6mm XC seating depth

[bullfrog]

My 6mm XC has a 7.5 twist Bartlein 5R and was built by GA precision. I am having trouble with consistent performance. Shoots very well (under 1/2" 5 shots) one group then crappy (barely under 1" 5 shots) the next group with the same load. I have always had the best luck seating close to the lands on all my rifles so most of my load development has been close to or into the lands. I did try a few from .060 to .120 off but did not seem to matter. I have tried 105 berger hybrids, 105 hornady bthp, and 117 matrix vld's using H4350 and H4831SC. I FINALLY got in some 115 DTAC's and will try these next. I am hoping to get a little advice to save time and bullets. What distance from the lands has worked the best or been the most consistent for you shooting the 115 DTAC's and 105 hybrids? Also, what powder and primer has given you the lowest ES with good accuracy? Finally, what neck tension have you found to work the best?

Thank you very much for any advice. I have not had to do this much load development for any of my other custom rifles and I am starting to get a little frustrated.

 

[zipollini]

Load info for 6XC

Gun - Tubb 2000
Barrel - Krieger that was melonited
1:7.5 twist
barrel length = 27in

Bullet - DTAC 115 HBN coated - weight sorted to .1g, bearing surface length and base to ogive length sorted to .001 in.
Bullet seated .020 in long
Powder - H4831SC - 45.2g weighed to +/- one kernel - load was slightly compressed
.002 neck tension
Primers - Wolf large rifle - weight sorted to .01g
Brass - Norma weight sorted to .1g

range temp. = 55 deg. f
Sample size - 15
avg. MV = 2985
ES = 8
SD = 3.4

Note - at a range temp of 70 deg F normal MV is approx. 3000fps

 

[rcw3]

Did you mean 45.2 gr of H4831SC? That would be real hot in a 6XC. Was that a typo and should have been 42.5 gr of H4831SC?

In the 6 SLR the "go to load" is 42.5 gr. of H4831SC with the 115 bullet and it runs around 2950 fps with that load. A 6XC has a smaller capacity than a 6 SLR and having a load pumped up close to 3 gr more in a smaller capacity case to get the same velocity does not make sense.

Robert

 

[zipollini]

Yup - went back and rechecked my notes - It's 45.2g of H4831SC @ 55 deg. F for HBN coated DTACs

I run 39.5g of H4350 @ 70 deg F for an MV of approx. 3000fps with HBN coated DTACs
I run 42.5 g RL-17 @ 79 deg. F for an approx. 2970fps with HBN coated DTACs

Used MagnetoSpeed V3 for crony.

I'm guessing the difference you are seeing is that I use HBN coated bullets and the temp. was 50 deg F. Just a guess.

 

[LitLBoy]

Norma brass BR-2 41.7 7828SSC 105 BH 20 off the lands
LitLBoy Lilja 3 grove

 

[rcw3]

Zippolini

I am not saying you're not seeing what you're seeing, but I can only say that I have three 6XC barrels and 45.2 gr. of H4831SC would be a seriously hot load in all of them with the DTAC 115's BN. Query if there's something different with your barrel, with your lot of H4831SC or something. I have an Oehler 35P chronograph with the double check screen set up to "double check" the velocities.

Robert

 

[spclark]

My experience supports what RCWIII's added; I'll check my notes from propellant testing back in 2008 that included RL17 & get back here with an update. PM me if you want to have a copy of the test results from that day @ 600 yards in PDF format.

The barrel used in that test - 30" Bartlein 1:7.8, Hugh Henriksen's 7/03 6XC reamer (have print that came with another identical reamer that arrived last month), rifle built by Carl Bernosky in 2008 - still shoots beautifully to 1,000 yards.

I had it built with the 115 DTAC in mind but initial testing proved to me they were no better than Berger's 105VLD which have been more easily found anyway..

hBN home-coated Berger 105VLD's using Norma 6XC brass, KVB7 Wolf primers, 36.7 grains of IMR 8208XBR (five different lots since 2008) 3,050 fps SD<8 (Oehler 35P configured for proof channel) seated 0.020" off the lands.

I've made 6XC brass from Lapua's superb Palma brass too (LOTS of work!). Loaded exactly the same - save for using KVB223(RE)M Wolf small rifle primers - they give performance equal to Norma brass.

I don't shoot F-Class (yet) or BR, preferring a sling & match sights for as long as I still can so groups aren't something I worry about much. Holding the NRA LR target's 10-ring? Yes, hopefully with a majority of rounds centered in the smaller X-ring. This rifle can do that with that load spec.

