Signs of over-pressure in a semiauto

[frumious]

Hi, I have read threads about signs of over-pressure, but in some of those threads someone comes along and points out that some/all of those signs are relevant to bolt-action rifles only. So what are signs that are relevant to semi-auto pistols?

The reason I ask is that I have recently switched to Precision's hard-coated bullets in .45ACP (230gr .4515"). And I think that's when my forearms started getting speckled with unburnt powder residue. I don't crimp these things very much (Lee factory (taper) crimp die) because I have read about cracking the coating and causing lead fouling as a result. I mean, I guess I could crimp more...right up to the breaking point of the coating...but these things are really slick. Not sure I'll be able to crimp enough.

So I thought about increasing my powder charge. But I'm not sure where to stop. Normally I find a low-ish load that works the action OK and stick with it, so I'm not used to heating up loads in a semi-auto, and I don't know how to interpret the conflicting load data I see in the manuals I own.

Right now I load 4.2gr of Bullseye under this precision 230gr. That's OVER MAX per my Lee 2nd manual (230gr lead bullet), KINDA LOW per my Lyman 49th manual (225gr #2 allow bullet), and UNDER MINIMUM per my Hornady 7th manual (using a 230gr LRN bullet).

I know that different manuals use different testing methodologies, different test weapons/reference barrels, etc, but come on...there's a 1.7gr spread (4.0, 5.0, 5.7) among my 3 manuals for the max load. That's a pretty big spread for a 4ish-5ish grain load.

So back to my original question...valid signs of over-pressure in a semiauto. I don't have a chrono, but I suppose I could get one if I need to. Am I just looking to push that 230gr projectile no faster than about 850fps, or are there other things I can look for?

-cls

[Unclenick]

You can check my list of pressure signs, here.

The speckles don't mean much of anything. Bullseye has a lot of graphite coating and it makes soot that permeates the weapon at any load level. I competed for years with a gallery load that was 3.8 grains under a 185 grain cast SWC, and that worked fine in a Goldcup with reduced power recoil spring. Some unburned powder was always left behind as it had been contaminated with bullet lube or followed the bullet down the tube while peak pressure was dropping and before it got hot enough to light well.

As the bullet gets heavier the pressure and recoil get higher, so that was a pretty light load compared to yours.

4.2 grains of Bullseye under a 185 grain JSWC has always been a standard way to replicate commercial and military match loads. Under the 200 grain Hornady JSWC, I found 4.2 grains of Bullseye to be the most accurate load I've ever shot in the Goldcup (see image of 25 yard 5 shot group, below). 5.0 grains of Bullseye under a 230 RN FMJ (hardball) was the standard military load around the time of WWI. It's about 350 ft-lbs of ME from a 5" tube, same as today's commercial hardball loads. It takes about 5.3 to 5.4 grains, depending on the brass, to reach military ME, but let me caution you that this is with the RN bullet seated to average 1.270" COL, as the military does, and not deeper in the case as some manuals suggest. None of these loads exceed SAAMI maximum pressure or are +P if assembled as I described, paying attention to the COL.

Lee's manual is made by looking at minimums and maximums from different data and using the lowest maximum published in most instances. The data was never tested by Lee. It is usually the most conservative source, based on its selection method. Note, also, though, what I said about seating. Seating deeper confines the powder more and raises pressure. For that reason, two sources using the same powder and same bullet could have legitimately different maximums if the seating depths are different. Primer brand difference can affect pressure, so that may be a cause of 5% or so charge difference in some books. I've used the Federal 150 (and 150M) and the Winchester WLP and the CCI 300 with my light loads without problems.

Since your bullets are soft, I wouldn't drive them to super racing levels. The old military 5.0 grains is about the upper limit I would apply, using the 1.265" to 1.275" COL.

[frumious]

Thanks for the info, Unclenick. On the subject of crimp, what do you think is the right thing to do in a semiauto that headspaces via the case mouth like the .45ACP? I hear a lot of conflicting info about crimp. I think I want to crimp enough to ensure complete powder ignition and to prevent bullet setback as much as possible, but not enough to mess up the headspace. But I've read lots of places that say "for pistols, only use enough crimp to iron out the flare you made in order to get the bullet started". And I also hear about too much crimp swaging the bullet but the case springs back.

Also, it seems that you seem to consider Precision bullets "soft". I thought the coating made them pretty hard. But maybe it is a different kind of hard than hard-cast lead, or copper jacketing?

-cls

[dmazur]

I believe the information about excessive crimping actually making bullets looser is true, due to brass springback.

Tension is controlled by the sizing die, and if your die doesn't match the bullet diameter, you can have issues with setback. The solution is to buy bullets that are the correct diameter, or buy a die that matches the bullets.

