300 RUM, 168 grn TSX, 106grns Retumbo

[bassin93]

I have a question. I recently purchased a Sendero II in 300 RUM. I had a box of 168 grn TSX and thought I would try to find a load that would shoot with what I had in the reloading room.

I started at 100 grains and had no pressure signs at all. I did the shoot clean shoot clean break in then tried groups of three clean three clean. The groups were in the 1 1/2 range.

I loaded three each with 101grns, 102,103,104,105 and 106. they shot about 3inches at 200 yrds with hardly any pressure signs till I got to the 105 loads. The group shrunk about in half and the primers started to flatten. The 106 loads went down to about 1 inch with the primers flattened pretty good and the bolt lift was slightly changeing.

My chronograph was not working and am wondering if anyone else has chronographed this load so I have an idea what it does for velocity. Anybody? Thanks, Jeff

[MontanaRifleman]

Your probaly not going to get good groups by shooting 3 and then cleaning and shooting 3 more, etc. It usually takes at least one shot to foul a barrel for consistant grouping and usually more than that. My Sendero 300 RUM takes about 5 shots to settle down after a cleaning.

At 106 g of Retumbo, your loads are compressed. 100% capacity is usually about 100 g of Retumbo, depending on how deep the bullet is seated. So most, if not all your loads are compressed. Have you heard the powder crushing during bullet seating? Have you noticed the bullet being pushed back out of the neck? Have you measured the COALs after seating to see how consistant they are?

It's impossible to say what velocity your bullets are going without a chrony and and checking drops at various ranges. My gues would be about 3500-3550 give or take with 106 gr.

A couple of things I would recommend..

Go with H1000 with the 168's which is a faster burning powder and more suited to the lighter bullets. You will use less powder and the load will be less compresed. You might even try RL17 for that weight bullet and velocity. I maxed at 86 g of RL17 with 180 E-Tips, so a good starting point for the 168's would probably be about 82 g. My guess is you max will be about 88-90 g, but that's just a guess.

Or... go with heavier bullets and Retumbo. IMHO, this is your best option.

Mark

[Robbin]

Can't help you with an estimate on the MV, but my step sons 300RUM likes 101 grains of retumbo and 180 grain Barnes TSX. Consistanly shoots 3 to 4 inch groups at 400. It would do better than that if it wasn't kicking the crap out of me every time I pull the trigger.

One 900lb Bull elk at 200, the only complete pass thru out of 6 elk killed that week.

Retumbo LIKES to be compressed....

[MontanaRifleman]

I would agree that a mildly compressed load is OK, but IMO, going over 102% or 103% can cause problems, especially if you dont have a lot of neck tension. It also starts crushing powder which may lead to inconsistant burning.

[bassin93]

Mark, I should have included that the breakin was done at 100 yrds. It was a couple days later that I went back with the loads that I had loaded to check for grouping, and there again was just what I happened to have on my shelf. I do plan on trying the 190 and 210 berger vld when I can find them. They should be in before X-mas at the local Sporting Goods store or Spokane when I get over there. Thanks for your reply. Jeff

[bassin93]

Update. I chronographed the 106 and 105 grains of retumbo loads and had to do a double take. The 105s ran pretty much the same as the 106 grn loads. The average of 5 shots was 3730 with an es of 25fps. I went back a week later and shot the same 105 loads and they still read 3728 or so for the several I shot but the bolt was slightly sticky. I then tried 104 grains and they ran 3708 average. Unbelievable. I then tried the 208 Amax with rutumbo and had five each loaded starting at 93 grns to 95 grns. The velocity was only 3080 with the 95 grn load, but the es was only 5fps. I got 2.18 five shot at 300yds. Not great but I need a warmer day so I'm not shaking as bad. LOL. I was hoping for around 3200 fps. I still have room to go as the pressure signs aren't there yet so I am going to try 95.5 and up till I get the velocity or the pressure.

[sambo3006]

Just a guess but you might not be burning all the powder if you are increasing the charge and the velocity is staying the same, especially with compressed loads. That velocity is way up there with the 168 and I would think that your barrel's throat is crying for mercy.
My favorite bullet in the 300 RUM is the 200 gr Accubond with a BC of .588 . You can run 3100-3200 fps tops and the downrange energy is impressive. Give it a try if you get the chance.