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Old 02-02-2011, 10:56   #1
Jitterbug
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10mm Jacketed bullet setback

RCBS .40/10mm dies

I noticed that my jacketed loads, 135 Nosler and 155 Hornady’s (old style H.P. not XTP’s) are experiencing 10-20/1000 setback after chambering. I had worked up some “mild” 155’s and they seemed much hotter then I expected which lead me to double check this.

Gun is Dan Wesson CBOB with a 22# recoil spring and when chambering the bullet does seem to hit the frame ramp vigorously.

Nosler 135’s are 3 times loaded Remington brass colored brass
Hornady 155’s are 1 time loaded Starline, both nickel and brass.

I tried cycling some factory loads and some .401 “cast loads I have and they appear fine, and only setback a 1/1000 or two, with the exception of some 200 grain Blazer which setback 10/1000 on one round, one did and one didn’t setback at all.

The RCBS die set has 91 stamped on the die, I’m assuming 1991 which would be about the time I purchased them.

Sizer ID is .417”
Expander is .397”
Inside Case ID after sizing is .397-.398”

I searched all over the internet, and what I’m finding is this is somewhat common, what with the .40 guy’s seeming to notice it more, no doubt because there are more of them.

Recommendations have been EGW U dies and/or Lee Dies, EGW U dies are made by Lee? My understanding is that they are sized to make the case 1/1000 smaller.

I’m convinced it’s not a “crimp” issue due to what I learned in my research and the fact that I adjusted my crimp from .422-.416” in an attempt fix it, which of course didn’t work.

I just got off the phone with RCBS, they said to mail in the sizer with 5 fired cases and said they’d look at it.

They also had me try to insert a bullet into a sized only case, and it wouldn’t go.

Have any of you guy’s experienced this?

Solution?
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Old 02-02-2011, 16:05   #2
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You are exanding case mouth too much...use less expansion/flairing.
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Old 02-03-2011, 16:50   #3
MakeMineA10mm
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Combination of several things.

First off, you've correctly surmised that the 22-lb recoil spring is exerting more force during the feed cycle, than you'd get from a lighter spring. (On Glock's the standard weight is 17-lbs, but I'm not sure on the DW, although I think most standard 1911s in 45 use 18-lb springs, IIRC...)

Second, those light bullets have shorter bearing surface which means there's less frictional surface bearing between them and the case walls. This results in less resistence to movement (either forward or backward). With being set back, this would increase, which is probably one aspect of what stops the bullets from being setback farther.

Third, you didn't mention the load, but if you are going for high-velocity, I'd suggest switching to a slower or bulkier powder so that you get 100% loading density. The powder column bearing against the bottom of the bullet will help to prevent set-back. With those 135s, Alliant 2400 might be interesting...

Fourth, and probably the most-important, is what Shadow mentioned. This is probably an issue with the neck/mouth expander. They build them to work with middle-of-the-road brass and with the most-common bullet diameter and length (weight) for the caliber, and this often fails when you get to the extremes of weight (which is where you are at) or want to use a larger-diameter bullet (such as a cast lead one). I've had to modify the plugs in these dies a lot, as a cast bullet shooter.

In your situation, you may need/want to grind off the bottom of the plug, so that it does not go down inside the case so far. This will leave a "shelf" where the sizer die has reduced the case so that the base of the bullet will ride against it. This is easily noticable even on standard dies with a tapered case, like the 9mm. I've got some around here somewhere that have a distinctive "hour-glass" shape from this effect. For the 10mm, you want the end of your plug to be the same distance from the taper which flares the mouth as the base of your bullet from it's crimp location. If you set it up for the 135, you can use it for any weight bullet in 10mm. (The longer bullets will just get forced down by the seating die, which will expand the brass -- Of course, this has the danger of also pinching closed the mouths of JHPs, depending on how much pressure it takes and how thin the mouth of the bullets are.)
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Old 02-06-2011, 09:52   #4
Jitterbug
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Setback dilemma solved.

I haunt several different reloading forums and posted this to a response from Sevens on another site and thought maybe some of you guy’s might find it helpful.

Sevens, I think you've hit the nail on the head and yes setback it is an issue with serious potential consequences. You also make an interesting point about factory loads being loaded with a long bullet, then reloaded with a shorter one.

Shadow, after giving your suggestion some thought I thought I’d re-check my expander routine and especially more so after measuring fired cases.

It's a bit early for me and I'm on my first cup this morning, but I'll take a stab and try to be concise.

Yesterday, I took 2 new Winchester cases, one of the 3 times fired R-P cases and a 1 time fired nickel Starline case. I measured all 4, the new cases were the longest and the 3 times fired case significantly shorter and the 1 time fired case in-between.

So, I individually resized, expanded, reseated and re-crimped in a separate step, and topped them all with new bullets, I applied a 1/2 turn on the RCBS taper crimp die, each time taking into account the shorter or different case and OAL.

For some reason I was setting my resizing die a few thousands off the shell plate, but after re-reading the directions it said to set it so it slightly cams, which I did.

The 135 Nosler and 155 Hornady I tried out in the same "old cases" and with the new Win cases, a 135 Nosler and a 180 XTP, these were all dummies.

I then vigorously cycled them three times, recording the OAL each time.

The new Winchester cartridges with the 135 Nosler and 180 XTP experienced no setback at 1.244” and 1.251” respectively.

The one time fired nickel Starline with the 155 gr. Hornady went from 1.251" to 1.249", 1.248" and 1.237"

The three times fired R-P with 135 Nosler went from 1.244" to 1.244", 1.238" and 1.235"

To further complicate matters my start load data for the 155 grain Hornady H.P. and AA5 from six published data sources over the last 15 years varied from a low of 7.0 grains to 9.6 grains.

Though 2 of the 6 loads was for a 150 gr. H.P, Lyman 49th listing 7.0 gr. as a start and the Sierra 3rd listing 9.0 grains.

The Hornady 4th lists 8.1 grains and the Hornady 7th lists 9.6 grains! The general consensus of the 6 sources was 4 out of 6 at about 9.0 grains, which is why I went with a 9.2 grain start load.

Lessons learned

Be more diligent in segregating brass and setting the dies accordingly for different case lengths, especially the expander die.

For Jacketed loads use new or newer carefully segregated brass.

Designate “mixed several times fired brass” for .401” mild, cast loads.

When confronted with large variables in published load data, load small samples on the side of the lower charge weight.

Always load dummies and vigorously check and double check, then check again for potential setback.

Invest in a Lee FCD to have on hand.

I’ve been shooting the 10mm since 1989 or so, and did a bit of reloading for it back then for a Smith 1006, mostly mild cast loads with mixed brass, then after a 17 year break from reloading I just got back into it.

Thanks for the help guys; I apologize if I wasted anyone’s time with my 10mm re-learning curve.
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