Refresh my memory...


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therealsteamer
July 25, 2007, 11:03 AM
Is there a difference in the seating depth when going from Round Nose to Flat Point in 9mm

I grabbed a box of flat points last week and realized it last night as I finished up a box of plated RN 115 grainers.

I vaguely recall loading some flat points years ago but I just don't remember if I used hollow point or FMJ seating data...

FWIW my 9mm jacketed/plated 115gr RN load of choice is 5.9-6.0gr of Unique seated to 1.125

Thanks...

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ReloaderFred
July 25, 2007, 11:42 AM
Over all seating depth addresses several issues. The first is the volume of the case. If the volume is reduced, then a given powder charge will produce increased pressure. The second is the ability to fit the ammunition in the magazine. If the round is too long, it will either not fit the magazine or bind. The third is whether or not the bullet contacts the rifling at the throat of the chamber. If it does, then pressures will spike again. A fourth issue is whether or not the round will feed with a given OAL.

All these issues come into play when adjusting the OAL. The short answer to your question is "yes", there will be a difference in the seating depth when changing from round nose to flatpoint bullets.

Check your loading manuals for the suggested OAL for a bullet of the same configuration and go from there.

Hope this helps.

Fred

Walkalong
July 25, 2007, 11:55 AM
I shoot or have shot the

Ranier 115 Gr. RN at 1.130 O.A.L.

Ranier 124 Gr TrFP at 1.060 O.A.L.

Rem 124 Gr GS JHP at 1.060 O.A.L.

Master Match 115 Gr. JHP at 1.070 O.A.L.

Winchester 115 JHP at 1.075 O.A.L.

Berry's 124 Gr. HP at 1.030 O.A.L.

They worked for me in my guns. YMMV.

Follow Freds advice as well.

therealsteamer
July 25, 2007, 12:14 PM
I just checked Lee's Modern Reloading again and they have nothing listed for Flat Points specifically.

fecmech
July 25, 2007, 09:29 PM
Steamer--A good starting point would be to load the flat point bullet so that the same amount of bullet is in the case as your rn loading. Your oal will be less than the rn and as long as the bullet is not jammed into the rifling when the round is chambered you should be good to go. I'm assuming that you are talking a 115 flat point bullet in relation to your 115 rn. BTW Alliant shows 5.5 Unique as max for the 115 jacketed rn.

therealsteamer
July 25, 2007, 10:17 PM
I have seen acceptable top end loads for 115gr FMJs using Unique, I believe, as high as 6.2 ... I have had good luck using 5.9-6.0 gr of Unique for years now. Very easy to see the charge, impossible to double charge, and with Unique I have a powder that I can use for every caliber I load, pistol wise...

Upon further "research", I am going to drop my charge down to 5.3-5.4gr and essentially do the comparative seating at around 1.120.

nitesite
July 25, 2007, 10:34 PM
It helps to remember that when a round nose bullet is substituted with a flat point, the volume of material that made up the nose has been shifted to the bullet base.

That means there is more bullet inside the case and less available volume for your powder. If you don't download a bit for the change in volume then pressures will increase.

The same principle also applies with hollow points, as the weight of the cut-off nose and the additional hollow cavity has to go somewhere and still weigh the same amount. Reduce your load and carefully work up.

Stinger
July 25, 2007, 11:02 PM
I vaguely recall loading some flat points years ago but I just don't remember if I used hollow point or FMJ seating data...

If you kept a set of records you would know.

therealsteamer
July 25, 2007, 11:54 PM
I really should have kept records back then... Sadly when I started, my press was attached to a pine board, which was then attached to the kitchen table with C-clamps. I had no dedicated loading area. Everything I had for loading could fit in a 5 gallon bucket when I started. I didn't really keep any records so to speak, other than duplicating more of whatever I had written on the masking tape labels of whatever shot well. Live and Learn...

Walkalong
July 26, 2007, 08:24 AM
I measure bullet diameter and lentgh and record those things in my log. That helps to show how much case volume one load has vs another with a different bullet. (how deep in the case it is). Take your seater set at where you used it for your RN bullets and seat one of the FP's. If your seater is one that pushes on the ojive instead of the top of the bullet it will get you real close to where that FP will feed (assuming your RN did) Unless it mics way to short I would try that O.A.L. to start. Adjust powder charge down to start and work up.

I shot some 124 Gr. Flat points at 1.060 and they did fine. I do not shoot them anymore as they are finicky feeders and the Ranier 115 Gr.RN is just as accurate for me as far as casual plinking goes.

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