What makes a load +p?

[ManNamedJed]

Im pretty new to reloading. I've found a nice load that works great for me in production class (4gr TG + 124gr MG RN bullet) and have been crankin' em out. However, I also shoot some steel plate and bowling pin matches with my 9mm though. A soft 9mm load isn't ideal in these situations.

For those I'd like to develop a hotter load with a 147gr bullet. That got me to thinking about what constitutes a +p or +p+ load. I take it these are beyond the 'max' loads published in the reloading books correct?

Is a 'max' load in a manual considered 'spec'? or is it a +p? Are the max published loads in manuals fairly conservative to accomodate older WWII era guns?

Oh and if you have any experience with TG and 147gr bullets I'd love to hear it!

[Matt Wheeler]

A +p designation is indicative of having a chamber pressure higher than standard(max). Not all rounds have a +p option. There is no recognized designation of +p+. If the round has an industry rating for +p it is usually a few K over standard maximum. All the published data that I have seen is inside of indusrty max and for +p data it is with in that standard as well according to the publisher. That is not to say that the load they got may not be over for your fire arm. Is the 147 you want to use jacketed or lead?

[Allgoodhits]

Im pretty new to reloading. I've found a nice load that works great for me in production class (4gr TG + 124gr MG RN bullet) and have been crankin' em out. However, I also shoot some steel plate and bowling pin matches with my 9mm though. A soft 9mm load isn't ideal in these situations.

For those I'd like to develop a hotter load with a 147gr bullet. That got me to thinking about what constitutes a +p or +p+ load. I take it these are beyond the 'max' loads published in the reloading books correct?

Is a 'max' load in a manual considered 'spec'? or is it a +p? Are the max published loads in manuals fairly conservative to accomodate older WWII era guns?

Oh and if you have any experience with TG and 147gr bullets I'd love to hear it!

The standards are available through SAAMI

MJ

[ManNamedJed]

So if you have a gun that is rated safe to shoot +p, then it is reasonably safe to exceed max published loads by a small bit? Of course I'll 'work up' to it.

I have some 147gr Montana Gold CMJ RN. My manual lists starting load for TG and 147s to be 3.2gr and max is 3.6gr. I loaded up some rounds with 3.4gr, 3.6gr, and 3.8gr to test out (I've loaded some before at 3.4 that worked fine and were fairly mild, so I started there).

I don't want to blow myself up, or damage my gun. I just want some 9mm with a bit more juice for those steel plates and pins.

Its a CZ SP01 BTW.

[Matt Wheeler]

So if you have a gun that is rated safe to shoot +p, then it is reasonably safe to exceed max published loads by a small bit? Of course I'll 'work up' to it.

I have some 147gr Montana Gold CMJ RN. My manual lists starting load for TG and 147s to be 3.2gr and max is 3.6gr. I loaded up some rounds with 3.4gr, 3.6gr, and 3.8gr to test out (I've loaded some before at 3.4 that worked fine and were fairly mild, so I started there).

I don't want to blow myself up, or damage my gun. I just want some 9mm with a bit more juice for those steel plates and pins.

Its a CZ SP01 BTW.

With relaoding an increase of powder charge does not equate to a linear progression in pressure especially when near max loads. I load a PD 147 fmj at 3.1 grs of TG for 890ish and that is PF of 130ish. Since you have to only make 125 pf I'm sure that the 3.6 gr load is in the 140 area and should be plenty for steel. I shoot an SP01 in IDPA and steel matchs and I don't have any issues with steel as long as I do my part.

[Carlos]

So if you have a gun that is rated safe to shoot +p, then it is reasonably safe to exceed max published loads by a small bit? Of course I'll 'work up' to it.

