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Discussion Starter · #1 ·
We know that bullet setback can occur in cartridges that have been chambered into a P365/X/XL multiple times. But what is the actual cause and how can we avoid or reduce the amount of setback the bullet has into the shellcase? I've heard of at least 4 different theories which may be wholely or partly responsible for the setback.

Theory 1. The friction during the chambering of a round can cause the bullet to set back into the shellcase.

Theory 2. When a full loaded magazine is inserted while the slide is in battery, the bullet contacts the underside of the slide. When the slide is retracted, it exerts a rearward frictional force on the tip of the bullet which causes it to set back into the shellcase.

Theory 3. Some magazine loaders require you to push the cartridges by the bullet tips backward into the magazine and that this can cause the bullet to set back into the shellcase.

Theory 4. After a failure to eject, the following round is slammed into the rear of the spent round, forcing the bullet backward into the shellcase.

If any of you are aware of any other possible reasons for the cause of bullet setback, let's hear them.

As they say, one test is worth 1,000 opinions. So I'm proposing the following tests to see if any of these theories are valid.

Theory 1 Testing Procedure:

Step 1. Measure and record the overall length of the cartridge.

Step 2. Carefully insert the cartridge under test into an empty magazine without pushing on the bullet. You may need to use a tool to push the cartridge backward into the magazine by the lip of the shellcase.

Step 3. Lock the slide backward.

Step 4. Insert the magazine.

Step 5. Release the slide.

Step 6. Eject the round and measure and record the overall length.

Step 7. Repeat the procedure at least 9 more times or until you measure any significant setback.

Theory 2 Testing Procedure:

Step 1. Measure and record the overall length of the cartridge.

Step 2. Load the magazine to one less cartridge than capacity.

Step 3. Carefully insert the cartridge under test into the magazine without pushing on the bullet. You may need to use a tool to push the cartridge backward into the magazine by the lip of the shellcase.

Step 4. With the slide in battery, insert the magazine.

Step 5. Retract the slide and lock it backward.

Step 6. Remove the magazine.

Step 7. Remove the round under test.

Step 8. Measure and record the overall length of the cartridge.

Step 9. Repeat the procedure at least 9 more times or until you measure any significant setback.

Theory 3 Testing Procedure:

Step 1. Measure and record the overall length of the cartridge.

Step 2. Load the magazine to one less cartridge than capacity.

Step 3. Load the cartridge under test using the magazine loading procedure being tested.

Step 3. Remove the top round in the magazine.

Step 4. Measure and record the overall length of the cartridge.

Step 5. Repeat the procedure at least 9 more times or until you measure any significant setback.

Before performing this final test, has anyone ever heard of a round firing when it was slammed into a shellcase that had failed to eject? I'm sure that this is extremely unlikely, but I have to ask.

Theory 4 Testing Procedure:

Step 1. Measure and record the overall length of the cartridge.

Step 2. Carefully insert one cartridge into an empty magazine without pushing on the bullet. You may need to use a tool to push the cartridge backward into the magazine by the lip of the shellcase.

Step 3. Retract the slide and lock it backward.

Step 4. Insert a spent shellcase into the chamber. (DO NOT USE A LIVE ROUND!)

Step 5. Insert the magazine.

Step 6. Release the slide.

Step 7. Retract the slide and lock it backward.

Step 8. Carefully remove the magazine

Step 9. Remove the round under test and measure the overall length of the cartridge.

Step 10. Repeat the procedure at least 9 more times or until you measure any significant setback.

Keep in mind that some cartridges retain the bullets more firmly into the shellcases than others, so your tests results may vary with different brands of cartridges. It would be prudent to do these tests with different brands of cartridges.
 

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More gobbeldygook.
When are you gonna come up with theories and tests that actually involve firing the gun. :ROFLMAO::ROFLMAO::ROFLMAO:
This is the outcome when the theories are inversely proportional to the amount of actual experience 😆.

Bullet setback always happen to a different degree. Some are unnoticeable while others are so obvious and can be dangerous due to high pressure.
 

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More gobbeldygook.
When are you gonna come up with theories and tests that actually involve firing the gun.
I'll swear. What is up with this sub-forum lately?

