20 practical primers caved

[enrique]

It seems my primers are caving in. I bought some Norma 223 pre primed brass and neck sized.. I am getting these craters with 23.7 gr benchmark with 40 gr Vmax But getting a 1 hole group. Could it just be the primers are soft? Maybe my chamber to tight? I can push a bullet into fired case by hand but it takes a little effort.. could this be causing high pressure? I’ve seen flattened primers before and ejector marks but not caved in such as this with no ejector marks. Pierced 2 primers at 25gr (no ejected marks or hard bolt lift) so i backed off quite a bit to 23.5, 23.7, 23.9 bit didn’t fire 23.9 as they are still there and bullets will be pulled. Resized some cases and going to try cci 450 and br4 primers at 23gr BM and go up by .1gr to 23.7 hoping its just cheap primers causing the issue. I generally shoot 4 round groups, new 22 inch pac nor barrel with about 75 rounds through barrel now. Maybe I’m still just to hot but it seems that many other peoples/barrels tolerate Benchmark around 25 gr in their rifles but this is a 0 freebore chamber seated about 15 thousand off lands. 1st firing, brass doesn’t seem stretched out and fired rounds re chamber easy enough to just neck size and run sinclair mandrel. Haven’t checked primer pockets. Maybe lube didn’t get cleaned off well enough? I don’t think it was excessive headspace? we shall see when weather gets better. Maybe I should jump down to 22.5 and work up by .2 gr increments, seems pretty low and want/need all the speed I can get.. 25gr BM was at 3500 fps per couple shots off lab radar. Any slower and i should just have stuck to 52 gr 223 using same amount of powder just seated further out and 24 inch barrel - 2 inches must make a difference - in velocity that is. Also, I usually don’t chronograph until I get the group size I want then I just input into BC - maybe I should just take to time to set up my chrono - Always learning

 

[DLT]

I’ll be following. I have never seen a primer do that

 

[Mark M.]

Most likely they used a standard thickness primer, in mine I have to use the 205m which has a little thicker cup.

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[Coyotefurharvester]

I have used 450, 205AR and Rem 7.5 in my AR 20p. Never any issue. I have ran BM, 8208, and Exterminator pretty warm. Mostly run exterm, because of availability now. I don't load to 204R data levels, 25 BM and a 40 is 204 R numbers.

 

[NorCalMikie]

First thought? Headspace. (not chamber) Brass "too short for the chamber", when firing pin hits the primer, case gets pushed forward in the chamber, goes BANG and primer tries to back out of the pocket. Cratered/blanked/pierced primer from firing pin.
When you resize, don't push the shoulders back "too far". Neck size and reload.

 

[L.Sherm]

I wonder if its a combo of soft primer and to much firing pin protusion.

 

[fkimble@charter.net]

Doesn't look like a hot load. The ridge around the firing pin strike is most likely from an over sized firing pin hole in the bolt face and thin walled primers. If they were "soft" primers they would be flattened out and not still factory rounded on the edge if the load was too "hot". As Walt mentioned they are probably regular primers. A switch to match or mag(thicker walled) will probably take care of the problem. The "caved" in doesn't show up too good in the pics but the only time I've seen it was after repeated pin falls on a fired primer. Again high pressure would push the caved in area back and flatten it on the bolt face. Take a new primed case and and fire it(no powder or bullet) and see what it looks like. And carefully remove a factory primer and insert a mag or match and fire it and compare. To rule out headspace, do a measurement on an unfired case and one of your fired cases. You will need to remove the fired primer so the ridge doesn't doesn't give you a false reading. You can remove decapping assm from die and use it and a small hammer to remove the primer.

Frank

 

[jepp2]

maybe I should just take to time to set up my chrono - Always learning

I always find it helpful to collect velocity data on everything I shoot, so my chrono is always in service.

Regarding your primers, the only time I have seen that is in two cases:
- when I fire a load that doesn't go off - this has happened twice. First time the primer ignited but it didn't set off the powder charge. Second time the primer didn't have any compound in the cup.
- when I fire a primer in a case without any powder or bullet.

So neither of these apply to yours. When you deprime, measure the primer pocket depth and compare it with the standard. Off chance the pocket is cut too deep?

