XTP / SPORTMASTER Differences ?

[fourdollarbill]

I'm not the expert by far so I have to ask. Why is the XTP load data for a 357 mag 125gr XTP with 2400 17.7 max in different books and the Sierra Sportmaster 125gr JSP/JHC shows 19gr max in the Sierra book? Their both quality jacketed bullets so why the large jump in powder charge?

 

[JimKirk]

Two different testers ...Two different bullets... two different guns.

 

[fourdollarbill]

Two different testers ...Two different bullets... two different guns.

True but... don't you think the max load spread is pretty large? 17.7 to 19

 

[bullseye308]

The only thing I can see making a difference would be bearing surface, but it shouldn't be that much of a difference.

 

[JimKirk]

If you'll look ... you'll find "that" on lots of reloading data, not just on your two examples.

What I was trying to say... that you have two different testers, from two different labs(test facilities),different test equipment. They used two different guns to arrive at their test data... so may be one gun could tolerate more pressure than the other or gave a different pressure altogether. Then you have the different bullets ... one may be of harder lead or harder jacket material, just because they weigh the same don't mean they are the same.

It no different than two cars built exactly the at same, one tops out at 130 mph the other 120 mph. One get 13 mpg the other 15mpg.

That is the reason that they say to start 10% below Max and work your way up until you get to a safe point for your gun ... not mine gun, but your gun. If I use Hornady bullets, I use Hornady data, if I use Serria, then Serra for starting loads. I may to other data after I have found their data to be safe in my gun.

Clear as mud!

Jimmy K

 

[DWFan]

quote:
"Two different testers ...Two different bullets... two different guns."
Add to that different seating depths and probably different maximum pressure levels.
For example: the Hornady 158gr XTP-FN seats .012" deeper than the Sierra JSP. On the other hand, the 158gr Sierra JHC seats .023" deeper than the Hornady XTP-HP. I don't know if a difference exists for the 125gr bullets, but it probably does.

 

[rcmodel]

It's because those Hornady tester guys are a bunch of Fraidy-cat Sissy's.

Seriously, Hornady data has historically been lower then Sierra data for whatever reason.

I have one old Sierra handgun manual that is downright scary compared to any modern data from anybody.

rc

 

[noylj]

Load Compilation

Years ago, I started compiling load data for the calibers I am interested in. This allow me to see the lowest of many starting loads. For example, here is a compilation of data for a 200gn jacketed bullet in .45ACP using Unique:
JHP 200 Unique 4.0 604 Start
PJM 200 Unique 5.2 700 Start
JSWC 200 Unique 5.6 684 Start
JSWC 200 Unique 6.1 791 Max
Speer Gold Dot 230 Unique 6.1 950
Rainier P-HP 200 Unique 6.3
JHP 200 Unique 6.4 Start
Speer TMJ-SWC, JHP 200 Unique 6.5 860 Start
JHP 200 Unique 6.5 927 Max
JHP 200 Unique 6.6 863 Start
JHP 200 Unique 6.8 955 Max
JHP 200 Unique 6.9 920 Start
Spr JHP 200 Unique 7.0 844 Accurate
JSWC 200 Unique 7.0 950 Max
FP 200 Unique 7.1 937
JHP 200 Unique 7.1 975 Max
FP 200 Unique 7.1 1042
Speer JHP 200 Unique 7.2 887 Favorite
JHP 200 Unique 7.2 961 Max
JHP 200 Unique 7.3 976 Max
Speer TMJ-SWC, JHP 200 Unique 7.3 984 Max
Speer Gold Dot 200 Unique 7.3 984 Max
PJM 200 Unique 7.4 950 Max
Gold Dot 200 Unique 7.4 Favorite
Hornady HP-XTP 200 Unique 7.5 1015
Speer Gold Dot 200 Unique 7.8 1005
JHP 200 Unique 8.9 Max

Thus, I start somewhere between 4.0-5.2 and work my way up. I have never intentionally determined the max in any of my guns, though I have hit what I consider max a few times.
Always work up and always compare a couple of different manuals. Do accept anything you read on the 'net as gospel.

 

[Hondo 60]

I don't have any Sportmaster bullets, so I have to ask where is the cannelure (if it even has one)? The difference might be determined by how much bullet is in the case.

For example: I sometimes use HSM bullets. When set to the cannelure I get an OAL of 1.445. I recently ordered Zero brand bullets (both are .357 in diameter & weigh 125 gr).
Yet I get an OAL of 1.425 with Zero.

By measuring how much of the bullet is inside the case, I found that it's the same for both, so the same 3.7 gr of Titegroup works perfectly.

In your case the amount of bullet that sits inside the case may vary greatly. That would infact produce a very different amount of powder needed.