What is "special vented barrel" in 38 special testing, how does it effect load data?

[clearwater]

Lyman #47 and #49 differ greatly in load data for the 358429 (170 grains) Keith bullet.

Example #47 max load Unique 5 grains, 860 FPS
#49 max load Unique 4.2 grains, 841 fps

same OAL, same barrel length-- difference is "special vented barrel in the #47 manual.

What is that all about and what data should I use?

[poppy42]

Well first off you should never start with a max load you should always work your way up.I would suggest you start with a load in the middle of the load data and work your way up from there. Check for signs of high pressure on the way

[skeettx]

Vented pressure barrel

https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.3-CFP-and-R-Approved-2015-12-14-Posting-Copy.pdf

Page 18
2)Vented barrel velocities are provided for information only.Vented test barrels are used for the establishment of catalog velocity values for cartridges normally chambered in revolvers.

And sooooo vented means introduction of a cylinder gap

Mike

[clearwater]

Well first off you should never start with a max load you should always work your way up.I would suggest you start with a load in the middle of the load data and work your way up from there. Check for signs of high pressure on the way

Yes mom, by the way how do you check for pressure signs in a 38 special revolver?

[clearwater]

Vented pressure barrel

https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.3-CFP-and-R-Approved-2015-12-14-Posting-Copy.pdf

Page 18
2)Vented barrel velocities are provided for information only.Vented test barrels are used for the establishment of catalog velocity values for cartridges normally chambered in revolvers.

And sooooo vented means introduction of a cylinder gap

Mike

It doesn't effect pressure but does velocity is what they are saying. The reduction in charges between manuals by Lyman has nothing to do with pressure measured in the two different barrels, but will show slower FPS with the vented barrel.

No explanation about the difference in min and max charges then? It looks like several powders are effected.

[Winger Ed.]

Kid,
A vented test barrel is one that duplicates the cylinder gap like a revolver has.

A real good sign of high pressure in a revolver is when you have difficulty pulling out the spent cases.

[clearwater]

Can expect I the velocities in the old manual with the vented barrel to be more accurate then?

Also what is difficulty in removing the brass? Factory loads in my Blackhawk have to be pushed out but my cowboy loads fall out. "Difficulty" as in hammering out? Do a ladder test and at some point decide it is too "difficult" to push them out?
In the past I used book velocities and a chrony to keep things in the ballpark. So back to my original question, what data for that?

[VariableRecall]

From my experience with a couple of bad apple handloads, a factory cartridge should require gentle pressure to extract from the cylinder. However, hotter loads require a firm amount of pressure or a good slap to get moving out of the cylinder. Always use factory ammo for reference if you're wondering about the firmness relationship from round to round.

[farmbif]

when putting together a new load it is always smart and safest to start at the low powder charge listed in a data book and work your load up.
and when using data that just gives one powder weight, like the Alliant online data, starting load is 10 percent less powder than the max load which is what they post in their online data.
ill let some of the more experience experts here on the site explain what high pressure indications might be.
one bad load can very quickly cause firearm damage, injury or even death. reloading in a safe Manner is the only way to live.

[clearwater]

when putting together a new load it is always smart and safest to start at the low powder charge listed in a data book and work your load up.
and when using data that just gives one powder weight, like the Alliant online data, starting load is 10 percent less powder than the max load which is what they post in their online data.
ill let some of the more experience experts here on the site explain what high pressure indications might be.
one bad load can very quickly cause firearm damage, injury or even death. reloading in a safe Manner is the only way to live.

Wow, did you read the questions? Its like calling IT and being asked repeatedly "Did you try turning if off and on?"

[farmbif]

I read the question, someone else answered it, but with the talk about what load to start with, in my opinion the lowest is what you start with, 4.2q gr, excuse me for butting in on reminding of being safe when reloading.

[Texas by God]

19 FPS difference is within the margin of error. If you want to start out with the max loads, use your Blackhawk. Your gun will tell you if the loads are too warm by hard ejection. Your gun will tell you which load is more accurate if you are shooting well that day. Your question was answered. Different editions of the same manual reflect differences in that days bullets/powder/primer combo tested on that day. No one gave you a bad answer; when you start a post talking about maximum loads, you will- and should- recieve advice about loading safety.

[blpenn66502]

As to what data to use? The data from the 49th. Why, I'd say because they actually retested loads for that particular combination and probably measured the max pressure in psi rather than using the old cup method. Not every load is retested with each new manual publication. My 1973 Lyman cast bullet manual shows 5gr unique as max with that bullet at 925fps and 15,800 CUP (7.71" universal receiver). I was disappointed when I got the Lyman Cast Bullet Handbook, and it was clear some cartridges weren't updated, e.g. 45 AR.

With respect to your pressure question, one way to get an idea for pressure is to fire some factory load and measure head expansion to give you a baseline measurement and compare what you get with a reload of the same cases. Micrometer, not calipers. Not crazy precise, but a method if you don't have a real pressure testing set up like Larry Gibson.
My $0.02

Sent from my LG-H918 using Tapatalk

[Kosh75287]

I HAVE started with the "max" load in .38 Special cases, but only when shooting them in a .357.
When working up .38 Spl ammo for use in .38 Spl. revolvers, I try to back off the max load by at least 5% and 10% is usually better. All other things being equal, use the more recent loading data for work-up. Sometimes, between reloading manual editions, one propellant or the other might be reformulated to burn cleaner, meter better, or whatever, and in the process, its burning rate might change. If the burning rate changes, the reloading data will almost certainly change, also.

