Some Long Time Favorite Contender Barrel Rechambering Options
Of all the hundreds of different chambers I have cut, there are certain ones that I think are especially good for a variety of reasons. Others I simply like out of personal prejudice.
If you have an accurate TC barrel, it isn't broke, so you probably should not fix it. However, I find serious fault with most of the barrels Thompson/Center makes, and focus my attention on chambers that cut out the throat misalignment in factory chambers.
Rechambers that make superlative barrels out of mediocre barrels 14" or longer will be the focus here.
.22 LR factory barrels rechambered to: .22 Win Mag.
With the .22 LR factory barrels, you have a better assurance the groove diameter will not be larger than .224" as it often is in factory .22 Win Mag and centerfire .22 cal. barrels. The 1-15" twist is also much better suited to the light .22 Win Mag bullets than the 1-12" twist the factory uses. The .22 Win Mag. normally has a forcing cone instead of a cylindrical throat, but I cut a cylindrical, long leade angle throat for it just as I do the centerfire .22s. By so doing, the accuracy from my .22 Win Mag rechambers is absolutely superb. Sub moa groups at 100 yards are quite common. My customers love it, and so do I.
I guess I would be remiss if I didn't at least also mention all the little centerfire cartridges like .218 Bee, 218 Ackley Bee, .22 Super Jet, .22 Carbine, .221 Rem. Fireball, and of course .22 K-Hornet. These all work well in the .22 LR factory barrels, but I normally refrain from chambering larger .22 centerfires in the .22 LR barrels.
.22 Hornet factory barrels rechambered to: .222 Remington or .222 Rem. Mag. Imp.
Remember, I confessed to prejudice in the beginning. I have nothing against .223 Rem, but from an accuracy standpoint with bullets up through about 52 gr., I still prefer the .222 Rem.
If you want absolute maximum velocity from the Contender and superlative accuracy, you cannot beat the .222 Rem. Mag. Imp. From an 18" barrel it pushes 50 gr. bullets 36-3700 fps. Reports are that it does 3400 fps from S-14 barrels. The only down side is the cost of custom dies, but the performance is well worth it. Note that .223 Rem Imp 40 degree dies will work for this chamber also.
But if the standard .223 Rem is your cup of tea, a factory .22 Hornet barrel is the best platform from which to build an accurate .223 Rem.
What I like best about this rechamber conversion is that there is enough difference in diameter between the Hornet chamber and the .223 Rem types that I can lathe bore the misalignment out of the factory chamber, and there nearly always is substantial misalignment. You can dial the bore itself true in the lathe and often find about .020" runout in the mouth of the chamber. So starting with a Hornet is the best way to go for any of these chambers.
.222 Rem. and .223 Rem. factory barrels rechambered to: .222 Rem. Mag. Imp.
For all the reasons noted above, with allowances for .223 Rem. fans.
.223 Rem. factory barrels rechambered to:
.222 Rem Mag or .223 Rem using Mag brass.
If your factory .223 Rem chamber doesn't shoot well, and note I said the chamber since most all of the factory .22 barrels will shoot quite well except for ones badly oversize in groove diameter, you can rechamber to the standard .222 Rem Mag and continue to use your standard .223 Rem. dies if you want. Helps economize.
Ok, you're saying " I have heard of .222 Rem Mag, but what is this matter of using .222 Rem Mag brass in a .223 Rem. chamber?
The .222 Rem. Mag. brass is about .1" longer than .223 Rem. Without altering the body of the chamber, the neck can be lengthened to accommodate .222 Rem Mag. cases run through a .223 Rem size die, which is used to push the shoulders of Mag cases back the correct amount to still headspace on the existing .223 Rem. chamber shoulder. The .1" longer chamber neck cuts out most of the factory throat and lets me cut a new throat of minimum diameter that is properly aligned with the bore. The "fix" is pretty inexpensive. The chamber neck and throat work is $45 plus shipping costs, and the .222 Rem Mag brass is reasonably priced. Pretty cheap way to make a shooter out of a potential tomato stake.