No - that is not a safe assumption. (welcome aboard BTW) Here is the problem: sometimes the "max published loads" you refer to use powder and load combinations that have been found unsafe. In ANY gun. As the charge increases, the resulting peak pressure "spike" may increase in a linear fashion, or it might be a very steep curve that is unpredictable. Some time back, there was an article in Front Sight about one reloader's experience working up a hotter 9mm load with (I believe) Bullseye. The chrono showed steady increases until suddenly the velocity was WAY off the chart and (luckily) the gun just held together. Plus, for the new reloader, there are other dangers to learn about, including set back. Don't assume all published data can be exceeded. BUT - read on:

I don't want to blow myself up, or damage my gun. I just want some 9mm with a bit more juice for those steel plates and pins.

Its a CZ SP01 BTW.

Good news!

1) Besides the published loads (which have been tested as safe) there are hotter loads that are safe and our humble forum here is the place to find them. Leave the expiramenting to the more experience loaders and just read up on loads here for info. WARNING: many hot 9mm loads you see here will have an OAL that is WAY TOO LONG for your CZ. DON'T USE THOSE LOADS!!! They cannot simply be shortened.

2) Your CZ-SP-01 is an extremely strong gun; about the only guns regularly used to digest a steady diet of hot 9mm (+p++) we call 9Major are: ramped barrel 1911s, "75" or CZs and their clones and some Glocks with aftermarket barrels. The SP-01's barrel is EVEN THICKER than the old TZ-75s that digested 175 Power Factor ammo back in the early 90s.

3) Though the 9mm is not a very good caliber for Pins, there happens to be a heavy 147 load from Vihta Vouri that is safe and should get you to about 1100+ FPS - I believe its either with N105 or 3N38. Please use the MAX OAL for that load.

4) Finally, for steel you want a lighter load with a light bullet. What you are using should be fine.

Edited June 5, 2008 by Carlos

[Joe4d]

max published loads are just that, Max. And they may not even be safe in your gun. No amount of tweaking a 9mm is gonna make it an effective bowling pin gun. I dont believe there is any standard for +p. It is basically a marketing thing, just take a look at midway and compare some of the socalled +p ammo to non +p. I dont believe any US ammo company would intentionally sell ammo loaded over SAMMI max specs, The standard ammo might be less than max and the +p near max but not over. Now all the companies would put all kinds of gee wiz lables and use slow burning powders that create more flash and recoil but dont increase pressure or even increase velocity but 99% of the shooting world doesnt have a chronograph so will assume any round with more flash and recoil must be more powerful. The 9mm case can be safely pushed faster than published data but they sre long loading it to the point where it really isnt a 9mm luger anymore, people shooting 9mm major do it all the time but the entire gun is set up for it including non standard chambers, springs, etc. Stick within published data if that isnt enough power go for a bigger round.

[ManNamedJed]

Thanks for all the info. I appreciate it.

Just to clarify a few things - I know 9mm isn't ideal for pins. But I go to the match on 'Load em up' day so the 19 rds in my mag allows me quite a few shots before reloading. I did one recently with some factory 147 AE and did fairly well. Many were surprised that a 9mm was knocking the pins off so well. Hence my thought to figure out a hot 147 load and not pay $14 a box for the next one.

By Steel Plate I mean man on man falling steel, not steel challenge type. The area matches have rather heavy steel that can be hard to knock down with a 9mm.

Of course the answer is to shoot a larger caliber, but I shoot these matches for fun and to practice with my IPSC Production setup. However if I get eliminated quickly, its not so great of practice!!

I'll try out the rounds I loaded up this weekend, starting with the ones that are within the acceptable range. If I see any indications the rounds are too powerful I'll scrap the rest.

[Patrick Sweeney]

To get the most juice out of a 9mm, you're going to have to go with slower powders. The problem with that approach is that slower powders tend to be bulkier than fast powders. The 9mm, being a small case, runs out of room real fast.

Consult the Viht manual, you'll get good loads there. Also, if you're going to use +P loads on pins, invest in new recoil springs. While the recoil spring might be good for 5,000 rounds (to pick a number) with regular ammo, a steady diet of +P ammo will do the same to it is fewer shots.

[superdude]

some cartridges have defined +P pressure standards. as per the SAAMI booklet:

9mm Luger 35,000 psi

9mm Luger +P 38,500 psi

38 Special 17,000 psi

38 Special +P 18,500 psi

45 ACP 21,000 psi

45 ACP +P 23,000 psi

published velocities suggest significant velocity increases in some (probably not all) +P loadings.