Bullet setback from repeatedly loading the same round in a semi auto weapon is nothing new so "testing" is redundant. The solution is to NOT reload the same round into the chamber numerous times - Rotate the rounds a few times and eventually use the loaded rounds as range fodder. Or, leave your firearm loaded at all times and when not on your person secure said weapon in a proper lockbox or safe for the love of Pete. Be advised, an excessively setback round can generate unsafe pressures upon firing.

Google the subject and one can read or watch videos on YouTube for days or better yet, get some proper training.
 

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After many years and I have no idea how many rounds sent downrange, I've never experienced any noticeable bullet setback. I checked for it when I started reloading for semiautos, but it has never occurred. I also don't chamber the same round multiple times. Bullet setback has earned a place on my list of things to not worry about. Let us know how your tests come out, Allen.
 

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There is no mystery to bullet setback, it occurs with repeated chambering of a round. The bullet strikes the feed ramp which in turn pushes it deeper into the case each time. This was a big problem with .40 caliber Kahr arms pistols. These pistols have steep feed ramps. I know this for a fact because it was an issue with the K40 I owned in the past. I addressed the issue with Kahr, sent the pistol back to them and was informed that there was no issue with the pistol. The fix was simple, I did not repeatedly chamber rounds.
 

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Look to the physical momentum as the gun fires to put Newton's principles to work as far as mass and motion.

You can set the mouth tension a little tighter with taper crimping a 9mm cartridge to help the bullet resist movement into the case more, but that's about it. Depending on the design of the feed ramp, it should deflect the bullet into the chamber at angles that do not push the bullet into the case.

Unless you're physically pressing the bullet into the case, it should not set back unless it's in the magazine while the firearm is fired - and then the set back should be minimal if at all.

If you have cartridges that are displaying set back, it's likely that the maker didn't crimp them at all, or has used a bit too little taper crimp or it's inconsistent.
 

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I posted on this subject awhile back as it involved the .357 Sig cartridge. I came away believing that multiple chamberings of the same round was a probable cause.
 

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Discussion Starter · #11 ·
I'm seeing a lot of theory backed up by very solid opinions. Someone commented that using a Makershot magazine loader can cause bullet setback. It seems a bit improbable to me. HOWEVER, I entertain the possibility that it could happen.

It should also be noted that these testing procedures can be used to test your ammunition. I've heard one person complain that a bullet actually fell out of a shell casing and other bullets had shifted position in the shellcases while bouncing around inside the box inside their range bag.

Some bullets are actually sealed into the shellcases. I recently saw a video of someone using some extremely old ammunition that had the bullets sealed into the shellcases with wax. Not a single misfire.

Instead of speculating, I'll actually perform some testing to find out what is true and what is BS. One test is worth 1,000 opinions. Why leave to opinion what can be tested in fact?
 

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I'm seeing a lot of theory backed up by very solid opinions. Someone commented that using a Makershot magazine loader can cause bullet setback. It seems a bit improbable to me. HOWEVER, I entertain the possibility that it could happen.

It should also be noted that these testing procedures can be used to test your ammunition. I've heard one person complain that a bullet actually fell out of a shell casing and other bullets had shifted position in the shellcases while bouncing around inside the box inside their range bag.

Some bullets are actually sealed into the shellcases. I recently saw a video of someone using some extremely old ammunition that had the bullets sealed into the shellcases with wax. Not a single misfire.

Instead of speculating, I'll actually perform some testing to find out what is true and what is BS. One test is worth 1,000 opinions. Why leave to opinion what can be tested in fact?
.
 

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I'm seeing a lot of theory backed up by very solid opinions. Someone commented that using a Makershot magazine loader can cause bullet setback. It seems a bit improbable to me. HOWEVER, I entertain the possibility that it could happen.

It should also be noted that these testing procedures can be used to test your ammunition. I've heard one person complain that a bullet actually fell out of a shell casing and other bullets had shifted position in the shellcases while bouncing around inside the box inside their range bag.

Some bullets are actually sealed into the shellcases. I recently saw a video of someone using some extremely old ammunition that had the bullets sealed into the shellcases with wax. Not a single misfire.