7mm TCU factory barrels rechambered to: 7-30 Waters
7-30 Waters is still one of the very best cartridges in the Contender when properly chambered.
7-30 Waters factory barrels rechambered to: 7mm Bellm
If you have not gotten to the pages on The Bellm Triad Cartridges, you might do so now. See links to The Bellm Triad Cartridges at the bottom of this page.
The main thing I like about the 7mm Bellm is that it is based on the longer, larger in diameter .444 Marlin cartridge. This allows me to cut a chamber and throat well aligned with the bore, and throat dimensions that are minimum diameter. Though the 7mm Bellm does offer increased velocities and handles heavier bullets better than the 7-30 Waters does, the main benefit is improved accuracy. And like the other "Triad" cartridges, it uses common, economical dies to form and load cases.... all the benefits of a wildcat cartridge without the custom dies cost.
.30 Herrett: Good choice for the best .30/30 Imp. since it lets me cut an entirely new throat in the barrel. When you rechamer a .30/30 to Imp., you still have whatever the factory cut in the barrel for a throat. But starting from the shorter Herrett chamber, I can then cut a new throat that is of minimum diameter and aligned with the bore.
.30 Herrett and .30/30 Win. factory barrels rechambered to: .308 Bellm
Again, for background info, go to The Bellm Triad Cartridges page linked to from the bottom of this page.
The .308 Bellm is my all around favorite for a number of reasons, not the least of which is top accuracy and excellent ballistics.
The recent .30/30 factory chambers have no throat in them, just an overly long neck and a little chamfer on the ends of the rifling. Accuracy from most of these is somewhere between mediocre and simply dismal. These barrels respond to rechambering to .308 Bellm very well, turning in superb accuracy.
70% of the at-random combinations of powder, bullet, primer in our test barrel grouped 5 shots under 1.5" at 100 yards. 30% were under 1," and one load in particular shot .330," just one ragged hole. It simply begs to group.
You do not have to have anything more than a set of .308 Win. dies to form and load, unless you want to get more sophisticated and use small base .308 Win. dies or standard .308 Win. dies in conjunction with a .444 Marlin size die. These last two options let me cut a smaller web diameter than when using standard .308 Win dies that are meant for larger diameter factory type chambers.
And again, the diameter difference between the .30/30 body and the .308 Win size body lets me bore out the factory chamber runout before doing the chamber work. Thus, the chamber and throat for .308 Bellm are aligned with the bore very well.
.308 Bellm has a capacity that is well suited for bullets from 125 gr. to 165 gr., the heaviest one would normally use, though it will handle 180 gr. bullets well also.
With 165 gr. bullets, .308 Bellm is probably the king of long range Contender rounds.
.308 Bellm simply makes a treasure out of trash. I love it.
.357 Magnum factory barrels rechambered to: .357 Rem Maximum
The Max. does well in shorter barrels also, but in this section we are talking about 14" and longer barrels. The factory uses a .4" long forcing cone instead of a throat in their .357 Mag. chambers. The .357 Maximum cuts most of this out and improves accuracy tremendously. The Max. is inherently one of the most accurate Contender cartridges there is, uses standard .357 Mag. dies, and a moderate amount of powder to get a lot of horsepower from a small package. Brass is pretty cheap when Remington does its periodic run of brass, and factory ammo is still pretty common from commercial loading companies when there is brass available on the market. It uses any of the .357 Magnum bullets as well as bullets intended for .35 Rem.
I have always liked the .357 Maximum and heartily recommend it. One might want more bullet and horsepower for bear, but for deer it is hard to beat. It is easier to handle than the .44s and gives a better trajectory for longer shots out to about 150 yards even from 10" barrels, 200 yards from 14-15" barrels, and a good 250 yards from rifle barrels.
This little rascal shot with 180 gr. bullets in rifle length barrels comes to within about 100 ft/lbs of the same energy produced by a .308 Win. firing the same 180 gr. bullet weight......roughly 2400 ft/lbs! It is NO pip squeak!
