375H&H, 250 Sierra, R17, velocity results

[gte901m]

While breaking in my new Talkeetna, I burned a little RL17 to see what it could do. Thought I would share.

Kimber Talkeetna, 24" tube
Sierra 250 GameKing
Norma Brass, new brass necked up to 416 and then sized back down to create a false shoulder 0.025" forward for a snug chamber fit, annealed, 94.5gn h20 fired case capacity
fed215
3.600" col
95F, sunny, humid

74 - 2640 fps
75 - 2688
76 - 2693
77 - 2743 (maybe a cloud affected my chrony?)
78 - 2743
79 - 2754
80 - 2777
81 - 2824
82 - 2830
83 - 2867

Absolutely no signs of pressure; brass heads and primers looked pristine without any marks; one finger bolt lift.

I'll will push beyond 83 gn later, and then shoot for accuracy.

 

[fan300mag]

hello Mr. gte901m

did you have some news about your load, i have a 375 and i thinking to use the same poder and bullet, and also the 260grs partition

So i be waiting for your new loads.

 

[fan300mag]

what about your groups???

 

[memtb]

It certainly works with 250 TTSX's in my AI. Got to 3160 fps, but groups were starting to open up.... backed her down to 3130 fps. Decent groups, no obvious pressure signs. Did some cold weather testing, with the 270 TSX ( load development was done at 90 and above) prior to going to the 250's, and found no velocity loss and great accuracy.

The test: ambient temp. at start -4 F and end -3 F, left ammo and rifle outside for about 2 hours prior to test. Haven't done any cold weather testing with the 250's yet, but hoping for and expecting similar results.

 

[gte901m]

what about your groups???

Scope mount issues....
I wasted a range trip and half my RL17 handloads before realizing my lightweight talley's were allowing my scope to move under recoil. Slingin' 250's 2800fps+ in a light weight 375 quickly identify any weak links.
In early August I installed a one piece DNZ game reaper mount, and tested 250's with previously loaded RL15; accuracy was adequate but not great, 1.75" groups.
I have not had time to reload 250's w/ RL17 and retest. That will have to wait until spring.
If 260 AB ever become available, I'll test RL17 with those as well.

 

[Lefty7mmstw]

I have been using weaver bases and burris rings on my lightweight m700 375 h&h for years and never really have had any scope creep issues. I did have the one ring get loose after several hundred rounds, but a bit of blue loc-tite and re-torqueing set that straight. I have shot the 260ab in my rifle with 72 I4320 and it shot well, but I'ver been using either the 300tsx with I4320 or the 285gs with rl15 with sub moa results for both. If I want to shoot a 250 grain slug my 338 will do just fine; I'm after weight getting tossed with my 375, and I really don't see much reason to go below around 300 grains for the pill...

 

[memtb]

Scope mount issues....
I wasted a range trip and half my RL17 handloads before realizing my lightweight talley's were allowing my scope to move under recoil. Slingin' 250's 2800fps+ in a light weight 375 quickly identify any weak links.
In early August I installed a one piece DNZ game reaper mount, and tested 250's with previously loaded RL15; accuracy was adequate but not great, 1.75" groups.
I have not had time to reload 250's w/ RL17 and retest. That will have to wait until spring.
If 260 AB ever become available, I'll test RL17 with those as well.

My wife and I both have Leupold QD bases/rings, on our rifles.. her's - a 8 1/2 lb. .338 WM, mine a .375 AI @ 9.0 lbs ( both scoped,loaded, slung and "NO" muzzle brake on either). They've been that way since the mid-90's, and have never had an issue with the QD's. This gives us the ability to have a back-up scope already zero'd, or back to irons, if so equipped! memtb

 

[Gregg C]

While breaking in my new Talkeetna, I burned a little RL17 to see what it could do. Thought I would share.

Kimber Talkeetna, 24" tube
Sierra 250 GameKing
Norma Brass, new brass necked up to 416 and then sized back down to create a false shoulder 0.025" forward for a snug chamber fit, annealed, 94.5gn h20 fired case capacity
fed215
3.600" col
95F, sunny, humid

74 - 2640 fps
75 - 2688
76 - 2693
77 - 2743 (maybe a cloud affected my chrony?)
78 - 2743
79 - 2754
80 - 2777
81 - 2824
82 - 2830
83 - 2867

Absolutely no signs of pressure; brass heads and primers looked pristine without any marks; one finger bolt lift.

I'll will push beyond 83 gn later, and then shoot for accuracy.

Please clarify, that bit about the false shoulder twenty-five thousands of an inch forward ? Thanks.

 

[Gregg C]

Scope mount issues....
I wasted a range trip and half my RL17 handloads before realizing my lightweight talley's were allowing my scope to move under recoil. Slingin' 250's 2800fps+ in a light weight 375 quickly identify any weak links.
In early August I installed a one piece DNZ game reaper mount, and tested 250's with previously loaded RL15; accuracy was adequate but not great, 1.75" groups.
I have not had time to reload 250's w/ RL17 and retest. That will have to wait until spring.
If 260 AB ever become available, I'll test RL17 with those as well.

That's funny. Or, not funny, but laughable. I have a 338378Wby-after much heart ache, hard head scratchin, blood (literally), sweat (summer in Arizona) , and tears(figuratively) I had finally gotten it to shoot like I thought it should. I remember being so happy! So I'm shooting along, thinking the stars are all aligned in my favor, maybe I should buy a lottery ticket, when all of a sudden the hits were off. Only a little, just enough to make me go huh, that's odd. The next shot off a little more. Now what? Third shot off by 6 inches! What the hell? Standing there scratchin my head(yup, back to that) and I reach out and touch the scope....and it falls off!!! What a lot of fun I have had with this rifle ! You gotta admit, that's some funny stuff!

 

[gte901m]

Please clarify, that bit about the false shoulder twenty-five thousands of an inch forward ? Thanks.

Even on belted cases, I measure brass from the base to the shoulder with a Hornady comparator bushing and calipers (what would be called headspace on a non-belted, bottleneck case).

Fired brass was 25 thou longer than my new brass. Instead of just letting the new brass stretch 25 thou on the first firing, I expand the neck with a .416 expander (which on a 375HH creates an almost straight wall case) and full length size to create a new shoulder ~20 thou forward of the original shoulder (must adjust sizing die w/ comparator measurements to get correct base to shoulder distance). Most call this creating a "false shoulder".

Why? Stretching 25 thou during one firing could stretch the brass closer towards the case head, and lead to case head separation (short brass life).

You can bend a paper clip a hundred times before it breaks if you barely bend it, but you can only bend it a few times if you bend it 90 degrees each time. Not the best analogy, but close enough.

Hope that helps.

 

[Gregg C]

Even on belted cases, I measure brass from the base to the shoulder with a Hornady comparator bushing and calipers (what would be called headspace on a non-belted, bottleneck case).

Fired brass was 25 thou longer than my new brass. Instead of just letting the new brass stretch 25 thou on the first firing, I expand the neck with a .416 expander (which on a 375HH creates an almost straight wall case) and full length size to create a new shoulder ~20 thou forward of the original shoulder (must adjust sizing die w/ comparator measurements to get correct base to shoulder distance).

Why? Stretching 25 thou during one firing could stretch the brass closer towards the case head, and lead to case head separation (short brass life). Most call this creating a "false shoulder".

You can bend a paper clip a hundred times before it breaks if you barely bend it, but you can only bend it a few times if you bend it 90 degrees each time. Not the best analogy, but close enough.

Hope that helps.

Thanks very much, it made perfect sense.
Gregg