ammo)once noted that .50 BMG barrels were intended to lay down a cone of fire, and were never intended to be very accurate. You probably have a lot better chance of getting a good blank than you do of stumbling into an accurate surplus .50 BMG barrel. It's going to cost you a hunk of money to find out if that barrel is any good. Another reason to go with a blank from a reputable maker.

I am in the middle of restocking my .510-.505 Gibbs, which I do not use as a sporter, and which does not currently feed from the magazine. However, out of the amazingly cheap Choate plastic stock in which it was originally fired, it shot just over one MOA with 700 grain M2 ball pulls at 2075 fps (it will go faster than that) out of a turned-down M2 HB .50 BMG barrel (new) and made round holes, and I think with a better stock and better ergonomics, it just might shoot 1 MOA or a little bit less. I'll find out sometime next year. Restocking is proceeding at the rate of about 2hrs/week.

Notes on WC 852 (slow):

This stuff might burn more like a 4350 than a slow 4831. 37 gr. out of a .22-250 case with an 80-grainer out of a 24" barrel went 3060 fps, a speed like a 4350, with near-max-looking primer (primer picked up a little grain pattern off face of rough bolt, but edge radius still fairly round). 37.5 gr. worked as well, though I have no velocity for that.

In .510-.505 Gibbs I didn't get past 135 gr. for 2350 fps (note: 32" barrel) before quitting to restock, and this appeared to be a very low pressure load, with the outsides of the necks still getting smoked.

In whatever cartridge I used, I would be inclined to take very seriously the recommendation to begin reloading with reduced loads when using WC852 (slow).

Can't add much to what the others have said. Mine is also a 500 Jeffrey, and used a 1-15" Douglas 50 bmg unturned blank, though not chrome lined. As I recall, the original Jeffreys used a 1-18" twist.

While the faster twist is nice for shooting the heavy 50 BMG pills, it isn't necessary per se, and may be detrimental to the best accuracy with cast bullets.

I see no reason why black powder wouldn't work, just make sure the case is full.

I plan to shoot lots of cast through mine, once I get around to putting a proper stock on it so that it is enjoyable to shoot. I have a 470 gr LBT mold, and I really don't see a need for a heavier bullet. The heavier bullets are longer, and in the Jeffrey, would have their bases below the neck. I prefer to load cast bullets with the base in the neck, not that I need any more powder capapcity.

I don't think you'll need a break, so long as the gun is over 10#'s. I shot 600 gr @ 2200 fps, and the recoil wasn't bad even with the crappy stock, though it did move me reward after each shot

460WBY- The majopr reason not to use a .50BMG barrel is they are generally crap, Usually stellite lined so that they will ruin your reamer in very short order!! In addition, the process of lathe turning one to a dimension you can actually use ( profiling) will result in the bore actually opening up beyond .510. No accuracy is the result! I totally understand your situation and comiserate, but trust me and just buy a pac-nor 1:15 barrel and save yourself lots of bucks later. Remember you still have to fit and headspace it. As my mechanic says to me, you can pay me now or you can pay me later, but you'll still pay me=!Rob

[ 09-06-2003, 06:52: Message edited by: Robgunbuilder ]

Ditto the nix on the surplus barrel. I bought one once at the Knob Creek shoot and show. A Ma Deuce "new" barrel. I looked down the bore and saw cosmoline. Took it home and cleaned it. Large chunks of the lands in the rifling were missing and chewed up. That was kind of rough feeling as the patch snagged on the ragged metal in the bore!

Use a 1 in 10" twist and you will get better penetration with the lighter hunting bullets (570 to 600 grains), and better accuracy with the milsurp plinking bullets and target bullets (~650 to 750 grains are practical).

Here's my chance to trot out a couple of the few photos that I have bothered to have access to, if they still work. I am proud of my BRNO ZKK 602 and Ruger No.1 in 500A2, though I call them .510 JAB. Somebody else calls his the 50 Peacekeeper. Its the most gun I will ever have a use for.





