Finally...time to test the 375 rum and the 320 ce

[Doublezranch]

The long awaited time is over!! Headed to the range tomorrow for a little test and tune with the 375 rum and the 320 ce bullet. These are loaded at 3.907 coal and my ladder is rl 22 90 through 94 grains in .5 increments. Hoping to get around 2700-2800 at 94. You all know me, if no pressure signs at 94 I might push the envelope. I've been waiting for months for this day. If it works out, there a Wyoming antelope with its name on one!!

 

[Doublezranch]

Oh my gosh I forgot the pic. Here she is next to a 300 win...

 

[Doublezranch]

Sorry...you will just have to turn your head...

 

[HARPERC]

You are excited, got that keyboard drifting and sliding in sideways , good luck with the antelope.

 

[Doublezranch]

Thanks Harp!! My surgery patients will see a smile from me all day long!! By the way, reread some of your bear literature you gave me. This year has been way different. Took your advice and have over 5 big bears coming to the bait. I have a 260 accubond waiting for one of those bruins!!

 

[midwesthunter]

interested in the results as I have a 375RUM barrel waiting to be screwed on.

 

[HARPERC]

I look forward to seeing a big bear picture.

 

[Doublezranch]

First powder results are in. Man, what a fun gun to shoot. Amazing power and accuracy. 1-12 twist seems to be a perfect match for the Cutting edge 320. The results are as follows:

Reloader 22
90 - 2636
90.5 - 2640
91 - 2655
91.5 - 2670
92 - 2684
92.5 - 2690
93 - 2710 good accuracy
93.5 - 2740 best accuracy
94 - 2750 extractor marks and group opened considerably.

In discussion with Barnesuser28 (thanks Riley), we talked about loading a 93.3 to see if there is a better group splitting the difference. We agreed that 2740 for a 320 grain bullet is cruising!! Especially out of a 26 inch tube!! Hopefully by the end of the week I can shoot the 7828 ssc ladder for comparison. I'm betting that my pressure signs would be further down the ladder than 94 but might not be worth the trek.

 

[Doublezranch]

Here is a pic of 93 at 100 .898 MOA

 

[Doublezranch]

Here is a pic of 93.5 at a 100 .761 MOA

 

[benchracer]

Optimum barrel time data says best accuracy should come between 2680-2740fps with RL-22. Your actual shooting results appear to back that up. You may wish to tweak seating depth from here. CE says best performance typically lies with the seal tite band seated between .025 off the lands and up to half way down the case neck.

QL shows IMR 7828SSC reaching optimum barrel time between 2670-2730fps, slightly slower than RL-22, but not enough to make a measurable difference. Neither powder has enough headroom to reach the next node before passing pressure limits. It will be interesting to see if your rifle shows a distinct preference for either powder.

 

[Doublezranch]

It is seated right at the sealtite band. Do you think I should go another 10 thou longer?

 

[benchracer]

It is seated right at the sealtite band. Do you think I should go another 10 thou longer?

Do you mean relative to the case mouth, or relative to the rifling?

I had an e-mail exchange with one of CE's tech guys awhile back (I would have to go back through the e-mails to tell you his name), who stated that it is common for the MTH type bullets to shoot better with some jump. I would start with the sealtite band about .020 from the rifling and back it off in three or four increments of about .030 or so and see what you get.

 

[Doublezranch]

The mouth of the case is right exactly at the band. So if I here you correctly, I should seat the bullet further into the case making it shorter coal. Correct?