Instead of speculating, I'll actually perform some testing to find out what is true and what is BS. One test is worth 1,000 opinions. Why leave to opinion what can be tested in fact?
You have too much time in your hands. Time better spent going to the range to shoot and practice to get better 🤣
 

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Instead of speculating, I'll actually perform some testing to find out what is true and what is BS. One test is worth 1,000 opinions. Why leave to opinion what can be tested in fact?
Here is something that is not opinion, not speculation, but my actual firsthand experience - I have run many rounds through a couple different P365s along with a lot of other pistols. Along with that I have re-chambered defensive rounds multiple times, frequently without any appreciable setback occurring.

I have even used the same boxes of carry ammo for up to a year at a time, re-chambering those rounds more times than I could keep track of. Occasionally, I would line all those rounds up on a level surface, and 'weed out' any that showed an obvious amount of setback, and put them in a separate box to be fired on an upcoming range trip.

These are my results from direct experience over numerous years (not an opinion) - I have never once had any of those defensive rounds not fire properly when taking them to the range. Not the rounds that had been re-chambered multiple times, nor the ones I weeded out that showed noticeable setback. They all still fired properly and did not create any malfunctions whatsoever.

The above is not advice on what anyone else should do. We all need to make our own decisions. I'm just relating what my experience has been, using quality defensive ammo from Federal, Speer, etc.

Now here's my opinion - setback is an over-exaggerated concern. If you have a particular round that shows a fair bit of setback, take it out of circulation, largely for peace of mind. Otherwise, there are far more important things to focus on - like the ability to shoot accurately under duress. How is your practice coming with that, as opposed to these mechanical rabbit holes?
 

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If I have to unchamber the JHP round when I practice shoot, I am putting back the round in the open chamber, instead of letting it be racked in, hitting the ramp.
Or just shoot the JHP at the beginning of the session, freshen them up.
Instead of speculating, I'll actually perform some testing to find out what is true and what is BS. One test is worth 1,000 opinions. Why leave to opinion what can be tested in fact?
Some guy was really determined to check the kaboom effects of bullet setback... and was disappointed:
Battered Bullets: Does bullet setback matter? | The Daily Caller

PS: I am so tempted to get a Berretta PX4 Storm. One of the advantages, from many, is that the feed ramp is very small, because of rotating barrel unlocking mechanism.
 

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Discussion Starter · #19 ·
Here are the results of two tests using Remington Range FMJ 9mm cartridges.

The initial cartridge overall length was 1.114".

Using a Makershot magazine loader with a stock 12rd Sig mag with 11 rounds already in the magazine, I loaded and unloaded the 12th rd using my finger on the tip of the bullet to push it back into the magazine 10 times. At the end of the test I measured the cartridge OAL to be 1.114". No change.

Using the SAME cartridge and the same Makershot loader, I proceeded to load it into a stock 12rd Sig mag with 11 rounds already in the magazine, making 12 rds in the magazine total. I inserted the magazine into my Sig P365X with the slide in battery. I retracted the slide and locked it backward. I removed the magazine, removed the cartridge under test, and measured it. I repeated the test 9 more times. At the end of the test I measured the cartridge OAL to be 1.114". No change.

Which means that using the Makershot loader, I loaded and unloaded the same cartridge as the 12th round in the magazine 20 times with no change in setback. This doesn't necessarily debunk someone's claim on Sig Talk that using the Makershot loader caused bullet setback for him. But I'd like to see him replicate the setback using the same ammunition with which he originally had the setback problem. It could have been that the cartridges he was using had loose bullets. But for myself, I'll perform some type of test on every brand of ammo that I use to make sure that they won't be prone to bullet setback problems. Eazy peazy.

On the second test it required a considerable amount of effort to rack the slide with 12 rounds already in the magazine. It didn't cause the bullet to setback, but it did cause deep scratches in the brass that I can feel with my fingernails.

The question that this raises for me is: "When carrying with one round in the chamber and 12 rounds in the magazine, could the amount of force that the magazine springs exert upon the cartridge increase the friction against the cartridge enough to cause a failure to feed?" If there no failures to feed in this condition when the RSA is new, could failures to feed in this condition occur as the recoil spring becomes weaker with age?
 

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Discussion Starter · #20 ·
Here is something that is not opinion, not speculation, but my actual firsthand experience ......
I'll grant your first hand experience, however I would have preferred to see more quantitative data of actual measurements.

I don't think that anyone is going to claim that a bullet with severe setback won't fire. But it may just cause problems if it is fired.
 
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