If the case head to datum is too short, the primer will back out of the case when fired, then the case will either partially or fully reseat the primer as the case comes back against the bolt face (the firing pin will drive it forward) and the primer will either have a mushroom top looking like high pressure, or be proud. I've had both occur with some Fiocchi factory loaded 204 Ruger rounds.

 

[JSH]

The bottom two look like some pressure, may just be picture distortion.
Those others with the deep dish almost with no primer flow or flat would almost make me think primer we’re not seated to the bottom of the pocket. I have seen similar on military rifles with large primers and cast bullets with some soft loads.

I just saw this past week a couple of folks with issues using Norma and Lapua brass with tight necks on 20 Practical. Also one with a zero freebore found his chamber to be a bit short.

I had primer issues last summer using 10X. I am going back to 71/2’s or 450’s.

 

[L.Sherm]

I had primer issues last summer using 10X. I am going back to 71/2’s or 450’s.

I never use anything but 450's and 7.5 in my 17 and 20 cal stuff.
Maybe if I had a Hornet case.

 

[enrique]

Thank you for the responses. This next week I will try my own primers as I usually do since this was necked down 223 pre-primed Norma brass. I will just neck size 4 or 5 fired rounds and I already have some that I have resized. I will load both with cci 450. If both primers look good then I will know its just a primer issue. If only neck sized look good then it was a headspace issue and will back off die 1/4-1/2 turn from touching shell holder as I am currently. I did measure with hornady comparator and both sized and fired headspace appear to be the same currently so I’m hoping just primers. If I still have issues I am going to assume my neck might be to tight from brass flow of necking down in one step, then not releasing the bullet properly without causing pressure. So I have currently ordered a 20 cal neck turning mandrel and will turn 1-2 thousandth off neck and retry pending primer trial

 

[L.Sherm]

So I have currently ordered a 20 cal neck turning mandrel and will turn 1-2 thousandth off neck and retry pending primer trial

Whats a fired case nk measured compared to a loaded round?

 

[enrique]

Lol, Maybe I have a tight neck 20-223 chamber

 

[enrique]

It was 1 thousandth more. It won’t easily slip a bullet in a fired case. It almost feels like I could just reload a bullet without resizing and have enough bullet tension to shoot it just fine

 

[L.Sherm]

It was 1 thousandth more. It won’t easily slip a bullet in a fired case. It almost feels like I could just reload a bullet without resizing and have enough bullet tension to shoot it just fine

To tight of a neck in my opinion, not saying its your problem. Most 20 Prac no turn are .232 chamber unless you wanna use Lapua then its more.

 

[Varmint56]

If a fired round is tight on the bullet turning a couple thousands off the necks would help! That tight can cause pressure problems.

 

[enrique]

That’s kind of what I was thinking but hoping that is not the issue. I really dont want to have to turn all my 20-223 Norma necks but I will in the name of science, if primers are not the issue. I should measure velocity pre and post. Maybe if neck is too tight and post turning I can increase powder and get more velocity. Plus it will probably take a couple weeks before I get my .20 hornady mandrel so it shall be primer change first - Thanks to all

 

[JSH]

I never use anything but 450's and 7.5 in my 17 and 20 cal stuff.
Maybe if I had a Hornet case.

I think some 400’s snuck in on me.
Sure hope with the changes with all of Remington that their 7 1/2’s stay up to snuff. Won’t hold my breath on seeing any soon. I did hear someone mention they got some a month or so ago, I suspect NOS.

 

[JSH]

My 22BR is a no turn. I was happy with results on paper but thought it could do better from what all I had read. I did a skim turn to just knock off the high spots. All of my flyers pretty much disappeared and group shrank down to what really made me grin.

If you have to turn I feel your pain. I got fed up with no 221 brass and then $1 each most times. I made all my own from 222, had to neck turn all of them, 300+. Got all the gear to chop brass in short order, a trim and turn system set up, along with the 222 brass, spent about $200.
Lol, should probably seek out some type of professional counseling.

 

[Coyotefurharvester]

My loaded rounds LC brass Berger 35 .230 mid neck. Win brass same bullet 0.2285. Speer 10 brass 32gr max 0.2305. Pmc 40 gr NBT 0.2285. Tried some new Win brass, final bushing 0.224, .201 mandrel Berger 35 final neck 0.2285. BHW AR barrel. Fired Speer brass 0.2325. I have not had any chambering, extraction issues even in the winter hunting.