Don't understand the misfires. Factory loaded ammo has a lot more clearance than you have. Whenever I had a misfire it was caused by not seating the primers to the bottom of the pocket. I don't believe in setting to some depth.
problem with bumping the shoulder
- Thread starter rebs
- Start date
The problem with this very accurate method, is that it does not work on many (most?) factory rifles. On custom actions and blueprinted actions sure. But many/most factory rifles require resistance to close the bolt on an empty chamber. Some require significant force to close the bolt, the bolts certainly don't just "fall" closed via gravity alone. You'll never be able to feel the difference between 2 thou vs zero headspace.
I see this bump method referenced often, but it does not apply to many/most of the guys asking the question.
Coyotefurharvester
Silver $$ Contributor
I wonder why 0.004 hs would be a misfire. New brass/ammo often has more hs, seen 0.006-0.007 fires just fine. Get to 0.006+ and primer will back out a few thou, that will tip off to look at "extra" bolt clearance.
Before there were "bump" gauges this was the methodology used and it worked quite well with factory rifles. The key is removing the firing pin assembly so you can better assess the degree of resistance in chambering the case. You also will be able to tell immediately, qualitatively, if you sized enough or too much. This why you see this "bump" [measurement] method referenced often especially by old timers like me.
However, I'm not advocating replacing the use of modern bump gauges and measuring bump. I'm just saying that checking in the rifle is an effective way to verify that your measuring and sizing is adequate.When the firing pin assembly is removed, at least on my factory rifles, there is no or very little resistance to the bolt locking and unlocking. You can easily and accurately feel the amount of resistance the case encounters when chambering.
It takes some experience and technique to precisely and consistently measure shoulder bump. Because of inexperience and operator error in precisely and consistently measuring shoulder bump, just blindly using a certain shoulder bump without verify the adequacy of the case chambering can result in cases either oversized or undersized.
I agree that you will not be able to feel the difference between 2 thousandths bump and zero headspace, but you don't have to. As long as the case chambers without excessive resistance, that's enough sizing. There is nothing at all wrong with zero case headspace as long as the case chambers without excessive resistance - this is what a neck sizing die does - it does not size the body or bump the shoulder. Often, you can get several reloads on a case without FL, just neck sizing.
The advantage to FL even with zero headspace is that the radial dimension of the case is also sized which significantly assist in adequate chambering. This is why I prefer FL sizing over neck sizing. While the .001 to .002" shoulder bump is an effective rule of thumb and works most of the time, you should only size enough to permit the case to chamber adequately. I believe it's always a good idea to spot check, in the rifle, to verify that the sizing used results in adequate case chambering. I mean, that's the ultimate purpose, isn't it?
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First if you're loading a bolt gun .004" set back from bolt resistance close, that will not stop the firing pin from reaching the primer....going bang. Something's wrong with you're initial measurement, recheck, use the fired cases in your chamber. You shouldn't even have to FL resize a case fired the first time in a boltgun, you could go 2 or 3 times before FL resizing with a neck sizing die or collet die. I loaded 30,000 308 for a bolt gun by doing that neck bushing size in progressive to completed cartridge, after a few (2 or 3 )loads the bolt would have a little resistance on closing ...FL size these cases and bump shoulders back .002" off progressive press, then finish cartridges in progressive...next time or two use neck bushing die in progressive, and repeat.
I Always FL size off the progressive press, except pistol calibers...in a stout single stage. Only sized rifle cases enter the progressive. The Hornady shell plate is kinda flimsy and flexes..I have 2 and 2 Dillons, but never FL size in progressive presses , for all rifle, and definitely FL size all cases for all auto loading rifles...in a Forester or Rockchucker single stage.
Ccrider
Gold $$ Contributor
Sounds like you are overworking your brass if the difference between a misfire and firing is .002. You should stop moving the shoulder back until you feel difficulty closing the bolt and then bump back .002 from that point.
Or, you have something else going on and the misfires are not being caused by the difference in bumping the shoulder. Excessive lube, weak firing pin, bad primers etc.
Or, you have something else going on and the misfires are not being caused by the difference in bumping the shoulder. Excessive lube, weak firing pin, bad primers etc.
Everyone forgets that with an empty chamber the firing pin will extend about 0.040" beyond the bolt face. The real issue is the firing pin pushing the primer farther into the pocket and/or pushing the entire case forward losing firing pin energy to set the charge off. Factory ammo with 0.005" bump space always goes off. Read an article about firing pin wire. I will try to find it on internet. Traditionally firing pin springs were made with what's called music wire, a plain carbon steel used to make guitar strings. This alloy loses spring tension very quickly. The tension is measured by recording the number of spring cycles vs strength. The only FP springs you should buy are made from a carbon steel alloy containing silicon and chrome. These springs retain tension almost for ever.
