38spec &44spec blowby in magnum chambers

[olafhardt]

It seems to me that it would be virtually impossible not to have blowby when shooting specials in magnum chambers since the area between the case mouth and the throat is not filled. I read people talking about how well it works to ream out a 357 handy rifle to 357max. Does this sacrifice accuracy in lower loadings?

[Bret4207]

I'm not sure if I follow you exactly, but the case will expand to seal the chamber area and the boolits front drive bands will be in the throat before the boolit exits the case with most normal boolits in those calibers. So, given proper dimensions and fit, that extra 1/8" or so of the Mag chamber should be nearly inconsequential.

HAve you ever seen blow by shooting shorts in a 22 LR chamber? Neither have I.

[williamwaco]

. . .since the area between the case mouth and the throat is not filled. . .




Imagine if you will a revolver cylinder alligned with the barrel.

The .38 special cartridge is there just waiting for the hammer to fall. There is a space in the cylinder between the case mouth and the cylinder gap. Depending on the length of the cylinder this will vary but in a K-Frame Smith it will be 0.556".

Now replace that .38 Special cartridge with a .357 Magnum. What has changed? The .357 Magnum case is .135" longer than the .38 case so that gap has shrunk to 0.421" but it is still there.

So, the ". . . throat is not filled . . . " in either case.

That said, most blowback is caused when the powder charge is not heavy enough to expand the diameter of the case to fill and obturate ( seal ) the cylinder. It has nothing to do with the length of the case.

[firefly1957]

The only problem I have encountered was fouling from shooting a lot of 38"s then not being able to put in a magnum until chambers were well cleaned but it took a couple hundred 38 wadcutters in a short time.

[GP100man]

That .135" space is what the OP is refering to , the boolit jumping this gap to the throat of the cyl.

To answer your question is to take some measurements of the boolit to the front driving band .

For simplifying things lets say it`s .500"

The throat is .500"

So the rear driving bands that are exposed to hi pressures is .135" since .365" is in the throat already .

Then the driving bands are subject again to hi pressures the length of the forcing cone when it makes the jump from the cyl. to the barrel.

This is why it`s easier to get a longer boolit to shoot more easily from a 357 magnum or any revolver for that part.

& yes the whole side get a bit of blow by when the case seals the chamber ,how much is a timing thing & powder burn to peak pressure.

[tommygirlMT]

I think the OP is refering to blow by around the boolit not back around the case --- case sealing is a matter of pressure and case wall thickness --- I have had a few light loads in heavy 454 brass not seal correctly due to thick brass wall cases at low pressure but that has nothing to do with whether they are fired in a longer chamber (460 mag for example) or not

To answer the question --- I think its mainly a question of how big a gap vs. how long a boolit --- you fire off a load in 45 cowboy special brass (shortened 45-Colt brass) in a 460-mag chamber you are going to have blow by problems unless your using a boolit that is really long which wouldnt make sense since usually you load light weight boolits in 45 cowboy special --- but I think for the OP original question (357 max) he shouldnt have too many problems with shooting 357 mag in the chamber since 357 max case length is 1.605" and 357 mag case length is 1.290 so that is a gap of 0.315 which the bearing length on most boolits is longer then that --- might have a problem with 38 special (1.155 case length) since that would produce a gap of 0.450 which is getting a little long compared to the bearing length of some boolits --- yah a lot of boolits have longer bearing length then that but how much longer?

[Bwana]

I'm not sure if I follow you exactly, but the case will expand to seal the chamber area and the boolits front drive bands will be in the throat before the boolit exits the case with most normal boolits in those calibers. So, given proper dimensions and fit, that extra 1/8" or so of the Mag chamber should be nearly inconsequential.
HAve you ever seen blow by shooting shorts in a 22 LR chamber? Neither have I.

The .22LR analogy does not apply as the case and the bullet are the same outside diameter in both rounds.

[whisler]

I was just wondering yesterday if the 357 Magnum Handi-Rifle would take the pressure of a 357Maximum. Anyone know if this is a good idea? I think I would really like a 357 Maximum single shot rifle.

[MT Gianni]

I did it with a 357 mag bbl. No pressure problems at all, the gun is rated for 300 win mag.
Accuracy with 38 special is not as good as the same loads in 357 Max brass but well under 1" difference at 50 yards. I mean a 150 gr 38 groups around 1 1/4", 357 Max 3/4". Step up the pressure and the 357 Max steps further ahead. That is my theory anyway, gun has a 3x Weaver and I have only tried it with two comparison loads. I bought it to shoot the 357 max with, not a lot of 38 plinkers. As casters, we can plink with a lot of calibers.

[Bret4207]

The .22LR analogy does not apply as the case and the bullet are the same outside diameter in both rounds.

Yeah, okay, whatever. It was the most common "short cartridge in a long chamber" I could think of. How about I use the 32 S+W and 32 Mag? Never had any blow by/gas erosion there either.

