Why would a scrupulously clean AR-15 fail to chamber the third or fourth round fired through it? I was just out shooting and had this problem on all three ARs I had with me. One is an original Colt, the others are handbuilts by me. They have all run rounds through them like obama through a goose in times past. But not today. I resize the cases with a small-base RCBS die. I set the die right on top of the shellholder. I do not set it just that tiny bit past the stop to get that "cam-over" effect. The diameter at the bottom of the shoulder is 0.346; SAAMI is 0.3542. Neck diameter is 0.244; SAAMI is 0.253. Diameter at the lower datum is 0.374; SAAMI is 0.3759. I am slightly under on all measurements. The bolt stops just about 1/8-inch from fully closing. I have no idea what is wrong. I hope it isn't my ammo because I have a ton of it loaded up and I am loathe to pulling it apart to fix it. I have no commercial ammo to do a side-by-side test. I use 20-round and 30-round USGI contract magazines. Any ideas?

What is the OAL? Have you used the bullets before to reload?

Sounds to me like the shoulder wasn't bumped back enough, Dave!

Do you have an RCBS precision mic or similar device that you can accurately measure headspace length to shoulder datum?!!!

Small base dies shouldn't be needed! Check the head measurement of the cartridge!

Also check case length! Did you squeeze these SOBs down with those small base dies and not check the OAL of the case and trim as needed?!!!!

The cases are either hanging up on the shoulder or a case neck that is too long.

If you had an RCBS precision mic, I'd recommend you take the reading on a couple of FIRED cases and then bump that measurment back about 3 thousandths when resizing.

The .223Rem./5.56x45mm rimless cartridge headspaces on the shoulder. Your "small base die" is overkill and won't help you if you aren't bringing the shoulder and case length back to match chamber length.

quote:

What is the OAL? Have you used the bullets before to reload?

I have no idea what the OAL is. I set the bullet to clear the forward face of the magazine by about 1/16 inch. The actual length (from head to tip) is 2.234, but I get a variance of several thou because mil-surp pills ain't all that consistent. From head to ogive is 1.857 on the one I measured. The same ammo chambers just fine in my Thompson/Center Encore. Shoots accurately in that gun, too.

quote:

Originally posted by homebrewer:

quote:

What is the OAL? Have you used the bullets before to reload?

I have no idea what the OAL is. I set the bullet to clear the forward face of the magazine by about 1/16 inch. The actual length (from head to tip) is 2.234, but I get a variance of several thou because mil-surp pills ain't all that consistent. From head to ogive is 1.857 on the one I measured. The same ammo chambers just fine in my Thompson/Center Encore. Shoots accurately in that gun, too.

If it feeds through the magazine, OAL of loaded cartridge is not the problem!

An Encore has more cam power. When closing the action you can actually push back the shoulder a bit.

Check the headspace on a couple of fired cartridges. Bump back about 3 thousandths.

Case neck is often an issue. I've seen cases that had a flair at the mouth after loading and would not chamber.

Went to the range today with three offending AR rifles. Two are Shorty carbines with (effective) 11.5-inch barrels and collapsing stocks. The third one has a 16-inch barrel and fixed, A2 stock. I had two boxes of the "white box" Winchester ammo with me, as well as a few hundred of my handloads from various dates in the past. The handloads were of various powders and charges; all used 55-grain FMJ bullets. My friend did all the shooting while I did all the watching and studying of what was going on. What we were able to discern is that my handloads are not sized correctly, that the powder charge is either insufficient or is the wrong powder for the length of the barrel. All of the Winchester ammo chambered, fired and extracted perfectly. Many of my handloads did not fully chamber and a few caused the bolt to only retract about halfway. A few failed to strip the next round after a successful extraction of the previous round. My picture at the top shows the indentations in the cases caused by unburned powder. This is why I think I have the wrong powder or too much powder. But if I have too much, why did just two or three fail to fully push the bolt back? I used BL-C(2), Accurate Arms 2230 and Accurate Arms 2200 Data Powder in these loads. All were loaded to middlin' charges. The recoil of all my loads was discernably less than the Winchester ammo. The questions arise when for some firing strings, the handloads functioned flawlessly in strings of four, five and six shots or more. At other times, it was a victory to get two shots off pop-pop. We used all three mags and all three guns, mixing the commercial ammo and handloads in various combinations to try to cover all the bases. I think we did OK.

