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Undersized cases constricting plated lead bullets causing accuracy issues


impact

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Hi Folks.

 

I'm currently trying to improve both the accuracy of my pistol and PCC loads (123gn copper plated bullets with N320).

Lately, I had some weird flyers when testing new pistol ammo, that first made me question my form, but then one of them even keyholed, so there's something going on there.

Since the barrel is brandnew (~300 shots) it's likely the ammo. (I used 145gn Copper plated and 124gn FMJs before)

 

I use the same ammo (just with ~.040" longer OAL and a smaller charge) in my 13" PCC too, and while it's not the most accurate load ever it's at least somewhere around 4" at 50 yards, mostly ruined by flyers, 80% of the shots cluster pretty tight, this could be me too though).

 

Now, since keyholing is pretty serious, I tried to identify the cause and came across a thought that I tested out:

I'm using Dillon's standard 9mm carbide resizing die on a 750, the die that is known for restricting the cases quite a bit giving the loaded rounds the known coke bottle type shape.

I wondered if that would potentially resize the bullets bearing surface upon seating, and cause issues. The bullets OD were averaging pretty close at .356, and 5 that I pulled after seating were .0016" smaller on average, lowest measured around .354-.3535 . I'm not sure if that's normal with (copper plated) lead bullets but I feel It's not.

 

Have you experienced something similar?

I'm about trying another sizing die and compare results, but there might be issues with lead hardness too? Or is it perfectly normal and the solution likely to be found somehwere else...?

What do you think?

Edited by impact
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Are all your dies Dillon?   

This is usually a crimp issue.

The only way that I have gotten good accuracy with plated was with single head stamp brass and careful crimp adjustment to just remove the flair .

Edited by AHI
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As stated, check you crimp die first and hardest. If you’re running a lee factory crimp, we’ve likely found the problem. 


Here’s the mindset you need to have:


Just barely remove the flare from the case mouth and do nothing more, or you’re hurting all aspects of ammo quality when it comes to lead, plated, or coated 9mm bullets.


The wasp-waist / cokebottle shape of your ammo is no problem. In 9mm the tension from the undersized case is what holds the bullet in place. You are not crimping to lock the bullet into position - this isn’t a lever-action or revolver caliber. The die sizes the case below .355, and then it gets flared just enough to press a bullet back into it. So much friction/tension results from this interference fit that the bullet cannot move rearward. The crimp die is then used to remove the flare, rather than actually crimping the bullet into the case.

 

Edited by MemphisMechanic
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1 hour ago, George16 said:

What brand of crimp die are you using? I think you’re crimping too much. It should just be enough to remove the flare and nothing more.

 

You don't have a bullet set back problem doing this? I have to load for 1911s and a Glock. I can do this with the 1911s, but not the Glock. I do get bullet set back. 

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Just now, Bobkoh said:

 

You don't have a bullet set back problem doing this? I have to load for 1911s and a Glock. I can do this with the 1911s, but not the Glock. I do get bullet set back. 

No I don’t. 
 

It’s very important that the case is resized correctly because it provides the bullet tension to prevent setback and not the crimp. Crimp (taper crimp) is actually a misnomer since all that needs to be done is to remove the flare on the case when it was expanded to accept the bullet. It’s not done (crimp) to hold the bullet in the case to prevent bullet setback.

 

For 9mm, I’m using a Redding sizing/decapping die.

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Impact,

     I am currently looking for a solution to this very problem. I have Dillon, RCBS, and Redding sizing dies for the 9mm, I use the RCBS the most, it  does not undersize as much as the  Dillon. The best I have been able to do is deformation of about .0006 on the plated bullet, this is with no crimp, insert bullet and then turn around and pull the bullet.  At 5 yards the bullet seems perfect, at 10 yards, on a new target the hole is not round. It took a while to notice this, not paying attention I guess. A careful look shows the bullet starting to tip.  At 25 yards 1/4th of the holes in the target are a noticeable tip, can't miss it. This pistol will shoot Aguila 124gr into a 2 1/4 group off bags if I hold steady at the 25 yard mark. I am trying to make these bullets work, I just can't get what I really want, a good cheap jacketed bullet. I think they are too soft for use in a pistol cartridge, bullets I can move with the pressure of my thumb, pressing as hard as I can, when those bullets are pulled, not all but most don't measure the same as they were before being seated. Please if someone has the answer share it.

