I did something stupid with my 7.5 swiss

D

deanyang

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People always say starting low and work your way up. I guess I went too far.
Powder:CFE 223
Bullet:147gr FMJ
The suggested starting load for 308 Win 150gr bullet is 48.4(this powder has no data on 7.5 Swiss)
Powder weight I used 37gr and 39gr.
Beside the nasty bolt. I got a puff of air blowing to my face with 37gr load. 39gr are fine.

Is it because my under load this waaaaay too much? The powder cannot push the bullet out? I would like to know why this happened.

Thank you!
Dean
 
Well you definitely pushed the limit. If you had gone lighter, it could have been much more serious.

K31 actions are very strong and well vented, to do just what it did with your experiment.

Milspec primers are usually just as hot as magnum primers, so they should have provided enough "flash" to properly ignite the powder in the cartridge.

Still, I'm surprised at what happened.

The 7.5x55 case capacity is closer to 303 British and was loaded to similar pressures.

CFE223 and BLC-2 have very similar burn rates but BLC-2 is slightly faster.

The lightest load listed for BLC-2, for the 303Brit is 37.3 grains under 150 grain bullets.

This would also indicate that with a slightly slower powder, you would need more powder.

The 7.5x55 case is slightly larger, so you would need a hair more powder to get by without impending issues.

That's why your 39 grain loads were OK.

I'm not sure where you're finding your information.

One very valuable thing to have on hand is a "Powder Burn Rate Chart"

There are several available over the internet.

Once you have the charts, there are several, look up the powders you are interested in to compare their compatabilities.

Such as the difference between BALL and EXTRUDED.

Single base/double base and of course burn rate.

Some powders will take more to achieve a proper working pressure, even though they have a similar burn rate. Some will spike their peak pressure very suddenly, after a long slow curve to that pressure.

Before experimenting with powders, without, already tried and proved loads, you really need to educate yourself on what to look for with powders not listed in the manuals for a particular cartridge.

IMHO, CFE223 should be a useful powder for the 7.5x55

Look here for more information:

More CFE223 results - Swiss Rifles dot com
https://www.tapatalk.com/.../more-cfe223-results-t14157.html
2015-08-13 · I just got back from the range with more results in my effort to find a decent load for the 7.5X55 round using Hodgden CFE223. I have about 8 pounds o I have about 8 pounds o More CF
 
Thanks again for the detailed info, I was seaching for minimum weight online and came across this data. actually the data came from the same page you just posted, someone replied OP on what he tried for 50 yards, I figured my bullet weight is less so I can try 37gr as well, here's what I took from that page:


'Second session was at 50 yds with loads going from 37 to 39.6 gr. 39.6 was the clear winner with a 1.5" 4 shot group. However, the spread was greater than with the 40gr. (none touching). I am planning on going to try the 40 gr loads at 100yds and see how they group. I also am thinking of trying more granular loads ranging from 39.8 to 40.3, just to see if there is a sweet spot.'
 
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The 7.5X55 Swiss has the same bore diameter as the 308 Win and the 30-06. Its case capacity is about 65.0 grs of water, with the 308 being about 56.0 and the 30-06 at about 68.0.

I typically load it with 30-06 data using the 30-06 Start Load as a Max Load. I settled in 46.0 grs of IMR4064 with a 150 gr bullet for about 2750 fps. I'd have tried CFE223, which is a bit slower than IMR4064, but I sold my K31.

I'd work in the 46.0-50.0 gr range with that bullet and CFE223.

P.S. the notion that if a Start Load is "safe", then going well below it is "safer" is a fallacy, as the opposite is generally true.
 
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Andy said:
The 7.5X55 Swiss has the same bore diameter as the 308 Win and the 30-06. Its case capacity is about 65.0 grs of water, with the 308 being about 56.0 and the 30-06 at about 68.0.

I typically load it with 30-06 data using the 30-06 Start Load as a Max Load. I settled in 46.0 grs of IMR4064 with a 150 gr bullet for about 2750 fps. I'd have tried CFE223, which is a bit slower than IMR4064, but I sold my K31.

I'd work in the 46.0-50.0 gr range with that bullet and CFE223.

P.S. the notion that if a Start Load is "safe", then going well below it is "safer" is a fallacy, as the opposite is generally true.
Click to expand...

I guess it does not matter if I only intend to shoot indoors for like 40 yds?
 
deanyang said:
I guess it does not matter if I only intend to shoot indoors for like 40 yds?
Click to expand...

Then you probably need a different powder if you're looking for watered down loads. A guy I worked with had a 12 gauge and wanted some light loads with a slug. I don't recall the powder, but it was something like 30-35 grains for a normal load, but he figured 18-20 grains would be fine. When someone shows up to test loads over a chrono with a rod to pound slugs out, you know how it's gonna go. Powders aren't like cooking or baking, where half the salt makes it half as salty. You need to find the right powder for the job you want it to do.
 
deanyang said:
I guess it does not matter if I only intend to shoot indoors for like 40 yds?
Click to expand...

