300 PRC, 225 ELD Match

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kilotanker22

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I picked up my Browning X-Bolt in 300 PRC today. I could not find brass anywhere so I bought some factory ammo to get brass. The 225 ELD Match bullet shoots well from the factory Hornady stuff so I ordered 500 bullets from Midway and bought 5 pounds of Retumbo today locally.

For powders I have IMR 7828 SSC and Retumbo. Have any of you all here used either powder with the 225 ELD Match bullet? What velocities were you able to obtain safely? The attached photo is a three round group shot with the factory stuff. I shot 8 three round groups today. This is the best one, however the others were close behind. Biggest group was 1.1". Most average between .6-1 MOA. Factory velocity was average 2830, ES of 43 and SD of 14.8. would like to keep about this velocity and tighten up that spread.

Bullets won't be here for a few days yet so I figure I would start this thread and see what your experiences were here.
 

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Well I went ahead and loaded some up. I am gonna use Retumbo and use Hornady data. Hornady lists a max charge of 78.9 grain Retumbo behind the 225 ELD Match bullet. I basically never start at the bottom of the load data. If I wanted to launch 225 grain bullets at 2400 fps, I would buy a 30-06 and do it with twenty percent less powder.

Anyway, midpoint in my loads is 78 grains of Retumbo. Figured I would do one percent increments, but that would be .78 grains. I decided to do half grain increments instead.

Oal 3.720"(.020" from contact). Loaded 5 each.
77gr, 77.5gr, 78gr, 78.5gr, and 78.9gr. Stopping at Hornady's published maximum load.

Using Winchester LRM primers and once fired Hornady brass.

My primary concern here is getting close to factory velocity or a.little better. While keeping an ES less than 20fps. Then tune seating depth of needed. Ideally I would like to see half MOA or better. I know the rifle is capable with this bullet. Pretty sure with a tight ES and tuned for harmonics it will be a tack driver. The factory Hornady ammo is consistently sub minute.

The barrel on this Browning is hot after just three rounds so my plan is to shoot one shot at a time with 10 or so minutes between shots. I wish I had more time. I would like to test these all as cold bore shots. Since my goal is a first round hit at one.mile.
 
Kilo i use a air mattress pump with a hose that fits the chamber to cool the barrel. Works pretty good.
 
The hose i use is 1/2 od clear vinyl i got at the hardware store. Fits the chamber pretty snug. I'm going to take a old cooler and coil up soft cooper tubing inside and fill it with ice. And put the hose on both end of the tubing.
 
Shot's walking as the barrel heats up ain't the barrel's problem. The receiver face isn't squared up to the barrel tenon axis. A decent gunsmith can fix it.

Then it'll shoot 10 shots a minute to point of aim.
 
Bart, It does not seem to be walking. Today I was shooting while it was pretty warm and shooting 5 shot groups. Point of impact did not really change. Group size opened up slightly, but I was shooting different powder charges.

The 78.9 grain charge shot pretty well. .57 MOA for a 5 shot group, but my ES was 60 fps. All shots were within 20 fps except for the very fist shot in the group, which actually was the first shot of the day. That one was 40 fps faster than the next fastest shot in that string. I have not yet decided which route I want to go. I may continue with my load development and add a bit more powder.

Hornady listed a velocity of 2850 fps with that load and my average velocity was 2830 fps. I also have two extra inches of barrel over their test barrel and I am loaded .045" longer than the Hornady data suggests.

What I am trying to decide is whether I should seat the bullet deeper into the case, or keep depth and add powder. I have found with my other rifles that seating a bullet deeper definitely increases pressure and velocity.

Regardless of where I end up with my load, the rifle is shooting pretty well for having less than 100 rounds down the tube.
 
Your barrel's bore and groove diameters are probably different from the ones Hornady used. They used a different powder lot. These will easily cause the velocity difference you're getting.

I've seen two people get over 60 fps velocity difference shooting the same rifle and ammo
 
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Bart B. said:
Your barrel's bore and groove diameters are probably different from the ones Hornady used. They used a different powder lot. These will easily cause the velocity difference you're getting.

I've seen two people get over 60 fps velocity difference shooting the same rifle and ammo
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Yeah I know about the difference in barrel speeds. My 22" Ruger American 6.5 Creedmoor shoots the exact same ammo as my 24" Franchi. Yet the Ruger shoots the ammo 35 fps faster than the longer barrel.
 