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Case mouth measurement should be somewhere between .377-.379. Check a pulled bullet, no more than a faint line should be visible.

 

Don't do this...

 

Crimping - You're over doing it: - IDPAforum

 

In the meantime, tell us more about this brand new barrel that clearly isn't the problem...

 

 

Edited by 4n2t0
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6 hours ago, impact said:

 

Since the barrel is brandnew (~300 shots) it's likely the ammo. (I used 145gn Copper plated and 124gn FMJs before)

 

 
Have you slugged the new barrel?

What is your charge weight?

What type of crimp die are you using?
Does it keyhole with FMJ bullets?

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Thanks for tuning in everybody!

I haven't been able to tackle the problem as systematic as I'd like to, thats why there a still some pieces of the puzzle missing, but I'll try to answer the most important questions and keep working from there. Next range trip will probably be wednesday, that's when I'll be able to collect more "hard data".

 

The new barrel is a OEM Glock barrel, for a Glock 17 Gen 4. I've got a new "upper" (slide and barrel) so I can switch between Production and Production/Carry Optics.

I have not slugged it, and I'm not exaclty sure what is meant by that and what eqipment I'd use for that. I've heard the term before regarding (mostly) rimfire rifle barrels to make sure the tightest spot is at the muzzle, not the widest, to get the most accuracy out of non elastic lead and copper plated lead bullets.

 

I'm using all dillon dies right now. I got my PCC (and Glocks, which is not a hard thing to do) set up dead reliable and well managable and focused on my shooting skills the most in the last couple of years, not so much on equipment and ammo. Now I started to reconsiderate my loading techniques. I've done precision rifle stuff sucessfully but have not tinkered around much with pistol ammo. I've considered upgrading to a redding pro carbide set but I'm not sure how much of an improvement that might cause. Or maybe one can tell me whats that best die for each step to get that will run on a progressive press and I'll try that out.

 

The crimping die is also Dillon, and set to where it will leave marks on the bullet from a crimped case mouth, still not as pronounced as on the pictures shown above. But with all other stations left empty, I can feel some slight resistance of the cartridge going into the die the last ~.060" on upward travel. Here's a picture of what that would look like:

20201004-120648.jpg

Is that considered too much? Then I'll try a lighter crimp. Case mouth OD with seated bullet (just barely below the slight chamfer the crimping die setup causes) is mostly between .375 to .376.

I checked bullet OD constriction, with and without crimp. I measured with (german made) calipers about .070" above the base of the bullet. Restriction was averaging (10 rounds) .00145" with and .00115" without crimping. So while there is a measurable difference, I'm not sure if thats statistically or practically relevant to be the culprit of accuracy loss. But who knows.

 

--The load I'm using for PCC right now is 3.7gn N320 with a 123gn RN copper plated bullet set at 1.142" OAL. Groups at about 4" at 50m, typically tight center and 30% flyers. Mixed brass. Which likely contributes to precision, I just haven't tested how much.

--In the new Glock I shot 124gn FMJs with 5.2gn N340 and 1.142 OAL before, that grouped well. I mainly made that load to mimic the ballistics of a factory 124FMJ load. While the Glock is not exaclty a benchrest rifle accuracy was fine to the point where I knew flyers were caused by my shooting skills and weren't unexplainable. Still mixed brass.

--What I shot in the new glock, that gave accuracy issues was 123 RN copper plated with 4.1 N320 at OAL 1.102". Mixed brass too.