.357 Herrett and .35 Rem. factory barrels rechambered to: .358 Bellm
This one is a bit of a beast to shoot without a brake, but it definitely gives ample capacity and stronger brass for better performance than either the Herrett or the .35 Rem. offer. Like the .308 Bellm, it, too, lets you get by with just one set of dies, .358 Win., to do all forming and loading. Again, if you want to get more sophisticated, use small base dies or standard dies plus a .444 Marlin size die.
Because there is not much difference in diameter between .35 Rem and the .358 Win case bodies, I cannot always bore out all of the factory .35 Rem. chamber runout.... but I can get most of it. With .357 Herrett, I can bore out all of the runout, making the Herrett a slightly better platform to work from building your economy dragon slayer, especially if the Herrett is one of the older barrels with the preferred 6 groove rifling configuration and closer to true .358" groove diameter. These are the better barrels.
Tip: A fair number of people have had problems dealing with the .35 Rem, and a lot of people just don't want to form .357 Herrett cases. Thus these barrels often can be picked up cheaper than most, making the .358 Bellm conversion even more attractive.
I'll deal with the .375 JDJ in the next section, but will add here that on this side of The Big Pond, I think the .358 Bellm is as good a choice as any, and certainly more economical.
.35x.444 Marlin, aka .358 JDJ, is another favorite, but I prefer the .358 Bellm, myself.
See the links at the bottom of this page if you want to go to The Bellm Triad Cartridges pages for more info.
.375 Win. factory barrels rechambered to: .375x.444 Marlin, aka .375 JDJ
So far we have dealt largely with chambers that do not require custom dies, but there is no way to get around custom dies in this instance.
I get warm and fuzzy over the accuracy from my .375 rechambers, and the cartridge has gotten all sorts of press, making it popular, but I think folks are just as well served with .358 Bellm chambers----- with one exception......
The 8 groove factory barrels run undersize for .358 caliber and generally do not turn in accuracy as phenomenal as the .375s do. There is excellent accuracy latent in the .375 Win. barrels.
.44 Magnum factory barrels rechambered to: .445 Super Mag and .444 Marlin.
Between the two, it is hard to say which I prefer..... they are both pretty awesome. To me they are much more effective than the .45/70, which I have never had much interest in.
If you really want to reach out and touch something, these are the two to do it with.
If one has .44 Magnum dies, all he needs is rechambering and .445 Super Mag Starline brass to start shooting. Since rechambering for .445 Super Mag is basically a matter of extending the neck and throat of a .44 Mag chamber for a 1.6" case, I do this conversion for less money.
HOWEVER, DO CHECK THE DEPTH OF THE EXISTING RIM COUNTERBORE IN THE BARREL AND COMPARE IT TO THE RIM THICKNESS OF THE STARLINE BRASS. OFTEN THE COMBINATION OF THIN RIMS AND COUNTERBORES CUT AT MAXIMUM DEPTH RESULTS IN EXCESS HEADSPACE THAT WILL QUICKLY SEPARATE AND RUIN THE STARLINE BRASS.
Note: Ask about case rim bending dies for bending case rims forward to correct for excess headspace.
.444 Marlin offers the advantage of factory ammo, but only 240 gr. bullets are offered. This is fine for critters up through deer size, but the concensus is that you need to use bullets 265 gr. or heavier for larger game like bear and elk. This applies equally to the .445 Super Mag.
These two boomers are exceptionally accurate when properly chambered and throated. Even factory .444 Marlin ammo generally groups around an inch at 100 yards, but both are best served by reloading.
Muzzle brakes are HIGHLY RECOMMENDED for both. The .444 Marlin passes the .45/70 for energy, and trajectory for that matter, and thus the recoil is substantial. .445 Super Mag comes so close to .444 Marlin that it leaves little for discussion. Both need a muzzle brake. I know of very few people who routinely shoot either without a brake.
This is only the tip of the iceberg so far as cartridges for the Contender are concerned. There are a lot of other possibilities, but the ones noted here are good solid performers that by and large offer a lot of good shooting at nominal cost.
If you have a factory Contender barrel that just isn't cooperating, consider one of my favorites above.