XTP vs JHP data and C.O.A.L.

[wk5h]

I'm only 2-3 months new to reloading, and still in the paranoia stage of things, so I wanted to run this by someone more experienced than I...

I bought a box of Zero 9mm 147g JHP. I was told to use the Hornady XTP data with Titegroup. Hodgdon's site gives min/max of titegroup of 3.2/3.6 with a COAL of 1.100". I loaded up 20 with 3.2, 20 with 3.4, and 20 with 3.6, all with the recommended 1.100" coal.

I was going to head out to the range tomorrow with my chronograph and see how they did, but, something told me to double-check everything one more time. I consulted the 2015 Hodgdon annual manual, and it lists the 147g XTP with the same data as their website, BUT, it also lists a 147g JHP with a longer COAL of 1.169".

Have I decreased the case volume to a point where I could get some dangerous pressure spikes?

 

[joneb]

From Hornady's 8th ED
9x19
147gr HP-BT-XTP #35580 COL 1.100"
147gr FMJ-RN-BT #35597 COL 1.165"
IMO Titegroup is a bit fast for this weight of bullet, so your load window is narrow.

 

[JamieC]

Such is the dilemma of using different load recommendations. I've loaded quite a few XTPs, 147gr @ 1.100" using Power Pistol so it's not a direct comparison. They've all shot well, no pressure signs that I can see. They are averaging 1050fps, they are a bit 'warm', wanted to make sure they will expand. If the Hornady manual states you are OK with those loads and OAL, start with the lowest charge, check CLOSELY for over pressure signs. If you are really concerned, load some starting @ 3.0gr, 3.2gr and work up. That's what I did, start about 10% under the starting load if there is confusion about OAL and you are going shorter.

 

[Gadawg88]

It is hard to answer your question without knowing how the dimensions of the two bullets compare, specifically their respective lengths. If one is longer than the other and both are seated to the same OAL, there will be less internal volume in the case with the longer bullet. Since you have a chrono, start with the rounds loaded at 3.2, check the velocity against what the load data suggests then shoot the 3.4 loads. Maybe that will give you an indication of whether to try the max load rounds.

 

[Potatohead]

Those XTPs really freak me out. The data for them seems really whacky compared to other bullets I load.

 

[steve4102]

Hodgdon lists 1.100 for the 147gr XTP as you already know. Your OAL will be fine according to Hodgdon, but will it be fine according to your Pistol?

OAL is always Bullet AND firearm specific, not manual specific.

Go here and read on how to find the Correct OAL for your pistol.

http://www.thehighroad.org/showthread.php?t=506678

 

[gamestalker]

Steve4102 is good advice.

GS

 

[wk5h]

I took the advice of shooting the 3.2gr loads, and seeing how they looked. No signs of over pressure, and shot pretty nice. Went to the 3.4gr, and again, no signs of pressure, and still felt nice. Felt confident in the 3.6gr, so tested those, and no issues with those loads either.

Chronograph showed the following (not posting all the individual shots due the length the post would be; if you want the info, I'll be glad to post)
Each was a group of 10, shot from an H&K VP9 using Zero 147g bullets with Titegroup.

3.2gr
Min: 884fps
Max: 897fps
Avg: 890fps
Spread: 13

3.4gr
Min: 912fps
Max: 923fps
Avg: 919fps
Spread: 11

3.6gr
Min: 920fps
Max: 945fps
Avg: 937fps
Spread: 16

 

[joneb]

Those are nice numbers, I often find the best #'s doesn't always produce the best accuracy. Seems like you are on your way to a good load, if doing this in cold temps be aware it can change.

 

[Gadawg88]

Glad it worked out for you. Just curious, which load gave the best accuracy?

 

[wk5h]

I don't have much of an accuracy report on them yet. The pistol range was full the entire time, so I only had the rifle range to use.

I will say that I setup for a target someone had left on the 100yrd target backer, and I was able to keep most hitting in the general area of the target.

I plan on loading up some more of these, and hitting the range when the pistol range is clear, and I'll try to remember posting up the results.

 

[Sunray]

The 147g XTP is kind of an odd shape for a pistol bullet. BTHP. Suspect it'll be a tick longer due to that. However, like Steve4102 says, 1.100" is what Hodgdon lists for a 147 and manuals vary. 1.169" may not fit the mag either. Nothing is going to be damaged either way.

 

[7mmb]

You can safely use Hornady's data with your bullets but you need to make sure you are seating your bullets to the same depth that Hornady is. This is an easy calculation to make but you will need to know the length of the Hornady bullet. Simply subtract the bullet length of the Hornady bullet from Hornady's OAL and this will equal the distance between the case head and the bottom of the seated bullet. Add this figure to the length of the bullets you are using and you now have the OAL using your bullets seated to the same depth as the Hornady bullets. You'll still need to do the plunk test to make sure they will chamber in your pistol.