Is OAL 1.225 too short for 38 Super?

[vernonsmith]

Have been using this load for the past few weeks without any problem but am worrying there might be pressure problem? There is no indication it is over pressure at all. I am shooting a Trubor.

[Alan550]

That OAL is OK so long as the pressures don't go through the roof. I'm shooting light loads at 1.230 with no problems, but you have to adjust the load accordingly. If it feeds, fits the mag , goes bang every time and works with no pressure signs, no problem. It would have helped if you'd included the powder charge and other pertinent info.

Alan~^~

[Jaxshooter]

I am loading 10.0 gr of 3N38 with a 125 gr. Zero JHP at 1.230. The gun is an SV IMM with Schueman two port barrel plus comp. I don't have any pressure signs. I use SRP and a long FP.

[Jaxshooter]

His load is in the title 8.6 gr 3N38, but no bullet weight.

[vernonsmith]

Argh... sorry. Yup the load is 8.6g 3N38, 125g projectile, Federal small rifle primer 205 with a little crimp just to remove the belling from a Dillon Square Deal machine.

[G-ManBart]

Have been using this load for the past few weeks without any problem but am worrying there might be pressure problem? There is no indication it is over pressure at all. I am shooting a Trubor.

What weight bullet? Have you chronographed it? I've used 10.0gr of 3N38 with a 115gr JHP at 1.230-1.235" (they always vary a thousandth or two either way) and it showed zero pressure signs.

VV shows a load with 8.9gr and a 130gr FMJ in .38 Super Lapua cases which have a bit less case volume than Super (which means you'd be able to go a couple of tenths more with a standard Super case to get the same pressure).

If the gun like the oal, the velocity is what you need to make power factor, and you're not seeing pressure signs, I wouldn't worry about it.

Just keep in mind that all using a shorter OAL does is get you to the same pressure as a longer OAL, but with a bit less powder, and it's often less critical with the slower powders like 3N38 than it would be with something faster.

VV actually lists loads as high as 190PF in Super with a 147gr XTP and N105 (8.5gr). In comparing 3N38 and N105 with 115gr and 121gr bullets I found it took a pretty consistent .5gr more powder with N105 to get the same PF. If that translates to other bullet weights even reasonably well, that would put a max charge of 3N38 at something like 8.0gr with a 147gr XTP...give or take.

[G-ManBart]

Just saw you listed the bullet as a 125gr....you're fine. VV lists a max load with 123gr FMJs and 9.6gr in a Super Lapua case. Even taking into account the difference between Super Lapua and Super, you should still be .5 to .8gr below max. R,

[vernonsmith]

Gee thanks for all the helps and infos guys, really appreciate it. Argh.. again forgot to mention PF is 170 which is where I like it to be. Brass are Starline 38 Super +P. The gun seems to like the load and zero malfunction. No problem with feeding and extracting. Cases are thrown about 2 to 3 metres 4 o'clock position using an Aftec. I like to load short to let the bullet to compress against the powder as I heard the extra room for air inside affects the velocity from a cold winter weather to the hot summer weather, or is this a myth?

Edited March 11, 2010 by vernonsmith

[G-ManBart]

I like to load short to let the bullet to compress against the powder as I heard the extra room for air inside affects the velocity from a cold winter weather to the hot summer weather, or is this a myth?

Wow, I don't think I've heard that one before. It's a great question, and I'd love to know the answer.

I'd go out on a limb and say I really doubt that open space in the case makes any difference in velocity hot or cold. I'm pretty sure that each powder varies with temperature based upon it's own characteristics more than whether there's more or less open space in the case. The other thing is that VV powders tend to be very temperature stable, so it may be even less of a factor to consider.

I would expect that the bullseye shooters would know more about this if anybody does. They can't accept anything but the best accuracy and they're using very small charges of powder that invariably leave a lot of open space in the case.

I like to set the OAL for what the gun likes and everything else is a distant second. Most Super/SC guns seem to work really well at 1.235, but if you're getting good results with 1.225" there's no reason to change. R,

[XRe]

If the gun like the oal, the velocity is what you need to make power factor, and you're not seeing pressure signs, I wouldn't worry about it.

This

VV actually lists loads as high as 190PF in Super with a 147gr XTP and N105 (8.5gr).

I've even entertained using that load to take some piggies...

Wow, I don't think I've heard that one before. It's a great question, and I'd love to know the answer.

I'd go out on a limb and say I really doubt that open space in the case makes any difference in velocity hot or cold. I'm pretty sure that each powder varies with temperature based upon it's own characteristics more than whether there's more or less open space in the case.

