Press checking and it’s affect on ammo
16 Responses to “Press checking and it’s affect on ammo”
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September 3rd, 2013 at 6:46 pm
That much change in OAL in a 9mm round is pretty trivial to case pressure when you fire the round.
September 3rd, 2013 at 6:52 pm
for my pistols that don’t have nice little holes to see brass through, I just point them at a mirror and look down the barrel in the mirror before putting it in the holster, easy enough…
September 3rd, 2013 at 8:17 pm
yeah, laughingdog – that change in OAL isn’t gonna cause a kaboom. And by the time you press-check your gun 4-500 times, you need new ammo anyway..:)
September 3rd, 2013 at 8:31 pm
so if you do a crazy thing nobody would ever do, you might cause a nearly imperceptible change in OAL. oh no.
also, i hope he doesn’t do press checks as they’re indicated in the photos. that’d certainly put anybody off them.
September 3rd, 2013 at 8:35 pm
Seems to me he didn’t check the OAL after it fed from the magazine the first time. I would imagine that the force of it hitting the feed ramp would be more likely to force the bullet into the case. I can’t see the physics of the round getting shorter with press check…if anything, it should get longer with the slide moving forward holding the casing, and the bullet “inching” forward with each close of the slide.
It seems the repeated ejecting, then feeding through the magazine onto the feed ramp is more an issue.
September 3rd, 2013 at 9:53 pm
Umm… Well… I guess I won’t press check my chambered round HUNDREDS OF TIMES!
Seriously, WTF
September 3rd, 2013 at 10:23 pm
I use my X-Ray vision for this task.
September 3rd, 2013 at 10:35 pm
Anderew Tuohy did an interesting experiment on setback awhile ago. I remembered reading it, but couldn’t find it on his site or Lucky Gunner Labs, but behold the power of Google:
http://dailycaller.com/2013/03/05/battered-bullets-does-bullet-setback-matter/
September 3rd, 2013 at 10:49 pm
200 press checks? Sure, and lab rats develop cancer after drinking 7000 gallons of diet soda per day. Yawn.
September 3rd, 2013 at 11:57 pm
I still don’t get it, headspace should be on the case mouth, meaning the bullet should not bump the throat/rifling enough to push it back. Please help.
September 4th, 2013 at 8:20 am
I suppose it’s possible for a press check to cause bullet movement in the case, you’re talking about thousands of an inch of clearance so the ogive could contact the chamber throat every time you press check. The question is does it matter?
For the past couple of years I’ve been reloading 9mm for USPSA shooting. At one point I was having a lot of problems with crimp. When checked with the calipers, my crimp was right on, but the bullet wasn’t being held very well. On 1 out of five rounds I could push the bullet all the way into the case until I compressed the powder (titegroup).
Now, titegroup is a pretty excitable powder with a min charge of 4 grs and a max charge of 4.4 grains for the bullet I use. I run 4.2 grns for a PF of 138. During this period I know I sent several bullets down the barrel in that compressed state without any signs of overpressure.
Why? Bullet speed is directly changed by the pressure behind it. If the bullet is loose in the case it isn’t really going to start building pressure until it hits the rifling.
I guess somebody out there really is looking after idiots.
Moral of the story? Make sure your crimp is tight enough to hold the bullet, then check the round to make sure it’s still indexing on the case mouth. Calipers are a great starting point and they’ll help you diagnose issues, but they don’t tell the whole story.
September 4th, 2013 at 8:46 am
I’d been interested to determine the frequency that he presumes press checks are done at. For LE and CCW holders, once a day? Twice a day? As required to have a warm fuzzy that my weapon will perform if needed?
If you’ve had that same ammunition in your firearm for 500 press checks, do not pass go and at least watch some more Yeager videos. This is one of those solutions in search of a problem, and I’m sure we’ll now see a YouTube video of what happens to my duty round after it’s been cycled 2500 times.
September 4th, 2013 at 8:52 am
And my carry ammo is Federal which has a 2nd crimp below the base of the bullet. Not that I press-check THAT many times before the round gets shot for practice.
September 4th, 2013 at 9:44 am
Colour me skeptical. Like David, I can’t see the physics of the round getting shorter with press checks, unless he’s pulling back a fair bit and then just releasing the slide so it slams forward (and I don’t see where he specifies his method). Even then, I would expect the inertia of the bullet to cause OAL to increase, rather than decrease.
I don’t doubt it’s possible, and I don’t doubt his results, but I suspect there’s something else going on that he’s not accounting for.
September 4th, 2013 at 3:14 pm
“Seems to me he didn’t check the OAL after it fed from the magazine the first time. I would imagine that the force of it hitting the feed ramp would be more likely to force the bullet into the case.”
Bingo.
It would not be a bad idea to check your ammo for setback from chambering, by dropping the slide from lock-back, once or twice. If it sets back more than a few thou, you may want a better crimp, or different ammo.
The way the article reads, he SEEMS to be assuming that that the press-checking is causing the setback, without having tested the initial chambering from the magazine as being the far more likely culprit. Some guns are wicked rough on the ammo during the chambering process.
But don’t knock the guy too much. He’s at least exploring the possibilities after having experienced and witnessed bad situations. How many of us have had an FTF and just sloughed it off as; “Oh well; bad primer” without really looking into it?
September 5th, 2013 at 2:13 pm
His methodology is wrong. Setback is caused by chambering from a magazine. I wrote a long post on the Glocktalk forum in a thread titled “Kaboom!” several years ago. Ran an informal test on a G27 Glock. Scary how much setback there can be in the .40sw from the Glock. Presschecking doesn’t cause it. It may damage the primer if someone is stupid enough to do it constantly and hard. Slamming the slide home in a presscheck is not proper.
Administratively unloading and loading a duty weapon from the mag may be the underlying cause of police Glocks, and other brands, grenading. If you want to continue loading the same round (in a Glock), lock the slide open w/o mag, drop the round in the chamber, and slowly lower the slide until it stops. Then lightly bump the rear of the slide to cause the extractor to snap over the cartridge rim. NEVER do this with a 1911 type.
After doing the test, I decided to never again buy re-manufactured ammo in .40sw, as the setback I measured was very scary. This caliber is already a high pressure round, and I saw .069″ setback from one chambering. Factory ammo also moves, just not as much, maybe one or two thou per cycle. This will vary from brand to brand, and probably batch to batch.
Accuracy really suffers from noticeable setback. Targets tend to look like buckshot patterning, probably due to variable amounts of setback.
One of the possible side effects of setback is to rob the slide of it’s closing momentum, leaving you with a malf. The bullet sticks on the ramp, and the energy is wasted shoving the case up on the bullet. I’ve observed this in a govt model .45, with a bad batch of Blazer Brass. My Officers Model didn’t choke on it, but the inaccuracy was evident. Same thing observed with the G27, it will load anything, setback be damned. The bigger guns, with weaker recoil springs, are more sensitive, it appears.