The upshot is I have many, many, many shells already loaded. If I had to pull them all apart, resize and reload, I'd be doing it for months. I can't do that. I am sick. I don't know what to do...

you could always fire them in a bolt action.
Although,with that much unburned powder,I think you have either bad powder,or way too slow for the barrel length.The only time I have seen that much unburned powder was with an old lot of 2400 in my 41 mag.If you are getting powder like that in your chamber,it will not feed.

Do you have the different kinds of powder separate,or all they mixed together?Try to see if one powder is better than the others.


Have you ever trimmed these brass? Measure an unfired rounds brass length.measure several.
I always trim once fired brass,to make them a consistent length,especially for semi auto rifles.Some semis are pretty picky about burn rate and case size to function correctly.
Also,if you crimp,the cases have to be pretty consistant length,or the longer ones will get a bulge that will impede chambering.

quote:

Originally posted by homebrewer:


Went to the range today with three offending AR rifles. Two are Shorty carbines with (effective) 11.5-inch barrels and collapsing stocks. The third one has a 16-inch barrel and fixed, A2 stock. I had two boxes of the "white box" Winchester ammo with me, as well as a few hundred of my handloads from various dates in the past. The handloads were of various powders and charges; all used 55-grain FMJ bullets. My friend did all the shooting while I did all the watching and studying of what was going on. What we were able to discern is that my handloads are not sized correctly, that the powder charge is either insufficient or is the wrong powder for the length of the barrel. All of the Winchester ammo chambered, fired and extracted perfectly. Many of my handloads did not fully chamber and a few caused the bolt to only retract about halfway. A few failed to strip the next round after a successful extraction of the previous round. My picture at the top shows the indentations in the cases caused by unburned powder. This is why I think I have the wrong powder or too much powder. But if I have too much, why did just two or three fail to fully push the bolt back? I used BL-C(2), Accurate Arms 2230 and Accurate Arms 2200 Data Powder in these loads. All were loaded to middlin' charges. The recoil of all my loads was discernably less than the Winchester ammo. The questions arise when for some firing strings, the handloads functioned flawlessly in strings of four, five and six shots or more. At other times, it was a victory to get two shots off pop-pop. We used all three mags and all three guns, mixing the commercial ammo and handloads in various combinations to try to cover all the bases. I think we did OK.

The upshot is I have many, many, many shells already loaded. If I had to pull them all apart, resize and reload, I'd be doing it for months. I can't do that. I am sick. I don't know what to do...

Looks like you have one or all of the following problems:

1. Too light a powder charge for the bullet used.
2. Too light a bullet for the powder charge.

3. Wrong burning rate powder - too slow

4. Wrong powder charge used - too light

Pull a few down and check the powder charge.
If that does not give you a clear answer pull down about 20 and load them with 3031 or 4198 starting loads. Sounds like your sizing is ok.....unfortunately...

quote:

Do you have the different kinds of powder separate, or all they mixed together? Try to see if one powder is better than the others. Have you ever trimmed these brass?

I have used just a few powders in all my 223Rem loads. I use AA2230, AA2200DP, BL-C(2) and "H380" that has a label on it that says it's the equivalent of WC-852 mil-surp powder. I don't have the charge weights written down for much of the stuff that's already loaded. I just decided on what I thought would be a safe charge and loaded up bazillions of them with whatever powder I was using for that batch.

sounds like you got a mess,bud.
I did a little look around the net,see what I could find on wc-852,as the reference to h380 being like it, sounds funny,as h380 is widely used and wc852 is not.
The reference should be the other way around.(I.E., this is wc 852,use h380 load data)
Seems to me it sounds pretty slow for a 223,with a 55 gr bullet.I could be wrong ,here,because Im not sure what you DO have.But too slow of powder does leave unburned powder in the gun.(The worst part is,because the loaded rounds arent separated by powder type,you cant break them down and salvage the powder.)

Here are some quotes from around the net.



"More on WC852, this is a rolled double-based speroidal powder original purpose was for loading Cal. .30 APM2, suited for 165-gr. and heavier bullets. Much of this was sold by Hodgdon as H414, burning rate is similar to W-W760. "

"Clarification on WC852(s)

Original application was cal. .30 ('06) Ball M2. and APM2. Uses data for surplus H414.

New production Hodgdon H414 product is similar to WW760."

"
WC852(s)
lot #47287 is more like RL-19/H4831."

"wc852 and wc852f can be used for 30-006 use imr 3031 or imr 4895 data.reduce and work up."

