Here are the pics of the work up. Fairly new at load development, thought my SD and es would be a little lower than this. Thoughts?
6Mm GT load. Any help appreciated.
- Thread starter MFFI579
- Start date
More info needed. Powder? Primer? Brass? How many times fired? Brass prep process, especially how the case necks are resized? What scale are you using?
I agree that your ES values are high. Fwiw, if I get an ES of around 30 and SD under 10 over dozens or hundred of rounds, I'm satisfied. The only time I've ever achieved sub-20fps ES values and sub-5fps SD over more than ten rounds was when my resized necks were so loose that I had no confidence that recoil wouldn't move bullets in cartridhes in the magazine.
Your increments are too close together. I use ~1% increments, so in a 30ish-grain capacity case I would use .3 grain increments.
First guesses would be neck sizing - too tight or inconsistent - or you're at the low end of the powder charge range (I shoot 6BR, not GT, and I've seen more velocity variation with light-for-caliber charges).
I agree that your ES values are high. Fwiw, if I get an ES of around 30 and SD under 10 over dozens or hundred of rounds, I'm satisfied. The only time I've ever achieved sub-20fps ES values and sub-5fps SD over more than ten rounds was when my resized necks were so loose that I had no confidence that recoil wouldn't move bullets in cartridhes in the magazine.
Your increments are too close together. I use ~1% increments, so in a 30ish-grain capacity case I would use .3 grain increments.
First guesses would be neck sizing - too tight or inconsistent - or you're at the low end of the powder charge range (I shoot 6BR, not GT, and I've seen more velocity variation with light-for-caliber charges).
Mistakenly added double same picture. Here's the original work up
Virgin alpa brass. Now that I've done some homework may be my first issue. Hornaday FL sizing die stock. Don't have my paper in front of me, but all seated same measuring cartridge base to ogive. Varget powder at charge on paper. Cci 450 primers. I'll start over and be more meticulous this next time. On first page semmed to be a medium node at that area, so did 5 leading middle and top of what looked like that node. Still learning. Very good chance I was not as precise with steps as I thought.
Im gonna start another batch around the high node. Powder measurer is a rcbs chargemaster.
There's very little useful information here.
Case? - brand, times fired
Primer?
Powder?
Bullet seating depth? Granted it's a 105 hybrid so it probably doesn't care.
Reloading process?
- what you're using to throw powder
- die set & press
Rifle?
- barrel manufacturer and smith if custom
- action if custom
Case? - brand, times fired
Primer?
Powder?
Bullet seating depth? Granted it's a 105 hybrid so it probably doesn't care.
Reloading process?
- what you're using to throw powder
- die set & press
Rifle?
- barrel manufacturer and smith if custom
- action if custom
- I started 6BR with Alpha brass, Varget, and CCI450 primers. You're golden there. (I won't buy Varget anymore; Vihtavuori N150 is way cheaper and has doen great so far.) Variety of bullets, including your Berger 105 Hybrids. All have done fine.
- I'd advise against putting all your chips on data obtained from virgin brass. Check that initial data against the same load from brass fireformed in your chamber.
- I have found my best accuracy at .060" off the lands.
- Consider getting an expander mandrel. Remove the expander button from your decapping stem, run the expander mandrel into resized neck as a separate step.
- You'll need to anneal at some point, as well as trim. I anneal after every firing. I haven't had to trim my Alpha 6BR brass now in 2-3 firings; I'm on 9th reload of this batch.
Enjoy the ride.
How did you prep the virgin cases?
If you skipped a chamfer/deburr, it could cause erratic results.
Virgin Alpha has always shot about the same as fire formed cases for me and many of the guys I shoot with. So much so, that it's an ongoing discussion on whether to even bother reloading once fired cases rather than selling the once fired and buying virgin cases again.
If you skipped a chamfer/deburr, it could cause erratic results.
Virgin Alpha has always shot about the same as fire formed cases for me and many of the guys I shoot with. So much so, that it's an ongoing discussion on whether to even bother reloading once fired cases rather than selling the once fired and buying virgin cases again.
Mid to low 2800s and mid to low 2900s with 105-110gr bullets using H4350. I have several barrels that shoot 115 dtacs very well around 2810-2830 with a dtac jumping 50-60k. I run 170 freebore in all my 6gt barrels. I've ran 108 and 109 Bergers at 2920-2940 in a few barrels as well. Cci450 always.
Virgin Alpha brass is going to shoot very tight ES/SDs as long as your powder charges are consistent. Virgin Alpha brass really only needs a chamfer and maybe a debur before it gets loaded. I do go the extra step to mandrel to .002 under, but it really isn't necessary and just gives me a warm fuzzy before I prime, charge, and seat.
With those kind of extreme spreads, finding the "node" is anything but... especially with single shot samples. Sorry, it just is a waste of components. I know that the trend a few years ago by everybody who wanted to be anybody was to shoot single-shot velocity ladders and "find the flat spots", but truth is that you need to shoot quite a few rounds to get reliable data. It's like relying on the data after shooting a one-shot group. If you have an ES of 30, you're going to potentially cover several tenths of a grain (or more) in normal distribution... and fool yourself into thinking you found a flat spot or a spike.