--I used to shoot 145 RN and 147 RN with 3.9gn N340 at OAL 1.142" a lot though my older glock (~30k rounds) that hadn't got bullseye accuracy but seemed to work fine. Mixed brass, you guessed it.

I never really tried to tweak any load to max precision, since overall accuracy seemed fine to the point where I could tell flyers were caused by me and not the ammo. With the glock I can confidently hold 4" at ~14 yards with 80% of the shots beeing inside 2" and probably 30% to 40% inside 1".

With PCC its the same at ~55 yards.

 

Upon using a inertia/hammer type bullet puller, I noticed differenced in neck tension... regardless of crimping or not. Some would come loose after a fist solid impact, with some it took 3. So I guess mixed brass with unknown times of reloading is causing that. While I understand that's for sure not aiding accuracy, I'd find it hard to believe it's causing issues to the degree I experienced them. But who knows, maybe it's a combination of all things that could be improved...

Edited by impact
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That’s way too much crimp based on your picture. Raise the Dillon taper crimp die a little bit more until there’s only a faint line (.377-.380” at case mouth). It makes a bit of difference if you’re also going to use the same headstamp. Variations between loaded rounds will be less.

 

Make sure all the other stations are full when setting up your dies. That’s according to the Dillon instructions too.

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Back the crimp die off 1/2 to 3/4 turn. then ck. That is way to much crimp.

All we are trying to do is remove the flair/expansion created to start the bullet into the case.

Just straighten out the case end.

Edited by AHI
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Alright, thanks guys! I'll modify the setup and load some test ammo I can compare to the old setting.

And yes, usually when I'm setting up dies or taking measurements I'll have all stations full. I just wanted to isolate the crimping die that one time so I could feel what's actually going on. Fair suggestion though, thanks.

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Slugging the bbl is where you take a soft lead bullet and drive it through the bbl and then measure the slug. You’ll need a soft lead bullet preferably .356 or .357. A brass rod close to bore size 5/16” is close, a heavy hammer, some oil and a solid surface with a block of wood. Take the bbl out of the gun and clean it well. Oil the bore well and also the bullet. Drop the bullet into the chamber end and set the muzzle on the wood block square, and try to keep it square and vertical. If you have a threaded muzzle install the protective cap or comp.  You can also put a folded rag on the block too. DON’T rest bare threads on the block! Take the rod and hammer and gently tap the slug into the bore being careful to not nick the shoulder of the chamber. Try and keep the rod in the center of the bore and slug while you drive it all the way through the bore. Once you get the bullet engraved it will go easier. Try and notice tight/loose spots along the way and it should be a bit tighter at the muzzle end. Tap the slug out and measure the largest diameter. You’ll have to pick the bbl up and hang on to it to tap the slug all the way out. 
The reason for using a heavy hammer is that it pushes where as a small light hammer peens. 

Edited by Farmer
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12 minutes ago, Farmer said:

Slugging the bbl is...

 

Thanks! Does it work with Copper pated bullets too? I don't have anything else at hand right now.

For driving out bullets I got 8mm (~.315") brass rods. What about using a lathe's tailstock feed to push the rod through the bore? This way I might be able to better feel what's going on and don't run into the risk of damaging or misalingning anything.

Does the procedure/measurement also work for polygonal profiled barrels?

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Jacketed or copper plated bullets won’t work. They are too hard and Very difficult to push through and risk getting stuck. Also on the brass rod slightly chamfer the ends, and that’s a good size you have there. I suppose you could push with a tail stock but you’ll need to put the bbl shoulder against the chuck to keep it from slipping and that may put allot of load on your tail stock threads. You know anyone close that has any lead bullets or does casting that you could get some from? Heck I’ve used 00 buckshot and fishing weights before as long as they are close in size. And yes it’ll work on your poly bbl. Actually they seem to push through easier than std rifling. 

Edited by Farmer
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Yeah, I would not have used jacketed bullets for sure. But I'll try to find someone who's shooting lead bullets and have him maybe give or send me a couple.