Also this... Now... there could be an argument that as the powder expands/contracts to take up some of that air space, it could alter the effective case volume, but... I wouldn't really buy that. Most powders will have some type of response to temperature - some will actually respond in reverse of what you'd expect (that is, your loads get hotter as the temperature goes down... 7625 is one example). Some of them may get erratic, as well, at some point...

The other thing is that VV powders tend to be very temperature stable, so it may be even less of a factor to consider.

Ummmmm.... I haven't seen much in the way of temp issues with N105, but N350 had some effect for me, and N320 changed quite a bit (over half a grain between winter and summer in my gun w/ my .40 load). So, I don't think you can make a blanket statement about VV stuff

[Pat Miles]

. I like to load short to let the bullet to compress against the powder as I heard the extra room for air inside affects the velocity from a cold winter weather to the hot summer weather, or is this a myth?

I find this hard to believe. Figuring the bullet, brass cartridge and powder are going to be at the same temperature, hot or cold, I doubt that a tiny air pocket would have any effect on the velocity from a temperature standpoint. I would be more concerned with a compressed powder situation but as Bart mentioned 3N38 is a very forgiving powder.

A suggestion when building loads for a gun. Use small pistol primers for the load development. Having a softer cup they will show pressure problems earlier than small rifle primers. After finding the load of your dreams you can use the small rifle primers.

CYa,

Pat

[Action Pistolero]

I like to load short to let the bullet to compress against the powder as I heard the extra room for air inside affects the velocity from a cold winter weather to the hot summer weather, or is this a myth?

I have just recently heard about this. This guy was loading 9mm with 231 and was not seeing the normal slower velocity when cold and faster when hot.

As soon as I can get my gun back from the smith I will be loading my 9x23 to a OAL of 1.220" with a Sierra 115 JHP. I'm anxious to see what it will do with velocity and pressure. It would be nice to minimize the temperature effects that I'm seeing with WST.

[gm iprod]

I did some research on this myth / thoery some years ago.

It would seem that with certain slow burning powders and most (but not all) ball powders there can sometimes be a little variation when the case is less than 90% full. Obviously with fast powders filling the case with powder may be a bit of a problem as far as safe pressures are concerned.

It has as much to do with case volume as temperature variation, but if you are trying for minimum ES and loading hot at the same time then some care is to be used.

Now my 38Super AP gun runs about 1180fps with a 115gr using 4.8gr TG, it would at best fill the available space below the projectile to about 70% no more and possibly less. I run 115gr JHP Zero at 1.225". With a 125gr JHP I run 4.0gr, you can double charge it easily and still not touch the powder with the projectile, I did ONCE. Both these loads generate the same speed here in New Zealand in Fall as they do in Missouri in your spring. Seeing as I used to bring ammo up for the Bianchi Cup.

When I loaded some slower burning powders here where I live and went away to a shoot 6 months later, much colder and somewhat less humid, I noticed that my ES was very high and teh average had fallen by some 5%, can't remember the exact data but I very nearly got dropped to minor. That was with N350 and a 125gr JHP.

Ball powders show some signs of increasing velocity and increased ES when it gets cold. Unless as some have suggested you reduce the air space appreciably. Flake powders (primarily designed for Shotgun) like Green and or Blue Dot don't like having air space, remember shotguns have the wad pressed onto the powder to allow the heavy (by our standards) projectile sit into teh sace properly.

Sometimes making sure the crimp suits the load will help. SOme powders like a little mnore crimp if you are at less than 90% Load density. A lot of this is down to experimentation with the components you have at hand top determine you best coarse of action.

I now no longer bring ammo up to teh Bianchi Cup. I am lucky enough to be able to stock pile all the components I need for myself and just load what I need when I get there. That way the ammo is fresh and made to suit the exact conditions I am about to shoot in.

[G-ManBart]

Ummmmm.... I haven't seen much in the way of temp issues with N105, but N350 had some effect for me, and N320 changed quite a bit (over half a grain between winter and summer in my gun w/ my .40 load). So, I don't think you can make a blanket statement about VV stuff

I haven't finished my testing (need the weather to change more), but I've actually seen a bigger difference with N105 than I have with N350 or N320. I'm not saying that VV powders don't show any sensitivity, but they aren't known to vary a great deal like some others are. That's why I said that they "tend to be temperature stable and may be less of a factor"

The other factor is that the individual gun will have some influence on any change brought about by temperature, so it's not purely a powder thing. Two guns with the same ammo may very well show different increases or decreases in velocity based on temp...I'd bet that's more true than we realize, it's just not something people are likely to really test for. Now I wish I'd done more cold weather chrono work with my backup Open gun to compare as it gets warmer....drat, project for next winter. R,