How much does pressure go up with under length cartridges?

B

BANNED
CGN Ultra frequent flyer
Rating - 100%
241   0   0
I made up a bunch of 10mm target loads (180 jhp\10 grains Blue Dot). Seems the brass might be pooched. I can physically push the bullets in, up to .05". If I cycle them through the gun they shrink around 0.001-0.008. Are they safe or should I pull the bullets and start over? Thanks.
 
9mm, 40S&W and 10mm are high pressure cartridges and seating too deeply will cause the pressures to rise unproportionally to the depth.

If they are too deep, pull them aprt and start from scratch.
 
9mm, 40S&W and 10mm are high pressure cartridges and seating too deeply will cause the pressures to rise unproportionally to the depth.

If they are too deep, pull them aprt and start from scratch.

Exactly as I thought:(. I figured since the charge was so low and the difference in length so small maybe I'd be ok. Rather than rip them apart maybe I will save them for use in that 610 I am going to buy one of these years. I made 200, pulling them will be a ##### with an inertia puller.
 
I saw a CZ 75 in .40 blow up when a bullet was compressed into the case during feeding resulting from poor neck tension. Viper 7 saw it also. He was holding the gun. We were both o.k., the gun was not.
 
Pull Them

Exactly as I thought:(. I figured since the charge was so low and the difference in length so small maybe I'd be ok. Rather than rip them apart maybe I will save them for use in that 610 I am going to buy one of these years. I made 200, pulling them will be a ##### with an inertia puller.

My advise would be to play it safe and pull the bullets,this is an accident waiting to happen if the bullets move on you.
 
This is where software like Quickload comes in handy. You can diddle around with parameters and see what the effects are. Seating depth is a biggie. Push a 45ACP bullet in by 6/100 with a fast powder under it and pressures go from normal to "Dangerous, Do Not Use".
 
Quickload and a few other programs are on the shortlist. If someone could maybe run it for me for information purposes I'd appreciate it. I am relegating the ammo to the dud pile to be disassembled. I don't seem myself buying a 10mm revolver so rather than risk it I will just chuck em.
 
Quickload and a few other programs are on the shortlist. If someone could maybe run it for me for information purposes I'd appreciate it. I am relegating the ammo to the dud pile to be disassembled. I don't seem myself buying a 10mm revolver so rather than risk it I will just chuck em.

On Quickload, the combination you have listed above, if I've got it right, looks a little weird. It indicates you are dealing with a compressed load and pressures are very low. I've assumed a 5" barrel.

Pressure = 4845 psi, thats what it says, not a typo !!!

MV = 1158 ft/sec

Case filled to 115.2% = compressed

Powder burn rate = 78.45% (within barrel)

Ballistic efficiency = 25.6%

Looks to me like I've entered the wrong powder. Is it Alliant Blue Dot ?
 
Last edited:
10mm auto, 180 jhp, Alliant Blue Dot, 10 grain charge, CCI 300 LP primer, 1.25" is proper COL, the lowest I saw was 1.242". Try 1.240". Thanks a bunch.
 
Last edited:
10mm auto, 180 jhp, Alliant Blue Dot, 10 grain charge, CCI 300 LP primer, 1.25" is proper COL, the lowest I saw was 1.242". Try 1.240". Thanks a bunch.

OK, see above, sorry I edited it and confused things.

With COL = 1.240 the pressure drops to 4830 psi ??
MV = 1186 ft/sec and the load is now compressed to 121.9%

By the pressures indicated, you'd be safer shooting this than throwing a spitball but something must be wrong.
 
Definitely. If 10 grains is compressed than my loads with 11.2 are getting crushed into pill form. Not to mention the super low pressure. My guess is at 1.25 they would run maybe 30KPSI?
 
Last edited:
Using 180gr Sierra JHP, 10gr Bluedot, 1.240" OAL, => 29,400 psi

BUT it seems that there is a glitch in QuickLoad with this particular combination.
 
Last edited:
I have NEVER had this problem with pistol cases...and I have re-sized and used alot of 10mm cases that were REALLY hot(the 2nd loads were for target only)???

Maybe your resizing die is out of spec?

Are you using a crimp die...

If not might I suggest a LEE FCD....that little jewel is worth it's weight in gold.:dancingbanana:
 
I am using an RCBS carbide 3 die set. 1st load was factory, second was 11.2 grains Blue Dot(HOT) and the third was 10 grains(min).

If your single staging the FCD would add 1 more function....I would try more crimp with the RCBS.

The FCD also has the advantage of resizing the finished case as it crimps making sure it will cycle better.

Your problem is akin to someone loading the same round at the top of their mag everyday(if they carry) the bullet takes a little hit each time and eventually sets back in the case....and could lead to a KaBoom.
 
Some of the rounds are set back easier than others. I will try crimping again and just chuck the ones that are too short. I will look into the FCD but I don't think I understand the advantage? My brass is sized long before a bullet is seated and I crimp anyways.

EDIT:I tried more crimp but by the time I get enough my OAL is thrown outta spec.

This batch is fubar, it's odd I used the other half of this brass with a different JHP and all the same components. They went off just fine, though I never thought to push on them to see if the were staying put.
 
Last edited:
Pulled this off another forum....can explain it better than me....:D



You have more control over the seating and crimping if you perform each in separate steps.

With the bullet seating die, there is a built in crimper. When you seat and crimp with this die, you do it all at once. You adjust the die to seat to the depth and turn the die in a half turn to set the crimp, then adjust from there for the amount of crimp. When you do this, the crimp is applied at the very end of the press cycle. If the bullet isn't seated to depth before the crimp hits the case, you will have a crushed case.

With a separate crimp die, you simple adjust your bullet seating die to seat the bullet to depth, then the crimp die is adjusted to apply the crimp. Each station does its own operation. With a crimp die, you can also elimiate variables while problem solving, as it is apparent whether the problem exists in the seating stage or the crimping stage. It either happens while seating or crimping. It reduces frustration.

Specifically, the Lee Factory Crimp Die (FCD) post sizes the round on the way out of the die. This is to insure it will fit and feed well. Many feeding and chambering problems have been solved with the application of this die. The FCD is not recommended in some calibers with lead bullets, as the opening of the die where the post sizing takes place will actually swage (squeeze) down the bullet to a smaller diameter, thus inducing leading into the gun.
 
Back
Top Bottom