Velocity spread issues. Bartlein barrel

[DogDown1994]

I recently got my 338 lm build complete. My gunsmith opened up the bolt face on a 300 win mag howa 1500, did all machining, I had him put a 30in bartlein 5r 1-9.5 twist bbl with apa fat bastard muzzle brake on it, he did a trigger job tuned to just under 2lbs and put a McMillan a5 on her and I got a razor hd gen 2 4.5-27 for it.. Other gun smithing and add ons were done but these are the main parts. Anyways after breaking in the barrel with light loaded 250 gr hornady bthp's, I started working up loads for the 300 gr smk. Today I tested 5shots each of 85, 87, and 89grs of retumbo all seated at 2.600" at 100 yards. 85 grs, I didn't chrony just because I thought it might be pretty slow and didn't know if the gun would like them anyways. 87 grains shot 1.6 but only had an extreme velocity spread of 14 fps(2687-2701) I may try that load again to see if I can shrink that group but I know I was shooting good today. Here comes my problem, when I tested my 89 gr load, the 5 shot group was easily under 1/2 inch. Didn't have my calipers and left target in my truck but possibly 1/3". Great group, seems like a great load BUTTTT the chrony didn't like it, velocities were (2768,2764,2796,2809, and 2894). 2894........ What the heck happened, and how is that bullet even close to the other 4 shots. We're talking 130fps max spread. I would love to test this load further, but is it a lost cause, was my chrony off, am I making a rookie mistake? I'm using a caldwell chrony. I'm going on 3 years of reloading and know a good amount but am still definitely learning.. I also should note that I was using brand new lapua brass that I neck sized before loading and fed 215m primers. I need expert advice, please help. Thank you

 

[Deleted member 46119]

What brand and model of chronograph.

 

[DogDown1994]

Im using the "Caldwell Balistic Precision Chronograph"

 

[FearNoWind]

Reviews I've read on that chrony are either "I love it" or "I hate it". There doesn't seem to be a middle ground. I'd try the load with another chrony to see what the differences in results might be. You can buy a MagnetoSpeed Sportsman for under $200 .....

 

[Korhil78]

Like others have said, I would not trust that chronograph. If it was cloudy or the sun wasn't high enough in the morning yet, it will do crazy things to the lower end chronos. If you are not gonna buy a higher end chrono then take that load and shoot it at 300-500 yards and see how it does and use your chrono to get a base velocity even though it may not be correct, it will get you in the ball park velocity. You can then get your velocity figured out based on drops out to 1000 yards. Not as precise or easy as getting a quality chrono like a magneto speed but it will work.

You don't have to stop verifying at 1k either. The further out you verify, the more precise you will be.

 

[isaaccarlson]

Yep. Distance will tell you what you need to know.

 

[Lefty7mmstw]

2 screen optical chrono's can lie to you and you will not have a clue... Get an Oehler 35 or magnetospeed and you will rid of your headache... Your head won't hurt so much from banging it on the table trying to figure out what the heck is wrong with your loads.

 

[DogDown1994]

Okay I'll take that load out to 300-500 and see how it performs there. Thank you guys for the info. Glad I became a LRH member.

 

[Korhil78]

Also, if you are going to shoot 5 shot groups, it is really important to let your barrel cool down between shots. Just take another rifle with you and shoot it while you let your Lapua cool down. Let us know how your longer distance groups look and we can go from there.

 

[SabreCross]

I've had great results with the Competition Electronics Prochrono (digital) chronograph. It's around $100 and you don't strap it to your barrel.

 

[wwbrown]

Dogdown,

Does the 1500 feed the 338 Lapua Magnum or are you shooting it as a single shot?

Thanks
wade

 

[DogDown1994]

It feeds 338 perfectly. My smith put a bottom metal kit from pacific tool and guage on it. Mag length is a little short 3.615, but it is a tactical match chamber so im still pretty close to the lands. also to machine out the grooves on the side of the mag to hold the wider lapua case. After that it feeds great. Entire rifle all said and done was under 3k. I would post a pic of it if i knew how.

 

[Hired Gun]

It sounds like a beautiful build. Please post a picture. I like the Vanguard actions.

I agree I wouldn't put much stock in the repeatability of any light sensor chronograph. Even the fabled Oehler can't agree with itself most of the time. I used to run 3 chronographs on the same bar and I spent hours calibrating them to get them super close to each other but as the light varied the differences between them grew on their own. One was an infrared model and it varied too. A magneto speed seems much more consistent to itself. I'm looking to get one of the new Lab Radar units once they get the bugs worked out or at least develop a bit of a track record.

As long as the Bartlein is fully free floated from the action forward it should hold zero for 5 shots on a Lapua. I have yet to see a cut rifled barrel wander in 5 shots. I just wouldn't do it on any of the 3200 fps and up velocity cartridges. At 100 or even 200 yards 130 fps isn't going to change vertical very much. At 500 it starts to show and 1000 is better yet but then atmospheric makes it hard to know what is moving the impact around.

My personal Lapua has the PTG Tactical Match chamber and with Bergers I am still off the rifling at 3.900". I haven't tried SMK's but it is good to know they end up shorter. That will be very good for repeaters.

 

[DogDown1994]

Hello everyone. Sorry it took so long for me to return, truck broke down and havnt had much time for anything. Anyways i coulndnt afford a new chrony for the time being butttt after taking your advice and shooting groups at 400 yards in the first place rather than 100 yards, i found that my current loads (300smk&retumbo) were inneficient, finaly i wised up and went with a 300 berger otm and some h1000 seated at multiple lengths, left the chrony at home and now consistently shoot 3 inch or less 5 shot groups @400. My best group was .66 moa and .74 is average. Generaly 4 of the shots being .5 moa or less then the guy behind the trigger pulls one, mabye after more work i can tighten them even more. BUTTTT what is odd to me is that the rounds loaded closest to the lands actualy shot the worst. (COAL to lands with that bullet is actualy 3.895). After backing them up multiple times im actualy set way back to BERGERS RECCOMENDED COAL of 3.681. Sounds crazy to me that that bullet likes to jump over 2/10ths of an inch but its workin for me. I shot my 18"unpainted gong at 1000 yards with 5 left over rounds i had that day and hit every shot. Soon i will paint the target and get a group size for 1000 then report back. THANK YOU for the advice everyone. You can imagine its hard for a 20 year old kid to obtain any information about reloading when most kids my age are either on their x box or arnt even interested in firearms that arnt AR's. Thanks again. Any other tips are also appreciated