A McMillan stock on the BRNO, and an epoxy bipod base on the factory Ruger stock. Both good for 1000 yard paper punching with proper sights. That is a Schmidt&Bender on the Ruger. Sighted 3" high at 100 yards with the 750 grain Hornady A-Max, it will deliver right on target at 945 yards with a 5 mil holdover. Work out a table, hit anything out to 1000 yards. MV was 2150 fps with 110 grains of IMR4350. Still supersonic well past 1000 yards.

Yes, it does 80% of a 50 BMG in a much shorter and lighter rifle.

The BRNO is 10.75# as pictured with 23" McGowen stainless barrel, 1 in 10" twist. The muzzle brake is not included, but it is an oversize screw on like a Weatherby Accubrake.
Barrel is 0.875" at the muzzle.

The Ruger is about 13.5# with the scope and slimline muzzle brake, though that muzzle is 1.000". Again, a 1 in 10" twist stainless McGowen, 27" without the brake, 29" with the brake.

Hard to beat a 45 Lapua, however, for a practical big bore. Thanks for the idea!

The 500A2 is definitely the most practical 50 cal.

[ 09-06-2003, 14:17: Message edited by: DagaRon ]

Carcano91-My understanding is that button rifled barrels are more susceptable to this effect than cut rifled barrels due to the radial stresses than are put on the barrel during the button rifling process. Removing metal from the barrel outer diameter in addition to the heat involved results in a small but measureable bore expansion. Upon cooling it does not return to the original conditions due to the stress relief. The more metal removed the worse this gets. Depending on the profile of the barrel, I actually wonder if this will not produce tight and loose spots in the barrel. I've tried this on some large button rifled barrel stubbs I have laying around with precision plug guages and it's definately true. I have also had this confirmed by two other very knowledgeable .50BMG machinists/FCSA compeditors during Benchracing sessions.
Basically, I do not re-profile barrels at all anymore on rifles expected to provide top-drawer accuracy especially since douglas/shilen barrels are so cheap these days and to re-use a barrel generally necessitates too much time in parting off the old thread stub and re-machining. If it's for a fun-project and your accuracy expectations are modest, then by all means go for it.

Anybody who has to bear the burden of excessive interest in this matter may search on the topic "autofrettage", and then perhaps read the article maintained online on the topic by Harwood Engineering, entitled "The Effects of Machining After Full Autofrettage." RGB is right, of course. Empiricism is a great strategy for getting the right answer.

I knew to search on "autofrettage" because I read a book on M1 tank development a while back, and the subject of making relatively lightweight cannon barrels was included. This was popular literature, by the way, and the readers were spared the headaches of a treatment in greater depth.

Thank you, Rob. (and all others)
I have been convinced!!
I've just spoken to a friend of mine here in Norway, and he said that he had bought a barrel from Pac-Nor with NO problem. It wil of course cost me a bit more, but as you said; I might pay the same price after all, when the job is done. And maybe have a rifle with poor accuracy.
I maybe come back with a few more questions when the project is started, but thanks for now!

Sorry to digress - but a Norwegian might easily be tempted to build his own "special" 8mm with a military 8x61 MG barrel, wouldn't he ? An interesting cartridge, as much as the Swedish 8x63 MG.

As to Rob's advice, thank you very much. The unaltered 8mm Breda MG barrel would indeed be much too heavy for almost everything except a rail gun :-). I wonder a little about the gas port opening of the MG barrel; it would have to be plugged. My concern is not the pressure, but rather how to machine the plug/screw as to conform exactly to the barrel profile... ?