Others' rifles must be evaluated by their owners with regard to the safety of this load for their needs. I dropped back 0.3 grains after two seasons after losing two primers one hot summer afternoon. Nothing significant was sacrificed with the reduction & no further primers have gone missing.

 

[expiper]

HI Zippy,,,,I also think your load is tooooo much,,,,I use 43.5 (fourty three and a half)...gr of 4831 SC in my plane jane .243 ---Panda/Krieger 8 twist/Lapua brass/etc--- and I dont pussy foot around with "mid range" loads....this is near MAX in a .243,,,,,Roger

 

[jcampbellsmith]

...Thank you very much for any advice. I have not had to do this much load development for any of my other custom rifles and I am starting to get a little frustrated.

Have you checked your fired brass for donuts? I have some donut issues and I'm seating ahead of the neck/shoulder junction to minimise these issues.

Regards JCS

 

[powerline]

26" krieger
Norma brass
Br2
107 smk
43.5 gr 4831 sc
10 thou off
3030 fps
This is my go to load, but honestly during load development
I did not have any really open groups.

 

[Ledd Slinger]

Tagging this thread because I have a 6XC hunting rifle being built on a Sako A7 action. Will be wearing a 22" X-Caliber barrel with a 1 in 8" twist set up for the Berger 105gr VLDs. Should make a really nice lightweight mountain deer rifle.

 

[bullfrog]

Have you checked your fired brass for donuts? I have some donut issues and I'm seating ahead of the neck/shoulder junction to minimise these issues.

Regards JCS
[/quote]

I have not checked for donuts. The 105's do not reach the neck shoulder junction. The 117 VLD's did seat into the case far enough to hit the donut if there is one. I see the same results with both bullets.

The thing that confuses me the most is the ES changing. I will shoot 5 shots with an ES of 12 then load up the exact same load again to proof it and will get an ES of 40. My range is right out my back door so both strings are shot in the same conditions with the same setup within less than 30 minutes using an Oehler 35P. I have used F210M, CCI, Remington,and Tula primers without seeing any real difference. This is driving me nuts. I even bought a gempro scale to weigh out the powder to .02 grains and this also made no difference.

One of the reasons I decided on the 6XC was the supposed ease of working up loads. Not this one.

The only thing I can think of that I have not done is annealing the cases. Have you gentlemen found annealing to make much difference?

 

[spclark]

I have not checked for donuts. The 105's do not reach the neck shoulder junction.

What I've noted also.

The thing that confuses me the most is the ES changing. <snip> This is driving me nuts.

No surprise that!

One of the reasons I decided on the 6XC was the supposed ease of working up loads. Not this one.

The only thing I can think of that I have not done is annealing the cases. Have you gentlemen found annealing to make much difference?

Oh yeah, big time.

I started annealing back maybe 8, 9 years ago when I was messing around with a 6.5 Grendel match upper. Had issues trying to achieve uniform shoulder set-back when resizing.

Since then I've come to appreciate the myriad benefits of annealing at least every second firing. Brass lasts longer (if you factor out primer pocket expansion), bullets seat easier, necks & shoulders size uniformly with dies that don't have to be moved....

All the prone match ammo I load now I try to achieve neck tension of 0.0010" - 0.0015" uniformity. That'd be miserably frustrating IMHO with fired cases that haven't been annealed. My 6XC load for the one barrel I've been shooting since late in 2008 has been consistently reliable (earlier post has details) all the time since then.

Just as a thought... how often do you clean your barrel & how thoroughly do you feel is necessary?

 

[bullfrog]

For load development I clean about every 30 rounds. I'm not seeing much copper fouling. I do clean when I change bullets no matter the round count.

 

[Frankr]

bullfrog I don't judge a loads ES on 5 shot strings...I will shoot at least 25 rounds before I call a solid ES..and sometimes you may even find a load that has a 5 FPS SD and every 20 rounds or so you may pop a 50 FPS ES..

first I would look at your case sizing ? Bushing die? is the die sizing the case too much? try a little crush on a sized case..

second did you uniform the primer pocket and flash holes?

third I would weight sort the cases. try to keep them in 1.0 grain lots.

forth check your neck thickness for uniformity and neck chamber clearance. check the loaded round as to the chamber neck size.

seating depth in my 6XC is just touching the lands.. But I shoot the Hunting 105 VLD.

I have found neck tension to be the biggest factor in ES numbers...as neck thickness(variance in neck clearance)
and neck tension..if you are using a bushing die try .001 more neck tension..if not using a bushing die get one.

things I can think of for you to look at...