I don't shoot the 300 PRC--but I do shoot the 300 wby and win mags. Hornady's ELD's I've found generally are not "jam 'em as close as you can to the lands" bullets in my experience, so you might want to vary your seating depths (or just use the Cortina method). I'd highly recommend trying some of the Berger heavier .308 offerings (which may be more available), they have many to choose from. Keep an eye on your rifle's throat and first inch or two of bore as you might inadvertently cook 'em prematurely when running extended ladder test sessions.
 
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Kilotanker,

Be sure you seat your primers firmly. Ideally, you want them to seat 0.003" beyond the point where you feel the feet of the anvil touch the bottom of the primer pocket (that number from NIOH testing almost 40 years ago, but still holds AFAIK).

"There is some debate about how deeply primers should be seated. I don’t pretend to have all the answers about this, but I have experimented with seating primers to different depths and seeing what happens on the chronograph and target paper, and so far I’ve obtained my best results seating them hard, pushing them in past the point where the anvil can be felt hitting the bottom of the pocket. Doing this, I can almost always get velocity standard deviations of less than 10 feet per second, even with magnum cartridges and long-bodied standards on the ’06 case, and I haven’t been able to accomplish that seating primers to lesser depths."

Dan Hackett
Precision Shooting Reloading Guide, Precision Shooting Inc., Pub. (R.I.P.), Manchester, CT, 1995, p. 271.​

But, assuming you are doing that, a first shot being different from the others isn't unusual. If you are in a match where you get sighters, use a couple. Otherwise, I just try to know what the first shot difference will be by collecting first shot locations and seeing if they group well.

G. David Tubb says people using his hBN-coating on bullets don't get first shot differences. More possibilities to explore.
 
Unclenick said:
Kilotanker,

Be sure you seat your primers firmly. Ideally, you want them to seat 0.003" beyond the point where you feel the feet of the anvil touch the bottom of the primer pocket (that number from NIOH testing almost 40 years ago, but still holds AFAIK).

"There is some debate about how deeply primers should be seated. I don’t pretend to have all the answers about this, but I have experimented with seating primers to different depths and seeing what happens on the chronograph and target paper, and so far I’ve obtained my best results seating them hard, pushing them in past the point where the anvil can be felt hitting the bottom of the pocket. Doing this, I can almost always get velocity standard deviations of less than 10 feet per second, even with magnum cartridges and long-bodied standards on the ’06 case, and I haven’t been able to accomplish that seating primers to lesser depths."

Dan Hackett
Precision Shooting Reloading Guide, Precision Shooting Inc., Pub. (R.I.P.), Manchester, CT, 1995, p. 271.​

But, assuming you are doing that, a first shot being different from the others isn't unusual. If you are in a match where you get sighters, use a couple. Otherwise, I just try to know what the first shot difference will be by collecting first shot locations and seeing if they group well.

G. David Tubb says people using his hBN-coating on bullets don't get first shot differences. More possibilities to explore.
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Thanks Unclenick, when developing precision rounds I hand seat primers. I generally insert them as far as.my priming tool will seat them. There is always a wee bit extra after the primer finds the bottom of the pocket.
 
I just got back from the range. Pretty sure I might have found my powder charge, or at least close to it. I won't share it here, but velocity and velocity spread is right about what I am looking for. ES 19fps, SD 7fps. I need to measure the group yet.

My second shot in this group was out of the group by like .5". I called this as my mistake. I was not steady enough when I squeezed the trigger. Either way, I am pretty happy with the results. After I measure the group I will post a photo here.
 
I just got back from the range. Pretty sure I might have found my powder charge, or at least close to it. I won't share it here, but velocity and velocity spread is right about what I am looking for. ES 19fps, SD 7fps. I need to measure the group yet.

My second shot in this group was out of the group by like .5". I called this as my mistake. I was not steady enough when I squeezed the trigger. Either way, I am pretty happy with the results. After I measure the group I will post a photo here.
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Happens to me a lot--the rifle tells me it can shoot better than what I'm doing.
 
Here is the group from one of the loads I shot today. I wrote the measurements of the group on the paper. 4 rounds into .5" and the shot I pulled opened it up to .8". Will load more of these and try them a few more times before I settle on the powder charge. If it continues to shoot like this, I might not even bother tuning the seating depth.
 

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The horizontal dispersion of the shots in this group does not bother me. It was not windy, but the breeze we did have was randomly changing directions. If I can shoot a few more groups like this one with this load, I will test them at longer distance.
 
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