Carcano

[ 09-10-2003, 21:46: Message edited by: carcano91 ]

I used to work at PAC-NOR, and they ship overseas all the time. I built myself a 500 A-Square on a 1917. It is a PAC-NOR CM 14" twist. It shoots the military bullets fine. I have built and owned lots of BMGs and noticed with a borescope that the CM seems to do a little better. (416 project 70 Stainless from Carpenter vs. 4140 CM). The 24" barrel is threaded for a brake, but I found that with my ears going out, I prefer the recoil that the concussion. I have a merc tube that I need to put in it. I have a thread cap on it that nobody ever can see since it is polished to the contour. I used 7/8x24 TPI threads. On the breech end, I made the contour the same as the action. 1.355" or so, the same as a REM front ring. The od goes out for a couple of inches then swoops down to 1.15, I think. A couple inches later, it goes back to 1.355" for 1.5", then back down to 1.15". The sides of the second big dia are milled off to blend in with the 1.1". It sits in the stock well like that. Now I have two spots to mount my scout scope with REM 700 mounts. I have a 2x Leupold scope with Quick detach rings and irons for back-up. The front post is a Hi-viz. It shoots under 1" with 570 woodleighs. I am sure it will do better once I have my 1 piece rest in. I haven't done much accuracy testing yet. The recoil on the bench seems to scare my trigger finger. Mabey it shares a nerve with my shoulder. It is 13 lb and certainly an offhand gun. Some hunters go with a 9" or 10" twist for the drilling bullet effect, although to stabilize, a 14" should be fine for most heavy bullets. This has all been said. Under the front sight mount, I milled the ring square so that It would act as a recoil lug. The walnut stock has three cross bolts, one is by the barrel lug. I am still doing lots of load development, and looking for data other than what the a2 book says. The 300 Barnes orig is up to 3000 with no pressure. I have filled the case with 126.5 gr 4895 and moved on to faster powder. I had some delayed ignitions with h335 from not having enough powder in it. The 450 Barnes is up to 2750 fps. with 120gr 4895. I am going to 122.5 next. The 570 woodleigh does 2475 or so, but my log book is blank here. I need to do it again. I went over this, but the book ends here with 119.2 gr 4895. I have used the 460 gas checked lead from Huntington. I met a bullet caster here in Oregon who is making some .510" 535 gr bullets for me. He says they do not need a gas check since the bullet has so much dia and mass, it cand get hot enough fast enough to melt. I have them here, but haven't loaded them yet. The 700gr AP bullet shoots at 2100 with 109 gr RL-19. The 645 API gets 114 gr. RL-19, and the 625 INC gets 115 gr RL-19. All the BMG bullets show pressure signs (cratering) on the primer. I do not know if it is the sloppy firing pin/hole fit, or accual pressure. The webs seem to stay put, and there is no brass flow. Put the sling stud on the barrel, ouch!

[ 09-10-2003, 06:33: Message edited by: jnrifleworks ]

A comment on cast bullets and gas checks. Not all leading is caused by the base of the bullet melting. Leading can also be caused by lube failure, and the rifling stripping the lead off the bullet. The faster the barrel twist, the lower your velocity before leading becomes a problem.

I would suggest using gas check bullets for full patch loads, and keep plainbase bullets for 1800 fps and lower loads.

Thanks for the cast bullet advise. I am aware about some leadfouling being caused as you stated, but I am courious what the main advantages of the gas check are. I can imagine it cleans up the lead fouling left in front of it. And it must check the gas. I have seen the bullet flying through the air with the gas check. What is there to the bullet melting? Thanks.

My understanding of the advantages of the gascheck are,

1) it provides a means of transfering the rotational forces from the rifling to the bullet, which prevents the lead from stripping.

2) it provides a better base seal between the bullet and bore.

My thinking is, there are two primary causes of bullet leading, gas blowby between the bullet and bore, and the rifling stripping the lead from the bullet.

The gas blowby can be caused by lube failure, or poor bullet fit. An undersize bullet that doesn't obturate can't seal the bore. The cure for this is either a softer bullet that can obturate, or larger dia bullets. The disadvantage of the softer bullet is it will start to strip at lower velocities then a harder bullet. The other cause of blowby is lube failure, the higher the pressure, the more difficult it is for the lube to seal.

The gas check solves most of these issues, and makes bullet hardness, and to some extent sizing less critical than a plainbase bullet.

Then again, a gun set up with the proper dimensions in the chamber can be more tollerant of cast bullets as well.