For .45 ACP and others that headspace on the case mouth, Dillon recommends a taper crimp. And your information is correct, the die should be adjusted to just remove the bell done by the powder-thru expander. The case is then nearly straight. For powders used with these cartridges, ignition is generally not affected by crimp.

For .44 Mag and other similar cartridges, a firm roll crimp can be necessary for proper ignition of slow powders commonly used to achieve high velocities, as well as preventing bullet pull from the recoil. However, a lot of folks load mild "target" loads in .44 Mag and don't bother with a roll crimp. The loads they are using don't require it, and there isn't a bullet pull concern if there isn't high recoil involved.

From another forum -

It's tougher to read pressure signs for semiauto than rev. The auto ejecting of the round doesn't lend itself to feeling sticky extraction. So look for excessive case head marking from the breach face, flattened primers or any smiley face bulging. All will mean you are already over max & need to back down 5%.

Revolvers will show sticky extraxction but that doesn't always mean high pressure. It could be a rough chamber or two.

Stick w/ book data & stay off the max loads & you won't have to worry much about over pressure.

A chronograph won't guarantee you are safe, either. Velocities that are higher than you "expect" from published load data would be an indication that you are in a bad area, but not proof of what the pressures actually are.

The coated bullets are still lead. The coating probably protects the lead from the heat of the burning powder (thus the "indoor range safe" claim and reduced leading claim), but it just isn't a jacketed bullet. I agree that you shouldn't assume they are interchangeable.

[Jeff H]

IMHO, the 45ACP is a rather low pressure round. You aren't likely to see pressure signs until you are way over max.

[Unclenick]

Precision's coating, from their description, is a resin matrix with moly in it, probably not dissimilar to some of the paint-on-then-bake-on lubricating gun finishes available today. These bullets are not as hard as guilding metal, though. If you read the FAQ on the company's site, it says they are for lead bullet loads and have not worked well or without fouling in HK's polygonal barrels. So these are more like lead than like jacketed bullets.

With jacketed bullets, ironing out the crimp is all you need to do. The gilding metal is not pure copper, but a form of mild brass, so the case brass and the gilding metal have pretty good friction between them. With lead bullets and any kind of plastic coated or soft copper plated bullet, they are softer and slip in the case mouths more easily. For these, but especially for lubricated lead, which sometimes may be pushed deeper into the case by thumb pressure alone, I like the case mouth to dig in by a few thousandths to form a step. They are soft enough that this does not cause a problem. In .45 ACP the mouth simply has to remain within the specification range to work. That specification is 0.466" to 0.472". Unless you have very thin walled cases, like R-P, which I just won't use, the mouth will start to bite a little into a .452" somewhere within that range. Even a couple of thousandths helps prevent bullet setback on chambering.

But more than that, yourself all the bite you want if you seat out to headspace on the bullet contact with the throat instead of on the case mouth. Most of the out-of-box 1911's I've looked at have actually been headspacing on the extractor hook before the case mouth gets to the end of the chamber. That doesn't seem to affect jacketed bullet accuracy much, but has a pronounced negative effect on lead bullet accuracy. Seating out to headspace on the bullet improves accuracy and prevents leading by getting the round straight in the gun at the start. The only limitation is if the bullet shape is long, like a round nose, you sometimes cannot seat out that far and still fit into and feed from the magazine smoothly. Your flat tipped ones will probably be OK, though.

The image below shows how to use your barrel's chamber to gauge when you are seating out enough to headspace on a lead bullet (3rd illustration). My Goldcup's 25 yard groups with 200 grain H&G 68 type bullets fired off sandbags over 3.8 grains of Bullseye came down from about 1.5" to just under 1" when I made this change. Several folks I've spoken with have said it ended their leading problems, as well.

[brickeyee]

A chronograph won't guarantee you are safe, either. Velocities that are higher than you "expect" from published load data would be an indication that you are in a bad area, but not proof of what the pressures actually are.

A chrono can only tell you what the average pressure was all the way down the barrel (since that pressure and the time it is applied produces the velocity of the bullet).

The problem is that the peak pressure is what causes guns to fail.

Getting a high average pressure while keeping the peak pressure within safe limits is the complicated part.

Between adjusting burn rates (for reloaders choosing an appropriate powder) and selecting charge weights we try for an acceptable average pressure to create the desired velocity while no blowing things up by letting the peak pressure get out of control.

There plenty of other things that can raise peak pressure.

The temperature of the powder when it is ignited, jump before the bullet hits the rifling, bullet hardness, case volume, etc.

Much of this applies to handguns, but the .45 ACP is a rather low pressure round (mid 20,000 PSI range).

By the time brass or primers are showing signs of pressure they are WAY over for a low pressure cartridge.

A chrono is better than nothing, but only if you are starting with a decent peak to average pressure from a reliable load source.