9mm cast downsizing test results

[Highway41]

So I have been curious about whether during the seating and crimping process the 9mm casings were sizing down boolits to under bore diameter.

I have read that use of the Lee powder through expander plug for 38 S&W would help eliminate the downsizing due to it being both larger diameter and longer than the Lee ptx 9mm plug.

Since I had to order a few parts from Lee I put a 38 S&W expander plug into my cart to give it a try. As it turns out the 38 S&W ptx plug is a drop in that needed no adjustments to the ptx die body as the main body of the 2 plugs is within .01". The main difference is in the expander end. (Note - where possible all measurements made with a Millers Falls 712R micrometer which reads to .001, all measurements stated to the ten thousandths place are my extrapolation as my vernier micrometer has not arrived yet.) On the 9mm the actual expander portion is .175" long with a diameter of .3545". The 38 S&W expander portion is .305" long with a diameter of .3562" making it just under .002" larger than the 9mm plug.

I selected ten cases - two each of FC, WIN, Speer, Blazer and RP. Checked all for uniform case length .750" and case wall thickness at mouth .01".

I do not cast for 9mm yet but a member sent me some Lee 358-125RF at my request to check for function in my 9mm 1911 RIA project gun. I selected 10 of these boolits that measured exactly .358" with all traces of lube removed.

Seated each boolit to 1.03" which is the length that passes the plunk test in my RIA and taper crimped all of the rounds to .379". Used an hammer puller to pull each boolit and remeasured the boolits.

I expected the results to vary more than they did but the only outlier was the boolit that had been seated in the RP case expanded with the 9mm plug and it measured .355". The remaining 9 boolits from both both sets measured .356" exactly.

I did check for potential setback and all the boolits were seated firmly and did not change in length when pushed against the edge of my bench firmly. The boolits seated after expansion with the 38 S&W plug did seat significantly easier than in the cases expanded with the 9mm plug and I did not observe any lead shaving while seating either set.

I reslugged my RIA bore after getting the micrometer and got a result of .355" so these should work good for me.

I have messaged asking about the alloy of the boolits but have not heard back yet, I'll include that info when I find out.

[Cherokee]

Interesting test. So, correct me if I understand wrong: FC, Win, Speer, Blazer cases using either expander ended up resizing the .358 bullets to .356. The RP brass (9mm exp) resized the .358 bullet to .355 but RP expanded with S&W expander yielded .356 when pulled. .002" downsizing is a lot from neck tension. Did your taper crimp die exert any sizing effect on the rounds ?
I have found the RP brass to be heavier, or at least harder to expand and seems to give more case neck tension so I save them for jacketed bullets.
BTW, 1.03" is a very short OAL so be careful when developing a load, start at the minimum and only load a few. The hardness of the alloy will impact the downsizing that takes place, I use a 3/3/94 alloy for my 9mm bullets (Lee 120TC, lube grooves). The Lee 125RF as a full diameter portion that contacts the abrupt rifling (seen in most 9's today) sooner than the 120TC bullet, forcing a shorter OAL for the 125RF. Good luck.

[Highway41]

Interesting test. So, correct me if I understand wrong: FC, Win, Speer, Blazer cases using either expander ended up resizing the .358 bullets to .356. The RP brass (9mm exp) resized the .358 bullet to .355 but RP expanded with S&W expander yielded .356 when pulled. .002" downsizing is a lot from neck tension. Did your taper crimp die exert any sizing effect on the rounds ?
I have found the RP brass to be heavier, or at least harder to expand and seems to give more case neck tension so I save them for jacketed bullets.
BTW, 1.03" is a very short OAL so be careful when developing a load, start at the minimum and only load a few. The hardness of the alloy will impact the downsizing that takes place, I use a 3/3/94 alloy for my 9mm bullets (Lee 120TC, lube grooves). The Lee 125RF as a full diameter portion that contacts the abrupt rifling (seen in most 9's today) sooner than the 120TC bullet, forcing a shorter OAL for the 125RF. Good luck.
I have shot some of the 358-125rf seated to 1.03" over 4.6gr of True Blue. To me the recoil was slightly less as compared to my usual 5.5gr TB 124 Berrys. The thing that really impressed me was the accuracy, which since I was only really shooting to check function was a nice surprise.

I did not think to pull bullets after seating and before taper crimping to see where in the process the downsizing was occurring. Possibly I'll rerun the test sometime with that in mind. The only difference in the brass that I noticed was that the Blazer cases were much easier to size.

Side note - grabbed a couple of random cases and used the 38 S&W plug to expand them then seated 124gr Berrys in them and crimped. Both bullets setback into the case with very little pressure. Just in case anyone was curious.

