Contender barrel not closing

[xgrunt1944]

Just as a matter of interest - a couple of years ago, I finally got around to trying out my second-hand .357 barrel in my G2 Contender (old model). I had a lot of my own cast 180 grain Silhouette bullets, gas-checked and I loaded some of them in W-W .357 cases with 10.5 gr of Alliant 2400. They went 'bang' OK, but the TC was VERY hard to open, to the extent that I had to "dry-fire" on the empty case a couple of times before the gun would open. (I assume the primer was being blown back some?) I tried the same load with Federal SP primers, Remington SP Magnum primers & Federal Small Rifle primers and I also tried using a roll crimp and a taper crimp. - same result. Then a mate of mine, who is a trained gun-plumber, suggested I up the load to 12 grains of 2400, and Lo! It worked! I have no idea why an increase in powder charge would work, seems counter-intuitive to me, but it does. Depending on the crimp, I'm getting between 1330 and 145 fps from this 10" barrel. Perhaps someone out there has had a similar experience or has an answer?

[Tatume]

Welcome to the list.

The most common cause of the condition you described is the old one-piece locking bolt. If you can get your hands on a newer "split" bolt, you may find that replacement alleviates the condition.

[dale2242]

My guess is that the load was not expanding the case enough to make it grip the chamber and it was backing into the frame locking the gun.
Dry firing was pushing the case forward enough to allow the gun to open.
Welcome to Cast Boolits...dale

[Parson]

Another possibility, upon firing all primers back out, most to the bolt face, then as the bullet leaves the case, gases expand etc, the case backs up to the bolt face and resets the primer, sometimes with light loads the case does not get set back far enough or hard enough to reset the primer

[wonderwolf]

I'm with the school of thought the load was not hot enough, one extreme example I have is a issue like this with experimental 500 S&W mag loads using very light bullets 65gr and traveling around what we thought was at least 2500 fps. The issue was the dwell was no wear near long enough nor the pressure high enough to seat the case back, in turn the primer backed out and tied up the cylinder.