Bullet set... forward?

[MrRob96]

Your chamber pressure will likely be all over the place, affecting velocity. I'd be curious to see how much it affected standard deviation. Have you been chronographing these by chance?

No, I have no chrono data as I haven't fired the rifle with anything but factory Aguila loads. 40 rounds down the tube so far with this SCAR.

In my factory Aguila loads, I did see mild cratering of the primer, but none of them are flattened, no pierced primers, and no primers are blowing out. Also cratering of the primers appears to be not uncommon in SCARs.

 

[MrRob96]

Yes.

The inertia of the bullet being chambered and stopping is making the bullet jump forward.

Crimp and this won't happen

There is a crimp on my bullets as applied by the Hornady seating and crimping die.

Welp I'm gonna have to get a taper crimp die and probably reduce the expander ball diameter like @ConcernedCitizen mentioned above.

What a pain in the neck......

 

[ConcernedCitizen]

Ok, update time. ...

... In the above data, light land mark means I can see a faint horizontal line on the bullet jacket, and my thumbnail can feel the line as well. ...

... That is when I'm seating the bullet, I can see the base of the bullet is bulging the neck when I don't seat fully, indicating the neck is being stretched around the bullet's bearing surface.

First of all, incredible job on the testing! Very thorough, with excellent choice in test samples. The only minor criticism I would offer is the sample size per group could have been larger, but even without it, this data tells a pretty good story.

A few quick questions and comments for you...

When you say that you see faint land marks, that's quite surprising to me, given how little the bullets jumped upon chambering.

Can you describe where these marks are? Are they on the ogive, or right in front of thecase mouth? Do you see one line going completely around the circumference, or 5-6 short lines evenly spaced around the bullet?

Basically, my question is whether the mark you are seeing is from the throat, or if it's the indentation left by the crimp. If the distance from the case mouth to the indention is consistent with the bullet jump, that would confirm it. I'd still recommend coating the bullet with a sharpie, or blackening it with soot from a match or candle, and trying at least one more with your reloads. The sharpie or soot acts like layout fluid, clearly showing everywhere the bullet made contact while chambering.

Last point regarding your post is that if you're seeing the bullet actually stretch the brass when being seated, your case mouth tension is probably okay. You can always try pushing the bullet into the case mouth by pushing against the floor or a table, if you'd like to double check.

... In my factory Aguila loads, I did see mild cratering of the primer, but none of them are flattened, no pierced primers, and no primers are blowing out. Also cratering of the primers appears to be not uncommon in SCARs.

Cratered primers without flattening is often just the primer extruding into an oversided firing pin hole on the bolt face.

There is a crimp on my bullets as applied by the Hornady seating and crimping die.

Welp I'm gonna have to get a taper crimp die and probably reduce the expander ball diameter like @ConcernedCitizen mentioned above.

What a pain in the neck......

Since it sounds like your case neck tension should be sufficient, I'd recommend holding off on modifying the expander ball just yet.

Start with the Lee FCD, which is usually only $10-$15, and try that first. The FCD is also designed to let you crimp bullets that don't have a cannelure, which is exactly what you need. Best of luck!

 

[AirResq]

I had the same issue loading .223 for my ARs. I reduced the expander ball by .002" and started cleaning the lube from the inside of the neck after resizing. Cured. I don't crimp.

 

[gmerkt]

Very good analysis by OP and Concerned Citizen. Many good comments from others. The exercise here at hand demonstrates that case mouths crimped into a cannelure on ammo intended for semi-autos serves not one but two functions. One, keeping the bullet from getting pushed further into the case, but two, also prevention of inertial movement out of the case. It's interesting to note that OP's experiments with a few different service cartridges showed, however slight, inertial movement of the bullet forward when the bolt was allowed to slam into battery.

Conventional wisdom has it that a cannelure for crimping isn't typically favorable for match shooting. The manufacturing step of adding the cannelure introduces possibilities of slight inconsistencies in the bullet product. But cannelured bullets are often associated with milspec ammo, never the highest quality. Likely you'd find that commercial bullets made by Hornady, Sierra, etc., with a cannelure these days shoot pretty well. I'm not a match grade shooter, more like a service grade shooter so I don't normally shoot bullets without cannelure in my semi-autos. Sometimes if I have once-fired brass that has very tight bullet pull, I'll use bullets without cannelure in an M1 Rifle.