"Special Vented Barrels" are a confusiion to me, but appear to be some attempt to approximate the velocity loss experienced when a round is fired from a revolver, vs. an unvented test barrel. Here again, I'm a big believer in the "all factors being equal" proviso, and suggest that the lowest reported velocity be used as the most optimistic estimate of actual velocity for a given load.

[Outpost75]

At the pressure levels generated by .38 Special standard and +P head expansion and primer flattening are not reliable indicators, as these don't come into play until you far exceed proof pressure. Instead I benchmark standard and +P factory loads in in my guns and attempt to approximate those velocity levels for similar weight and shape bullets with approximately equal seating depth in my handloads. Larry Gibson's published pressure data being a sanity check.

[M-Tecs]

At the pressure levels generated by .38 Special standard and +P head expansion and primer flattening are not reliable indicators, as these don't come into play until you far exceed proof pressure. Instead I benchmark standard and +P factory loads in in my guns and attempt to approximate those velocity levels for similar weight and shape bullets with approximately equal seating depth in my handloads. Larry Gibson's published pressure data being a sanity check.

I just wanted to say thanks to folks like you and Larry for continuing to share your extensive actual knowledge and experience as opposed to regurgitating some of the same old misinformation about checking for pressure signs in cartridges that require SAAMI pressures to be doubled or tripled before pressure signs appear.

I've been loading 45 Colt's since 1968 for 1873 Colts. Recently I've been loadings for a 460 S&W and yes I have loaded 45 Colt brass to the point it shows pressure for use in the 460.. My guess is that's 250 to 300 percent over SAAMI for the 45 Colt. Point in some firearms/cartridge combinations the first sign of overpressure sign is the firearm coming apart.

[Larry Gibson]

"A real good sign of high pressure in a revolver is when you have difficulty pulling out the spent cases."

A "real good sign of high pressure" for sure!

With normal chambering these days that indicates 40 - 45,000 or more psi. With older or newer revolvers having burnished chambers sometimes even more.

[Outpost75]

Having to stretch the crane arbor on an S&W to remove end shake after firing only one box of ammo is a sure indicator of high pressure too!

[poppy42]

Yes mom, by the way how do you check for pressure signs in a 38 special revolver?

Ah how bout split cases blown out primers and a few other signs. Kinda like checking for precious signs in any cartridge.

[M-Tecs]

Ah how bout split cases blown out primers and a few other signs. Kinda like checking for precious signs in any cartridge.

In some low pressure cartridge/firearm combinations pressure signs don't appear until you have damaged or destroyed the gun.

[clearwater]

Ah how bout split cases blown out primers and a few other signs. Kinda like checking for precious signs in any cartridge.

See below. He said it better than I can.

"In low pressure cartridges pressure signs don't appear until you have damaged or destroyed the gun."

I think I will ask for the Lyman #50 for Christmas and use that data for velocity to compare loads for pressure. thanks for helping me under stand about vented test barrels.

[clearwater]

Kid,

A real good sign of high pressure in a revolver is when you have difficulty pulling out the spent cases.

"same old misinformation"

[poppy42]

Well not your mother, don’t even know the woman. I’m certainly not interested in getting into a mine is bigger than yours contest with anybody. Based on your comments and vast post count, you obviously have waaaaaaay more knowledge than me. I was simply stating, in an open forum that in my opinion I see nothing wrong with using load data from old are reloading manuals. As long as that data contains information on currently available components. And I stand by my previous statement. As far as anything else goes? Well you just have a wonderful day.

[Texas by God]

Firmer than normal ejection of fired cases from a revolver is a warning sign of higher pressure than normal - just like stiffer opening of a rifle bolt is a warning. Call it a clue if you want, but it isn’t misinformation. It is your gun telling you to back off of the powder charge.

[M-Tecs]

Firmer than normal ejection of fired cases from a revolver is a warning sign of higher pressure than normal - just like stiffer opening of a rifle bolt is a warning. Call it a clue if you want, but it isn’t misinformation. It is your gun telling you to back off of the powder charge.

That is highly dependent on the firearm/cartridge combination. Works fine in full size modern magnums. Not so much in a lot of the older designs. I shoot loads in my Ruger Blackhawks and TC Contenders that show zero pressure signs with higher end 45 Colt loads yet these same loads will take 1873 Clones apart in one shot. Personally seen the results twice.

As Larry pointed out sticky extraction normally happens around 42K -45K in case like the 38/357. SAAMI max for the 38 Spec is 20K. Even firearms like S&W 19 don't tolerate a steady diet of SAAMI spec 357 loads. Lots of pre 60's revolvers are much less tolerant of those pressures. Same applies to rifles. Most modern rifle cartridges don't show pressure signs till above 65K yet lots of rifle designs don't tolerate 65k plus pressures. My siamese mauser 45/70 loads at 50K don't show any pressure signs yet lots of 45/70 firearms will come apart if fired with those loads.