.090 jump?

[onebreath280]

I'm reloading for a new 204 ruger shilen barrel. I measured my chamber and with a hornady v max 40 grainer my OAL is 2.340 toutching the lands. Hodgdon called for 2.250 OAL giving me 0.090 of jump does this seem excessive to anyone else?

[Rick in Oregon]

one: Your new Shilen barrel was most likely chambered with a SAAMI spec reamer....which means that .090" jump is typical for the 204 Ruger.

This jump is the primary reason the cartridge reaches the 4,200 fps factory velocity, a la Weatherby freebore. Nuthin' to get your shorts in a twist about; it's standard for all SAAMI spec 204R chambers, and somthing we all have to live with unless you get a custom reamer ground. And then if you do, you won't be able to shoot factory ammo in a non-spec 204R barrel for fear of extremely high pressures.

In the end, you'll be surprised at just how good that barrel will shoot, even with almost .100" jump.

[Gleedaniel13]

one: Your new Shilen barrel was most likely chambered with a SAAMI spec reamer....which means that .090" jump is typical for the 204 Ruger.

This jump is the primary reason the cartridge reaches the 4,200 fps factory velocity, a la Weatherby freebore. Nuthin' to get your shorts in a twist about; it's standard for all SAAMI spec 204R chambers, and somthing we all have to live with unless you get a custom reamer ground. And then if you do, you won't be able to shoot factory ammo in a non-spec 204R barrel for fear of extremely high pressures.

In the end, you'll be surprised at just how good that barrel will shoot, even with almost .100" jump.

Sounds very interesting when we surprise with the amazing jump results. Hopefully I can better understand it in the future.

[Bill K]

one: Your new Shilen barrel was most likely chambered with a SAAMI spec reamer....which means that .090" jump is typical for the 204 Ruger.

This jump is the primary reason the cartridge reaches the 4,200 fps factory velocity, a la Weatherby freebore. Nuthin' to get your shorts in a twist about; it's standard for all SAAMI spec 204R chambers, and somthing we all have to live with unless you get a custom reamer ground. And then if you do, you won't be able to shoot factory ammo in a non-spec 204R barrel for fear of extremely high pressures.

In the end, you'll be surprised at just how good that barrel will shoot, even with almost .100" jump.

Sounds very interesting when we surprise with the amazing jump results. Hopefully I can better understand it in the future.

If you can obtain one of Roy Weatherby's books, you will and can read as to why he did his chambering and freebore to obtain the velocities he did. This is what RIO is referring to with his comment " a la Weatherby freebore". Bill K

[ALP]

I also have a long jump distance.2.485 to the lands.remington factory barrel.I can't seat the bullet that high,so what should I do? Should I test rounds starting at 2.250 and work my way up in.015 increment? I know I can get up to 2.4oo but am I going about this the right way? any help would sure be thankful for.

[onebreath280]

What I didn't realize when I made my original post is that my absolute max OAL is 2.280 due to the magazine length in the AR15 platform. I could load it longer if I wanted to hand feed each cartrige individually, but why have an AR at that point? It is shooting really well as far as I can tell, I got out yesterday and shot a few rounds before this wind storm we are having. It shot about a 1" group in 20 mph wind and I am happy with those results... for now. I will start doing load workups with diferent powders as soon as the weather will cooperate a little bit.

[onebreath280]

As for the "la' Weatherby freebore" I will have to do my homework, I have not had the pleasure to read Mr. Roy Weatherby's books. I will have to see if I can get my hands on one, is there one in particular I should look for?

[Rick in Oregon]

one: You don't need to get a Weatherby book to understand freebore. There's many references on the net to better understand the term and what it affects. Here's a link that may help explain it and why it's used:

http://www.hornady.com/ballistics-resource/internal

Suggestion: Just load your 204 loads for your AR per book OAL, and I think you'll be close to where you want to be. Forget the freebore, just load per book length and shoot.

The only time loading long in a 204 pays off is if you're shooting single shot with a bolt gun or falling block (or Contender etc.) in the rat patch and need all the potential accuracy you can muster, but no need to fret about it if you're shooting an AR or bolt gun using the magazine. The 204R offers impressive speed and accuracy with the SAAMI spec loading length.

[Bill K]

As Rick said, you do have to look for a Weatherby book, the internet does have much to offer. But, if you are like me, I enjoy reading various books, especially the older one's that were put out by the likes of Roy Weatherby, Jack O'Conner, P.O. Ackley and others that brought many innovations to our shooting sports, Many of those applications are still with us and being improved on. But it was a thought I put into the conversation/question. Bill K

[dsandfort]

I also agree. Load to AR specs and forget the jump. Like you said, unless you go single shot, there's nothing you can do about it. I have the same barrel and it shoots just fine. I don't even know what the jump is. I'll accept this from an AR any time (yeah, I know, I yanked one).

[onebreath280]

dsandfort, I would love to pick your brain on your load data some time. It would be a big head start for me as to what powders and bullets work well for this barrel, most of the load data and bullets and experence are for 1-12" barrels. FYI with a hornady v-max I measured 2.340" COAL into the lands giving me 1.995"ish from the bolt face to the lands. With my 280AI I seat .010" off the lands for great accuracy, so when I measured my chamber it seemed a bit crazy but I am starting to understand some of the "magic" that happens with the jump in the 204R.

[dsandfort]

No real secret. I picked my bullet (Sierra 39g) and when the "shortage" screwed with us, I had to go to Nosler 40g. Using Nosler data, I picked a powder I had plenty of (H322) and started working up loads keeping seat depth constant. Kept finding a node at a certain charge weight that gave me about .3 or .4 MOA as long as I did my job. Your combo will likely have a different node or nodes.
Interestingly, Nosler listed H322 as an accuracy load. Can't recall COL at the moment (I'm away from my notes) but it's close to max for the AR to fit and feed. I also use a side charge upper with an adjustable gas block so I can shoot single shot. I don't like to chase brass at the range. My combo will feed under any setup. I do like the 40g's since they seem to buck the wind better than my .204 bolt gun running 32g Sierras. Just a feeling, no real data on this.
Del

[Jim White]

In my experence, the only time jump has ever been an issue was when I was competing and using a VLD style bullet. Generally speaking this style of bullet can be tempermental to shoot with long throats. In the AR world, years ago (and maybe still) the throats were shorten in order to shoot the heavy 80 grain bullets from a magaine for ATC, vice shooting different bullets up close.

Don't let a long throat bother you and always remember, barrels are a consumable item, just like TP. So shoot and enjoy it. Accuracy is what matters.

HTH,