Author Topic: 124 RNFP, anyone else have issues with OAL in a 75b?  (Read 9004 times)

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Offline outdoor_guy

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #45 on: July 30, 2012, 01:02:56 AM »
Yeah, the taper had occurred to me, but bullet manufacturers could take this into account, it's not like it's rocket-science  ;D

If you look at the typical (from SAAMI measurements) 9mm cartridge, it's got a volume of 0.2522 cu/in. 
If you look at the volume difference between my 124gr RN and my 124gr FP bullets in question, it's .0309. 

The delta is roughly 10% of the total volume, to me this sounds like a signficant "guess" when it comes to seating the bullet?
I don't have the data on what threshold causes pressure-spikes, roughly, but I'm guessing the delta is far less than 10%, between "totally safe" and "really marginal" to use two totally unqualified terms, but I think it gets the point across.

The more I think about it, I wonder why this isn't used as the standard, the delta between your bullet length and seating.  This would allow a MUCH more accurate case volume result, which is really all we're shooting for here, volumes >= a given threshold, correct?

-pete

Offline 1SOW

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #46 on: July 30, 2012, 01:49:43 AM »
Pete, my "guess" comment was about "how to use your idea", not on bullet seating depth.
Although,  I have successfully used "distance above the powder to get a rough starting OAL with same weight and type bullets, with the same powder with light loads.

I think there are a LOT of variables at work here:
Powder type: large volume  (light weight) flake like unique, vs low volume (and very heavy) small ball-like AA5.  (I can drop almost 3 loads in one 9mm case)
9mm has the widest variations of case dimension,  thickness and resulting internal volume.
Reloader Sizing differences exist resulting in the pronounced "coke-bottle shape", to almost flat sides.  This recountours the cases' tapered sides.

To me, it seems it would be less than precise, or at least very complicated,  to have a  formula for oal and seating depth.




 

 

Offline Wobbly

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #47 on: July 30, 2012, 10:28:49 PM »
Will that be enough of the bullet in the case ?


All I can say is that my bullets don't fall out onto the floor, and usually shoot fairly good. You can load any length you want between 1.140 and 1.075". I suggest you try 4 or 5 different lengths between those 2 and see if you can tell a difference. That's the only way to answer your question.

 ;)
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Offline Wobbly

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #48 on: July 31, 2012, 07:57:40 PM »
The pressure will rise dramatically with .010" increments in 9mm.  I'd highly suggest simply making up 5 or 6 test cartridges (no primer; no powder) and manually dropping the slide on the mag over and over. Start at 1.140, then you can shorten them .010 and try it again. With RN you'll not see any difference.


If you must use powder, then you'll want to use a very docile load like 4.1 or 4.2gr of Win231. And don't mistake having enough powder to cycle the gun's action for "feeding good". One is a power issue; one is a mag-bullet-chamber physical alignment issue.

« Last Edit: February 06, 2019, 03:22:55 PM by Wobbly »
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Offline Wobbly

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #49 on: August 02, 2012, 07:37:06 PM »
Ok I make up some no primers or powder, I found out that my Cz75 with the 9mm efk fire dragon
will not take the FP's  RN 100% . Now my BHP just eats them up. Looks like RN only for the EFK.


So may I ask what max OAL the bullet push test yielded for your bullet in your barrel? FPRN do seem to be the worst offenders in any "tight chamber", so i don't doubt it's short.
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Offline Wobbly

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #50 on: August 03, 2012, 12:10:27 PM »
Well on the EFK berrel it was 1.160-015= 1.145 and the BHP was at 1.145-.015=1.130.  That EFK
chamber is so tight I'm staying with RN only. The FP work great in the BHP.

Either I don't understand, or you got a typo. The number you quote on the EFK is longer than the BHP.
« Last Edit: August 03, 2012, 07:30:23 PM by Wobbly »
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Offline Wobbly

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #51 on: August 03, 2012, 07:31:13 PM »
That won't help without a look at your bullet too.
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Offline outdoor_guy

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #52 on: August 03, 2012, 10:18:16 PM »
Geez, I'm no feed expert, but I'd say your chamber mouth needs to be chamfered a little.  Even with RN bullets I could see there being a potential problem, if things weren't just *exactly* right during the feed process.

BTW: Where'd you get your EFK barrel?

-pete

Offline Wobbly

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #53 on: August 04, 2012, 03:53:19 PM »
Ok I make up some no primers or powder, I found out that my Cz75 with the 9mm efk fire dragon
will not take the FP'  RN 100% . Now my BHP just eats them up. Looks like RN only for the EFK.


Your communication is so unclear and your needs so specific that I highly suggest you get your own thread.
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Offline sixgunal

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #54 on: January 31, 2019, 04:40:12 PM »
I know this is an older forum but here's my 2 cents.

  I have been reloading Bayou Bullet 135grain RN's @ 1.135" for my CZ Shadow 2 which chamber and shoot excellent. I recently bought a few Berry's bullet 135 RN & 147 FP to try. The Berry's 135 RN can be loaded a little longer @ 1.150 with no issues.
 Unfortunately the Berry's 147's would have to loaded @ 1.04 to chamber properly so I will probably save those to try in one of my other 9's later.


Offline Wobbly

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #55 on: January 31, 2019, 04:49:42 PM »
Unfortunately the Berry's 147's would have to loaded @ 1.04 to chamber properly so I will probably save those to try in one of my other 9's later.

That is not the Max OAL we have found for the Berry Mfg 147gr RN.

Besides, I highly doubt any 147gr can be loaded to such a short OAL. Did you really mean 1.140" ?

 ;)
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Offline IDescribe

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #56 on: January 31, 2019, 08:07:18 PM »

Offline Radom

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #57 on: February 06, 2019, 02:29:57 PM »
Time to Confuse the Issue:

Based on skimming this thread, with no real insight at all, I suggest that the SWC concept is "better" than the RN-FP concept, precisely because it does not engage the rifling until the bullet leaves the case and the pressure drops. 

I only mention this because I have seen many people suggest that RN-FP and SWC are the "same thing/different terms."  To be fair, I haven't seen that claim on this forum.
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Offline CzechnoWizard

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Re: 124 RNFP, anyone else have issues with OAL in a 75b?
« Reply #58 on: February 23, 2019, 10:41:17 AM »
I use berrys flat point (truncated cone, not RNfp) with great results in several cz 75 variants
124g HB FP TP
LOAD AT 1.060 oal
I was running 5.5g cfe pistol (near max but not +p) but tired of the long ejection distances. No issue with brass life, flattened primers etc but tossing empty too far.
Recently backed off to about 5.2g and seems to be equally effective on steel knockdowns but more controlled ejection.
The HB bullet is longer, so it already intrudes into powder space more than a normal fp and considerably more than a RN.
I share this to say - my experience is that you will not have pressure problems caused by seating at 1.060 unless you are trying to make 9mm major or some such already risky thing. 1.060 is correct with 124 fp