"These are some 100 yard groups I fired today with my Browning A-Bolt Medallion in .30-06. The load was a Sierra 180 Grain Matchking in Winchester brass. Primer was a Federal 215 Magnum, and 54.0 Grains of WC-852 Military Surplus Ball Powder. I love this powder! The stuff is so consistent it's not funny. It flows thru a measure effortlessly without all that crunching and shearing you get with stick powders. The best thing is the price, $40.00 for an 8 pound jug. I get it from Jeff Bartlett over at www.gibrass.com (http://www.gibrass.com) Whats nice is if you buy 6, 8 pound jugs he pays the Haz-Mat fee. Pretty hard to beat. I bought 3 jugs of WC-852 which I use in all of my medium bore cartridges in the .30-06 class. I get excellent velocity and accuracy without any signs of high pressure. The stuff is very clean burning as well. It all comes with cross reference data to get you started. This stuff is so slow burning it's pretty hard to get into trouble with it."
"
Slow powder out of an -06 - any idea of the velocity you are getting?"


"In the .30-06 with 54.0 Grains of WC-852 and the Federal 215 Primer I'm running right around 2,600 FPS according to my Pro Digital Competition Electronics Chronograph. This stuff is quite slow, and seating out to almost touching the lands, along with the Federal 215 Mag Primer helps to give constant ignition along with stable velocities. WC-852 along with WC-872 are mostly for large capacity, magnum rifles. There are other Milsurp powders available for cartridges in the .223 and .308, as well as handgun rounds like the .45 ACP and small cased rounds such as the .30 M-1 Carbine round.

Did you use magnum primers w/ the BLC(2)?
H380 is way to slow!! The slowest I have used is IMR4064. I'm using a 20" DCM. A combination of BLC(2) without mag primers and H380 is to slow. You are everywhere. AA2230 is just right! If you pull the neck button you can resize without dismantling the cartridge. If the shoulder is to far forward it may help all of your issues. The BLC(2) and H380 may work fine on a hot summer day. I would give it a try.

quote:

If you pull the neck button you can resize without dismantling the cartridge.

This where I was heading. I'd have to pull the bullet, dump the powder, apply beeswax lube by hand to each one, resize, wipe the lube off and then finish the job. My poor fingers will be so sore they'll want to fall off...

nomebrewer

First get a headspace gauge, I use Mo's, but a Wilson would work.

Second see if your rounds will chamber in a friends bolt rifle...
This would be a good excuse to get a 223 Bolt gun...

If not get an H&K 93, they shoot most anything...

quote:

First, get a headspace gauge...

I ordered a Wilson case gauge from Sinclair the other night on the recommendation of a recently-departed (or is he?) member. I have no idea how to use it when it gets here. I assume I am to measure the protrusion (if any) of the head above the gauge to determine where to set my dies. I also assume there will be instructions. I set the mouth of the die smack on the shellholder. I do not screw the die in that extra quarter-turn. If the gauge indicates that I need to set my dies down .010 inches farther, I have no place to go. I will need the shellholder trimmed down that amount or better yet, trimmed down by .020-- then I set the die with a feeler gauge. This what I do on my 300WSM target gun. I have headspace set to .002 on that one. We'll know a lot more when the gauge thingy gets here...

did you trim these cases?

Yes. I use my Lee trimmer which trims them .005 inches under the SAAMI 1.760 standard. Every case gets trimmed after it gets shot-- no exceptions...

Are the bullets contacting the lands? Chamber a round,extract it,and see if it has rifling marks on the bullet.

Measured my handloads and commercial loads with my "hexnut" comparator. They are essentially the same. Problem has to be in the sizing of the case...

Got the case comparator. Head sticks up by anywhere from .0065 to .012-some inches, depending on which case is measured. Interesting this is some fit exactly like commercial ammo, even though all were resized in same die with die set right on shellholder. Any of you reloadin' experts have an opinion as to why? I'm baffled...

quote:

Originally posted by homebrewer:

quote:

First, get a headspace gauge...

I ordered a Wilson case gauge from Sinclair the other night on the recommendation of a recently-departed (or is he?) member.

If you are referring to me, I'm not departed and I think think you would have been better off getting an RCBS Precision Mic rather than the Wilson/Sinclair case gauge (it's not a headspace gauge..... unless you bought a headspace gauge).

