Pressure Signs in Semi Auto

dtknowles

What to look for when loading for 38 super, .380 ACP or 9 x 19 mm

I have been loading these for a while and about the only two signals I ever get is:

Not enough power to operate the slide and chamber a fresh round

or

Man it is really throwing the brass a long way.

No difficult extraction, flattened or cratered primers.

Do you measure the head expansion or something like that to check for excessive pressures?

Tim

perry shooter

Hello the bad thing about looking for pressure signs in a semi auto pistol is sometimes they show up in BAD ways. Because of the feed ramp. the bottom of the case head is not supported this can lead to a buldged case "perch belly" to a blown case bad news as it then may set off rounds in the Magazine with nowhere for the bullet to go. My advice always follow reloading manuals and NEVER go over max load. A semi auto is not a type of gun you try to hot rod. Just my $.02 your mileage may vary.

RustyNail

Perryshooter
You raise a really good point about setting off rounds in the magazine. From now on I'm going to try the first couple of rounds single-shot when trying new "hot loads" in a semi auto.

Pearyw

I learn a long time ago, in a semiauto pistol, if you want more velocity go to a slower burning powder not more fast burning powder. Several years ago when the 40 S&W was new and there was not a lot of loading data, I found a load in the NRA magazine that they were recommending using AA2 powder. I dropped the load about .3 gr and loaded some 135 gr jhp. The second shot blew the back off the case. I later got Accurates loading data and saw that the max recomended load was 1 gr less than the NRA magazines load. I make sure I check several sources for any new cartridge or powder I start to load.

dtknowles

I am working on a couple guns for which there is very little or no relevent published loading data. I an not really talking about exceeding max. but when working up to max.

How would you know if you should stop prior to reaching the published max. load. I had always believed that the reason you started low and worked up to max was that the max load might not be safe for your particular gun. If there is no clue short of a blown case head, ugh.

For my more conventional handguns the handbook max. loads have not caused any problems but I always wondered how I would know if I was getting close to trouble. For the less conventional stuff I know I am in unknown territory and am even more interested in some warning signs.

I am also working on a couple guns for which there is very little or no relevent published loading data. I an not really talking about exceeding max. but when working up to max.

Case one, 7.62 x 25 mm in a CZ-52 most of the data I have is really for the 30 Mauser no where near the performance of factory or mil surp ammo I have tried. If I work to get the 1600 fps with an 85 grain bullet using Red Dot or Unique will my pressure be too high. Working up so far there is nothing to make me think I should stop increasing the powder charge or back off.

Case two, sabotted rounds with .223 bullets in 7.62 x 25 mm. I have used a case full of Red Dot and got velocities in the 1900's and wonder if I should try a faster powder to get over the 2000 fps mark. No pressure signs, full case of powder with a 40 grain bullet did not even reliably cycle the action. 45 grain bullet got reliable cycling, with a 60 grain bullet I am still short of a compressed charge but seems to be asking for more powder.

Case three, 60 grain .311" dia. Gold Dots in 7.62 x 25 mm. Have not chronographed these yet. Got the action cycling good but there seems like a lot more potential

Case four, 9 x 23 mm in CZ-52. 9 x 23 Win factory loads would scare me but the 9 mm largo data is too wimpy. I have used 38 super data and had not trouble even with max. loads. It would be nice to know if I am in the 30 KSI range or the 40 KSI range

The barrels in these guns are not throated and the feedramp (what little there is does not leave the head of the case unsupported. The head on the 9 x 23 case (I am using 9 x 23 Win cases) in an fully supporting chamber is not going to blow out a pressures in the high 40's but I really am not looking to go there.

Are there really no clues?

