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Sendero 300 win mag

18 Feb 2018
@ 08:40 pm (GMT)

David Baker

Hey all,

So I bought a Tikka 300 win mag. Sadly loading them is not the best as I found out from Nathan. So sold it, bit the bullet and bought the Rem 700 Sendero in 300 win mag. It's beeded and I installed a new timney trigger.

Just going through the reloading process, fairly new to it tbh. Now I have an Hornady OAL length gauge. Did the measurement and it came in at 72.03 mm

I have new Norma brass, CCI magnum primers 2217 ADI powder and some Nosler 180gn Spitzer ballistic tips. I just want to check from you lads, if this is ok? I will be doing 5 shots and jumping up in .5 grains from min to max.

I will run the barrel in with some 150gn factory rounds, then jump onto the reloading side of it.

My question is am I in the right ballpark, as I want to do it safely and get some feedback before I start.

These are the lengths I measured
OAL with the OAL gauge were 72.2mm with the Norma brass and Nosler pills
Factory norma 150 gn is 69.22 mm
Hornady ELDX is 68.22 mm

I hope this makes sense.Thanks for some feedback.


19 Feb 2018
@ 07:41 am (GMT)

Nathan Foster

Re: Sendero 300 win mag
Hi David, if you give me the actual OAL to the tip rather than the length to where your gauge was on the ogive, I can cross reference it. It does however sound about right compared to the others on your gauge.

For now, work with three shot groups, then come back through and shoot confirmation groups. Three will be enough to see trends.

If the rifle has an accuracy node up high, the Norma brass may prove a bit soft (or it may prove perfect). These days I generally start with a tougher case, although the Norma cases are generally the best for the Weatherby magnums. Also, there is no great need for a magnum primer at these 2217 charge rates unless you are hunting in temperature extremes. It has been quite a few years since I developed a load with the 180gr BT in a .300. This bullet can work quite well but it does have its limitations as I have written about in the KB and within the book series. You are going to be putting quite a bit of time into this so do make sure that you are starting out with a projectile that suits your goals. Also and depending on who did the work for you, it can pay to check the bedding over, make sure it has been done properly and relieved where necessary. Check for any high spots by performing the 1oclock test as described in the books. The Sendero often has high spots which must be removed prior to bedding, often missed when skim bedding by those unwilling to grind into the chassis. Also make sure the mag box is not pinched, that you can wriggle it. All of these factors were discussed in the book series including checking work done by others.

The more time you put into this prep work the better, right down to double checking the positioning of your optics, one of the most common mistakes I see, even on optics manufacturers websites (due to terrible body shooting positions). I am now finding that a lot of rig set ups, shooting methods and behavior are as a result of subconscious programming. Monkey see, monkey do. We are simply bombarded with so many images and information. I often ask a client "what influenced you to choose this method?" Many will simply shrug. They have no idea why. Very interesting to connect these dots.

You have a good rig David, it should serve you well.
25 Feb 2018
@ 01:00 pm (GMT)

David Baker

Re: Sendero 300 win mag
Hi Nathan,

When I spoke to the Gunsmith he did mention the high spots and that the mag was in an upright position and the factory used shims to get it level ( wasn't really level ) He leveleved it out and made it nice and straight. He also bedded around all the hollow spots near the trigger. He proceeded to explain to me what he had done in order to do the job properly. As when I first took the rifle there, he stripped it down and showed me all the area's where it was up against the stock and what was required to fix it.

The measurements are tip to head 87.67mm
Ogive is 3.01mm

I hope this info helps. Again thanks for the response.
25 Feb 2018
@ 02:12 pm (GMT)

Nathan Foster

Re: Sendero 300 win mag
Hi David, the OAL sounds fine.

Do keep in mind what I said about checks. I asked you to do the checks, not rely on the smith. A smith can have a lot on his mind and little things can go amiss. But things can also go amiss when you strip and reassemble during routine maintenance. I want you to familiarize yourself with this.

You would have a better understanding of these matters if you had a copy of the book series and were currently using the accurizing book steps. Other forum members who are reading this thread will know what I mean, this type of situation has been fairly common in the past.

In any case, hopefully all is well with the rig.

Keep at it.
25 Feb 2018
@ 03:02 pm (GMT)

David Baker

Re: Sendero 300 win mag
Hey Nathan,

I do have all your books mate :) I shall go and have a read.

The smith spent considerable time with me and explaining what he had done.

I will go and strip my rifle and have a good look at it.
I have done the reloads in lots of 3 and will be testing next weekend.

Will run the barrel in with factory rounds and move on from there

Again thanks for your guidance.
25 Feb 2018
@ 03:27 pm (GMT)

Nathan Foster

Re: Sendero 300 win mag
That process of familiarity will help a good deal. Just gives you more confidence in the rig and ticks off the variables one by one, removing all doubt.

The .300 Sendero's are a great rig once they are set up nicely. The Timney makes a big difference too.


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