The Wilson/Sinclair gauge will work..... just follow the instructions. First size for shoulder length (headspace) then trim (OAL).

From the photos, it looks like the cases you are using are stepped on Elko Shooting Range pick ups. I'd also guess that they were fired through a bunch of different firearms and are from both military and civilian brass. This may be why you are getting the crazy variences in headspace with the sizing die at the same setting.

No short recoil....... so forget all the powder/primer recomendations. And if the cartridge fits in the magazine, then OAL is probably not a problem.

From your posts, I think you might have installed these barrels yourself. Did you check the headspace on these firearms after you installed them? Sometimes barrels are furnished with semi-finished chambering.

Not trying to be insulting...... but sometimes the most obvious things are overlooked.

quote:

Originally posted by DaMan:



No short recoil....... so forget all the powder/primer recomendations.

"Many of my handloads did not fully chamber and a few caused the bolt to only retract about halfway. A few failed to strip the next round after a successful extraction of the previous round. My picture at the top shows the indentations in the cases caused by unburned powder."

Excess headspace does not cause unburned powder.Short stroke of the bolt, reduced recoil and unburned powder ,to me,points to too slow of powder.However,there could be more than one defect present.If as daman says,the brass is pick up brass,it could very well be some of it is still too large.Also if you have match barrels,the chambers you have could be rather small.
Some auto loaders I have loaded for are very picky about burning rate and case sizing,even with a small base die.
If it was me,before I started pulling bullets ,I would try some in a bolt or single shot to see if the problems are still present or not.

quote:

I would try some in a bolt or single shot to see if the problems are still present or not.

I shot a .370-inch, three-shot group from 100 yards with fodder that's loaded for my ARs last Sunday. Used my T/C Encore. I do not trickle the powder nor weigh the bullets for my ARs-- just drop it from my Lee Powder measure and slam the bullets in with my garden-variety RCBS dies. No problems closing the T/C, breaking it open after the shot or having the extractor lift out the spent casing. The T/C produced a .076-inch, three-shot masterpiece using nickle-plated Winchester brass and an unknown charge of unknown powder with an unknown bullet. I was going to write down the load data when I loaded the rounds several months ago, but never did. I have no idea what it is...

I have set my die to push the shoulder down such that I can now get the few primed cases I have resized to drop into the comparator slicker than snot. There is no light showing between the straightedge I use to check for protrusion and the top of the comparator body. I have to assume the cases now have the shoulder in the right place. Now here's the million-dollar question: Can I resize without using case lube considering I am just bumping down the shoulder by a few thousandths? I have so far done it for four cases. Didn't seem to exhibit any sticking, but I am cautious. I have a boatload of them to do. Really looking for a way to cut the time required without ruining the primers...

quote:

Originally posted by homebrewer:
I have set my die to push the shoulder down such that I can now get the few primed cases I have resized to drop into the comparator slicker than snot. There is no light showing between the straightedge I use to check for protrusion and the top of the comparator body. I have to assume the cases now have the shoulder in the right place. Now here's the million-dollar question: Can I resize without using case lube considering I am just bumping down the shoulder by a few thousandths? I have so far done it for four cases. Didn't seem to exhibit any sticking, but I am cautious. I have a boatload of them to do. Really looking for a way to cut the time required without ruining the primers...

I use Hornady spray on case lube,kind of like a wax.You may be able to get by, spraying it into the die as needed.If you have been able to do 4 without lube,I think it just might work.

I did four, made the post, did one more then got the sixth one stuck. Took maybe twenty minutes to remove it. I'm resizing primed cases, so that was a concern. I just drilled through the primer, the cup came off, I picked out the anvil, drilled the primer pocket per the instructions in the RCBS Stuck Case Remover Kit and lifted it out using the capscrew and little lifter cup thingy in the kit. I suggest to those who don't have one of these nifty little gadgets to get one. Just $15 and they save a bunch of frustration.

So far I have redone about thirty cases. That's enough to load 'em up and go test 'em for function...

quote:

I did four, made the post, did one more then got the sixth one stuck. Took maybe twenty minutes to remove it.

So far I have redone about thirty cases. That's enough to load 'em up and go test 'em for function

I hope to read whether getting a cartridge headspace gage helped you.

I have been shooting auto loading rifles in NRA Highpower competition for over 20 years. After an out of battery slamfire with a Garand, Gene Barnett the barrel maker, sent me cartridge head space gages for 308 and 30-06. Seems my cases were too long, too fat, and I was using Federal primers in a Garand. It was just a matter of time to the first slamfire.

