Home Forums Hunting & Shooting Hunting Rifles .300 WSM sensitivity to seating depth

I'm trying to develop a load for my Remington 700 .300 WSM. I'm using 165 grain Nosler Accubond bullets. I measured the chamber using the Hornady OAL gauge and bullet comparator with this bullet, then tried seating the bullets to achieve a 0.02" freebore. Problem is that the rounds won't fit the magazine when they are seated this far out. So it looks like I'm going to have to seat them deeper, resulting in a bigger "jump" to the lands of the rifle. Does anyone know whether this really matters? I've read that you want to have a 0.01" to 0.02" freebore but in practice a lot of bullets are too long to achieve that.

Incidentally, this rifle is driving me nuts. Getting a 1 MOA group out of it is proving to be really difficult. Remington 700 CDL SFs are supposed to be good rifles. I've had it floated and bedded, fitted a muzzle brake and had the trigger worked. But getting a group smaller than 1" at 100 yards hasn't happened yet with any of my handloads.

My 300saum like 168gr ttsx to jump to the lands. I ran into the same problem as you did, so I seated them just so they would fit into the magazine and accuracy didn't get any worse.

Dave, I have a couple 300 WSM's and they both shoot really well with 180 Partitions or a 175 SMK/Nosler Custom Comp.

64 grains of H4350 or R17 seems to be the sweet spot.

And FWIW they are way off the lands. COAL 2.850", your chamber will obviously be different but a big jump works in the Sako's.

try a different bullet, mine shoots 180 Hornady bullets well and 180 Accubonds well, and 180 Sierra's well.

I have the same problem with the magazine along with a short throat in my Remy.Seating depth is really critical in my rifle,so finding that sweet spot is the key to making her shoot the best.I was getting excellent groups at a 100yds with a Hornady 165gr Interbond seated at 2.860,but when I moved out to 200yds,they opened up more than I liked.I started seating the bullets in another .010 to 2.850 and that was enough to get the groups to tighten up at 200yds.Here is an article from Berger Bullets.It is quite interesting.I tried it and it works too.
http://www.bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

Other than buying a reamer to your specs with a shorter throat all you can do is seat to fit and feed and work up a load.

You may have to change bullets to get it to work.

A friend gave me a Browning a-bolt in 300 WSM with a 2.8" magazine to load for LR. I had some 230 gr Berger hybrids and gave them a try. The bullets are so deep in the case I jokingly say they are sitting on the primer. Darn bullets shot quite accurately from 100yd to 500M. RL-17 vel 2725.

You might want to try one of the heavier hybrids (215 or 230 gr) as they truly are insensitive to seating depths AND they are excellent on big game. If there are any doubts read these threads:

http://www.longrangehunting.com/forums/f19/berger-230-300-otm-hybrid-terminal-results-80283/

http://www.longrangehunting.com/forums/f19/comparing-berger-210-vld-215-hybrid-88657/index14.html



230gr Berger target hybrid in 300 WSM 2.8"OAL

I've got a couple of rifles that shoot well with the bullets being more than 0.125" off the lands. I no longer worry about it. When working with a new rifle I start with magazine length, assuming the bullet doesn't get jammed in the lands. After finding a promising powder and charge, I shorten the COAL in 0.005" increments until I find the preferred length.

66.6 RE17 with a 168 TTSX in two .300 WSM. 0.050" jump in both.

...............Many rifles prefer some bullet jump. Exactly how much jump will depend on any given individual rifle. Bullets that are either very close to, barely touching the rifling or even jammed into the rifling doesn`t necessarily guarantee better accuracy.

As a suggestion, using the identical powder and charges, start your reloads with the maximum OAL that your rifle`s magazine will accept where you can still cycle the bolt. Load a few. Then load a few more 15/1000ths or so shorter and a few more still another 15/1000ths or so shorter. Repeat until your last group is approx 60/1000ths from the rifling. Put each group of rounds into their own seperate small plastic baggies and label them with the OAL so you know which is which. Then test fire. Note the accuracy for each group.

If your groupings are still not to your liking, then you`ll either have to change your powder, the charge levels (or both) or change the bullet all-together.

