Need help, Load discrepancy Swift vs Hodgdon

[sgt_zim]

Buried in snow here, nothing better to do...
Using Hodgdon manual and of all the load data, only the 7mm-08 has data for hornady and swift a-frame same bullet weight. Here is the data:

Hodgdon Data:7mm-08		powder	charge	vel.	psi
139 gn hyd sp, OAL=2.800, 1.157, 0.382		h414	45.5	2710	43339
140 gn swf sp, OAL=2.750, 1.115, 0.390		h414	46.0	2791	57133
139 gn hyd sp, OAL=2.800, 1.157, 0.382		h335	37.5	2585	46825
140 gn swf sp, OAL=2.750, 1.115, 0.390		h335	37.5	2647	57588

As this shows, particularly for h335, with nearly identical seating depth, the A-frame has higher pressure.

Below is Swift Data. Pressure not listed but for the exact same charge, shows higher velocity and would in resulthigher pressure.

Swift Data:7mm-08		powder	charge	vel.	psi
140 gn swf sp, OAL=2.750		h414	45.5	2813	na

Using Quickload and fitting the hornady bullet to match the hodgdon data shows:

QuickLoad Data:7mm-08		powder	charge	vel.	psi
139 gn hyd sp, OAL=2.800		h414	45.5	2709	43377
140 gn swf sp, OAL=2.750		h414	46.0	2831	55836
QuickLoad Data:7mm-08		powder	charge	vel.	psi
139 gn hyd sp, OAL=2.800		h335	37.5	2585	46710
140 gn swf sp, OAL=2.750		h335	37.5	2634	55929

The default shot start pressure for hornady is standard 3625psi whereas the default for swift is 10733!
and this accounts for the higher load pressure. A-frames are suppose to be pure copper, thick jackets and with the copper partition, looks like harder to start into the rifling.

BTW, Quickload has the same 10733 shot start for all the A-frames in its database.

Steve

GRT shows same starting pressure for swift, talked to them about it on their discord channel because my MVs weren't anywhere near what GRT and QL say it should be, like a couple hundred fps slower than predicted

10k starting pressure is just wrong. My LD with A Frames shows them with an initial pressure of every other jacketed bullet I've ever worked loads for - 3625 psi

10k should be expected from monolithics, not from jacketed bullets.

 

[Jefferry404]

GRT shows same starting pressure for swift, talked to them about it on their discord channel because my MVs weren't anywhere near what GRT and QL say it should be, like a couple hundred fps slower than predicted

10k starting pressure is just wrong. My LD with A Frames shows them with an initial pressure of every other jacketed bullet I've ever worked loads for - 3625 psi

10k should be expected from monolithics, not from jacketed bullets.

Well, as the saying goes "a man with one watch knows what time it is but a man with 2 watches never knows" or as Bob Vyne of Motorola used to tell me as a young engineer "who's who in the zoo".
below is the data from the Hodgdon Manual No. 27 that I used:

for the same h335 load, swift shows higher pressure and velocity vs the Hornady.
below is the Saami data for the 7mm-08

and you can use the CUP and PSI to convert the Hodgdon table to PSI. Doing this,
shows the Swift has 8329psi higher pressure and higher velocity 62fps.
If one fits QL to the Hornady load and adds the 10733psi shot start pressure, then
QL Hornady load shows 2630fps and 58550psi which now compares to the Swift load
Hodgdon published data 2647fps and 58419psi!
If one then uses the Hornady fitted QL and runs the Swift bullets (with the higher shot pressure), the QL results: 2627fps and 59118psi
compared Hodgdon manual 2647fps and 58419psi.

So, is the QL shot start pressure a convenient way to model the Swift bullet or does it actually take more start pressure for it to engage the rifling?

PS
The Hodgdon data is based upon physical measurements, not simulations, so I would bow to their
authority.

 

[sgt_zim]

My understanding of at least the way GRT calculates IP is a function of 3 things

• bearing surface
• jacket composition - copper is softer than copper/zinc
• core composition - lead is softer than copper, gilding, and way softer than steel

What I have learned from both GRT and QL data is the importance of ladders. I do either 15- or 20-shot ladders in 0.2 gr increments for small bore, and 10-shot ladders in 0.5 gr increments for anything larger than 308 Win.

I wasn't aware that Hodgdon did actual physical pressure measuring. That certainly seems to be a better way of doing things.

 

[davidg8480]

Well, as the saying goes "a man with one watch knows what time it is but a man with 2 watches never knows" or as Bob Vyne of Motorola used to tell me as a young engineer "who's who in the zoo".
below is the data from the Hodgdon Manual No. 27 that I used:

View attachment 596754
for the same h335 load, swift shows higher pressure and velocity vs the Hornady.
below is the Saami data for the 7mm-08
View attachment 596755

and you can use the CUP and PSI to convert the Hodgdon table to PSI. Doing this,
shows the Swift has 8329psi higher pressure and higher velocity 62fps.
If one fits QL to the Hornady load and adds the 10733psi shot start pressure, then
QL Hornady load shows 2630fps and 58550psi which now compares to the Swift load
Hodgdon published data 2647fps and 58419psi!
If one then uses the Hornady fitted QL and runs the Swift bullets (with the higher shot pressure), the QL results: 2627fps and 59118psi
compared Hodgdon manual 2647fps and 58419psi.

So, is the QL shot start pressure a convenient way to model the Swift bullet or does it actually take more start pressure for it to engage the rifling?

PS
The Hodgdon data is based upon physical measurements, not simulations, so I would bow to their
authority.
View attachment 596756

You guys are on such a different level than I am when it comes to reloading ,so I kind of keep my mouth shut my ears open. Sort of.

Now, going back to my original post, now I see why there might be such a wide discrepancy in published load data; in a nutshell, ( hodgdon / swift) actual measurement / simulation. Maby ?

 

[Jefferry404]

Davidg8480,
actually, I compliemnt you for questioning! Your question stirred my interest and I generated the info in this thread from my study. Thanks
For now, my working hypothesis is that due to the thick copper jacket and copper partition, the Swift needs higher pressure to engage the rifling. This powder combustion peak barrel pressure adds to shot pressure and hence there is higher velocity.

below is cros-section of the swift and hornady. Clearly, there is a thicker copper jacket and the substantial copper partition (which to Mr. sgt_zim point regarding mono-bullets)

sgt_zim,
I checked my reloading notes and for my 338 winmag and 375HH using Swift A-frame was 100-150fps slower than expected. My QL file had app 4150psi shot pressure and my notes say was the default (2 years ago). I recently updated and now see the 10775 pressure and will use this going forward until more info. I do have an email into Neco regarding the Swift shot pressure.

I have moved away from ladders and have been using OBT (optimum barrel time) with good success. I modified that concept for hunting purpose. It takes 3 calibration shots and then usually 3 more to verify. If there might be interest in this, can post more info. thanks
Steve

 

[Rule 303]

A reloading manual I have lists 86 grains of AR2213SC as max load for a 275 grain bullet. No mention of what make.

AR2213SC is rebadged by Hodgdon to H4831SC and IMR4831SC. If the powder does not have the SC (Short Cut) and is branded H4831 this is AR2213. The SC is a slightly different powder. The strands of powder being shorter, hence Short Cut. Do not substitute one for the other.