Speed Anomoly!!

[Envillegc1]

Good Evning one and all.
My friend and I are seeking some advice about a reloading query / quirk we have come up with on our 243's.

At the Stalking Show, a purchased the new Gamin unit.
So on Sunday we decided to go and check to see what speeds where like when measured vs book and box data.

I first benchmarked the Chrono with 22LR, and it was on the money.

I then put my factory 50gr 22-250 rounds through it, and adjusting for barrel length, again bang on.

We then statred on the 243.
First up was 58 gr Vmax with 42gr N550. Disappoingly this was down at 3100 fps. Given the load, we should have been north of 3500fps, maybe more given at 44gr it should be 3800fps.
Then we tried factory load 95gr ELD-X, again bob on vs the packaging
Then we tried 75gr homeload and again speed was well down.
Sako Gamehead factory load up next and again bang on.

We have been scrating our heads for two days trying to figure out what we are doing wrong?
I am two years into loading, but my friend has 20 years experience.

The results where the same in both rifles, Mauser/Sauer.

I have heard that maybe we have not reached a critical pressure build up, dont know if this is true or not?

Finally, the recoil on the 58s was like a soft 223.
Also the report vs that of the 22-250 was makedly quieter.

Any thoughts?

 

[long_range_rob]

Personally I’m more interested in accuracy not velocity. I’ve never had a complaint from anything I’ve shot saying “That was a bit slow?”

 

[Envillegc1]

Personally I’m more interested in accuracy not velocity. I’ve never had a complaint from anything I’ve shot saying “That was a bit slow?”

Yep, couldnt agree more. Its more of a what am I/both of us missing?
I am one of those people that if something is not right I need to know why?

 

[Smellydog]

Lol, put more powder in them. Book data is deliberately safe.
They have to consider you loading in blighty then getting on a plane and shooting the same ammo in the Sahara.
It's called arse covering!
Measure a brass cartridge head just up from the rim. Keep adding powder until it's swollen by .003" to .004", now you'll be cooking.

 

[Smellydog]

My 243's use to shoot 100gn bullets at 3100.
My 308's shot 110gns at 3100+.
All loads above book but no excessive pressure.

 

[Selous]

How are you determining what velocity your bullets should be doing. It is probably more likely that the error lies with that than with the chronograph that gave some believable results earlier. Have you tried comparison with a second chronograph?

 

[takbok]

Yep, couldnt agree more. Its more of a what am I/both of us missing?
I am one of those people that if something is not right I need to know why?

You're just missing powder - add more for more velocity. The 243 has more room for it and you're using a slow burning powder for that light bullet. If you're still not getting the velocity then try a faster burning powder. Vihtavouri data is way off with its velocity figures in my limited experience.

 

[palo]

I never used n550 but I did use n530 and n540 in different calibres and never did get near the stated book velocity.
If you want more speed try a different powder

 

[Donkey Basher]

How accurate is your reloading data? - case capacity will impact velocity due to pressure. Establish the case capacity in grains of H2O & put that into your reloading software along with the powder weight, seating depth etc & then see whether the predicted velocity is nearer to what your chrono was showing.

 

[25 Sharps]

How accurate are your scales? It appears all the factory loads are where they should be but your home loads are a lot slower than they should be. Maybe you undercharged the cases?

 

[Will the chippy]

How accurate are your scales? It appears all the factory loads are where they should be but your home loads are a lot slower than they should be. Maybe you undercharged the cases?

On balance scales it's easy enough to be 5 grains out. I check mine with cheap digital just so I know I'm in the ball park.

 

[Selous]

On balance scales it's easy enough to be 5 grains out. I check mine with cheap digital just so I know I'm in the ball park.

But do you check the scales with a check weight? Any scale can give dodgy results and in my experience the cheap digital scales I have used have been unreliable but the balance scales I used for years (RCBS 505) were amazingly accurate when compared to a laboratory quality scale (FX120) that had been properly calibrated

 

[Will the chippy]

But do you check the scales with a check weight? Any scale can give dodgy results and in my experience the cheap digital scales I have used have been unreliable but the balance scales I used for years (RCBS 505) were amazingly accurate when compared to a laboratory quality scale (FX120) that had been properly calibrated

Yes I always calibrate and check the digital with the check weight, I don't use them to reload as I use the rcbs scales. There good enough to tell me if I'm at 32 grains or 37 grains for instance.

 

[Smellydog]

With n550 and 58gn bullets I'd probably be filling the case to the top of the neck and compressing it with the bullet.

 

[Steff]

The Vihtavuori data is simply not worth the paper it is printed on. No use quarrelling about the accuracy of scales in this case either.

 

[Smellydog]

The Vihtavuori data is simply not worth the paper it is printed on. No use quarrelling about the accuracy of scales in this case either.

View attachment 362004

That's less than 30-30 pressure....

 

[Envillegc1]

How are you determining what velocity your bullets should be doing. It is probably more likely that the error lies with that than with the chronograph that gave some believable results earlier. Have you tried comparison with a second chronograph?

We were bench testing against factory loads on the same day which all produced figures close to box stated speeds. Loads were done in conjunction with Hornady loading tables, Vhit data sets. Which is why we were both a little surprised with the results.. much scratching of heads has thus ensued!

How accurate are your scales? It appears all the factory loads are where they should be but your home loads are a lot slower than they should be. Maybe you undercharged the cases?

checked the scales with a number of bullet heads from 90gr to 35gr. All where there to within 0.1gr.

 

[Envillegc1]

How are you determining what velocity your bullets should be doing. It is probably more likely that the error lies with that than with the chronograph that gave some believable results earlier. Have you tried comparison with a second chronograph?

We were bench testing against factory loads on the same day which all produced figures close to box stated speeds. Loads were done in conjunction with Hornady loading tables, Vhit data sets. Which is why we were both a little surprised with the results.. much scratching of heads has thus ensued!

How accurate are your scales? It appears all the factory loads are where they should be but your home loads are a lot slower than they should be. Maybe you undercharged the cases?

the loads we produced were done separately on two different scales. Both of us have subsequently checked scales with bullet heads and found them to be within 0.1gr. Hence our head scratching

 

[Envillegc1]

How accurate are your scales? It appears all the factory loads are where they should be but your home loads are a lot slower than they should be. Maybe you undercharged the cases?

The bullet s were made on two separate scales. We have both checked them against bullet heads and they come out to 0.1 gr. hence head scratching

 

[Envillegc1]

But do you check the scales with a check weight? Any scale can give dodgy results and in my experience the cheap digital scales I have used have been unreliable but the balance scales I used for years (RCBS 505) were amazingly accurate when compared to a laboratory quality scale (FX120) that had been properly calibrated

We both use balance scales.