View Full Version : Pistol cases and pressure signs
September 24, 2012, 02:08 AM
I've just bought a new-to-me lever action (a Browning B-92 in near mint condition) in .357 magnum because I've been craving a lever action for years.
I'm probably going to stick to factory ammo until I build up about 500 once-fired cases and then start reloading for it.
I've been reloading rifle ammo for a while but this is both my first pistol calibre and my first lever action. Is there anything in particular I need to know?
Are pressure signs the same or do I need to look out for something else both in terms of the pistol case and the lever action?
Anything else I might need to know as well?
I also have questions about projectiles but I'll open a new thread for that.
September 24, 2012, 10:42 AM
I keep a list of pressure signs, here (http://www.shootersforum.com/showthread.htm?t=58763). The only one I know of that is unique for lever guns is sudden case growth, indicating stretching of the sides of the action by pressure back against the rear locking bolt. If that happens, the pressure is really at the gun's limits. M.L. McPherson references this indicator, but he's talking about .45-70's loaded very hot behind heavy bullets. I don't know that you'd ever see it in a .357.
It also occurs to me that if you have a slightly ovoid chamber mouth to assist feeding, you may see some bulge in head diameter that a perfectly round chamber won't produce. I don't know if that particular rifle has this or not, but it would allow heads to widen and loosen primer pockets sooner as pressure increases, and avoiding primer leaks and primers falling out would be a good idea.
September 24, 2012, 12:28 PM
It's virtually impossible to read pressure signs from straight walled pistol cases, especially those that headspace on the rim. While difficult extraction is a sure sign in revolvers, I doubt if one would notice it in a lever. I load for levers in both .357 and .44. Stick with published loads and you will not have to worry about too much pressure. Many manual recommend the use of virgin or once fired brass only for hunting type or loads at or near max because of case stretch due to the loose bolt lockup in lever type actions. When shooting mid-range to powder puff loads it doesn't matter. I tend to stay away from fast powders in my carbines, but Unique and anything slower will work. My best hunting type loads come from H110/W296 and IMR4227. When loading for plinkin' type loads I stay above loads that chrono above 800 FPS outta my revolvers to avoid stickin' a bullet in the carbines.
September 24, 2012, 06:46 PM
Keep track of case dimensions before and after firing.
Notice any increased effort needed on the lever.
Primers are not good sources, but I still look at my primers and compare to factory rounds fired in that gun.
Compare recoil to factory rounds.
In general, these are the various signs that people have brought up:
There is also no way to tell which sign will show up first in your gun and with your load combinations, so you have to learn to watch for them all.
1.Case bulging, particularly near an unsupported part of the head.
2.Case crack along side (may mean excess pressure, but may mean brittle, defective, draw mark scored, or worn out brass).
3.Case head expansion (CHE; may mean high pressure, may mean nothing in isolated case).
4.Case head separation (may mean high pressure, but may mean excess headspace or worn out brass). 5.Case splits in body in under 10 reloads-back loads down at least 2% (can also be due to ammonia vapor exposure or a brass defect in an individual case).
6.Case mouth split (may mean high pressure, but more often means case needed neck annealing).
7.Case pressure ring expansion (PRE; not much more reliable than case head expansion but may mean pressure is excessive).
8.Case primer pockets getting loose in five reloadings or fewer. 9.Case excessive stretching (this is actually visible pressure ring area stretching which may be due to excess pressure or to excess headspace).
10.Extractor marks appear on case head in semi-auto rifle after incrementing powder charge up (may be high pressure or bad timing or an extractor standing proud on the bolt face).
11.Fired case won’t fit back into chamber.
12.Gas leak (see Primer Leaking, below).
13.Groups start to open up at or beyond a suspected maximum load pressure.
14.Hard bolt lift. 15.Incipient case head separations (partial case head separation).
16.Incremental increase in powder charge results in lower velocity or at least in no increase in velocity (may also mean uneven bolt lug contact being forced to touch down on both sides; watch for stringing on the bolt lug axis as additional symptom of this). 17.Primer blown (primer falls out when gun is opened; same as loose primer pocket).
18.Primer cratering (may mean high pressure, or it may mean a worn firing pin or firing pin tunnel, or may mean you have a new production Remington bolt with chamfered firing pin tunnel).
19.Primer flattening (may mean high pressure, or may mean long headspace; some loads always make flat primers; softer primer cups (Federal) flatten more easily than harder ones (CCI), so it also can mean nothing at all).
20.Primer mushrooming (may mean high pressure, or may mean long headspace).
21.Primer piercing (may mean high pressure or may mean incorrect firing pin protrusion or incorrect firing pin nose shape).
22.Primer leaking around primer pocket (may mean high pressure, may mean loose primer pocket in case, may mean damaged primer was inserted, may mean primer backed out too far during firing, which excessive chamber headspace makes possible).
23.Short case life -back load off at least 2% (under 10 reloads in non-self-loaders or with military brass in self-loaders, 6 or less in self-loaders with commercial brass).
24.Sticky or hard case extraction (especially in revolvers this is a positive sign to knock the powder charge down at least 5%).
25.Torn case rim (from hard extraction).
26.Primer pocket expansion--this can be a more sensitive measure for those with tools that can measure the inside diameter of a primer pocket repeatably to the nearest ten-thousandth of an inch).
27.Ejector and extractor impressions on the case head (can also be due to ejector and extractor fit problems).
28.Increase in required trimming frequency (this is a sudden increase in case length growth per load cycle; it can be caused by excess pressure, but can also be a sign of increasing head space due to some other problem. It is especially common as a pressure sign in lever action guns because the greater span from bolt face to rear lug allows more steel stretch when pressure gets excessive.)
29.Increasing apparent headspace (this means the cases are coming out longer, including from casehead to shoulder. It can mean bolt lug setback, which is usually an extreme pressure sign. It can also mean a loose barrel or an improperly set Savage barrel. Whatever the cause, the gun should go straight to the gunsmith for inspection.)
30.Gas or Flame Cutting of revolver top strap. (Can also be due to excessive barrel/cylinder gap that needs correction.)
31.Gas cutting of rifle bolt face by gas leaks around primer pocket. (Can also be result of occasional leaks from normal rounds firing, as is observed in many military gun bolts.)
September 25, 2012, 01:17 AM
That was a comprehensive answer and i'll be referring back to it for a long while to come. I've printed it off and it's now in my reloading folder.
Thanks very much for the effort guv:D
I also intend to use .357 mag brass but create 38 special loads. The extra volume in the mag case means lower pressure, do you guys know how to compensate for that? I don't have access to a chrony to measure velocity. Is there a rule to go off?
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