[smkummer]

The only issue I have when shooting 38 special in my Colt .357 chambered guns is what was stated earlier that after several rounds, .357 will not chamber without force. That is why I always use solvent and a brush after shooting 38 in my .357 chambers. It I don't, the accumulated fouling is very hard to remove. Often when shooting 38 special in 38 special chambered guns, I just wipe off the outside surface of the gun and put it away.

[Bwana]

I did it with a 357 mag bbl. No pressure problems at all, the gun is rated for 300 win mag.
Accuracy with 38 special is not as good as the same loads in 357 Max brass but well under 1" difference at 50 yards. I mean a 150 gr 38 groups around 1 1/4", 357 Max 3/4". Step up the pressure and the 357 Max steps further ahead. That is my theory anyway, gun has a 3x Weaver and I have only tried it with two comparison loads. I bought it to shoot the 357 max with, not a lot of 38 plinkers. As casters, we can plink with a lot of calibers.

The NEF handi-rifle is not rated for the 300 Win Mag.

"Yeah, okay, whatever. It was the most common "short cartridge in a long chamber" I could think of. How about I use the 32 S+W and 32 Mag? Never had any blow by/gas erosion there either."

Sorry if I offended you. I was just trying keep the info correct. Too many people take anything posted as gospel, especially when they see it posted from someone with as many posts as you.

[Larry Gibson]

Blow by from lower pressure rounds not expanding the cases to seal the cahmber is the problem. Not enough psi to cause erosion.

Bajillions of .38 low psi practice loads through police .357s over the years show there isn't a problem. Most all low end cowboy action loads give blow by and they shoot a lot without problems of erosion in both revolvers and rifles.

Bret; shot some S&W, S&WL RNs and S&WL HBWCs out of my Ruger Single Six .32 H&R Magnum just yesterday. All had blow back around the cases and it was fun watching the bullets go down range to the 25 yard target.

Larry Gibson

[Bret4207]

"Yeah, okay, whatever. It was the most common "short cartridge in a long chamber" I could think of. How about I use the 32 S+W and 32 Mag? Never had any blow by/gas erosion there either."

Sorry if I offended you. I was just trying keep the info correct. Too many people take anything posted as gospel, especially when they see it posted from someone with as many posts as you.

Great gobs of goose grease man!!!! Don't ever take anything I say as gospel! I wasn't offended, irritated with myself maybe, but not offended. Got a fever going and the meds are making me a little loopy.

[Hang Fire]

The only problem I have encountered was fouling from shooting a lot of 38"s then not being able to put in a magnum until chambers were well cleaned but it took a couple hundred 38 wadcutters in a short time.

Ditto with me, the fouling ring buld up was the only problem I ever encountered.

[9.3X62AL]

Bret being loopy--someone get video, I see a YouTube moment on the horizon. :)

I never noticed a significant accuracy fall-off shooting Specials in Magnum revolvers. I did get annoyed at the carbon ring that formed ahead of the short case's mouth, though. PITA! So I use cases that actually fit these days. Probably the WORST case of that condition appeared in my S&W Model 16-4......a friend's daughter ran about 300 rounds of 32 SWL reloads through the revo (she REALLY liked the gun), and the carbon belts in the charge holes were DOGMATIC.

[Mk42gunner]

Bret being loopy--someone get video, I see a YouTube moment on the horizon. :)

I never noticed a significant accuracy fall-off shooting Specials in Magnum revolvers. I did get annoyed at the carbon ring that formed ahead of the short case's mouth, though. PITA! So I use cases that actually fit these days. Probably the WORST case of that condition appeared in my S&W Model 16-4......a friend's daughter ran about 300 rounds of 32 SWL reloads through the revo (she REALLY liked the gun), and the carbon belts in the charge holes were DOGMATIC.

Gee whiz Al, what's not to like about a .32 caliber K-frame? Another one of those I wish I had bought one when they were making them guns.

Oh well one day when the finances improve...

Robert

[firefly1957]

Hold on a minute I have had problems with my Model 17 S&W i shot a box of shorts in it and then could not chamber a long rifle cartridge in five of the cambers.

[BAGTIC]

I was just wondering yesterday if the 357 Magnum Handi-Rifle would take the pressure of a 357Maximum. Anyone know if this is a good idea? I think I would really like a 357 Maximum single shot rifle.

At one time the Handi-Rifle was factory chambered in the .357 Maximum. I have one.

The .44 Magnum cartridge for which the H-R is also chambered creates more strain on the action than the .357 Maximum will and many owners have rebored their .44 Magnums to .445 Super Magnums with no problem..

[troyboy]

"No pressure problems at all, the gun is rated for 300 win mag." Where did that come from? Ya better research a little more on that one. Maxi is fine but not a 300WM