help with unknown benchrest rifle

[leather5to1]

In my grandfather's collection of weird stuff (he bought anything he liked) we found a custom benchrest rifle. He had a couple of these but we though they were all 7x300 or 6.5x300 wby mags.  Yesterday we noticed one had a small bore.  We now believe it to be a 22 caliber.  The gun has no markings except for on the action it says pj hart, I believe it to be an unlimited short action.  We then couldn't even imagine what this is.  Also I forgot to add this gun is at least 30+ years old.  The only cartridge that we could get to chamber and extract is a 222 rem mag.  The only way I can figure out to prove it is to be fire a 222 mag and see after fireforming what it looks like.  I am afraid that if it isn't it will burst the casing.  Is there anything else I can do?  I never heard of a 222 mag in a gun like this it is built like a 1000 yard gun, 1.25 in bull barrel, hart action, 2 ounce trigger, and 6 inch thick stock forend. Thank you for reading and for any help/suggestions.

[dud]

dont just fire it get a chamber cast done first.

[leather5to1]

I saw that you can buy Cerrosafe and do this yourself.  Has anybody ever done this?  I would like to hear about some tips in doing it.

[Skunk]

leather5to1,

Attached (if it worked) is a "how to" on chamber casting that I picked up from the surplus rifle website:

[Frank46]

If you have the serial number suggest you contact Hart Barrrels in upstate new york. They may have some records that will able to tell you the chambering. If as you suggest it may be a 1000yd benchrest rifle in a 22 wildcat chambering. Or an unlimited benchrest rifle maybe in 222 remington. Years ago before the advent of the PPC cartridges the 222 rem was probably the most accurate 22 centterfire benchrest cartridge. Hope this helps. Frank

[leather5to1]

I appreciate all the help.  As far as serial numbers, the only numbers are hand scratched into the bolt.  I believe it is a six digit number, but doesn't look too promising from the way it is hand scribed.

[Mikey]

Leather5to1:  Cerrosafe the chamber and if possible, some of the bore for bore dimentions and twist and then contact Hart Barrels.  They are near Syracuse, NY in the 315 area code.  They may well be able to tell you the exact caliber and possibly even the action.  HTH and good luck.

[Wyo. Coyote Hunter]

leather, I am not sure what apart of the country you are located in, but the area in Pa. and southern N.Y. used to be a hot bed of benchrest shooters. As someone said, the .222 was the darling of the close range crowd. The mags. sound like they could have been made for the the 1000 yard club in northern Pa. there are others, that that was the original one. From what I remember, the guns should be a bout perfect for that time period.

[butch lambert]

I am pretty sure that it is an unlimited bag gun used several years ago. It was used in 100&200 yard competition. A lot of the guys used a version of the 222mag with 35-40-45deg shoulders. Some were called 23-40, 22-45, and 22-35 were common names for the cartridge. The cartridge went away with the advent of the PPC. I have one like the above mentioned one. It has a very heavy laminated walnut stock, but mine is in 222.
Butch
www.shadetreeea.com

[Catfish]

I have an old bench rest unlimited gun from that error in .222 Rem. mag. I used it for groundhohs for years. My guess would be you have the same thing. Mine is on a Rem. 40 X action with a blow shield and was built by Hart.

[iiranger]

Fairly easy. Cerrosafe is a standard alloy, bit costly, but permanent unless you beat it up, mail it... etc. Any machinist can measure and tell you fairly exact measurements.

Cheaper, garden sulphur. Yup, the mineral. Cheap at any garden store. Melt it. Outside is good. If it catches fire, it STINKS. No danger, just slip the lid on to put out the fire and turn down the heat. Plug the barrel with a tight patch ahead of chamber. Squirt of WD40 or the like doesn't hurt. Pour into chamber--funnel helps, let cool minute or three and GENTLY push out. If you break it, do it again. Big deal. Any machinist can measure this too and tell you what you got. Or you can hold it up to pictures of cartridges.

There is quite a list of .222 diameter sized rounds. (Also diameter of many 9mm's.) Some European ones get quite long and brass is scarce. With .204 Ruger on the .222 Mag case, I think, brass shouldn't be too hard to find/make. LUCK. 

[Mikey]

Leather - have you cast the chamber yet?

[leather5to1]

I did a cerrosafe cast but was unhappy with the results.  This action is so massive that it is very tough for me to do.  What I got was somewhat measureable and made me sure that it was a 222 rem mag though.  I decided to try casting another rifle to try and get the hang of it.  I have a 7x300 wby mag that I wanted to know where the lands started in so I tried that.  This came out alot better.  I was able to get the liquid into this chamber very easily (mauser action).  I then found that the mass of the 7x300 sporter barrel was much easier to warm up then the massive bull barrel of the 222.  This made a big difference in the useability of the cast. 
I thank everyone for their input, I plan on trying some loads out in this next week.  We'll see what happens, I'm anxious to see how it shoots.

[Wyo. Coyote Hunter]

 :DIt will be interesting to see how this one shoots. Especially with the new plastic tipped bullets.  how do you like you 7mm-300 sporter??? Had an stw, but never the 7mm on a  wea. case. Do you do some thousand yards shooting???

[Mikey]

Have you shot it yet??

[leather5to1]

I have been trying to post since last night, let's see if this works.

[leather5to1]

Okay that worked.
I got to take this beast out yesterday.  We loaded up about 8 different powder/bullet combinations and took it out.  It's mounts were only compatible with the uenertl scopes so we put an old 15 poweron and tried it out.  We boresighted and checked at 50 yards and then moved the target out to 200 yards.  All of our loads did well, this gun seems to eat anything you give it.  Two loads, one with blc2 and one with 4198 gave one inch 10 shot groups.  This is a fun gun to shoot, I had my doubts because it has aluminum rails on the forend and that rides a wooden hart front rest.  The back has a custom wood rest that rides an aluminum tube on the underside of the stock.  The back rest has windage and elevation adjustments.  I never believed that a gun on solid rests would shoot good but it did.  I look forward to finding a good load for this and possibly getting the receiver drilled and tapped for a modern scope.  Thanks for all your help.

Coyote Hunter:
I love my 7x300 sporter.  It is my black bear hunting rifle.  I don't do any 1000 yard shooting but only because of distance restrictions here in the northeast.  I have room to shoot up to 600 yards, but without going to the williamsport range which would be a drive just to shoot I haven't had the chance yet.  The 7mm stw is very similar in fact that is where I get my starting load data.