TJC

It has no discernible impact in shooting sports.  

20 minutes ago, ronzi83 said:

They say 6.5 creedmoor has around 3000 shoots on barrel life. I did some of my 2000 push it to 2900-3000 with mostly n150 or n550 powders. But now i was thinking to actually try 147eld with RS60. Some people say it is really temp stable and great powder, but i have never worked with it. 

Me neither without RS60, perhaps someone else will chime in.

Average for 6.5 CM should be 2500-3000 but if you’ve been pumping them out at 3000 FPS with N550 then that could be it, i bet you’ve got some throat erosion ?

I’ve heard good things about the 147 but you have to put them down at 2700+ to get optimal stability from a 1:8 twist, 1:7 seems to be a popular option for this particular bullet. 

4 hours ago, ronzi83 said:

Hey, i have around 2000 shoots on barrel. Lot it was same in past, but now i dont have same lot. 

Thanks. So it could be down to both round count and Lot variation in addition to 50 FPS or so of the difference coming from the change in temperature. 

2000 is a little on the low side to see velocity drop off so much especially if you’ve only been pushing a 139gr at 2800 but it depends on the barrel and how you’ve shot those 2000 (ie rapid hot strings) rounds.

Throw in a little variation in Lots and that could explain it. If you want to keep the barrel but push for more velocity then you could try N550. You shouldn’t need as much powder which will help avoid the crunch issue you described.

I’ve moved to buying components in bulk to avoid the Lot variation issues. Something to consider for the next barrel but it’s expensive upfront.

I doubt this is just temperature driven. 1>30C is approx 34F > 86F, a 52F change. If you said your velocity was c50 FPS different I’d imagine it would be temp driven but a 140 FPS change or 3 FPS per 1F is possibly too great. Some of the most temp sensitive powders are about 1FPS per 1F. I do think RS62 is more sensitive than they claim but not perhaps this much ??

How many rounds do you have through the barrel ?

Are you using the same Lot of powder ? There have been reports of considerable variation in Lot to Lot consistency with RS powders. 

2 hours ago, Steve steve said:

after doing a work up I just fired 20 rounds of the most accurate group

cci 250 , Hornady brass 2nd firing FLS,  44.3gr (compressed) , rs62, 2.810oal , no pressure signs whatsoever  , 140gr eldm, consistently shooting .3moa  24” tikka tac 

2660 clean cold barrel 

2702. 2695.  2673.  2672.  2672.  2759.  2692.  2691.  2662.  2715.  2738.  2686.  2688.  2730.  2732.  2718.  2665.  2691.  2686.  

Es 99. Sd 27.6 magneto speed 

So you are consistently getting 0.3 MOA with an ES OF 99 and SD of 28 !!! You aren’t going to be anywhere near 0.3 MOA at distance. 

I went to a course in the US. I was the only one shooting a SFP MOA. Learnt the hard way and now only run FFP MIL. 

Large primer. Tried some new loads. Incredibly there was no pressure signs. 

44.5 2955

44.6 2964

44.7 2951

44.8 2969

44.9 2976

45.0 2978

45.1 2994

45.2 2989

45.3 2992

45.4 3013

45.5 3004

I’m backing down to a 2800 FPS load but interesting to see. 

When do you get it ?

Very nice rig. Tubb has been at the top of the game for a long time now. 

Me too for .308 /.260 / 6.5CM thx

26” + mod. 

1 hour ago, VarmLR said:

Compressed loads?  Seems like quite a high charge.  I know that 260 rem has a little more case capacity than Creedmoor but effective case capacity is similar as the bullets tend to be seated deeper.  At 44.6gr I'm into quite compressed loads with the Creedmoor.  I'd expect 2800fps at between 42,5 and 43gr RS62 in the CM with large primer brass so not at all surprised that you're getting those velocities...seems like quite high pressure loadings? If so, I'd be backing right off!

Don’t think so. Def no crunch on bullet seating and I load them pretty long ie over 2.90” OAL. 

I was just testing a couple of loads and will be backing down. Thx

On 5/27/2018 at 10:28 PM, VarmLR said:

I don't know if you've considered RS62, but I'm managing considerably higher velocities than that behind 139 Scenars, albeit for a considerably higher load!  Were you experiencing pressure signs if loading up higher than 35gr using N150?  35.5 seems to be quite a light load compared with RS62 loads.  I also find velocities about 100fps down in LR brass.

What is your RS62 load with the 139gr and what velocity does that produce ?

I tried RS62 today for the first time in my .260 with the 139gr Scenar and was surprised by the velocity. 

Temp 75F / DA 1385
Three shot average velocity FPS:
44.5gr  2948 SD 11
45.0gr  2978 SD 9 

I wasn’t expecting it to be nearly this fast...should I have been at these loads / is this typical for RS62 ??

Thanks !

27 minutes ago, VarmLR said:

As a matter of fact, I did and found (much as expected) that it wasn't at all that temperature sensitive.

I took the exact same load tested at 24 degrees ambient (although powder temp was higher as the bullets had time to cook a little in the sun) which delivered a shade over 2700 fps from 44gr.

I re-tested at 20 degrees (a little under) and this time the rounds were kept in the shade and fed one at a time into the rifle.  The average from 6 shots was exactly 2700fps, so pretty conclusively it is the barrel that has speeded up for the first 500 rounds down the tube and has now stabilised at this velocity for this load.  My very first firings from it were considerably lower at 2633fps (new brass) and 2655fps (1F, 150 rounds down the barrel) to now where I have 500 rounds fired.  There has been no change in velocity from 400 to 500 rounds and for an ambient temperature range of about 6 or 7 degrees.  No change in 100 yd groups (still close on 1/4 moa for 5 shots).  ES rose slightly with temperature, and rose a little more than SD, but to be fair, I hadn;t batched the last lot of brass, just cleaned, annealed and loaded so it wasn't a fair conparison with earlier outings (my 24 degree ES/SD rose from single figure to ES 33(!!!) but SD was around 10.  I'm usually not happy unless both are single figure, so next time out I'll be far more careful with brass prep.  

The ES/SD of my 129gr loads were much tighter for the same conditions, coming in at ES6, SD4.

The same cannot be said of my Viht rounds which exhibit far greater changes in velocity with temperature, especially for anything north of a moderately warm load (pardon the pun).

 

 

Very interesting although a 7 degree spread isn’t perhaps wide enough to measure esp at the extremes of temp change. I’ve been testing VV N550 at 20F to 95F and found quite a lot of sensitivity with the same load lot / same number of rounds through the barrel with ES/SD remaining very constant. Just trying to understand if RS62 behaves consistently / linear at the extremes or whether it exaggerates at either end ? It sounds pretty stable in the mid-range for sure. 

Good thread btw. 

On 3/8/2018 at 5:13 PM, VarmLR said:

horizontal = wind?  I do initial testing at 100 yds then test the chosen load at 300 or 400 yds.  That shows up the importance of low ES/small vertical spread better than at 100.  Have a look at your ES figures for that 46 load...are they low there and either side for one interval?

I was wondering if you’ve done any detailed testing re temp sensitivity and how groups/ES/SD evolve at material changes in temp ? Thx

These look to be pretty interesting. A 6.5 bullet that can stay ballistic out to 2,000 yards. Expensive but a tool in the locker for specific circumstances.

If anyone is ordering some or hears of a European importer I'd love to pick up a couple hundred. Thx