Richard Lee claims that greater accuracy can be achieved by using his Lee Factory Crimp Die. I don't have any science against it; I think the die has more merit for reliability than accuracy. That is, how can crushing the case mouth into the wall of the bullet be a good thing for accuracy? Particularly with respect to bullets without cannelure. You'd have to show me that every single case was perfectly and uniformly trimmed one from the other. I mean perfectly. That's step no. one in getting any kind of consistency out of crushing the case into the bullet. It's my belief that the whole reason that some big factories (hence the name of the Lee product) use that method to crimp bullets is BECAUSE of inconsistent case lengths. The factory crimp allows them to ensure the bullet is adequately secured in the case, regardless of minor case length variations. I myself even have a few Lee Factory Crimp dies in diff. calibers, but I restrict their use to quick and dirty, one-off solutions.

Lee's premise as to enhanced accuracy for having used the factory crimp die is based on pressure build-up from a more firmly secured bullet. Once again, I don't have any science to prove otherwise. But it seems to me that factory crimp method has the potential to introduce more variables than it eliminates. Especially in the hands of 85% of handloaders. Like those who don't know about case trimming. Yes, I've met some. Just my opinion.

One last comment re. the Factory Crimp Die. They can make for ragged case mouths, guaranteeing trim work. Some WW factory ammo has really deep factory crimp that does this.

For decades, my preference has been for using taper crimp dies on most rifle ammo that I've loaded.

It's interesting to note that in the OP's experiences, he's never stuck a bullet into the leade and had it remain there upon case extraction. I'd say his brass has sufficient neck tension.

 

[gmerkt]

I had the same issue loading .223 for my ARs. I reduced the expander ball by .002" and started cleaning the lube from the inside of the neck after resizing. Cured. I don't crimp.

Without my asking a bunch more questions, I can't see why there would be any bullet lube remaining in the case neck by the time you got to the step of bullet seating.

 

[AirResq]

I tumble then resize.

 

[ConcernedCitizen]

I tumble then resize.

I tumble again after resizing to remove lube and hopefully clean the primer pockets a little. Even on a progressive press, I prefer to size and tumble separately, and sometimes even hand prime in advance.

What type of lube are you using where you don't have to remove it from the body, but do have to remove it from the case neck?

 

[AirResq]

I tumble again after resizing to remove lube and hopefully clean the primer pockets a little. Even on a progressive press, I prefer to size and tumble separately, and sometimes even hand prime in advance.

What type of lube are you using where you don't have to remove it from the body, but do have to remove it from the case neck?

I use a single stage. RCBS Lube 2. I tap the mouth of case on the lube pad once for every 10. I do wipe down the outside also. Not saying my way is best. It is slow and tedious, but it did stop the .007-.012 creep I was getting during chambering. It also reduced the velocity spread I was getting.

I will try running them through the tumbler again after resizing. Was previously told it would gum up the media (corncob).

 

[ConcernedCitizen]

I use a single stage. RCBS Lube 2. I tap the mouth of case on the lube pad once for every 10. I do wipe down the outside also. Not saying my way is best. It is slow and tedious, but it did stop the .007-.012 creep I was getting during chambering. It also reduced the velocity spread I was getting.

I will try running them through the tumbler again after resizing. Was previously told it would gum up the media (corncob).

If you're wiping them down individually, not tumbling afterwards makes sense. If it stopped the creep you were seeing, I'd say your method works just fine.

As for gumming up the media, it's a lot like adding new polish. It will clump up at first, but as it tumbles the clumps will break apart.

I use Imperial Sizing Die Wax personally, including the case mouth, and have never had any issues other than the occasional plugged flash hole. I can't remember having any issues with RCBS lube either. At most, you might have to replace your media more frequently.

If you really want to improve your tumbling method, look into wet tumbling with stainless steel pins. I'm just about ready to go that way myself.

 

[AirResq]

If you're wiping them down individually, not tumbling afterwards makes sense. If it stopped the creep you were seeing, I'd say your method works just fine.

As for gumming up the media, it's a lot like adding new polish. It will clump up at first, but as it tumbles the clumps will break apart.