I was using a standard RCBS sizing die and I was sizing to the shell holder plus a quarter turn. After all, those are the instructions that come with the die, it must be right?

Once you get case gages and are actually able to measure shoulder set back, you will find those instructions seldom, if ever, get you a properly sized round.

You will also find times where the die does touch the shell holder and the case is still too long. When that happened, I removed material from the base of the sizing die.

I buy Wilson type cartridge headspace gages for most of my calibers I shoot. I have the gages for all of my auto loading rifle calibers. That is .223, 308 and 30-06.

I also buy small base dies for as many calibers as I can find them. I want interchangeability between rifles. I don’t want to segregate ammo by rifle. One issue with small base dies is that you must use an adequate case sizing lube. I have tried spray on lubes, and ended up having to use a stuck case remover. I recommend RCBS water soluble case lube or Imperial sizing wax.

Cases that are a little "big" are not much of an issue for manually operated firearms. Bolt rifles have big cams and you can crunch in cases that will jam a semi autos. However, semiautos are much more ammunition sensitive. Cases must be smaller than chamber dimensions for proper functioning.

Resizing primed cases is not difficult. Just lube the exterior of the case. You can raise the decapping spindle in the die, or you can remove the decapping pin. Then resize.

Lessons learned here:

1. Always keep accurate records of your reloads.

2. Barrel length 11.5" or 16" makes NO difference in the gas pressure delivered to the gas port in the various "shorties". The gas port is the same distance up the barrel and they use the same gas tubes.

3. Segregate your brass before you size and adjust sizer die to match the various batches of brass. Brass varies in hardness. Also (believe it or not) the size of chamber the case was previously fired in effects how much you have to size it (just ask anybody who has reloaded 7.62 cases that were fired in an M-60 for their .308 Win).

I could sing the praises of the RCBS precision mic all day. I've used the Wilson type gauges in the past and like them, but the RCBS precision mic does way more than tell you if you've sized your brass to minimum dimensions. It also tells you a lot about your particular firearms headspace dimensions.

The RCBS precision mic even tells you more than headspace gauges. I have 3 AR-15 type rifles in .223. They all have slightly different chamber dimensions. I'm not talking much (.001"-.002").... but you can see the difference with the precision mic on the fired cases.

I'm not a fan of small base dies. In most cases they are not needed. The closer the cartridge fits to the chamber....the more accurate it will be. Most experienced High Power competitors push the shoulder back about .003".

Homebrewer, there's a High Power rifle match tomorrow (11-14-09) at the Elko Shooting Range. I would recommend you get out there and talk to some of the competitors using AR-15 platforms and talk to them about their reloading techniques.

Homebrewer

Your problem is simple and you have already answered it. Quit fooling with the headspace, dies, OAL etc. The problem is the unburned powder in the chamber is preventing the case from seating all the way. It is that simple.

Now that you understand the simplicity of the problem the solution is to pull the bullets and put an appropriate amount of the correct powder in the cases. H380 is indeed too slow burning as mentioned. Also AA2200 and it equivelents do not burn cleanly until the pressure is sufficient.

Hopefully you have not mixed them all up and still have them seperated by the type of powder your cartridges are loaded with. The solution is to pull all of the bullets and seperate at least the H380 powder out. If you can keep the other powders seperated so much the better but if not put them into one large container and mix them thoroughly. You will now have one "lot" of non-cannister ball powder of the appropriate burning rate. The arsenals and manufacturers mix lots of the same type of powder all the time so it is not hazardous. You must now do what you should have done in the first place. That is to work up the load and not guess at a load and then load a bunch of cartridges. With the one lot of mixed AA2230, AA2200 and BLC I'd suggest starting at 20 gr and work up in .5 gr increments to 26 gr. Use 10 shot strigs as this will ensure functional reliability. Stop when reliability is 100% and velocity equals M193 (white box Winchester).

I seriously doubt you will need to resize the case if a crimp is applied with a Lee Factory crimp die to the re-reloaded cartridges. If you do anything simply get a NS die and remove the decapping pin. No case lube will be needed when just resizing the necks.

That is about the simplest solution to your dilema. The future solution is not to "guess" at loads but work them up in the firearms they are to be used in. There are several very good reasons all of the loading manuals tell us to do just that. You have just encountered one of those reasons.

