Pressure Signs in a 40 S&W?

[leadchucker]

Almost all the semi-auto 40's I've seen have some of the chamber cut away to form the feed ramp. Some have more some have less. My Kahr PM40 and 40 S&W Shield both have some chamber cut away here. Not as much as in the older 40 Glocks I've seen, but some nonetheless.

I noticed a "Glock" style bulge in some of my cases that I recovered from a recent session at the range. The edges of the bulges roughly match the contours of the chamber edge of the Kahr.

I was working up a load, and I suspect that some rounds I tried may have been a bit too hot. They were up near the maximum charge.

The primers didn't look abnormal, but I suspect that's not always a good indicator. Recoil was fairly stout, but nothing I would call abnormal. So could a "Glock" style bulge in this area indicate higher than normal pressure?

 

[rcmodel]

Yes.

If the brass is bulging into the feed ramp cut, it is borderline too hot.

rc

 

[MtnCreek]

I would suspect the next pressure sign you would see is when the mag blows out the bottom of the pistol. Be careful.

 

[sexybeast]

The primers didn't look abnormal, but I suspect that's not always a good indicator. Recoil was fairly stout, but nothing I would call abnormal. So could a "Glock" style bulge in this area indicate higher than normal pressure?

Higher than normal? Not really. Brass fireforms but less at the base where the brass is thicker. Re size them and re load them. I do. All the 40 brass I toss starts splitting at the top, not at the base and I've never had a case failure with 40. Many guns leave a "bulge" at the base.
Its not an evil cartridge and yes you can shoot it again after its been shot in a glock.
I load and shoot at least 500 per month, and I use my brass over and over. Just spend some time inspecting them. Download them a little if it makes you feel better, I do for my Shield because I actually compete with it now and then.

I would suspect the next pressure sign you would see is when the mag blows out the bottom of the pistol. Be careful.

OK, whatever.

 

[gahunter12]

I would watch loading Glock fired brass at max loads. I have no problems loading Glock brass, but my loads are Minor PF loads. The Gen3, and Gen 4 chambers are better supported than the Gen1/Gen2 Glocks.

 

[AABEN]

I have been shooting 40 for 14 years and never had that happen. But when I reload I look at the reload book and take the low and the high and load in the middle. That way you will always be OK and your brass will last a long time and is better for your gun. GOOD LOCK That gun that you have is a good gun!

 

[gamestalker]

You are correct, it is difficult to read pressures for cartridges such as the .40 cal, as well as other AL cartridges that head space off the mouth. Reading primers is not at all effective for these types. A chrony can give some insight as to how high pressures getting, but this too can be deceptive to some degree.

I've been loading full tilt for the .40 cal. since it came into production, so I know your concerns. Bulging at the unsupported area of the case is generally a very good indication you have exceeded the safe maximum load for that particular cartridge / firearm combination. Of course, it is also possible you might be using brass that has been loaded one too many times and has lost it's integrity.

GS

 

[leadchucker]

If anyone is interested, I was loading a Precision Delta 165 gr FMJ FN at 1.115 OAL, .280 seating depth. I had ten rounds each at 5.9 gr, 6.0 gr, 6.1 gr, 6.2 gr, and 6.3 gr of W231. There were eighteen cases that showed a bulge. Sounds like a sure bet those were the 6.2 gr and 6.3 gr rounds.

That's as close to the dragon as I want to get.

Thanks for the replies!

 

[Coltdriver]

That bulge is what I got one of these for:

http://www.midwayusa.com/product/35...e-sizing-die-kit-40-s-and-w-357-sig-10mm-auto

How close you are getting to dangerous is another question but while a bulge may be a characteristic that appears along the way to dangerous it is fairly routine and common so probably not a great indicator.

Published loads from reputable sources are your best guide. Remember a .40 is already a fast round and there is no such thing as a magnum .40 load

 

[grandpawj]

+1, What Coltdriver said.

 

[steve4102]

If anyone is interested, I was loading a Precision Delta 165 gr FMJ FN at 1.115 OAL, .280 seating depth. I had ten rounds each at 5.9 gr, 6.0 gr, 6.1 gr, 6.2 gr, and 6.3 gr of W231. There were eighteen cases that showed a bulge. Sounds like a sure bet those were the 6.2 gr and 6.3 gr rounds.

Couple comments,
you loaded up 50 rounds, 10 each from 5.9gr to 6.3gr, but you didn't "Stop" and inspect your 5.9gr brass before firing the 6.0gr loads? You fired all the rounds, then picked up all the brass at once with no clue as to what bass was loaded with what loads? What was the point of the work-up then?

Where did you get your data from?
According to Hodgdon data, 165gr bullet has a "Start" charge of 4.3gr of 231 with a Max of 5.3gr. Did you check out their data before you loaded these rounds.
Also Lyman 48 lists a Start charge of 5.2gr with a Max of 5.8gr.

No wonder you are budging your brass.