semi-auto setback - how much is too much?

[str8wal]

RCBS has seen 9mm ammo more than double in pressure over a .003 set back.

I would like to see some documentation on that. I have had to seat bullets a bit deeper in the case than suggested in data to get them to plunk in some barrels and if .003" would double pressure I should have had a lot of guns explode, which I haven't.

[Outpost75]

I would like to see some documentation on that. I have had to seat bullets a bit deeper in the case than suggested in data to get them to plunk in some barrels and if .003" would double pressure I should have had a lot of guns explode, which I haven't.

He's off a decimal, its 0.030" clearly states in Speer the Handbook narrative on 9mm Parabellum in the 10th and following all later editions.

[tazman]

I would like to see some documentation on that. I have had to seat bullets a bit deeper in the case than suggested in data to get them to plunk in some barrels and if .003" would double pressure I should have had a lot of guns explode, which I haven't.

One of the reasons to work up to the load you want to use by starting low is right there. Making a cartridge/boolit combination work in different chambers can be tricky as far as OAL goes. 9mm chambers being so inconsistent, is a major reason I seldom use full power loads for my 9mm cartridges.

[wv109323]

The bullet should pass the compression or push test with just the interference between the brass case and the bullet with no crimp. A taper crimp is to remove the case belling and slightly reduce the case mouth to aid in functioning the round in a semi-auto.
A revolver round that head spaces on the rim has a roll crimp usually in a canalure to prevent bullet movement during recoil.(inertia) I expect the inertia in a mag. revolver exceeds the compression forces of a semi-auto.
At least that is what I have always been told and understand.
I would want no set back caused by cycling the ammo through a semi-auto. In fact I would not shoot the rest of that ammo and contact the manufacturer.
Some manufacturers put a cannalure in the brass case to prevent bullet set back as further insurance.

[dansedgli]

I went through this on the weekend trying to load 9mm major out to 1.161.

On my 1050 dillon I had to remove my backup die which slightly flares the case and change out my Mr Bullet feeder die to the factory dillon one to solve the setback issues with the push test.

The rounds don't look crimped enough to me but any more crimp and they setback. They feed fine and don't move so that'll do.

[Burnt Fingers]

He's off a decimal, its 0.030" clearly states in Speer the Handbook narrative on 9mm Parabellum in the 10th and following all later editions.

Thanks for catching that. I was trying to type with a cockatoo standing on my hand.

[Outpost75]

Thanks for catching that. I was trying to type with a cockatoo standing on my hand.

Understood. I just had a cat on my lap. MUCH easier.

[gnostic]

The bullet size may be the problem. I size 9mm to .358 and taper crimp, the bullet would show some serious damage before it would be setback. Also, my 9mm handloads have a Coke Bottle shape, I don't think my bullets are going anywhere...

[charlie b]

The bullet should pass the compression or push test with just the interference between the brass case and the bullet with no csrimp. A taper crimp is to remove the case belling and slightly reduce the case mouth to aid in functioning the round in a semi-auto.
A revolver round that head spaces on the rim has a roll crimp usually in a canalure to prevent bullet movement during recoil.(inertia) I expect the inertia in a mag. revolver exceeds the compression forces of a semi-auto.
At least that is what I have always been told and understand.
I would want no set back caused by cycling the ammo through a semi-auto. In fact I would not shoot the rest of that ammo and contact the manufacturer.
Some manufacturers put a cannalure in the brass case to prevent bullet set back as further insurance.

I had setback with .45ACP and lead bullets. The combination that got me was pan lube (no bullet sizing) and just enough on the crimp die to remove the bell. IMHO the thing that allowed the movement was the slight amount of lube left on the driving bands. I went to a taper crimp and they were fine.

I had the opposite of setback with the .357 and heavy loads with no crimp. Tried it just because I had nothing better to do. I had the idea it might improve case life. Two bullets came out of the case a good 0.1" (also pan lubed and not sized). Interesting too cause only the two next to the firing chamber reacted enough to notice. The bottom three only moved a little bit (had to measure them to see it). The issue would have been that a bullet that went through 5 shots may come out enough to jam things up (especially something like a 150 SWC or heavier).

[tazman]

I had the opposite of setback with the .357 and heavy loads with no crimp. Tried it just because I had nothing better to do. I had the idea it might improve case life. Two bullets came out of the case a good 0.1" (also pan lubed and not sized). Interesting too cause only the two next to the firing chamber reacted enough to notice. The bottom three only moved a little bit (had to measure them to see it). The issue would have been that a bullet that went through 5 shots may come out enough to jam things up (especially something like a 150 SWC or heavier).

That is a typical problem for revolvers. The recoil tries to pull the bullets out of the case. Sometimes they will move far enough to bind the action.
The S&W models 27 and 28 used to do this because of their shorter cylinders.

[Black Jaque Janaviac]

"Paying strict attention to seating depth, proper crimp and testing for "bullet push," no more than 0.005" shortening of cartridge OAL after 5 secs. at 50 pounds compression pushing against your bathroom scale, is very important. This should be a routine test precaution when setting up the loading machine and is essential to be repeated whenever you change lots of brass or bullets!"

Ah. This may be part of the problem. I just tested the Federal Aluminum FMJ factory ammo and it failed this test miserably. Pushed down to exert 50 lbs and the bullet set back. Original OAL = 1.15", after test 1.06".

[tazman]

Ah. This may be part of the problem. I just tested the Federal Aluminum FMJ factory ammo and it failed this test miserably. Pushed down to exert 50 lbs and the bullet set back. Original OAL = 1.15", after test 1.06".

That is a problem the manufacturer needs to have brought to their attention.

[DougGuy]

Ah. This may be part of the problem. I just tested the Federal Aluminum FMJ factory ammo and it failed this test miserably. Pushed down to exert 50 lbs and the bullet set back. Original OAL = 1.15", after test 1.06".

I would contact their customer support, that is NOT supposed ot happen. You may have gotten a bad batch of ammo. I would not shoot any of those until you have resolved the issue with Federal.