Each time you change anything whether it be the COAL, the powder, the charge levels, the bullet, the primer; etc, start over using the above process.

It`s just a matter of time along with some reloading experimentation before you find what components your particular rifle likes best.

My 300wsm extreme weather is minute of barn door with accubonds but shoots moa or better with partitions or hornady interlocks. I just haven't had much luck with the accubonds.

That's interesting, Sam. My best result so far was with 65.2 grains of RL19 behind a 180 grain Nosler Partition. I've read that RL19 burns at close to the same rate as 4350, but I'm using over 1 grain more powder than you are. Guess optimum load has a lot to do with barrel harmonics, twist rate, etc, and it sounds like you are shooting a different gun to me.

I guess you are measuring your OAL from case head to bullet tip. I've been using the Hornady bullet comparator to measure the length from the case head to the bullet ogive.

Dave how does the rifle shoot without the brake?

It kicks like a three-legged ninja. This is a fairly lightweight rifle. I initially sighted it in without the brake and came home with a blackened shoulder. Since then, I've only shot it with the brake. I've shot better groups since that initial session without the brake, but I can't tell whether that is because I'm less bothered by recoil or it's something inherent to the rifle.

I've just seated the bullet to give COAL 2.860" (which is what the book says is the maximum). These rounds will just fit in the magazine of my Remington 700.

But when I measure these using the Hornady bullet comparator and compare that length to the OAL gauge reading for my chamber, the jump is about 0.085" which seems huge to me.

It's going to be very interesting to see how these shoot.

My tikka 300WSM gave me fits trying to get a consistant accurate loads until I tried the Sierra 180 gr flat bases. They shoot 3/4 to 7/8" all day long if I do my part.

I wanted to shoot Nosler BTs or Accubonds 165s or under, but my rifle just didn't like them. I tried varying seating depths, but nothing seemed to work.

I guess I'll have to feed my deer steroids to justify using 180s

For starters, try some other bullets. I have had very mixed results with Accubonds in a number of rifles and calibers.

I own a Remington 700 CDL chambered in 300 WSM and had little problem getting 3/4 inch groups using the 168 grain Barnes TSX or 180 grain Nosler Partition. I simply load these bullets to an OAL length of 2.84 inches so that they will fit the magazine. Sure, they have a large jump to the lands, but it does not seem to matter.

I have worked up loads for six rifles chambered in 300WSM. All of them shot quite well with a load that consists of a Winchester case, Fed 215M primer, a near max load of H 4350, and the 168 TSX seated to 2.84 inches.

This load, in the hands of my friends, has not only proven itself here in America, but in Africa, New Zealand, and Spain.
No complaints.

IME the critical variable here is the bullet, not the rifle. Especially since you're dealing with one rifle having a magazine length that limits what you can do.

Some bullets are known for shooting well with a lot of jump and some are known to be very finicky, as far as distance from the lands. And some seem to shoot well at a variety of COLs. So the guys who've been saying "try another bullet" are giving you good advice.

0.085 does seem like a lot but I have one or two rifles that shoot well with more than that, I just had to find the right bullet. For example Ballistic Tips are more forgiving than Accubonds, IME.

The other thing to consider is that bullets with shorter, blunter ogives will let you get closer to the lands than those with long ogives. I think this is why a lot of guys seem to do well with Partitions, you can get close to the lands with a short magazine.

I jump 180 ABs 0.09 inches in my 30-06, because that's what the rifle likes. My magazine will take pretty much any seating depth with room to spare as my rifle has a short throat.

The rifle liked 0.130 jump also, but it kind of intrudes into my powder space and I have to seat several times to compress the powder. Here's a rundown of my seating depth variation test:

All measurements below Cartridge Base To Ogive (CBTO) as measured with a Hornady tool
Distance when seated to lands: 2.713 inches

All groups were 4 shots
2.703 (0.01 from lands): 2 inch group
2.663 (0.05 from lands): 1.6 inch group
2.623 (0.09 from lands): 0.9 inch group
2.583 (0.13 from lands): 0.9 inch group

Subsequent testing has proven the 2.623 inch group about a MOA performer, sometimes a bit better, sometimes a bit worse.