I use Imperial Sizing Die Wax personally, including the case mouth, and have never had any issues other than the occasional plugged flash hole. I can't remember having any issues with RCBS lube either. At most, you might have to replace your media more frequently.

If you really want to improve your tumbling method, look into wet tumbling with stainless steel pins. I'm just about ready to go that way myself.

Thanks for the info!

 

[gmerkt]

I use a single stage. RCBS Lube 2. I tap the mouth of case on the lube pad once for every 10. I do wipe down the outside also. Not saying my way is best. It is slow and tedious, but it did stop the .007-.012 creep I was getting during chambering. It also reduced the velocity spread I was getting.

I will try running them through the tumbler again after resizing. Was previously told it would gum up the media (corncob).

Basically, you need to clean the cases twice. Once, to make them clean enough to resize. Again, to remove sizing lube. It's true, you can prolong the life of tumbling media by keeping sizing lube out of it. But the trade-off in labor is huge. Corn-cob media is pretty cheap. Walnut is a bit more but the time and tedium of cleaning individual case necks is great.

My approach to cleaning cases depends on situations. If before resizing, they are oily, tarnished, spotted or sooty, they get cleaned with a liquid case cleaner like Iosso. Then sized, then rinsed to remove the RCBS sizing lube WHICH IS WATER SOLUBLE. Once dried, they are ready for the next step. Brass with a mirror-like shine isn't that important to me, that's for Nosler. Military shine is good enough for me. But if you like shine, you can always put the brass back in your clean media and run it to get the shine you want. Then you get the labor of poking random media out of the flash holes. Which you don't get in any case from rinsing with water.

If they are relatively clean and not oily prior to sizing, I tumble them. Then size, then rinse in water and allow to dry.

Rinsing the sizing lube off with water is way easier and simpler than wiping out individual case necks. True, there is air drying time. But I'm never in a hurry to do anything related to hand loading.

I've not yet tried wet tumbling in steel pins, ultrasonic cleaning, etc. I guess I've been happy enough with the processes I describe above.

Re. chemical case cleaners, I used Birchwood-Casey product for years but found that Iosso works better. BUT: Rinse thoroughly after using Iosso. When you think you've rinsed enough, keep doing it two or three more times. You can use the chemical case cleaners repeatedly but of course they degrade with use and eventually need replacement. Just like tumbling media wears out. Store in plastic or glass jugs, not metal.

 

[AirResq]

Basically, you need to clean the cases twice. Once, to make them clean enough to resize. Again, to remove sizing lube. It's true, you can prolong the life of tumbling media by keeping sizing lube out of it. But the trade-off in labor is huge. Corn-cob media is pretty cheap. Walnut is a bit more but the time and tedium of cleaning individual case necks is great.

My approach to cleaning cases depends on situations. If before resizing, they are oily, tarnished, spotted or sooty, they get cleaned with a liquid case cleaner like Iosso. Then sized, then rinsed to remove the RCBS sizing lube WHICH IS WATER SOLUBLE. Once dried, they are ready for the next step. Brass with a mirror-like shine isn't that important to me, that's for Nosler. Military shine is good enough for me. But if you like shine, you can always put the brass back in your clean media and run it to get the shine you want. Then you get the labor of poking random media out of the flash holes. Which you don't get in any case from rinsing with water.

If they are relatively clean and not oily prior to sizing, I tumble them. Then size, then rinse in water and allow to dry.

Rinsing the sizing lube off with water is way easier and simpler than wiping out individual case necks. True, there is air drying time. But I'm never in a hurry to do anything related to hand loading.

I've not yet tried wet tumbling in steel pins, ultrasonic cleaning, etc. I guess I've been happy enough with the processes I describe above.

Re. chemical case cleaners, I used Birchwood-Casey product for years but found that Iosso works better. BUT: Rinse thoroughly after using Iosso. When you think you've rinsed enough, keep doing it two or three more times. You can use the chemical case cleaners repeatedly but of course they degrade with use and eventually need replacement. Just like tumbling media wears out. Store in plastic or glass jugs, not metal.

Great info. Thank you!

 

[Whisky Tahoe]

I'm running into an interesting phenomenon that I'm not finding much info on the web and wondering if others have found the same issue and what they've done.

I'm reloading 7.62x51 for a semiauto rifle (scar 17s) and I'm seeing bullet set forward.

