Boolit Set-Back Tolerance On 45acp

[Foto Joe]

I'm curious as to the acceptable tolerance (if any) for boolit setback on 45acp.

I'm loading dummy rounds for a 1911 using COWW cast .452 160gr RNFP out of a 2 cav Lee mold I just got. The COL is nominally 1.115". They're cycling through nicely but I'm noticing that my COL diminishes to 1.105 nominally after they've been cycled.

Since these aren't your normal boolits for 45acp I'm being EXTRA careful on this. To be honest I've never measured the setback (if any) on the 230's that I normally load for this.

I'm using a Lee FCD and the crimp groove seats right at the case mouth. I can't thumb these boolits deeper after cycling and I haven't as yet seated them any deeper to check for setback when the case mouth is at the top of the crimp groove. Am I being overly paranoid here or is the minute setback normal?

[ultramag]

I've never heard of an "acceptable" set back, however I can tell you .010 after one trip through the action wouldn't be acceptable to me. I can also tell you I've ran my 230 gr. TC loads through my 1911's 4 or 5 times plus and had absolutely no set back.

I'd work on that crimp and/or seating depth some more if I were you.

[knifemaker]

First thing I would do is to mike the sized boolits and confirm that they are .452 in Dia. If they are, then you may have a oversized expander in your die that opens the inside of the case too much and prevents a good friction fit. On my cast 45acp I only use a slight taper crimp where the mouth of the case is sized down to .471 or .470 for reliable feeding. There is a sufficent friction fit between the inside case wall and boolit that I do not have the setback you are getting. too much set back can really spike pressures and cause a blowout at the web where the case is not supported in front of the feed ramp.

[nagantguy]

from what I have always been taught and read there is no "good" set back. it happens sometimes, like when a round for a carry gun gets put in the chamber several times and not fired and then cycled out, ect. but if its happening after one trip through the pipe I would say there is a problem and like wise old Knifemaker said will spike pressure may be to high maybe not but why risk it. Also you said you are using a Lee FCD, I do as well for .45 1911s always have love them and set back has never been an issue at all in many guns from different makers.

[Outpost75]

Bullet push test on M1911 Ball used to be 45 pounds compression sustained for 5 secs. with OAL not to shorten by more than 0.002"

You can check this by grasping rounds in the shell holder, the pushing gainst a bathroomscale. If they are telescoping as much as yours are in one feed cycle you have safety issues!

[gray wolf]

The crimp on a 45 ACP accounts for about 10% of the hold on the bullet.
It's frictional fit that holds the bullet, the Lee FCD can actually lesson the hold in some cases. + I believe that bullet has very little of it in the case.
And yes, set back is bad and I know of no allowable % for it.

[Cherokee]

None. You have boolits undersize or an oversze expander. Need to determine which and fix it.

[454PB]

I suspect the LEE FCD may be the culprit, they are designed for .451" bullets, not .452" boolits.

I had a case failure in a 9mm once that was caused by a telescoping boolit, I want NO setback.

[MtGun44]

ZERO!

Bill

[Foto Joe]

Okay, I think I got the answers that I was expecting. I was in a hurry yesterday when I posted this, doing it on my phone and leaving out a few things, sorry. The boolits are indeed .452's. My expander is set to "barely" allow me to get the boolit perched on the case mouth. I only ran the dummy rounds through once so as of this morning I can't say whether or not I get additional setback on successive chamberings, I will check that this morning once my coffee is working. Here's what I think I'm dealing with and it's a two-fold issue:

The 160gr boolits have a substantially smaller surface area touching the brass which of course means less area for friction to effectively hold it in place. Secondly, since these are RNFP's instead of RN's the COL is a LOT shorter than what I'm used to. As such I've been a little goosey about the COL and not seating the boolit appropriately to fully engage the top of the crimp groove with the case mouth itself. Meaning that the case mouth itself actually rests pretty much in the middle of the crimp groove. When the round is chambered it allows the less than ideal friction seal to give just a little and slide the boolit farther in so that the case mouth now rests on the far side of the crimp groove.

I need to grab a 230gr LRN and do a side by side comparison to see where exactly the boolit base rests inside the case versus where the 160gr RNFP boolit base rests. The "fix" I believe is going to be to seat the boolit (160's) so that the top of the crimp groove actually rests and is held by the case mouth instead of the middle. What I need to keep in mind is that what I see on the outside really has very little in this case to do with what is hidden inside that I can't see. I'll attack the issue here again in a bit and see if my theory holds true.

In the meantime, thanks for the replies.

[Shiloh]

Never had setback. I have tried and measured several times.
As stated in above posts, you have some other issue you need to find.

Shiloh

[gray wolf]

The "fix" I believe is going to be to seat the boolit (160's) so that the top of the crimp groove actually
The fix will be to replace that bullet with one that is correct for a 1911, loose the FCD
and recheck all your loading procedures.

[Foto Joe]

Problem solved...

It was as I suspected, I was seating in the midpoint of the crimp groove. I rechambered the dummies from yesterday and got no additional set back. I then ran up five more dummies and seated .010 deeper so the case mouth rested on the top of the crimp groove and wonder of wonders the setback issue disappeared.

I also did a side by side comparison with a 230 and a 160 laying beside one of the new dummies to see where the boolit bases were in relation to each other. The bases are identical in depth now.

So...after sitting here for twenty minutes pulling dummies I'm ready to put some powder in these things. I'll head out a little later with a chronograph and a rest and see where the little buggers print. As a side note: It's nice when you cast your own and can just dump the dummy boolit back into the pot after you pull 'em.

[gray wolf]

Just as a side note, it may matter or it may not, BUT
The loads developed for a 230 bullet may have taken into the consideration the amount of bullet in the case in relation to the pressure developed. The same would be in effect for the shorter bullet. The whole thing works as a unit, one playing off the other.

[Foto Joe]

No argument there. I'm using load data for 155gr which all I can seem to get my mitts on right now. And I'm using the low end of the starting loads for that to boot.

I'm all loaded up for now and going to go see how dead the battery is on my chronograph. I've got 25 rounds loaded with 6.7gr of Universal and 25 rounds loaded with 7.7gr of AutoComp. The AutoComps I matched cartridge weight to within .5 gr just because I'm anal and I'd like to see what the variance is on velocities versus the mixed brass unmatched Universal loads.

[Down South]

I didn't read all of the replies in detail but I'll give you my take. Dump the FCD or knock the sizing bushing out of it. I tried running .452" sized boolits through one and depending on the brand of brass, the die was sizing some of my boolits. I knocked the sizing ring out of the die and solved that problem.
Did you do the "Plunk Test"?. Field strip the pistol and drop your dummy rounds into the chamber. They should chamber easily and fit all the way into the chamber. If they don't, try seating a bit deeper.
On the crimp, use just enough crimp to take the bell back out of the case mouth. The 45 acp headspaces off the case mouth. Too much crimp could allow the case to chamber too deeply, too much crimp could also cause other problems as well.

[MtGun44]

Almost impossible to taper crimp enough for this to happen. Taper crimp to .465 to .470 works
just fine.

Bill