Tim

perry shooter

Hello What I am about to say is just my $.02 others will surely disagree . I like to experiment with loads but a Semi Auto pistol is the worst gun type to do this .I had a 44 auto mag 357 auto mag and 2 experimental auto mags down to 22caliber on the cutdown 308 case. talk about case forming[:(!][:(!] Colt found this out when they tried to make the 1911 into a 10 MM. "why do you think they stoped making them"? If you took say a 45ACP that was set up for light target loads with a 10 pound recoil spring and put +p+ loads in it and started shooting the gun would work at first but the slide would bottom out on the frame with such force during recoil that sooner or later "most likely sooner" the slide would crack or break if it broke you could EAT the back half [xx(].so now we say Ok put in a 23 pound recoil spring great except now when the slide closes it is so violent it shakes off the hammer from the sear and the pistol goes full auto[:0]Colt found out that the 10MM broke the 1911. and ammo makers were forced to download the factory 10MM A spring recoil system has to be matched to the load.Now we come to the feed ramp some designs are better then others a Slope grip pistol lends itself to a smaller /shorter feed ramp but most pistols are now more straight up grip frames a GLOCK is the worst with unsupported case head feed ramp. Only a gas operated pistol Like the BIG BOOMERS have IMHO any chance of hot rodding ammo and even these like a REMINGTON 1100 shotgun you must shoot the load that matches the gas load on the piston. Plus the gas operated pistols are too big for most people . If you want to Play with pistol loads my suggestion is to go with a TC ENCORE.....I had a single shot bolt action top in 308 Winchesterthat went on a 1911 frame that would punish you and quickly erase all skill one would ever have in pistol shooting[:o)][:o)][:o)][:o)]. Have fun but be safe "PRAISE THE HARD=BALL GUN"

mbsams

I was reloading a 10mm auto and became so concerned about case failure with reloads that I used only virgin brass. That got expensive - factory loads in 10mm these days would not cycle the action. I have since sold the 10 and gone back to the 45ACP and wheel guns. I had a case blow out in the ACP, very unpleasant, so now it's wheel guns only and 22 autos only. Don't keep pushing your luck with those autos - it's gonna come up snake eyes sooner or later.

dtknowles

So are you guys saying I am pushing my luck or just warning me not to push my luck? My luck seems to have been excellent. My 9 x 19's and .380 seem real happy with the loads I have been using for years. I have had the CZ 52's for less than a year and I have not standardized my loads yet and they are a little more challanging than the others because of the lack of data.

Clearly loads that barely recoil enough to cycle the action are not going to break the slide. I understand that when using light bullets I could have high pressures even if the action is barely cycling. I was asking for help because I don't want to blow cases to find out that I went too far.

The CZ is not going to go full auto even if the hammer follows the slide into battery. It has a firing pin block that locks the firing pin unless the trigger is pulled.

So what do you think about measuring case head expansion as a pressure indication?

Tim

Mobuck

I don't think your firing pin block will fly as as full auto prevention. Very likely your finger will still be holding the trigger back when the second round is chambered. I have experienced a case blow out into the mag well and while no injury it did destroy the magazine and grips. This was a load that I had used many times in other pistols. I found that the Star B had been "throated" by a previous owner and his butchery ruined the barrel. If you look around you can find safe loads for any purpose. The loading manuals contain loads which work so if it's not in there it probably didn't work.

dtknowles

About the firing pin block not stopping full autoing because I would still be holding the trigger. I will check to see if the disconnector forces you to release the trigger to reset the action.

I have had the barrels out of all three of my CZ 52's and inspected them. The barrrel in 9 x 19 is very slightly throated and I treat it as such. The barrel in 9 x 23 is not throated at all and full supports the case head. The both my 7.62 x 25 barrels are not throated no reason to throat a barrel for this bottlenecked round.

Very little data for the 7.62 x 25 that is intended for TT 33's or CZ 52's most is weak in regard of the 30 Mauser. Data is also very very thin for using light projectiles in the 50 to 65 grain range. I already have this gun out performing my 22 Magnum revolver by 300 fps with a heavier bullet. This is great but I need to decide if I need to get a weaker recoil spring for the light bullets or if I can up the energy a little more to get more reliable cycling. Sometimes the slide does not chamber a new round.

Tim