[ManNamedJed]

some cartridges have defined +P pressure standards. as per the SAAMI booklet:

9mm Luger 35,000 psi

9mm Luger +P 38,500 psi

38 Special 17,000 psi

38 Special +P 18,500 psi

45 ACP 21,000 psi

45 ACP +P 23,000 psi

published velocities suggest significant velocity increases in some (probably not all) +P loadings.

Thanks for posting these. The Max load in my Lyman manual for 147gr with Titegroup is 3.6gr and it is listed at 31,900. My Hodgdon manual lists a 147 XTP with Titegroup at 3.6gr to make 27,500. So these 'max' loads are a fair bit below SAAMI spec. In fact, the highest pressure listed anywhere for 9mm is 33,400.

Sooo if the pressure listed in the manual is less than SAAMI spec for that round, is it reasonably safe to assume that a published Max load round is safe to shoot in a modern quality firearm? I mean, but looking at the pressures listed above, and the ones in my manuals, a Max load is be low SAAMI and well below +p. (Im not saying I'm going to jump in and start shooting a bunch of random max loads, I'll work up to any loads, I'm just curious to understand this).

Hmm just noticed that all the +p's are about a 10% increase. I wonder if that is consistent with others.

[Guy Neill]

Some things to consider when looking at maximum loads.

The published max loads represent the testing and components used in the tests. Even using the same components, there will be differences. Different lots of the same components will show variances, and even the same lots will have variances.

The published max loads, even is listed comfortably below SAAMI max may represent the highest load that could be obtained with that powder without going over pressure. That is to say that the next charge increment (perhaps 0.1 grain) would push the pressure over the SAAMI allowable maximum.

Different chambers will produce different pressures depending on the size of the chamber, leade into the rifling and depth of the rifling.

Seating depth, especially in the 9mm is of great importance. Speer documents the change in pressure from seating teh bullet 0.033 inches deeper on a previously safe load. When playing at or near maximum you want o be certain the bullet will not telescope into the case during feeding.

Depending on the primer cup thickness, firing pin hole diameter and firing pin fit to the hole, primer flow may become a problem.

As others have mentioned, pressure does not build in a linear fashion. There are occurrences where the pressure will actually decrease as you continue to increase the charge weight, then resume increasing pressure much more rapidly with another slight charge weight increase.

It's often assumed that the load manuals have been "lawyered" - maxs reduced for overall safety. Not on the manuals I have worked on. The yhad max loads as close to the SAAMI listed maximum without going over as they could.

Guy

[RePete]

There is one other item to be careful of, if you get to look at older manuals, the pressures are listed in COPPER UNITS OF PRESSURE (CUP) and the new boks have POUNDS PER SQUARE INCH (PSI). There is no relationship between the two.

Example - .308 SAAMI pressure was 52000CUP or 65000psi , but for the 30/06 it was 50000cup but it's also listed at 65000psi.

[ManNamedJed]

Just a follow up on this. I loaded up some ammo as I stated before. I shot them through a Sig 226 and a CZ SP01. I started with the 3.4gr load (well under max), then the 3.6gr (max listed load) and then some 3.8gr (above max listed load). As both are considered to be overbuilt firearms I felt comfortable with this test.

After each one I examined my casings to look for any signs of trouble. The 3.4 and 3.6 loads all looked normal. The 3.8 showed signs of the primer flattening and the headstamp smearing, but no bulges, splits or other indication of trouble. We have a 9 major shooter at our club and I've noticed his brass shows more signs of overpressure than these did. They all cycled fine and didn't feel or sound abnormally powerful. The 3.8gr in my 226 felt like I was shooting my .40S&W 226. Unfortunately I don't have a chrono to provide more scientific results.

So I think I'll settle on 3.6gr TG (with the 147s) as my pin/steel plate load just to stay on the safe side of things.

Thanks to everyone that posted the detailed thoughtful answers! It did help me understand things better.