Fully prepared 308 ADI cases weight distribution

[Beiruty]

All cases (28)

 

[Beiruty]

No outliners (23)

 

[Straightshooter1]

No outliners (23)

View attachment 1376176

"Loaded"???

Those weights are what I have for my .308 Federal brass cases (not loaded or primed).

 

[Beiruty]

"Loaded"???

Those weights are what I have for my .308 Federal brass cases (not loaded or primed).

Not loaded or primed. Annealed, FS, Neck expanded, 3-way trimmed
175gr SMK over RAM TAC
44-43.7-43.4gr @ 2.222" and 2.212" BTOG

 

[Beiruty]

Loaded rounds weight difference is ±0.7gr out of 401gr total round weight

 

[Beiruty]

Not loaded or primed. Annealed, FS, Neck expanded, 3-way trimmed
175gr SMK over RAM TAC
44-43.7-43.4gr @ 2.222" and 2.212" BTOG

This load was hot in my rifle. 43.4gr showed flattened primer and 43.7gr showed extractor imprint.
Accuracy is not there. I will pull the bullets off the 44grs and drop by 1.8grs

 

[Straightshooter1]

Loaded rounds weight difference is ±0.7gr out of 401gr total round weight

Hmmm??? What the point of knowing the variance in total cartridge weight when all the components of the cartridge have variances?

 

[Beiruty]

Hmmm??? What the point of knowing the variance in total cartridge weight when all the components of the cartridge have variances?

The mean of the variances would average to the total weight, the SD of the variances would sum up (SD1+ SD2+ etc.)

 

[Martin52]

This load was hot in my rifle. 43.4gr showed flattened primer and 43.7gr showed extractor imprint.

I had to reduce the load using ADI .308 brass, it generally had less water capacity by around 1.6gr compared to Lapua.

 

[Beiruty]

I had to reduce the load using ADI .308 brass, it generally had less water capacity by around 1.6gr compared to Lapua.

I did a quick check, water case capacity is 54.5-55gr, less than standard 56.3gr.
I recalibrated GRTools and pressure was at 63.5KPS, 3.5KPSI more than SAAMI max pressure.

I will try again with 41.8gr of RAM Tac @ 2.800", expected MV from 22" barrel is 2600 fps

 

[Beiruty]

Note: Case length grew from 2.005" to 2.013"

 

[Martin52]

You seem to be loading at typical mag length - can you seat further out ?

 

[Beiruty]

You seem to be loading at typical mag length - can you seat further out ?

Yes, I can, but for this rifle, I prefer to load for feeding from the magazine. Yesterday, I looked into opening up the feeding ramp to load from a no-binder MDT magazines at max COAL of 2.955". In addition to the front lip, the sides of the receiver have to widened up a bit for the MDT magazine to lock in place.

I am using a metal box conversion kit from Atlasworx.

 

[Beiruty]

I dropped the load to 41.8gr of Ram TAC with ADI cases
and 42.0gr and 42.2gr with Lupua cases

 

[Beiruty]

If increase the COAL to 2.840" with the 175 SMK, I can increase the charge to 43gr and gain an extra 48 fps to MV 2648 fps. The bullet is supersonic to 1K yards

 

[Beiruty]

 

[Martin52]

If you have access to a chrony you can fine tune/calibrate GRT and run the OBT function.

 

[Beiruty]

If you have access to a chrony you can fine tune/calibrate GRT and run the OBT function.

True. However, at this indoor, I do not have a chance to use a Labradar or CompPro Chrono.

 

[Martin52]

True. However, at this indoor, I do not have a chance to use a Labradar or CompPro Chrono.

No problem, GRT should get you close with correct data inputs. GRT does highlight the impact of a different COAL and internal case volume on pressure.

 

[Zero333]

I wanna see the groups. Couldn't care less about all the other stats if it shoots like a trench scatter gun