Need help with T/C Contender...

[ShooterAZ]

This is in a .223 Remington barrel. The primers are "cratering". Not flattening as in a high pressure load, but are raised up and puckered right around the firing pin and appear like a crater on the moon. It is doing it with both factory loads, and handloads, with both cast and j-words at minimum load levels.

None of my other barrels do this, and I have several. I want to figure out why it is doing this, and correct it. Is this a headspace or sizing issue? What can I do to correct this? Thanks for any advise...Shooter.

[GrizzLeeBear]

Firing pin hole too large or firing pin too small / worn?

Have you checked the headspace with a set of gauges? Any descent gunsmith will have a set of .223 gauges handy.

[kyle623]

I'm thinking get the chamber checked, tc has had issues from time to time with them

[kir_kenix]

Try just neck sizing your brass so its a snug fit on closing. See if this corrects the issue. Sometimes TC does some silly things when it comes to chambering barrels (.357 mag/max anyone!?).

[Rocky Raab]

If I recall correctly, all my Contender .223 barrels did that. That's partly why I got rid of them. It's probably a combination of three things: generous headspace, non-retracting firing pin, and that spring-loaded extractor. It seems to be an issue only with rimless rounds, which require a pivoting extractor to be able to chamber ammo.

It's not a sign of excessive pressure, as you've noted. But that also means it removes one pressure warning sign. I'd load .223 at not more than 3/4 throttle for a Contender. The round is actually outside the pressure window for the original Contender frame; it is only the small case head area that makes it usable in the gun. And even then not by much.

[45-70 Chevroner]

I have two 223 TC barrels. One 14" and one 21" I don't have any problems with either one. I don't know what the problem is with your barrel, but have you tried factory ammo in it to see what it does. It could be some thing as simple as case sizing. There could be a problem with you reloading dies. Rocky Raab could be right, but I personally do not think "Thompson Center" would sell a barrell that was out side the pressure limits of thier actions. That would open up a very big liability problem.

[paul h]

Do the other contender barrels you have opperate at the same pressure as the .223? If your other barrels are lower pressure rounds, you're not going to see cratering.

It's kind of the nature of the beast with the contender that higher pressure rounds tend to crater, but it's really not a problem. It has nothing to do with the barrel, the crater occurs due to the size of the hole at the breach face, hence you'll get cratering with any other barrel that opperates at the same pressure.

[ShooterAZ]

Thanks Guys,

I have already tried neck sizing only, and yes factory ammo does this too. The barrel shoots accurately enough. If it is the nature of the beast, I won't worry about it.

[Rocky Raab]

I truly believe it is the nature of the beast.

When I said it is outside the normal pressure limits, I mean that MOST rounds chambered for the T/C have a max peak of 45,000 psi or so. The limitation is due to backthrust on the breechface when can stretch the frame at its thinnest spot just below the side cuts. The .223 has a much higher max pressure, but because the case head has such a small total area, the backthrust is the same as a .30-30 case that runs 20,000 psi less at peak. It's the "per square inch" thing. The very low pressure .45-70 and the .223 exert almost the same amount of backthrust on the Contender, due solely to case head area.

[ShooterAZ]

Rocky,

The next highest pressure exerting barrel I own is the 7x30 Waters. I have no issues at all with this barrel, although it uses large rifle primers. I also have a 22 Hornet barrel, and it does not do it either. This IS the only barrel I have that is truly rimless. I will try some reduced loads and see if that helps.

[leadman]

The breech block is replaceable in the Contender by taking out the screw in the frame where the hammer goes forward to hit the firing pin. You can also check the firing pins when you have it out.

My barrels in 223 have all done this and it is really nothing to worry about. You may try some harder primer like the ones for the semi and full auto guns. Then you might have misfires but it would tell you if it is a primer thing.
Fire some factory ammo, measure the case just in front of the head, reload it and fire again and recheck the expansion. If it is the same or less you are good to go. You should use the same cases for the reloads as the fired factory.