Larry Gibson

Larry, can you explain how you think the "unburnt" powder got deposited in the CHAMBER? I have never seen such a condition and I've been reloading for and shooting M-16/AR-15 many moons!

If there is enough pressure delivered to the gas port to eject the cartridge, then there was enough pressure to fully obturate the case..... which would make it impossible for unburnt powder to find it's way back into the chamber.

Interested to hear your thoughts.

Back when I was shooting heavy loads in my redhawk,heavy loads of slow powder would often leave unburned powder in the barrel and all over the shooting bench.
In an auto,once the bullet leaves the barrel and the gas pressure unlocks the bolt and it starts to open,a too slow rate of powder will have powder not yet burned still in the case.The case will be pulled from the chamber with powder still in it,allowing it to spread all through the barrel, chamber,and magazine.
I was trying to handload some 150gr bullets for an sks with the short 16" barrel using very slow powder for the application(either aa1680 or imr 4227,IIRC).There was enough powder left over to actually bind up the action in a few shots.
I also had a contender with a 10" 30-30 barrel that would leave unburned powder if I used factory 170 gr rounds loaded for rifle length barrels.150 grain loads would have a tremendous fire ball and muzzle blast from the powder burning outside the barrel.I had to use small amounts of pistol powder to burn all the powder in the case,and not have a huge muzzleblast

quote:

Originally posted by jb:
Back when I was shooting heavy loads in my redhawk,heavy loads of slow powder would often leave unburned powder in the barrel and all over the shooting bench.
In an auto,once the bullet leaves the barrel and the gas pressure unlocks the bolt and it starts to open,a too slow rate of powder will have powder not yet burned still in the case.The case will be pulled from the chamber with powder still in it,allowing it to spread all through the barrel, chamber,and magazine.
I was trying to handload some 150gr bullets for an sks with the short 16" barrel using very slow powder for the application(either aa1680 or imr 4227,IIRC).There was enough powder left over to actually bind up the action in a few shots.
I also had a contender with a 10" 30-30 barrel that would leave unburned powder if I used factory 170 gr rounds loaded for rifle length barrels.150 grain loads would have a tremendous fire ball and muzzle blast from the powder burning outside the barrel.I had to use small amounts of pistol powder to burn all the powder in the case,and not have a huge muzzleblast

Damn, I never thought of that....... unburnt powder in the barrel of a Redhawk would explain unburnt powder in the chamber of an AR-15!

maybe you not as smart as I thought you were.
The mechanics are the same.Too slow burn rate for the projectile weight and barrel length and some other factors will result in unburned powder spread through you gun.Get some AA870 and fill your handi rifle cases up with the lightest bullet you have and see what you get.

quote:

Originally posted by jb:
maybe you not as smart as I thought you were.
The mechanics are the same.Too slow burn rate for the projectile weight and barrel length and some other factors will result in unburned powder spread through you gun.Get some AA870 and fill your handi rifle cases up with the lightest bullet you have and see what you get.

Handi-Rifle is not a gas operated semi-auto!

no,but you will still get unburned powder in the barrel,and downrange .Take a bed sheet and place it downrange and you will be surprised how much powder can be left unburned.
My chrony has a lot of paint chips blasted off of it from unburned powder granules also.That was from IMR 7828 in a 25-06,with an 87 NBT.Too slow of powder for that bullet weight.

Explain how the slow burning unburnt powder got back into the chamber of an AR-15 !

not all the powder is burned before the bullet passes the gas port and leaves the barrel and the action opens,dragging the case out,letting the remaining powder spill out in the chamber and magazine,through the now empty case mouth.

another what have we learned here:

Stay off the homebrew while reloading.

Yo HomeBrewer ; What the heck are all the dimples ???.

My Bushmasters and Colt put a single ding right around the neck area upon extraction yours appear like

pinch pin extraction . Anyway before loading full size a case , then just bump back the shoulder

on another case . Cycle them through which is easier ?. Loading with Small base dies I

assume .Now Lightly lube the carrier and your problems are behind you least wise mine were .

The only thing that could have caused those dents is powder (debris) in the chamber. Like was earlier stated, unburnt powder in the case was strewn out when the case extracted leaving a dirty chamber for the next round. This is causing the loaded round not to fully chamber.

Homebrewer did you shoot these rounds at all in the summer. Shooting in colder temps will probably make the chambering problem show up more, lower gas pressures and if your bolt has a lot of lube it will slam forward with less force.