Failure to fire NMFT Combo .45

I am getting several, each of
the last two sessions with the acp cylinder. I am loading on a Lee Pro 1000 with Lee dies, Winchester brass and primers, .451 Lee expander, 185 Nosler JHP, 4.2 gr. N-310, 1.21 oak with a separate .471 Redding taper crimp. It is said to be the Marine Corps match load and it is giving me ten shots in a legitimate one large hole at fifty feet indoors with two hand hold,fair lighting and a braced elbow rest.
Before I send it in....what should I look for? Dirty primer pockets resulting in high primers?
I don't visualize that. Transfer bar that needs thinning for more firing pin protrusion? Replace the stock spring with an Old Army that I could canibalize.

Has anyone else had this problem and solved it?

If you're going too heavy on the crimp, the mouth of the case may be slipping past the shoulder in the cylinder.
Not saying this is what's happening, but try loading some with a light, or even no crimp and see if it works.
Also, make sure your seating die isn't overcrimping the round.

What does the primer look like after you tried firing? Light primer strike? Try firing again? If it does then high primer. Is this a new issue? Does it happen with factory ammo? Have you marked the cylinder? Maybe the chambers to deep on some. But my guess is to much crimp, round slips forward and light strike results in FTF. You can figure it out, just take one issue at a time. Start with using a chamber gauge. The gauge will show if round has to much crimp. If you are using mixed brass you can get varying crimps.

As mentioned,, take one issue at a time, to try & fix an issue.

You mentioned using the Redding taper crimp die. So,, I'd think that may not necessarily be the issue. BUT,, as noted,, a proper case gauge can determine if any ammo is not quite right.

I load my .45 acp ammo for USPSA competition. And to compete, I want 100% reliable ammo. Here is what I do;
I first wet tumble clean my brass. My brass is quality American made brass, but it is mixed. Unless I get truly deep into tiny changes.
Once dry, I use my Dillon 650 progressive for loading. It has Dillon dies.
Once loaded, I place each round in a plastic ammo tray, to look at each primer,,, all while running my finger over each case to try & feel any high primers. I RARELY have any.
But notice, I didn't clean my primer pockets. Neither do many of the competitors in USPSA who use a Dillon press for reloading. And we all rely upon the Dillons BECAUSE we get quality ammo if it's properly set up. So,, I'd say your issue is NOT dirty primer pockets.
Next, I have a Dillon chamber check gauge.
I check each & every round with the gauge. Occasionally, I'll get a round that for whatever reason doesn't seat quite right. That round gets set aside & used strictly on the practice batch. I also mark those cases & discard them after shooting them.

So, if I had to guess,, looking at your post,, I'd say you MAY have set the taper crimp to where it is crimping too much. OR,, maybe the sizing die is not quite right, and needs adjusting.

Have you tried any factory ammo to see if you get light strikes? I ask,, because oftentimes, people want to blame the gun, when it's the ammo at fault.
I doubt the transfer bar is an issue.
And if the gun functions fine with 45 Colt ammo, or factory 45 acp ammo,, then look hard at your reloading methods, setting, and such.
Even reloading dies can be made "wrong"!
Try a different set of dies if necessary.

Before contacting Ruger, be aware that their "non-warranty" (and we know what that means) does not cover problems with handloads, just factory ammo. They just might claim that all the problems are caused by the handloads.

Thank you all for the thoughtful suggestions....hadn't considered that a 471 crimp could be too small, but...I looked everything over again:
The taper crimp die is a Lyman and by trial and by plug gauging the die with various sizes, I won't be able to get a crimp larger than .471. The rounds come out of the press with an external diameter at the flare of .474.
As I related, the throats are all even at .451, so I thought...what about the chambers where one might be oversize and sure enough there was one lose one and one slightly tight chamber.
So....perhaps the loose chamber produced a dimpled primer misfire because the round slipped forward, and the other because the tight chamber did not allow the round to fully seat and kinetic energy was lost as the hammer pushed the cartridge forward to seat.

I will try a Lee taper crimp die as I am more familiar with the internal dimensions in other calibers. I will order one, try to find a more generous crimp that will still secure the bullet and with luck work in my two XD auto pistols.

Sending the gun back is last on my list. I can live with one chamber off a little if I know which one and everything else is so good.

You were all on the right track. There have been no misfires with the .45 Colt cylinder as you had guessed. I will report back.

Forgot to add that the largest plug gauge used for chamber assessment was .474. With throats at .451. the ledge would be .0115.
I can probably figure a way to measure the chamber depth. The oversize chamber may also be too deep.

snakeeyes4445: You Have Calipers So You Have A Depth Gauge.

Thanks Get Wood....Ur right. I tried the back end of the calipers but could not get repeatable measurement and the hard stainless instrument was beginning to nick the back edge of the throats no matter how careful I was. By bottoming a .474 pin gauge down and measuring from that to the front of the cylinders I got good repeatable measurements.
Working with the pin gauges, I found three normal chambers measuring just right at .474 diameter at the ledge. One was generously oversize at .4745, and two were snug where some force was required to bottom the .474 pin. My original reloads were all higher on those two chambers. They were estimated to be .465 to .467 by feel.

I theorized that these tight chambers would also be too short due to less reamer time or some other factor. That proved to be the case and the depth difference was .0015 compared to the normal chambers. The one oversized chamber then should have been extra deep which it was by .001.

Pretty sure my misfires were from too long coa length. Hammer energy probably lost due to trying to move the case into proper battery.

I had by that time increased the crimp to .473 and shortened the rounds to 1.2010. They dropped fine into the oversize chambers and the normal chambers but would not in the several tight chambers.

I learned a lot with your help and the courteous, non judgemental advice was most appreciated.
If I had it to do over again, I would have plunk tested my original rounds in my two XD auto pistols before loading several hundred rounds for the revolvers. I have a 1917 that I might look at to see how that one gauges. The improved ammo should shoot even better in this otherwise well set up gun.

Hopefully I can stop obsessing about the misfires (which should be over) and get back to improving the human element of my shooting!

My 1917 measured six uniform .474 chamber end diameters, but the depth measurements varied more than the NMFT. A difference of.002 was approximated....of no consequence with the moon clips of course.