In a nutshell..
1. Fire enough factory rounds to be sure your hand loads are the issue. Many things can cause misfires. Any rifle made halfway right should shoot factory without issue. If your not the greatest at troubleshooting; shooting factory should at least tell you if it's the rifle or the ammo.
2. Measure chamber base to datum on fired case. Hornady makes a version of a comparator for your calipers. Notate and use the same guage every time. SAC also makes some and the big boys use guages made from their reamer.
3. Set up "Full length die" so that your bumping the shoulder .001 to .003 back. .004 setback is more than necessary but in my experience shouldn't cause misfires.
4. When running the press handle slowly bring the case up into die until it bottoms out...just a gentle bump at the bottom...not a heavy push. This makes the "bump" more repeatable for each time you size. Some presses will bump more or less depending on the amount of force applies to the press handle.
5. Measure each case you sized from base to datum for consistency. This is typically not necessary if your experienced but if your trying to eliminate a possible cause for a problem;. you'll know each case resized is exactly .001 or .002 bumped back from your fired size.
Other causes could be:
Firing pin protrusion is too little.
Old/faulty primers-try different types.
Firing pin spring is weak.
Bolt is full of carbon inhibiting pin striles-clean bolt.
Primer seating depth isn't sufficient/seat deeper
I'm not a gunsmith so there are likely many others but maybe this will help. I clean and lube bolt & rest of gun everytime I shoot. 20 rnds or 100rnds, necessary for every application...no. but it's what works for me to be sure my next range visit begins at the same place my last one did.
Best of luck
1. Fire enough factory rounds to be sure your hand loads are the issue. Many things can cause misfires. Any rifle made halfway right should shoot factory without issue. If your not the greatest at troubleshooting; shooting factory should at least tell you if it's the rifle or the ammo.
2. Measure chamber base to datum on fired case. Hornady makes a version of a comparator for your calipers. Notate and use the same guage every time. SAC also makes some and the big boys use guages made from their reamer.
3. Set up "Full length die" so that your bumping the shoulder .001 to .003 back. .004 setback is more than necessary but in my experience shouldn't cause misfires.
4. When running the press handle slowly bring the case up into die until it bottoms out...just a gentle bump at the bottom...not a heavy push. This makes the "bump" more repeatable for each time you size. Some presses will bump more or less depending on the amount of force applies to the press handle.
5. Measure each case you sized from base to datum for consistency. This is typically not necessary if your experienced but if your trying to eliminate a possible cause for a problem;. you'll know each case resized is exactly .001 or .002 bumped back from your fired size.
Other causes could be:
Firing pin protrusion is too little.
Old/faulty primers-try different types.
Firing pin spring is weak.
Bolt is full of carbon inhibiting pin striles-clean bolt.
Primer seating depth isn't sufficient/seat deeper
I'm not a gunsmith so there are likely many others but maybe this will help. I clean and lube bolt & rest of gun everytime I shoot. 20 rnds or 100rnds, necessary for every application...no. but it's what works for me to be sure my next range visit begins at the same place my last one did.
Best of luck
I have an LNL press, I like it a lot.
I have found, that when loading rifle ammo, you need to have the same lot of brass and all the same head stamp if you want uniformity.
Txtaxman mentioned the shell plate not being "populated." Meaning, you have to have all the stations on the press working at the same time to get repeatable results. And the longer you hang on the handle the more things will change. You will get more shoulder bump and shorter bullet seating depths.
You can experiment by pushing the handle down and then immediately raise it back up, pull that resized case and measure it. Then push the handle down again and count three seconds, pull that case and measure the difference. Four seconds will make more of a difference and so on.
Consistency is the key.
I have found, that when loading rifle ammo, you need to have the same lot of brass and all the same head stamp if you want uniformity.
Txtaxman mentioned the shell plate not being "populated." Meaning, you have to have all the stations on the press working at the same time to get repeatable results. And the longer you hang on the handle the more things will change. You will get more shoulder bump and shorter bullet seating depths.
You can experiment by pushing the handle down and then immediately raise it back up, pull that resized case and measure it. Then push the handle down again and count three seconds, pull that case and measure the difference. Four seconds will make more of a difference and so on.
Consistency is the key.
Have your cases been annealed?
IMHO, you have other issues if .004" bump causes misfires.
no they haven't
Gargoyle
Finder Outer
Yup. I noticed the very same things!
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