You dont get it. The issue is that combustion of the powder becomes erratic at low pressures. So when you start going well below minimum loads, you can run into trouble. In your case, the light load did not generate sufficient pressure to expand the case and seal the chamber, which caused blowback and carbon deposits. If the combustion pressure becomes too erratic, you could lodge a bullet in the barrel - I hope I dont need to tell you what issues that may cause.
So you need to use powders in their appropriate load ranges. Trying to think outside the box, coupled with recipe guidance from the internet, is a good way to win a Darwin award.
 
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Your pressure is way to low. You need more pressure to expand the case and make it seal against the chamber. I don’t use jacketed bullets for my reduced loads. I use lead bullets with appropriate powders. I use 308 Winchester data for both jacketed and cast lead for my reloads. I don’t use MAX 308 loads, I stay at least a grain under MAX. Reducing powders too far is where people get into trouble due to not enough pressure or possibly accidental double loads.
The shoulder of your case is obviously not blown out the shape of the chamber. Pressure is too low.
 
saskgunowner101 said:
Then you probably need a different powder if you're looking for watered down loads. A guy I worked with had a 12 gauge and wanted some light loads with a slug. I don't recall the powder, but it was something like 30-35 grains for a normal load, but he figured 18-20 grains would be fine. When someone shows up to test loads over a chrono with a rod to pound slugs out, you know how it's gonna go. Powders aren't like cooking or baking, where half the salt makes it half as salty. You need to find the right powder for the job you want it to do.
Click to expand...

understood, I will make sure to load normally, 48gr to start
 
cosmic said:
You dont get it. The issue is that combustion of the powder becomes erratic at low pressures. So when you start going well below minimum loads, you can run into trouble. In your case, the light load did not generate sufficient pressure to expand the case and seal the chamber, which caused blowback and carbon deposits. If the combustion pressure becomes too erratic, you could lodge a bullet in the barrel - I hope I dont need to tell you what issues that may cause.
So you need to use powders in their appropriate load ranges. Trying to think outside the box, coupled with recipe guidance from the internet, is a good way to win a Darwin award.
Click to expand...

Thanks, I believe that was exactly what happened. I am going to start at 48gr like everyone else.
 
Snider shooter said:
Your pressure is way to low. You need more pressure to expand the case and make it seal against the chamber. I don’t use jacketed bullets for my reduced loads. I use lead bullets with appropriate powders. I use 308 Winchester data for both jacketed and cast lead for my reloads. I don’t use MAX 308 loads, I stay at least a grain under MAX. Reducing powders too far is where people get into trouble due to not enough pressure or possibly accidental double loads.
The shoulder of your case is obviously not blown out the shape of the chamber. Pressure is too low.
Click to expand...

that pic was taken after I resized the case, but yes not enough pressure was the problem. Starting with 48gr min from now on. Thanks!
 
deanyang said:
I guess it does not matter if I only intend to shoot indoors for like 40 yds?
Click to expand...

I'm starting to experiment with a 1889 and am mostly using a short indoor range too. Given that limitation and the cost savings I've opted for unique powder and cast powder coated bullets.
Something you might want to look at for plinking.
 
Andy said:
The 7.5X55 Swiss has the same bore diameter as the 308 Win and the 30-06. Its case capacity is about 65.0 grs of water, with the 308 being about 56.0 and the 30-06 at about 68.0.

I typically load it with 30-06 data using the 30-06 Start Load as a Max Load. I settled in 46.0 grs of IMR4064 with a 150 gr bullet for about 2750 fps. I'd have tried CFE223, which is a bit slower than IMR4064, but I sold my K31.

I'd work in the 46.0-50.0 gr range with that bullet and CFE223.

P.S. the notion that if a Start Load is "safe", then going well below it is "safer" is a fallacy, as the opposite is generally true.
Click to expand...

That CAVEAT should be in large case letters.

People need to get more knowldedge about powder burn rates and understand that none of it is proportional.
 
Try some IMR4895 if you want to use reduced loads. You can load it to 60% safely. Or better yet, get some trail boss.
 
vagrantviking said:
I'm starting to experiment with a 1889 and am mostly using a short indoor range too. Given that limitation and the cost savings I've opted for unique powder and cast powder coated bullets.
Something you might want to look at for plinking.
Click to expand...
Sure thing, what kinda powder is that?
 
Unique. Its awesome. You can run 10 to 13ish grains in any big rifle case with lead bullets and get like 1400fps. I use it in 455 webley too. 4.0 grains! 10 grains in 30/30 with a 110 grain lead bullet
 
Mulletard said:
Unique. Its awesome. You can run 10 to 13ish grains in any big rifle case with lead bullets and get like 1400fps. I use it in 455 webley too. 4.0 grains! 10 grains in 30/30 with a 110 grain lead bullet
Click to expand...

Thanks I wonder if we can purchase lead bullets? I am new to this cannot cast.
 
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