Slow barrel?

[lroy]

This is 11.2gr of aa7. 1.175 oal using 115 PD JHP.

 

Seems kind of on the slow side based on other's chrono results? 11.2 seems like a lot to only get 170pf.

[zzt]

Need more info.  How many poppels?  Describe the comp- number of chambers and number of ports.

 

Is you chrono accurate?  Did you make sure the bullet path was parallel to the sensor windows and straight down the centerline?

 

I shoot 10.8 under a 115 JHP and I'm North of 175PF.

[Guy Neill]

Numerous factors can affect chrono results.

 

What is the barrel bore diameter compared to the bullet diameter?

 

It's not unknow for the muzzle flash to start the chronograph, giving low velocity readings. I've not used AA7 recently, so I do not recall what sort of muzzle flash it gives. Still, a baffle to protect thestart screen may be of benefit.

[lroy]

No poppels. Three port comp. Its a honcho.

 

I was about 15ft from the chrono. Don't think the muzzle blast would effect it at that distance?

 

Is aa7 pretty temp sensitive?

Edited May 11, 2023 by lroy

[zzt]

1 hour ago, lroy said:

Is aa7 pretty temp sensitive?

 

No.  10' from the chrono is just fine.  Muzzle blast is a nonissue unless your comp is very inefficient.  Most important is each bullet travels the same path.  Straight down the long axis and parallel to the screens.

Edited May 11, 2023 by zzt

[lroy]

22 minutes ago, zzt said:

 

No.  10' from the chrono is just fine.  Muzzle blast is a nonissue unless your comp is very inefficient.  Most important is each bullet travels the same path.  Straight down the long axis and parallel to the screens.

 

Did it as straight on as possible. 

 

I was shooting limits prior to this, I guess my question is on every other recipe for aa7 I see, a 115 bullet at 11gr was more than enough to get 170pf+.  

 

I'm mainly concerned about going to 11.4 and having too much pressure. The primers are already flat at 11. 

Edited May 11, 2023 by lroy

[motherFNbrandon]

One factor could be a slow lot of AA7. My latest jug required .2gr more for the same pf as the previous jug.

But I'm still under 11gr.

Your OAL and bullet choice could be another factor.

Yet another factor could be primers. I found CCI SPP to be 1-3pf slower than Fed SPP. CCI SRP and Fed SPP about the same.

 

10.5gr AA7 with 115 MG JHPs at 1.165" to 170pf

10.7gr AA7 with 115 PD V2 JHPs at 1.165" to 170pf

All with new Starline brass and Fed SPP

 

The PD V2s are shorter than the MGs and when loaded to the same OAL, they needed an additional .2gr to match the pf.

 

It would be .2gr less for any of the above if it were my old batch of AA7.

 

 

Middy with 2 port comp and 2 poppels.

[zzt]

AA7 doesn't vary all that much.  It's not like SWMP where you have to add an entire extra grain in some lots.