New rifle and some questions

[Tater1985]

So i recently purchases my first bolt gun. I wanted something that could deliver good accuracy for the money. I ended up with a Ruger American Hunter with Magpul stock chambered in 6.5 Creedmoor. I topped the rifle with Vortex rings and an Athlon Ares BTR Gen 2 4.5-27x50.

From doing some reading i settled on a very basic and short break in as follows:
1 shot and clean (5x)
2 shots and clean (5x)
5 shots and clean (5x)

The only ammo i could find locally was one box of Hornady Match 140gr ELD-M. So i used that for the first 20 rounds of my break in. On the last 5 in the box i was able to shoot this group, with the flyer being the clean bore shot. Things looked promising.

I just got some components in this week and was able to start handloading. The only powder i could snag locally was W760, which doesnt seem popular for the 6.5, mostly due to temp volatility. But here is where i started.

Hornady lists 41.3gr as max for 140gr BTHP over W760. So i started at 38.6gr and moved up 0.3gr at a time watching for pressure signs. I actually ended up loading to 41.6gr (0.3gr over book max) since i didnt seem to be seeing much of any pressure signs.

New Nosler brass trimmed to 1.905"
CCI 250 primers
W760 powder
Hornady Match 140gr BTHP

So i have a few questions after getting some data. First off, Hornady dummy case is backordered, so i use a piece of FL sized brass and seated my 140gr BTHP at mag length (2.860) and started running bolt forward and seeing if i could close the bolt, all the while watching for makes left by the lands on the ogive. I used a piece of 0000 steel wool between seating depth adjustments and kept seating deeper until i could see no trace of marks from the lands. This measurement (cant do CBTO bc .264 comparator is not here yet) was 2.755 COAL, which i found strange since Hornady recommends 2.800 for this projectile. But i figured it was reasonably close and the gun shoots fine, so i ran with it. Is this alarming that this rifle has a lack of free bore or short chamber?

I figured i could do kind of a combination of break in, max load work up, and a Satterlee test across the chrono all at once. So i proceeded with shooting all of these loads and collected the following data.

Second thing that stood out to me with this data was that the velocities seem rather low when compared to other published load data. I understand i only have a 22" barrel, and most data is for 24" barrel. And i would not even worry about 25-50fps, but it seems like i am somewhere around 125-150fps lower than book values. Any thoughts on this?

With velocities this low, should i continue going up over max since i havent seen any alarming signs of pressure? The velocity data appears to be showing a node around 40.5gr give or take a couple tenths (the 40.4 charge was a clean bore shot and im not sure if that was why it was an outlier on the curve).

To summarize:

1) Is the short chamber measurement concerning?

2) Do the velocities in relation to powder charge seem way low?

3) Is it normal to have to go a fair amount over max charge to reach velocities?

Im sure left something out, so i will try to answer any additional questions you all may have.

 

[Doom2]

As for velocity, you noted that your barrel is 2" shorter than SAMMI test which can account for about 50 fps. Also SAMMI test chambers are tight and most commercial chambers are more generous. That typically contributes to lower velocity versus manufacturers test data.

As for the short chamber, that seems strange. I don't have a Ruger Am. but most factory chambers are typically long. Hopefully others can help here.

The velocity/pressure relationship that is published is for a particular combination of powder and components that were tested. When other componts, powder lots, chambers, etc, are used that relationship changes. Some rifles can go over book max and others can't. Some will reach published max velocities and some will not. That being said, if your desire is for accuracy, most bullets and rifles will typically achieve best accuracy at less than maximum chamber pressure and velocity.

Hope this helps.

 

[Seabeeken]

Every rifle is different, each has its own personality. If you have no pressure signs, you can work up until you find your pressure limit, then back off and look for an accuracy node Or do it while working up. Often, the cm case will run out of capacity before hitting pressure with slower powders. Reloder 16 is one of these powders.

 

[Doom2]

As for W760, most of the legacy ball/spherical powder are temperature sensitive and that is a good reason to shy away from max loads. This especially true if you will be outside and the ammo might be exposed to direct sunlight.

 

[JFriesen]

Right or wrong. This is how I measure distance to lands. Take a sized case and Dremel cut through the neck. Then I set bullets in the case way long. I repeatededly chamber and then measure until I get a consistent measurement that I am confident in. You can just squeeze or spread the brass neck to increase or decrease tension. Seems to work well for getting a reasonable COAL to work from. I tried the land marks on the bullet thing and found it too difficult to be consistent in visual judgement.
who knows on the velocity. I've got a few rifles that shoot slower than book and 1 that is so tight chambered it hits max book speed below the starting load from the bullet mfg.