COAL vs Pressures

[oldfox]

When loading the 204 and you increase the coal (not touching the lands), does this increase the pressures? I want to do a bit of testing and wanted to ask before I jump into it. At the present I am loading 26.6 gr of Benchmark behind a Sierra 32gr BK - CCI BR4 - Hornady case. With a coal of the 2.255 they shoot very well, but I wanted to tweak them a bit more... By running the bullet out to a coal of 2.345, I am well off the lands...and have the bullet seated .153 below the case mouth.. Will this create any problems?
Rifle is a Ruger American Predator...

[futuretrades]

If you are not into the lands, you should not have a significant increase in pressure. I would suggest a OAL tool just so you know exactly what your chamber length is. For my 39 SBK load, I pushed the bullet as close to the lands, as I dared, so I have only about .120 of the bullet into the brass. I am shooting a factory chambered Howa in 204.
Just my 2 cents

[oldfox]

If you are not into the lands, you should not have a significant increase in pressure. I would suggest a OAL tool just so you know exactly what your chamber length is. For my 39 SBK load, I pushed the bullet as close to the lands, as I dared, so I have only about .120 of the bullet into the brass. I am shooting a factory chambered Howa in 204.
Just my 2 cents

Thanks... I have ordered a Hornady OAL tool and will wait till it arrives...just to be on the safe side. I also ordered the Bullet Comparator to go with it.. More toys..does it ever end

[Darkker]

Suppose it depends on what you want to call "significant". Yes, the longer the COL, the higher the pressures. The deeper seated the lower, to a point; then pressures REALLY begin to spike.

[Jim White]

My 204 throats are so long I couldn't touch the lands even if i wanted. I just use the SAAMI SPEC for max OAL and adjust from there. It works

[oldfox]

My 204 throats are so long I couldn't touch the lands even if i wanted. I just use the SAAMI SPEC for max OAL and adjust from there. It works

Jim...I think my rifle is the same, but to be on the safe side I will wait on the gauges, which should be here the first of the week.. Been around for 76 yrs, and don't want to do something stupid at this point

[Bill K]

From what I have read, when you set a bullet out further the pressure will go down, but when and if the bullet starts jamming into the lands, then it will begin to rise again. So you must watch for pressure signals/signs and load according to your rifle. Bill K

[Darkker]

The longer the oal, the less jump to the lands and the less bleed-off. The less "run" the bullet gets at engraving into the lands. As a system it becomes about momentum.
If you think about driving your car. If you are driving the parking lot at 5mph, you won't need "extra" throttle to get over a speed bump. But if you almost not moving and cone to that speed bump, it takes a significant increase in throttle to overcome the bump. Same thing with engraving the bullets into the lands.

[MZ5]

From Dr. Lloyd Brownell's extensive work & data on the topic. Graph created by "Unclenick" on ShootersForum(.com):

[MZ5]

The graph, above, is of course in inches from the lands. Brownell's work indicates that if distance-to-lands is expressed in calibers, this general graph is basically applicable across high-power rifle cartridges.

[gundogblue]

Ive been loading since 1975, and I just bought Savage Model 12FV in 204 Ruger, and its my first 204. But the mechanics of reloading are the same, what I do when Im working up a load I use my Hornaday OAL gage, I start off by adjusting my bullet so it's 20,000ths off the lands, check for pressure if all is well I keep moving my bullet closer to the lands by 5,000ths incurments and keep an eye out for hi pressure signs until I find the sweet spot.
Paul

[Slowshot]

I have been loading 218 Bee, 220 Swift, 243Win., 222 rem. and now 204 Rugerfor years. As a general rule (like all such rules there are exceptions) I like to have a .01" (10 one thousandths of an inch) jump to the lands. Here is how I do this consistently. I start with a new, unused cartridge case that has no powder and no primer. Using my Wilson bullet seating die I load a bullet and create a cartridge that is so long that it will not chamber. Then I shorten the cartridge .01" and try again to seat it in the chamber. This exact .01" bump is possible because my Wilson die shortens the cartridge exactly .01" with each 1/4 turn of the seating stem. I continue progressively shortening the cartridge until it will just barely seat all the way into the chamber. At this point I am up against the lands with no room to spare.

Next, before I do anything else, I measure the OAL but also, I measure the length to ogive of the cartridge with a small ogive tool that attaches to my calipers. This is important because the place on the bullet that first contacts the lands is not the point. It is the that place behind the point where the bullet first reaches it's full diameter, commonly called the ogive. I write both of those numbers down. The first number tells me the OAL to the lands of bullets of that exact same weight and design. The second number (ogive length) can be used with any bullet design, as long as I use the ogive tool on my calipers when measuring the different bullets.

Now, I bump the bullet in .01" and have what I need to load that bullet .01" off the lands.

This system works just fine with a bolt action rifle, as long as you do not force the bolt closed. Forcing, could result in having the bullet stick in the lands and pull out of the cartridge, when ejecting. It works best in a falling block rifle, like my Ruger No. 1V in 222 Rem. That is because you can push the cartridge all the way into the chamber with your finger and feel when you contact the lands. You can even see how much it needs to be shortened. I see no way to do this procedure with a lever action rifle.

I have never experienced an overpressure problem, as long as I stick within safe powder loads. I always get best accuracy with less than max. powder loads anyhow.

[Jim White]

I believe I saw a video once of someone doing this. It was more time consuming than the ole' Stoney-Point for sure but it sure seemed accurate enough if one must use those type of bullets.