I would have machined an aluminium barrel sleeve with a bore and one inside flange where the barrel goes into and the muzzle face rasts against, and one outside flange that rests on the face of the chucks (if that discription makes sense), so I don't have to crank them down like crazy. I'll try it and stop the experiment depending on how hard the bullet moves. I've used the tailstock before to assemble some smaller press fit parts, but nothing crazy that made me fear to damage or bend anything. So we'll see.

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Fully understand. Or you could machine a bullet mold and cast some up. 😄 don’t laugh I’ve done that when lapping a rifle bbl. 
One other way is to load up a round with a very light charge of fast powder and then just shoot it into either a large bucket of water or a row of milk jugs. Just something to stop the bullet without damaging it. Don’t know what powders you have but something like 2-2.5 grains of Clays should do it. Remember to lightly lube the bbl too. 

Edited by Farmer
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slugging the barrel is a good idea.

 

the ammo problem you have is that the 9mm cases are swaging the lead bullet.

when I made 9mm ammo like yours a good number of bullets fell out...

 

every 9mm funnel I have will not expand enough and then lets the case swage .356 lead bullets.

consider using a ... oooof I think it is the short 38 powder funnel that has the longer expansion area.

 

the lee FCD will finish the swaging, do not use it. 

Lee's taper crimp is good.

 

9mm dies are for jacketed bullets.

 

miranda

 

 

 

 

 

 

 

 

 

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The last barrel I slugged I use some fishing lead sinkers and melted it in a fired 9mm case with a propane torch. It worked great the 9mm case has a slight taper to it so it’s easy to start and it’s the perfect dia. It was easy to drive Thur I used a brass rod but a wood dole rod will probably work.

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Just tested some low speed loads with 115g Berrys Seated 1.125. With Clays, 1.5 grains still gets them out of my 4.5” XDM. Kicks like a 22. Also if you choose to do this make sure you raise the muzzle and then slowly lower to your water jugs media ect to keep the powder back at the primer. I might try 1.3g. 

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20 minutes ago, Dwbsig said:

The last barrel I slugged I use some fishing lead sinkers and melted it in a fired 9mm case with a propane torch. It worked great the 9mm case has a slight taper to it so it’s easy to start and it’s the perfect dia. It was easy to drive Thur I used a brass rod but a wood dole rod will probably work.

That’s a good idea also. 

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1 hour ago, Miranda said:

slugging the barrel is a good idea.

 

the ammo problem you have is that the 9mm cases are swaging the lead bullet.

when I made 9mm ammo like yours a good number of bullets fell out...

 

every 9mm funnel I have will not expand enough and then lets the case swage .356 lead bullets.

consider using a ... oooof I think it is the short 38 powder funnel that has the longer expansion area.

 

the lee FCD will finish the swaging, do not use it. 

Lee's taper crimp is good.

 

9mm dies are for jacketed bullets.

 

miranda

 

 

 

 

 

 

 

 

 

You may very well need a bit larger powder funnel.....................

 

https://www.photoescapeinc.com/products/9htc-ptu.html

 

💡

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26 minutes ago, HOGRIDER said:

You may very well need a bit larger powder funnel.....................

 

https://www.photoescapeinc.com/products/9htc-ptu.html

 

💡

cool Item.

where was this when I was doing my hunt for a powder funnel?

I made three before I got one I liked to keep from swaging the fat bottoms.

 

the one on the right is closer to what I made.

 

I made the post as problem solution advice, I think I could have been more clear about that.

 

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cool Item.
where was this when I was doing my hunt for a powder funnel?
I made three before I got one I liked to keep from swaging the fat bottoms.
 
the one on the right is closer to what I made.
 
I made the post as problem solution advice, I think I could have been more clear about that.
 

I should have directed my post to the OP as I’m sure many have suffered under-expansion with oversized bullets.....[emoji106][emoji6]


Sent from my iPhone using Tapatalk Pro
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