Temperature swing Re-15 and 175smk .308

[Woodlanddude]

I have chronied my loads using 43.9 gr Re-15, 210 feds and 175 smks at both 60deg and now just below 30deg F. Loads were tested using a Shooting Chrony Beta Master. Is a drop from about 2635fps to 2565 fps a normal drop in velocity for about 35 deg or so for this combination? Would H-4895 have this much drop for this? I have an alternative load tested at 60deg I can change to with the H. How much of a velocity swing are some of you seeing for these powders in about a 30deg increment?
Matt

 

[rijndael]

Re: Temperature swing Re-15 and 175smk .308

I've had much better luck with H4895 and temp swings than RE-15.

 

[Woodlanddude]

Re: Temperature swing Re-15 and 175smk .308

Rij,
I guess I knew there would be some movement in velocity, but if my results are correct I may have to change. The H gave me good numbers at 2600fps, but the Re-15 shot great with anything between 2600-2650fps for a velocity.

 

[marc357]

Re: Temperature swing Re-15 and 175smk .308

Matt,

I tested Varget from 30deg to 90deg, for almost NO CHANGE in velocity. Matter of fact, at 30deg, it ran slightly FASTER (figure that one out, LOL) than it did at 90deg.

I know James (and many others) like H4895 alot, it is supposed to be very temp. stable as well- but I have not used it.

Marc

 

[Woodlanddude]

Re: Temperature swing Re-15 and 175smk .308

Brock saw the same phenomenon on his 7-08 with h-4350(faster by about 10-15 fps) on the same day I chronied. I wonder if with a stable powder the velocity increase could be contributed to a tighter bore/chamber in the cold? Interesting stuff. Initially I have stayed away from the V word due to lot to lot variations in velocity(and especially pressure

). Re-15 has been stable can to can. Yeah I know save up and buy the jug is the best answer. Accumulating gear at the same time as keeping myself in ammo has limited this so far. The H and varget are my only two other options IMHO. Just wondering how much 4895 will change? Thanks Marc!

 

[rijndael]

Re: Temperature swing Re-15 and 175smk .308

I have some data points on it - but I'll have to dig them up.

The problem with my data points is that I didn't have the same Low and High temp for the two powders. Your numbers for RE-15 sound similar to what I have, but I'm going from memory. I seem to recall .8 - 1 fps / degree.

If your goal is to calculate a fps/degree .... you can do this, but some powders don't follow the same linear scale throughout the temp range.
It could be 1 fps / degree from 60-90 .... but from 10 to 30 it may be 2 or 3 fps / degree.

 

[Hunt]

Re: Temperature swing Re-15 and 175smk .308

With 95 Palma chamber, Lapua brass, F210M and 175 SMK I have seen 42.3 gr of RL-15 go from 2700 fps @ 80 deg. down to 2580 fps @ 35 deg.

 

[Woodlanddude]

Re: Temperature swing Re-15 and 175smk .308

Thanks for the replies, gents! I think I know what I need to about Re-15. Looks like I need to try something else for bad weather stuff. Thinking of trying the H- first and seeing if groups get better as it gets over 2600fps.

 

[Grump]

Re: Temperature swing Re-15 and 175smk .308

Hmmm. 122 fps in 45 degrees F about = 3 fps/degree in the 35-80 degree range. What barrel length? 30 since you're running a Palma chamber?

The other report is from the OP, a drop of 70 fps in the 25-30 to 60 degree range, almost exactly 2 fps per degree. Again, barrel length?

Both are with 175s.

I think I was running 2 fps per degree with 168s and WW 748 six years ago (22-inch barrel), when I started looking for more temp stability. Went to 4064 based on a Varget ad (halfway between 748 and Varget) because I wanted to stay with domestic production for stability of supply reasons.

If RL-15 is as steep a curve as 748, I just might skip that powder in my current load development quest. H4895 is my next batch.

Anyone have data points on 155s?

Thanks!

 

[Hunt]

Re: Temperature swing Re-15 and 175smk .308

This was with a 24" Krieger...#10 MTU. First shots were with newly opened 5 lb. of RL-15 @ 80 deg. Shot @ 35 deg. were taken a month later.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: inode</div><div class="ubbcode-body">With 95 Palma chamber, Lapua brass, F210M and 175 SMK I have seen 42.3 gr of RL-15 go from 2700 fps @ 80 deg. down to 2580 fps @ 35 deg. </div></div>

 

[Woodlanddude]

Re: Temperature swing Re-15 and 175smk .308

Grump,
Stock 5R milspec 24" barrel. About 900-1000rds downrange.
I shot a smokin accurate 155scenar load with H-4895 that 3 other 5R users were shooting. It had an OAL of 2.82" if I remember correctly, and was supposed to be going 2925 fps out of those rifles. Group at 500yds was much smaller than handspan. Hope that helps you. I am headed back to try H-4895 again myself.

 

[Unsichtbar]

Re: Temperature swing Re-15 and 175smk .308

I will very interested in what others experience with RL-15 because I have plotted the fps at various temperatures and it comes out to .7 fps per degree. Also the military chose it for the M118LR load and one of the criteria was temperature stability. (for the conspiracy theorist yes I have heard the fix was in etc and sure the military has botched trials). The quote by on researcher that “there is more to temperature stability in a load than just the selection of powder” If I can find a better load I am open to suggestions.

 

[kombayotch]

Re: Temperature swing Re-15 and 175smk .308

That's about what I was seeing with the first batch of RL-17 (~0.8 fps./degree). I don't have any results with the latest batch. The words "stable" and "insensitive" don't necessarily have the same meaning. Kind of like "water proof" and "water resistant" when you're looking at a watch.

The green colored powders seem to exhibit less velocity change with temperature shifts...

 

[Unsichtbar]

Re: Temperature swing Re-15 and 175smk .308

You might fine this of interest please go to link www.shootingsoftware.com/tech.htm Pressure Factors: How Temperature, Powder and Primer Affect Pressure

I never had much if any variation lot to lot? Are any of the cans Marked Sweden?

 

[Woodlanddude]

Re: Temperature swing Re-15 and 175smk .308

W 748 may give you a couple hundred fps in a 30deg. change if it reacts as it does in a 250 savage according to a good source. No joy there either. BTW running my velocities at about 40deg. using 2fps of drop per degree of temp drop my trajectories were spot on to 925yds.