Factory .357 Max Contender barrel shoots low

[Whistler]

I've got a T/C factory made 14" .357 Maximum barrel for my Contender pistol. There are many reports that the Max has a overly long forcing cone cut instead of a nice rifle style chamber. This gives a free flight of about an inch... I still bought it and I love the cartridge, it is one beautiful piece of brass!

What I'm experiencing is that when shooting .357 Magnum out of it I have decent accuracy and I can adjust my sights normally (I outfitted it with the Bomar front and rear sights). However, when using the Maximum brass I find myself shooting about 3 feet low at 50 yards! I have to crank the sight up so that it almost let's go of the threads to hit point of aim.

The loads I've tried are with a 219gn TC that I've seated to .358" depth and then taper crimped to remove the belling. Loads have been 17-19gn Vihtavuori N110.

So here's my theory... The primer strike makes the boolit start moving before a proper ignition has taken place in the powder. Normally with a rifle cut chamber the boolit would stop somewhat at the lands and the ignition could go full force. However with the long free flight there is a dump of pressure and an extreme loss of velocity.

There could be two solutions to the problem:

1. Use a 240-250gn boolit for .35 Remington so that I can seat it to the lands but still have some case tension.

2. Seat the 219gn TC deeper (and reduce powder charge) so that the crimp groove is flush with the case mouth and do a proper roll/profile crimp, mimiking the way the .357 Magnum probably behaves.

The purpose is silhouette shooting, both on paper and steel up to 300 yards (yes, we do that in Sweden).

Am I on the right track or just way out in the air?

[Shooter]

Are you crimping your Max loads?

[uscra112]

What is your .357 Magnum load? Compared to the Max load you stated? I'm thinking about barrel time.

The SAAMI reamer for .357 Maximum does have a shallow leade taper starting right at the case mouth. It's not all that long, and the chief disadvantage is that the heel of the boolit isn't guided as it leaves the case neck. There's not a thing you can do about it except to seat way out. (That of course gives you more powder space - never a bad thing.)

The canonical boolit weight for the Max is 180 grains, by the way. I do use a 200 grain 358315 for deer, but only because that's the mold I've got for .35 rifles. (Old .35 Rem addict.)

Vihtavuori 110 is a too fast for the Max, especially with heavy boolits. Best powder in my testing so far is Lil'Gun. You'll get a lot of argument about that, but Lil'Gun is what works for me. I roll crimp pretty tightly, even though I reamed my barrel with a proper throat and can seat into the lands, the firm crimp and about .050 back from the lands gives me better S.D. over the Chrony using Lil'Gun. Lot of guys swear by AA1680 and H110.

[357maximum]

You really only have one GOOD solution. Load everything in MAX brass and shorten the height of the front sight.


or



Shorten the front sight somewhere to where the tracking on the rear sight will be suitable for both loads with minimal adjustment.


Sidenote: After shooting mag brass make sure you clean the chamber real well before shooting max brass.....trust me on this one....it will ring your chamber if you do not. :cry:

[Whistler]

You're getting me wrong here, guys. I'm not looking for a new front sight or a way to continue using .357 Magnum brass... What I'm looking for is the reason to why there is a totally different ballistic profile to the longer cartridge. I'm thinking there is an unusually large pressure dump right as the bullet exits the case mouth. This does not seem to happen when using Magtech factory .357 Magnum cartridges.

I measured how long the cartridge would have to be for the boolit to be seated against the lands. Here you get an idea of how ridicilously long the chamber throat is:

http://img402.imageshack.us/img402/1711/20120111204338.jpg

[Ben]

Whistler

I can't help but ask this question :

What did the T/C factory hope to accomplish ( other than dealing you " reloading misery " )
with a throat that long ?

[stubshaft]

T/C made the long throat to reduce pressures. The reason for your discrepancy may be that your 357 load is too wimpy. The longer throat has nothing to do with you shooting low. No you are not "dumping" pressure, if you were you would get zero accuracy and extreme leading from the erosion of the boolit, if that were the case then the mag would be even worse off because of the extra distance it has to travel. Use 296 or H110 to load the maxi and crimp it in the groove, if you are trying to short seat the maxi to engage the rifling earlier then you are creating a lower pressure situation.

I have shot tens of thousands of maxi's out of both 10" and 14" Tenders and the only thing that would create such a situation is an extreme velocity difference or a flinch.

[Whistler]

When sight is adjusted it groups about 4" at 120 yards, so I doubt it is flinching. ;) It is way too inaccurate for my taste though...
What could cause the velocity difference other than a loss of pressure caused by leakage?

The case is almost full... If I go to a slower powder it would be a heavily compressed load.
As I wrote above I did increase/decrease powder charge depending on seating depth to keep the pressure/velocity/fill rate as similar as possible for the different loads.

How would a factory j-word bullet get eroded? I do have some leading with the 219gn TC-bullet, and using the same in my Mod 28 .357 Mag revolver gives no leading. The boolit is slugged .357 and the bullet is .358 and has a gas check. I believe this is a clear sign that the gas flows past the boolit before it has had time to enter the lands.

[stubshaft]

I understand your contention but again if that was the case the mag problem would be magnified because it travels slower and has a longer jump to the leade. You simply cannot have pressure "dumping" from the maxi and not from the mag.

A friend of mine advised me to buy some TrailBoss for my 500 S&W. The difference between my standard load and the much slower TB load was about ten inches at 25 yds. Accuracy wasn't the issue but I had to make another front sight to keep it anywhere near the black. The faster velocity boolit almost always shoots lower as the bullet is in the barrel for a shorter time.

You could load both the 357 and the maxi with the same charge of let's say 2400 and utilize the same boolit. When shot at 50 yds the maxi should print a little higher due to the increased airspace lowering the velocity slightly.

