375 RUM guys

[Engineering101]

benchracer

I too found it very interesting. I did that comparison with all my good loads and they were all on a node. I then got to thinking of all the powder, bullets and barrel wear it took me to develop those loads which then got me to wishing that I had heard about this sooner. Anyway, now I can develop a good load in about 7 shots.

 

[benchracer]

Interesting results thanks for doing that. The velocities seem slow, with a factory 26"I was getting 3200 FPS with 102 gr of rl 22... Maybe it was a fast barrel... Maybe my chrono was off... I'll be working on a load very soon and using the magneto speed so I'm looking forward to comparing real world results... Have you found quick load to give you pretty accurate estimates when working up a load?

I have been looking at Barnes data for the 270 TSX and I think you may be right that QL is on the conservative side with this particular combo. Note the following:


QL shows the 270 TSX pressuring out with Ramshot Hunter at more than 100 fps slower, with a 4.5 grain lower powder charge, and a HIGHER load density (100% vs 95%) than Barnes data shows, with all other factors being equal.

Something is definitely off somewhere. I suspect that real world shooting from your chosen combination will have a lot to say on the matter.

 

[Engineering101]

benchracer

One of the things I've figured out about QL is to take advantage of published load data max loads from the various bullet makers handbooks since many of them use pressure barrels, max loads are known to be near max pressure. For example, 62,000 PSI is typical for a 65,00 PSI cartridge. By using the known pressure you can figure out what the WF needs to be.

I've also found that WF changes (drops) as you add powder to a case. I have data showing it drop from 0.63 to 0.53 while powder went from 39 to 41 grains in a 260 Rem with 108 grain Scenars.

 

[Tikkamike]

I finished load development with the 375 using hunter and ended up at 3108 fps using 99.5 gr of hunter. 5 shot group was a little under half an inch

I am going to try another slow powder to see if I can make use of that 28" tube a little better. I think I might try H1000 or retumbo maybe

 

[300 ultra]

Have you tried RL33 yet?

 

[Tikkamike]

looks like itll be too slow

 

[benchracer]

Without accounting for measured case capacity, QL predicted approximately 100fps slower than actual velocity with your stated powder charge, so it appears to be in the ballpark.

From what I can tell, H1000 or Retumbo will require 110.3 grains and 113.6 grains, respectively, to equal the velocity yielded with Ramshot Hunter. Those two charges are 12% and 14% compressed, respectively. It looks to me like you will run out of case capacity before either powder can offer an advantage over Hunter.

It appears that you will get best performance from powders like Accurate Magpro, RL-22, or IMR 7828 SSC with the 270 TSX. A 5% compressed charge of any of these should gain about 50-60 fps.

Of course, real world results trump everything else. Thank you for sharing your results. I look forward to seeing what you come up with!

 

[Tikkamike]

I lied before. I thought I has 3200 with rl22 before then tried it in this barrel with poor results but it was actually rl19 after looking at my notes. So rl22 which originally wasy first choice is a new venture. I'm loading some rl22 as we speak and will shoot them later today. I agree h1000 probably is too slow but I was going to try it thinking it was my only option I had based on powder on my shelf. Hopefully 22 gives me some good results

 

[Tikkamike]

Also oal is 3.780

 

[benchracer]

I lied before. I thought I has 3200 with rl22 before then tried it in this barrel with poor results but it was actually rl19 after looking at my notes. So rl22 which originally wasy first choice is a new venture. I'm loading some rl22 as we speak and will shoot them later today. I agree h1000 probably is too slow but I was going to try it thinking it was my only option I had based on powder on my shelf. Hopefully 22 gives me some good results

Also oal is 3.780

Hopefully, RL-22 will do well for you. I ran the numbers with the 3.780 OAL and velocity didn't change much (about 10fps). Judging by where you came out with Hunter, my guess is that you have a bit more than the QL default case capacity of 117 grains.

 

[Tikkamike]

I wasn't sure where to start with rl22 so I started pretty low. I got up to 98.5 gr and got 2994 FPS out of it. But no pressure signs and lots of case capacity left so I'll load up the next batch and maybe shoot it tomorrow. I'm a little out of shooting shape and my daily sessions with the 375 rum and 338 rum have me a little sore so I think I'm done for the night.

 

[benchracer]

This should give you an idea of where you are vs predicted:

 

[Tikkamike]

Nothing I'm seeing tells me I have a chance of achieving the velocities I had in mind. It's looking like I'll be lucky to hit 3200 .... Which is still flying, and I'm not hell bent on velocity I just had my expectations up based on what I saw in the past with the factory barrel. I'm thinking it was just a fast barrel/possible chronograph margine of error which I'm not getting now with the magneto speed. Hopefully I'll learn something tomorrow. Thanks for all the help!

 

[benchracer]

I'm glad I could help! I am guessing that you will top out around 3150 or so.

If my understanding of the information posted earlier by Engineering 101 regarding optimum barrel time is correct, you should encounter an accuracy node between 3000 and 3050 and another node between 3135 and 3185. If that proves out, 3150 should just get you into the upper node.

I don't know if that will hold true or not, but it may be worth watching.