Pressure loss using cast Gas Check type Bullets without Gas Checks.

[Graybeard96]

I am wondering how much pressure if any (Fps) on a percentage basis is lost using a Gas check type Bullet without a Gas Check. Presently loading .38 S&W mild loads.

Cheers

[popper]

Only if you get gas cutting. Your revolver loses a lot anyway.

[gwpercle]

I'm not aware of any pressure testing done with and w/o gas check in the 38 S&W .
Typical load is 150 gr. boolit @ 719 fps = 2.0 grs. Bullseye ... so there isn't a lot of pressure to loose ...with or without the gas check .
At those pressures and velocities the base of the boolit is not going to melt and there will be no gas cutting . The lead base will seal quite nicely ... the thing I would look at would be accuracy . Many times a gas check has improved accuracy ( most times it improves accuracy) But this may be a time , low pressure , low velocity when adding one doesn't do anything for accuracy .
Test you load both ways and see what happens . I'm not afraid of gas checks and if a boolit is cut for one , I use a check ...or ...use a flat base boolit .
Don't use a boolit too hard ...it needs to be able to fill the slightly oversize 38 S&W bore when fired .

The 38 S&W is a slightly strange round to load for ... most .358" boolits start out too small from the git go . I got best results using 148 gr. HBWC and seating them ...not flush with the case mouth ... seat the HBWC out far enough to leave adequate space in the case for powder .
Gary

[Outpost75]

Cylinder throats of most .38 S&W revolvers I have measured run .362+" and barrel groove diameters .359-.360".

I load bullets as-cast and unsized at .363" with good results. Soft-swaged .358" LRN Magtech bullets do OK with fast-burning powders like Bullseye, but you will get some leading. Hard .358 bullets are no good at all.

285796

[bakerjw]

It is my understanding that gas checks are not needed unless you are running higher velocities.
I have had this discussion with a fellow reloader a few times. He states that soft lead will lead up a barrel. The biggest factor for leading, from what I've learned here, is having a boolit not properly fit the throat and fill the grooves.
I am a proponent of powder coating boolits as I find them in the berm on our handgun range on occasion and the rifling doesn't disturb the coating.

[jim147]

I don't have a way to test it so not sure. I think bullet fit will mean more than a gas check.

[Winger Ed.]

The gas check might have a little more resistance to get on down the barrel, and lead to a higher pressure.
However; I doubt it would be enough to measure without some real expensive equipment.

For the old S&W, I wouldn't use a gas check, it isn't going fast or hard enough for any blow by or gas cutting anyway.

[Dieselhorses]

Just my 2 cents but in all my revolvers (except "big Bertha") and semi-auto's, I don't use gc's. I cast at 10-12 BHN (gets a little higher water quenching), powder coat (air cool). Regardless of gc mold or pb mold, I haven't seen the need. Of course fps stays between 700-1200. I also "slug" my bores to get an idea of whether to size or not.

[Graybeard96]

Thanks Guys,
I think I just give it a Try. If the Slugs don't Keyhole and group halve decently at under 20 Feet, I will be a happy Camper and that should work for my better halve.

Cheers

[Larry Gibson]

With such loads [2 gr Bullseye] in the 38 S&W the peak psi will be reached before the GC would enter the barrel past the forcing cone based on observing the time pressure curve of such loads in the 38 S&W.. Any resistance the GC would meet in the forcing cone would probably cause more psi to be vented at the barrel/cylinder gap which could result in a slight reduction of velocity.....whether any variance could be consistently measured is an unanswered question.