Ronson,
H4895 is an efficient and therefore good choice of powder for the weight of bullet.
The bullet on the Nosler website is the 123 Nosler Custom Comp. You are talking about a different manufacturer's bullet with different length and boat tail. Only the weight is the same. The 123SST loaded to Nosler's OAL will leave a different case capacity and this has implications for pressure. At the same weight this is not a big concern but it should be a concern if you are wanting max pressure in an unforgiving receiver like an AR15.
Quickload lists the length of the 123SST bullet at 1.243", and the Nosler CC as 1.200". The bullet with the plastic tip, the SST is longer and this means you need to shave 0.3gns off the Nosler tables to predict the same pressures.
Your suggested 27grains will be fine however (obviously load a few 5-10% below this to check safety in your gun).
At the OAL of 2.250" QL predicts 27gns as max for the SST, however Nosler suggest you can fit up to a max of 27.7gns (28 - 0.3 = 27.7). QL is notoriously conservative so in your shoes I would set 27.5 as max; being the difference between the two. For a bolt gun you can go higher and be more relaxed but a relatively fragile AR bolt is the canary in the coal mine of over-pressure.
H4895 is an efficient and therefore good choice of powder for the weight of bullet.
The bullet on the Nosler website is the 123 Nosler Custom Comp. You are talking about a different manufacturer's bullet with different length and boat tail. Only the weight is the same. The 123SST loaded to Nosler's OAL will leave a different case capacity and this has implications for pressure. At the same weight this is not a big concern but it should be a concern if you are wanting max pressure in an unforgiving receiver like an AR15.
Quickload lists the length of the 123SST bullet at 1.243", and the Nosler CC as 1.200". The bullet with the plastic tip, the SST is longer and this means you need to shave 0.3gns off the Nosler tables to predict the same pressures.
Your suggested 27grains will be fine however (obviously load a few 5-10% below this to check safety in your gun).
At the OAL of 2.250" QL predicts 27gns as max for the SST, however Nosler suggest you can fit up to a max of 27.7gns (28 - 0.3 = 27.7). QL is notoriously conservative so in your shoes I would set 27.5 as max; being the difference between the two. For a bolt gun you can go higher and be more relaxed but a relatively fragile AR bolt is the canary in the coal mine of over-pressure.