I would try 20.0 of 296 with the TC boolit and go from there.

There may be such a disparity between the mag and the maxi that you may have to use two different sights.

[218bee]

I use H110 with a 180gr Hornady SSP boolit and it has shot very well for me. Velocity is around 1800fps. BUT I bought this barrel with a scope so cannot comment about the height of the sights...Ive never shot 357mag in it.
As stated above if there was a problem with overly long leade..it seems it would be worse with the mag case as it is shorter than the max case

[Jon K]

Shorter front sight.

Jon

[Whistler]

I understand your contention but again if that was the case the mag problem would be magnified because it travels slower and has a longer jump to the leade. You simply cannot have pressure "dumping" from the maxi and not from the mag.
The magnum has a proper crimp, giving time to reach a proper ignition and pressure to seal the chamber walls before the bullet leaves. The maximum probably has the bullet halfway out just from the primer strike. I'm with you on the barrel time though, I just feel that it is very strange that the BoMar sights would be so ill fitted for the .357 Maximum.

If any of you have the BoMar rear sight for your Maximum barrels, what height do you use for the front sight?

[stubshaft]

I used the Ken Light Bomar rear with an adjustable front.

I'm sorry I forgot you were in Sweden and aftermarket parts may not be as available to you. I have modified the T/C front sights too by drifting out the roll pin and either filling the bottom of the sight so that it sat deeper in the groove or pulling it out slightly to raise the front height. T/C has 4 different blade heights but getting anything from them since their move is very difficult. BTW - after making the height adjustmens I use either solder or epoxy to lock the blade into the base.

[357maximum]

I would only do one thing with that barrel if I wanted to keep it. Buy an extractor for the 35rem and rent a reamer. TC should be given a boot to da head for doing what they do to Max chamber/throats. It is simply apalling. :sad:

[jblee10]

I love the 357 max, but it really was never loaded correctly by the factory to take advantage of more powder capacity. The factory has typically loaded it with lighter bullets than you are using. BUT!!!! A heavier bullet should increase barrel time and shoot higher. So I'm at a loss why you are shooting so low. I did have a Contender 22lr barrel that had the wrong front sight on it. (I think actually it is the rear sights that are different). I couldn't get it to shoot low enough. I drove the pin out, raised the front sight blade and drilled and reinstalled the pin. I suppose you could do the same by grinding the bottom of the sight blade and reinstalling in it a lower position.

[Whistler]

Yes, that was my thought as well. A 220gn .357 Max should shoot to pretty much the same POI as a 158gn .357 Magnum.

[Whistler]

I really should learn to take a closer look at things. I removed the front sight hood to measure the sight. I guess getting a shorter front sight is easier than I thought...

http://img37.imageshack.us/img37/5119/20120306182033.jpg

(For the record I am still baffled as to why there are different POI with Max and Mag)

[stubshaft]

LOL - Looks like a Lansing front sight. Now adjustments are ever so much easier. They don't come adjusted for anything when new, so you got lucky with the mag POI.

[Whistler]

I didn't wanna wreck the old front sight, but luckily I had some screws that were similar, however somewhat shorter. But wasn't shorter the whole idea from the start, right? ;)

Bring out the Dremel! It took some time, but finally I was satisfied and had decently straight edges.
http://img849.imageshack.us/img849/9554/20120308182028.jpg

Some cold blue (selenium dioxide):
http://img12.imageshack.us/img12/5831/20120308182156.jpg

And some olive oil for hardening the blueing:
http://img26.imageshack.us/img26/2279/20120308184415.jpg

I'm pretty much satisfied with the end result (I just wonder how it will shoot!):
http://img714.imageshack.us/img714/3136/20120308231108.jpg
http://img267.imageshack.us/img267/7218/20120308230858.jpg

My experience with milling and other metalworking is limited to listening to Metallica, so the Dremel was my best shot.

[stubshaft]

Looks great Whistler.

[357maximum]

I didn't wanna wreck the old front sight, but luckily I had some screws that were similar, however somewhat shorter. But wasn't shorter the whole idea from the start, right? ;)


My experience with milling and other metalworking is limited to listening to Metallica, so the Dremel was my best shot.





It looks good......might shoot too high now though. Thats alot of difference....might have to buy a screw and split the difference. A conjecture of MAYBEHAPS????


I did not realize Lars Ulrich offered a shop class.:p Thanks....that tickled me....and I needed tickled. [smilie=l:

[Whistler]

I calculated that I needed a front sight that was 6.7mm lower than the old one. The new one is 6.0mm shorter and I screwed it a few threads lower. I want the rear sight to be driven to almost to the bottom at 50 yards so I have plenty of elevation left for up to 330 yards.

[Whistler]

New front sight works great, I can adjust the rear sight to a perfect hold now.
Accuracy with the long throat seems doomed though.

After a whole lot of measuring I came up with three different loads where I had 100% case fill with Norma 200 powder.
On one the bullet seated deep to the crimping groove, the second a bit shallower and the third was really let out so that even the lube groove was outside the case. Keep in mind I still had 100% powder fill rate on all three loads, ranging from 21gn on the shortest to 28 grain on the longest.

Funny thing... All three loads held about the palm of my hand at 33 yards (30 meter), meaning they were all equally bad. The only thing I can think of to help is to get a 240-250gn boolit made for .35 rifles and seat it so it touches the lands and get proper stearing right from the beginning.

[PanaDP]

In BP cartridge rifles that have a relatively low muzzle velocity and relatively high recoil, this same thing can happen. The usual explanation is that the slower cartridge leaves the barrel slower and you are into the recoil phase by the time it exits. Recoil involves the barrel rising. If you try the same thing with a faster velocity, the bullet is out of the barrel by the time the muzzle is rising from recoil.