After chambering a round loaded with a 168gr Sierra Matchking, the round comes out of the chamber about .020" longer than it went in. At first this confused me, then I figured the sudden stop once in the chamber is acting like a bullet puller.

I measured a surplus L2A2 round after chambering and noted that bullet grew as well after chambering, tho not as much. It grew about .009". Lighter weight and the bullet has a cannelure where the Matchking doesn't.

Has anyone noted this before and what did you do about it? I can't imagine this helps accuracy.

Mr Rob, you want to avoid the scenario where the bullet mains in the lands but the case is extracted. The powder like cockroaches will scurry to every dark corner, nook , cranny, crevice, refusing to come willingly. I would like spare you that experience.

You have received good advice regarding seating and neck tension. I don't enough about the steps you are following to give you any advice but I'll share the steps I take when reloading for my semiautos.

1) Always start with quality factory ammo before chasing issues with reloads. There are more ways for reloads to cause a problem and you can have multiple issues at the same time.

2) at the range where it is safe, chamber a round then extract it. Are you seeing a problem with factory ammo bullets getting pulled? Use calipers if you have them to give you more precise measurements. If you have factory ammo exhibiting this problem you might have to stick with ammo marked exactly the same your chamber. 7.62x54 vs 308 Win. Hopefully not. I haven't heard of this being an issue. With .223 vs 5.56x45 the difference is freebore where the 5.56 chambers have more and 5.56x45 ammo generates more pressure in 223 chambers with shorter freebore.

3) If factory ammo works then we need to debug the reloading process.
a) full length resize including neck; Semiautos need more resizing than bolts
b) seat bullets so your COAL is below max. If you know the dimensions of your chamber, and throat, make sure you have jump to the lands by some amount.
c) consider a taper crimp step after seating
d) brass has a finite life unless you are annealing. try testing with fresher brass if you get stumped

 

[best defense]

The L2A2 I tried loading is a 147-8gr bullet. I was comparing the two.

I am trying to load to achieve high accuracy with the scar platform, which it has a reputation for. Hence the SMK bullets.

I'm thinking the set forward may actually impact that accuracy because the creep forward will be inconsistent I imagine.

**************************************************************
If you use a bullet that engages the rifling when it is chambered, it is possible to actually pull the bullet out of the case when ejecting a loaded round.
Hornaday makes a tool which holds a bullet in a special case that gets screwed onto a shaft.
The shaft is then inserted into the chamber with whatever kind of bullet you are loading in your ammo. A flexible rod is then pushed up through the special case against the base of the bullet to force the bullet up against the lands.
When you pull the shaft out of the chamber if the bullet did not get stuck up in the lands you can can see how long the bullet can be seated out of the case before it hits the lands. If the bullet did get stuck in the lands you can still push it out with a cleaning rod and place it back into the special case, then measure it.

There are arguements for loading bullets that engage the lands and for bullets that do not engage the lands when loaded. If you do enough load testing you will be able to determine which way works best in your rifle, but bullets that engage the lands frequently do get pulled out when a live round is ejected. So don't be surprised when that happens.

 

[ConcernedCitizen]

**************************************************************
If you use a bullet that engages the rifling when it is chambered, it is possible to actually pull the bullet out of the case when ejecting a loaded round.
Hornaday makes a tool which holds a bullet in a special case that gets screwed onto a shaft.
The shaft is then inserted into the chamber with whatever kind of bullet you are loading in your ammo. A flexible rod is then pushed up through the special case against the base of the bullet to force the bullet up against the lands.
When you pull the shaft out of the chamber if the bullet did not get stuck up in the lands you can can see how long the bullet can be seated out of the case before it hits the lands. If the bullet did get stuck in the lands you can still push it out with a cleaning rod and place it back into the special case, then measure it.

There are arguements for loading bullets that engage the lands and for bullets that do not engage the lands when loaded. If you do enough load testing you will be able to determine which way works best in your rifle, but bullets that engage the lands frequently do get pulled out when a live round is ejected. So don't be surprised when that happens.

You are correct about how to measure distance to the lands, or at least one method of how to. Unfortunately that doesn't apply to OP, as he's limited to loading to magazine length for a semi-automatic rifle.

The closest he can realistically get is an OAL of 2.820", which should put him approximately 0.065" off the lands, based on someone else's previous measurements.