Throating the 300 WSM for Hammers in a Tikka LA?

[Salmotrutta]

I could use a little help here! I have never specified a custom throat before and looking for advice and experiences.

I am building on a T3X LA to a 300WSM, light hunting build out to 1000 yds. My primary bullet is intended to be 181 Hammer Hunters, but may run 190 LRX or possibly 200 ELDX. It will be run supressed - so I am sticking with a 20" barrel and 1:8 twist (maybe its a little fast - but bullets are only getting longer these days and I think a little too fast is better than a little too slow - thoughts?). Mike at HCA is doing the build. So here are a couple questions. This will help me get the dummy round set for Mike to work off of.

1. Is it still a best practice to seat bullets into the neck the diameter of the bullet? In this case .308" of full diameter bullet?

2. Given I will have all the space I need to seat bullets out as far as I want - what preferred jump should I throat to? I am already running Hammers at mag length in my 300 PRC with great results - but a huge jump to the throat - any idea whats best?

3. I have heard people on here cautioning on throating too long and then not being able to chase the erosion. Its a hunting gun so if it sees 200 rounds a year thats a lot, given I have other toys to play with too. Do I really have to worry about this in a 300 WSM?

My current pondering and dummy rounds seems to lead me to a bolt face to bore diameter dimension of 2.47-2.5". If I just chamber for 300 WSM and throat as a 300 PRC - this would give me a start of the throat ramp at 2.36" and end up at bore diameter at 2.5286". Seems about right - doesn't it? Thanks in advance!

 

[L.Sherm]

Seat a bullet at or just above the neck shoulder junction were the boatail and bearing surface start and give it to your Smith to throat to that you should be fine.

 

[Mram10us]

My last custom reamer was for a 28 nosler. I knew I wanted to shoot the 195s but thought I would try the 180 class also. I seated 3 different bullets and picked the shortest one for the reamer spec. Just me, but I wanted to be able to start at the lands with each and have a full neck of hold on the bullet

 

[elkaholic]

I design my cartridges with long necks, for various reasons, but one plus is to be able to handle more bullets efficiently. I like to run the most desired bullets about .040" up into the neck. This allows for some jump without getting the boat tail/ body junction at or below the base of the neck. Besides using case capacity, there is more potential for forming the dreaded doughnut at the case neck/shoulder junction.

 

[Salmotrutta]

Thanks everyone! I think I am narrowing down the throating based on a dummy round with a 181 hammer and a COL of 3.094".

Any thoughts on twist? I originally wanted to match my PRC with a 1:8 - however every stability calculator says thats overkill. Based on running Quickload with 181 and 199 hammers the edge goes to the 181's and with Barnes its the 175 LRX. I choose my bullet based on which weight retains 1200 ft-lbs AND 1800 fps the farthest. The ft-lbs number is arbitrary but it does allow you to compare bullets energy over longer ranges and select the one that works best for your application. 1800 fps is the number both Barnes and Hammer use as minimum required for reliable bullet performance.

The WSM in a short barrel just can't get heavier (> ~190g) mono bullets going fast enough to increase their effective range over the 181 Hammer - this leads me back to maybe a 1:9.5 twist?

Any thoughts, experiences or recommendations on twist? It looks like I should get those 181 hammers going to just a little over 3000 fps in a 20" barrel and my nominal hunting elevation is 7000 ft. Thanks!

 

[tdot]

The more I shoot the hammers the more I lean towards shooting them as fast as possible and with a higher then recommend twist rate. I have stepped down in weight in 4 different calibers and they all just seem to shoot a touch better. The effect on game has been better then could be hoped for. Though I havent shot any game with the heavier slower spun bullets for comparison, i just dont see the terminal effects improving to any great degree.

 

[Mram10us]

I shoot 1-10 twist in my wsm. It prefers 200 hybrid and 215 hybrids, so you'll be fine with the 180 class

 

[dougduey]

I'd give Steve Davis a call at Hammer Bullets and tell him what you're doing. He builds enough rifles that he'll be able to help you achieve what you want.

 

[Salmotrutta]

Thanks again. Steve was also fine with the 1:8 twist. Not hearing any negatives to "over spinning" bullets I might just stick with that. I am starting to wonder if the "over spinning" theory is not as applicable to mono bullets? My reasoning is that they should have more concentric mass - especially the ones turned on a lathe, maybe?

 

[dougduey]

I haven't had any issues with a faster spin rate and any of the Hammer bullets. I went with a 1:8 twist in my 7 STW so I could shoot the 177 gr Hunter. But I also shoo the 143 gr Hunter as well. I push the 143 at 3500 fps and the 177 at almost 3100 fps. Both are a .250" moa if I'm on my game.

 

[tdot]

Thanks again. Steve was also fine with the 1:8 twist. Not hearing any negatives to "over spinning" bullets I might just stick with that. I am starting to wonder if the "over spinning" theory is not as applicable to mono bullets? My reasoning is that they should have more concentric mass - especially the ones turned on a lathe, maybe?

I think there is alot going on with the old ballistic theories no longer being as applicable as they used to be. I dont know if it's different equipment, products or simply different testing. But I feel like about 50% of the "rules" that I have tested with my guns and my reloading have proven to be incorrect.

 

[JohnnieB]

Checking in on thread.

 

[rgvt4]

TAG

 

[25WSM]

If you can get your hands on a uni throater from kiff you can do it yourself. Magazine length is the limiting factor. I like to set my bullets up so the boatail junction is in the neck at least 50 thou up from junction.
If you use bushing dies and leave the bushing looser in your die you can shoulder bump and leave a slight gap on the bottom of neck that stays it will help with donuts.
As far as over stabilization goes it just doesn't seem to be significant for most shooting. If it don't blow the bullet up they tend to still shoot nice. For the hardcore accuracy freak they seem to want just enough to stabilize the bullet.
Shep

 

[L.Sherm]

For the hardcore accuracy freak they seem to want just enough to stabilize the bullet

I dont know if I'm a hardcore accuracy freak but I dont believe in over spinning anymore than necessary either.
Theres guys running 210 VLDs in 1-11 but most are running a 1-10 in there 300WSM in the 1,000 yard benchrest world