I run .003 neck clearance in mine and im sure It could shoot a little better if I turned the necks slightly but im happy with 1/2 MOA or better most of the time...I use Norma brass necks unturned, cases weight sorted, primer pockets and flash holes uniformed. redding FL bushing die...268 bushing(I think)..(sized 7/8 of the neck). FL sized where a naked bolt has slight crush about 3/4 closed..105 H VLD just touching..Im shooting RL17 stiff load 40.5 GR.. recommend start loads of 38.0 gr....H4350 shot well in mine at 40.5 gr...but I just get more speed out of RL17 and for what ever reason in my air/alt RL17 is just more stable than H4350.

I'd like to say 40.5 gr RL 17 in my 6XC is pushing a 105 Hunting VLD out of a 26" 1-8 twist at 3,150 FPS. verified by several chronographs .. the most amazing thing is I have tested it at 25 deg F to 85 deg F and only see 30 FPS gain/loss yes at 85-90 deg F it's at 3,180 FPS...it's quite amazing...drop charts at the range have been on..

two guys who have witnessed it have tried RL17 in a 270 WSM and a 7mm WSM and have found the same temperature stability and great velocity..they have been testing for the last few weeks and at 9 deg F it was the same velocity as 40 deg F..the H4350 I have was a hot load at 40.5 gr, shot good 1/4 moa..at 3,050 FPS at 85 deg F..when the temp droped to 30 deg F the load slowed to 2,950 FPS. so I abandoned H4350..for what ever reason the H4350 I have seemed to slow of a powder, so I never tried H4831..I allways felt alittle faster then H4350 would shoot good. but RL17 has shot so well in mine I never tried any thing else.


wow I got a little long winded there and I haven't even been drinking.

 

[bullfrog]

I do use a redding FL bushing die, and I have tried different bushings to change the neck tension (again, no difference). I bump the shoulder .001"-.002" less than a fired case using the Hornady headspace measuring tools.

I do not judge the load by only one 5 shot group size and velocity. But it is frustrating to think you find a load that will work well only to have it fall apart when it is further tested.

I just haven't found the right combination to deliver good consistent performance in my rifle. I will work up to some of the recommended recipes you guys have courteously supplied. Hopefully I will find the combination that is right for my rifle.

FJIM - What primer are you using with RL17?

 

[Frankr]

CCi 200 LR

 

[jcampbellsmith]

CCi 200 LR

+1. The only primer I use. Regards JCS

 

[jcampbellsmith]

My other question was, have you tried factory ammo in your 6XC? I know it's pricey, but I got a couple of boxes of the Oryx and shot some roe bucks and red stags with it.

I found the Oryx grouped pretty well in my rifle. Norma also have some Nosler BTs.

http://www.norma.cc/en/Products/Hunting/6XC/

Regards

JCS

 

[Ledd Slinger]

Time and time again, I have found that a primer change can make a world of difference in a load. Couldn't tell you how many times I've seen a different primer in the same recipe take a 100 yard group from 1"-1 1/4" down to under 1/2". I've even seen as crazy as a 6" group being brought down to a 1" group in a friends rifle with nothing more than a primer change.

I personally have never had any luck with CCI primers. I have a lot of rifles, so many that I still haven't found time to shoot a couple of them that have been built for over a year now. Out of all the rifles I currently have, or have owned in the past, not one of them liked a CCI primer over something else. I usually start with Federal Match primers, but have seen a lot of luck had by fellow shooters with Remington primers as well. Never had luck with Winchester primers either. I still have some for testing, but the Winchester is usually so bad that I won't even try them unless nothing else works. I still keep some CCI primers on hand and often test them in hopes that one day they will be 'the one', but I haven't seen it yet. Not to say I havent found accurate loads with CCI, just havent found 'AS' accurate loads as I have with other brands.

What I'm getting at is that you should take your 2 best loads you have found to date, and load them with different primers, but keep everything else the same. I'm sure you will be surprised by the results. Some may be worse, but some may be a lot better. I would suggest, trying Federal 210's (either regular or match), Remington 9 1/2, CCI BR2 and what ever else you can get to test. And don't be afraid to try a Magnum primer. I have a 6mm Remington that loves shooting the 75gr Sierra HP bullets over IMR 4895 with Federal 215M Magnum Match primers. Though it's not a Magnum cartridge, it shoots way better with that primer than it does with any standard large rifle primer. Keep your mind open and try as many of them as you can. Just because 'Joe Blow' on the Internet says one certain primer works in his load, doesn't mean a dang thing in determining what your rifle will end up liking. GOOD LUCK!