[dverna]

Alloy may affect results as well

Don Verna

[Forrest r]

The length of the expander plug is what's important. Longer bullets need to have a longer expander plug that goes deeper into the 9mm cases.
http://i162.photobucket.com/albums/t242/forrestr-photo/expander9mmdepth_zpse6fc7qfk.jpg (http://s162.photobucket.com/user/forrestr-photo/media/expander9mmdepth_zpse6fc7qfk.jpg.html)

Traditionally die sets are sold for reloading jacketed bullets. Die set labeled for cowboy action or m-die sets are for lead. Jacketed bullets tend to be shorter and smaller in diameter than their lead/cast bullet counterparts.
A lee factory 9mm expander next to a custom expander. The lee is designed for .355" jacketed bullets, the custom .358" cast.
http://i162.photobucket.com/albums/t242/forrestr-photo/8121ce53-92ea-4a46-bdf0-b874c87f442d_zpsunjrpvqq.jpg (http://s162.photobucket.com/user/forrestr-photo/media/8121ce53-92ea-4a46-bdf0-b874c87f442d_zpsunjrpvqq.jpg.html)

A lee factory expander for the 45acp next to a lyman m-die factory expander for the 45acp
http://i162.photobucket.com/albums/t242/forrestr-photo/df94e6e6-3f6b-4d88-9140-bd3853861b70_zpsihajcgrb.jpg (http://s162.photobucket.com/user/forrestr-photo/media/df94e6e6-3f6b-4d88-9140-bd3853861b70_zpsihajcgrb.jpg.html)

Some .452" bullets (left) loaded in 45acp cases & some .358" bullets loaded in 9mm brass (right). All of the bullets pictured below were cast from nothing more than range scrap that is around 9bhn.
http://i162.photobucket.com/albums/t242/forrestr-photo/semiseat_zps9lbhbnez.jpg (http://s162.photobucket.com/user/forrestr-photo/media/semiseat_zps9lbhbnez.jpg.html)

What cast bullets look like when they're loaded in cases using the wrong expander. Typically when someone posts pictures of reloads that look like these there's the " gotta have good neck tension" somewhere in the post.
http://i162.photobucket.com/albums/t242/forrestr-photo/nice_zpsl0ovesk6.jpg (http://s162.photobucket.com/user/forrestr-photo/media/nice_zpsl0ovesk6.jpg.html)

Another common thing is when the right expander is used but the reloader " Only uses enough flare to start the bullet. It saves on brass wear and tear." The end result is the expander doesn't go deep enough to fully open the case up and the reloads look like these.
http://i162.photobucket.com/albums/t242/forrestr-photo/RollCrimp_zpsckaatvd0.jpg (http://s162.photobucket.com/user/forrestr-photo/media/RollCrimp_zpsckaatvd0.jpg.html)

I believe the person that posted that picture was actually showing how to use a roll crimp on a jacketed bullet.

It's the bases of the oversized lead bullets that get swaged down that cause problems. If the expander doesn't go deep enough to open the case the bullet has to when it's seated. Jacketed bullets stand a better chance of staying the same diameter when seated in a case that wan't expanded deep enough. Extremely hard cast bullets stand a better chance of staying the same diameter when seated in a case that wan't expanded deep enough.

2 different bullets loaded in 9mm cases both bullets are sized to .358" and cast with an alloy of around 9bhn (range scrap)
http://i162.photobucket.com/albums/t242/forrestr-photo/147hbandmihec124_zpscfdcd7f1.jpg (http://s162.photobucket.com/user/forrestr-photo/media/147hbandmihec124_zpscfdcd7f1.jpg.html)

A 10-shot 50yd group of that 150gr hb fn .358" bullet/9mm load (red) pictured above using range scrap to cast them (9bhn).
http://i162.photobucket.com/albums/t242/forrestr-photo/358709mm_zps9110adbe.jpg (http://s162.photobucket.com/user/forrestr-photo/media/358709mm_zps9110adbe.jpg.html)

A 10-shot group @50ft of that 125gr .358" bullet/9mm load (green) pictured above using range scrap to cast them (9bhn).
http://i162.photobucket.com/albums/t242/forrestr-photo/ro9mm50ft_zpslprjmumk.jpg (http://s162.photobucket.com/user/forrestr-photo/media/ro9mm50ft_zpslprjmumk.jpg.html)

Those groups/loads would of never happened with those .358" bullets if I would of used the lee factory expander.

[gloob]

I expected the results to vary more than they did but the only outlier was the boolit that had been seated in the RP case expanded with the 9mm plug and it measured .355". The remaining 9 boolits from both both sets measured .356" exactly.
Even using hard, 356 commercial bullets, my particular sizing die and cases causes a major problem. Calipers don't show the extent. You have to carefully measure right at the base and all the way around the bullet to detect anything, at all. Maybe a half a mil dent in the base at one specific point; or maybe it's just your imagination. In most guns, not a major problem. Just some minor fouling. But out of a Glock, full length o the bore lead streaks, hello. So even if you can't measure anything significant, you ought to give this some thought if you have fouling or accuracy issues out of your gun!

[Highway41]

Found out the alloy had bhn of 10.2 to 10.4.