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Help with Ransom Rest group?

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Dr.Don
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Post by jlow 6/26/2019, 7:41 pm

First topic message reminder :

First time out today doing load development with my Ransom Rest.  Testing Zero 115gr JHP at 50 yards out of my tactical pistol.  Groups were not great but I would like some help deciphering their shape.

To back up a bit.  This is my RR setup and it is attached to this block of concrete – very stable and the horizontal clamps can put down a combine pressure of around 2,000 lbs.  This setup allows easy windage adjustment and quick clamp down.

I fired the first group (ignore numbers and this dummy put the target upside down…) top right 5-rounds with my regular ammo to get the rest to settle.  As suggested by a member, the sixth round was left in the chamber and I reloaded with 6 more rounds, first five test group, one extra regular that I shot slightly over the target before I shot for group.  So five charges were tested with the same bullet/primer/same headstamp brass.  Powder increment was 0.1 grain between groups.  Brass was all trimmed to uniform length and tapered crimp applied.

The odd thing I found was group 1 (top middle), and group 3 (bottom middle).  Not much lateral dispersion but a lot of vertical stringing.  Have people seen this and know what may have caused this?

FWIW, my elevation was locked down for all groups.
Help with Ransom Rest group? - Page 2 Img_1715
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Post by Wobbley 6/28/2019, 8:09 pm

I agree that velocity seems low. Hodgdon lists their start charge as 4.5 with a MV of 1135 and OAL of 1.125.
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Post by james r chapman 6/28/2019, 8:16 pm

Help with Ransom Rest group? - Page 2 Img_1810

Bob Marvel shot these...115 on right.
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Post by jlow 6/28/2019, 8:22 pm

Thanks guys!  Will go there next!

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Post by james r chapman 6/28/2019, 8:40 pm

If I recall, the XD 5.25 has a 1:10 twist. it may like 147 gr bullets also.
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Post by S148 6/29/2019, 2:16 am

jlow, thanks for the information on your gun and load.  Which Zero JHP are you using, the RNHP or the Conical HP?

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Post by BE Mike 6/29/2019, 8:02 am

jlow wrote:BE Mike – I agree with what you have said.  What you say about 5 shot groups is correct.  It gives you a trend that you should not take for granted but follow up on and confirm one way or the other.  Basically good loads will not give you a bad group, but bad loads may give you a good looking group.

One thing I intend to do is to shoot some high quality factory ammo to access the potential of the pistol.  Would appreciate any suggestion of brand - Atlanta Arms 115 gr JHP?

The two vertical group with low side dispersion is also interesting because they were the ones with lowest MV SDev.  At least in precision rifle, we commonly find the most precise groups most frequently (but not always) have the lowest MV SDev.
I had good luck with Atlanta Arms when I had a Kidd Beretta. I never could quite match the groups with my reloads, but my loads shot well within the 10 ring at 50 yards. Barrel twist makes a difference in what ammo the 9mm likes.
Here is some chronograph results I got way back when and this is the load I used. I "borrowed" the load data from another bullseye shooter:
Beretta 92FS Kidd Custom, Atlanta Arms 115 gr. Factory  1238fps
Reload, 6.2 gr. Power Pistol, Starline, Rem. Primer             1263fps
                                                                                               1246
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Post by jlow 6/29/2019, 12:13 pm

S148 – I did not realize Zero made two different types of JHP.  I brought mine from Roze Distribution and they only had one choice for 115gr JHP.  My box says “9mm 115 JHP, QTY: 500 #125”

BE Mike – as Chapman correctly pointed out, the gun has a 1:10 test.  FWIW, I normally shoot Precision Delta 147gr FMJs out of this gun but at least when I first venture into precision reloading with pistol bullets which was with my SIG MPX, my sample Zero 147 JHP did not shoot well with my 4.5” barrel. 

I currently don’t have any more samples and so will likely stick with the 115gr Zero JHP for the time being.  I did talk to the folks at Roze when I first got into this and their opinion is of the 115/124/147 Zero JHPs, the 115 had the tightest group.

Thanks for the chrono data – those are really cooking, way past max load for at least TG and also for Power Pistol?  I was talking to another bullseye shooter at the range on Friday and he also told me my gun would likely shoot better on the hotter side which is where I am going.

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Post by S148 6/29/2019, 12:55 pm

jlow, Zero has two 115 JHPs.  Here is the other one:  

http://www.rozedist.com/mm5/merchant.mvc?Screen=PROD&Store_Code=RZD&Product_Code=R135-A&Category_Code=ZBJ-9MM

They call it "NEW" but they've been selling them for at least a couple years.


And they also have two 125 JHPs. RNHP and JHP-conical.

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Post by S148 6/29/2019, 1:06 pm

jlow wrote:

Thanks for the chrono data – those are really cooking, way past max load for at least TG and also for Power Pistol?  I was talking to another bullseye shooter at the range on Friday and he also told me my gun would likely shoot better on the hotter side which is where I am going.

I can't answer for B E Mike, but Hornady's load data has a max load of 6.7 grains of Power Pistol with their 115 grain bullets.

I've used 6.5 grains of PP with Zero's 115 JHP-conical. It runs a wee over 1300 fps from my 5" Kart barrel, and is very accurate (50-shots at 1.48" at 25 yards) with that load.

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Post by jlow 6/29/2019, 1:25 pm

I did not see it when I brought mine.  Mine is not the "new" JHP.

As for the PP load.  Alliance do list 6.7 gr for 115gr Speer, but the listed MV is only 1,212 not 1,263 fps, thus my comment.

I do appreciate the recipes but I am one of those reloaders who do not believe in jumping from powder to powder until I exhaust my options for a powder I am using.

For example, when I was doing load development for my SIG MPX, every other reloader told me to switch out of TG but I managed to get a load that shot 1.5".

Don't get me wrong, I do not believe in banging my head against the wall when something obviously does not work, so switching is always a GREAT option, but only after I carefully do my due diligence with what I have.

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Post by S148 6/30/2019, 9:51 am

jlow wrote:

As for the PP load.  Alliance do list 6.7 gr for 115gr Speer, but the listed MV is only 1,212 not 1,263 fps, thus my comment.

That might be simply due to barrel length. Most loading manuals use a 4" barrel for 9mm, many shooter here use a 5" barrel.

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Post by jlow 6/30/2019, 10:49 am

It could be but at least even in rifles, a 1" increase in barrel length only leads to a 25fps increase in MV.  Regardless, I was just surprised.

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