First, I'd be double-checking that RCBS Chargemaster against a quality scale. Second, quite often the velocity spreads will tighten up as you increase charge weights and fill the case more (that is not gospel and can't be counted on). You shouldn't have a problem getting up around 34.0gr in the GT and the 105 Hybrid in Alpha brass though. I think that it is possible once you get to 33gr and up with Varget that your velocity spreads will tighten a bit, and you can fine tune your accuracy with seating depth.
With those kind of extreme spreads, finding the "node" is anything but... especially with single shot samples. Sorry, it just is a waste of components. I know that the trend a few years ago by everybody who wanted to be anybody was to shoot single-shot velocity ladders and "find the flat spots", but truth is that you need to shoot quite a few rounds to get reliable data. It's like relying on the data after shooting a one-shot group. If you have an ES of 30, you're going to potentially cover several tenths of a grain (or more) in normal distribution... and fool yourself into thinking you found a flat spot or a spike.
First, I'd be double-checking that RCBS Chargemaster against a quality scale. Second, quite often the velocity spreads will tighten up as you increase charge weights and fill the case more (that is not gospel and can't be counted on). You shouldn't have a problem getting up around 34.0gr in the GT and the 105 Hybrid in Alpha brass though. I think that it is possible once you get to 33gr and up with Varget that your velocity spreads will tighten a bit, and you can fine tune your accuracy with seating depth.
What charges for those 109’s using h4350. I am at 36.5g and only getting around 2840 ish with a 26” CRB.
28in barrels, 36.3-37.0gr for 2920-2940, powder lot depending. Typically put em 40off, for half moa 10 Rd groups, leave the seating die alone, keep adding powder as throat wears to keep velocity where it belongs.
One of the best things I did was got a set of pin gages to measure exact neck ID (after resizing brass) - and with new brass (even Alpha), you likely need to at leachildrensmercy-dr.securelinkcloud.net st mandrel the necks to get them where you want them (if they're too loose from the factory, you'll have to size necks and mandrel them again to even them out).
Most "stock" size dies that have a little egg on the decapping stem aren't going to be great at giving you consistent neck tension. Pull that thing off the decapping stem and get a mandrel die - let the mandrel set final neck ID (aka, neck tension) - alternately, later, graduate to an SAC or A419 size die that incorporates a mandrel into the size die.
The Chargemaster should be able to throw reasonable powder charges, and get you to an SD of 10 or better (make sure you keep it wiped down with a dryer sheet - they're sensitive to static). Getting down to chargest within .02+/- would be better than .1+/- from a consistency standpoint, but the CM should be able to get you a lot closer than 60fps ES. Realize, though, a 60fps ES is what an SD of 10 will get you, fired across enough ammo (3 SDs+/- should account for something like 98.5% of your results).
Most "stock" size dies that have a little egg on the decapping stem aren't going to be great at giving you consistent neck tension. Pull that thing off the decapping stem and get a mandrel die - let the mandrel set final neck ID (aka, neck tension) - alternately, later, graduate to an SAC or A419 size die that incorporates a mandrel into the size die.
The Chargemaster should be able to throw reasonable powder charges, and get you to an SD of 10 or better (make sure you keep it wiped down with a dryer sheet - they're sensitive to static). Getting down to chargest within .02+/- would be better than .1+/- from a consistency standpoint, but the CM should be able to get you a lot closer than 60fps ES. Realize, though, a 60fps ES is what an SD of 10 will get you, fired across enough ammo (3 SDs+/- should account for something like 98.5% of your results).
I went up to 37.6g under a 108 ELD, before hitting pressure. Best accuracy was around 37.0, but best accuracy for my 105 Hybrid is 36.8...so it is the velocity window for this particular barrel. My barrel liked the 105s so much I gave up on everything else.
37.0 put me at 2,938 for a 27" Krieger (supposedly a .237 bore from Bugholes). If it is actually their standard .236, then I'm sold on the .236 (usually go for .237s in 6mm). That barrel hammers.
Hmm I may need to throw some more powder on there and see the results.
I didn't have any luck with accuracy going higher. I just edited my post. I tried the 108 ELD and 107 SMK... but I had such good luck with the 105 that I stayed with that bullet for this barrel.
I actually have 500 of the 109s still, and was going to give those a try... but with the 105s I'd be an idiot to shoot anything else. I'm putting together another 6CM, and will put those 109s to use in that barrel hopefully,
Be careful what you wish for.......my very first 6gt was a kreiger 236 bore 5gr 7.5tw, I ran 108bt Bergers at 2950 with rl16 and it was seriously a consistent 1/4 moa 10shot group every time on paper at 400y. One of the 3 most accurate barrels I've had ever. All was cool till bout 900 rds, then all a sudden psi hit, bolt lift ejector everywhere, I did the abrasive on bronze brush and Milwaukee trick, cleaned that barrel for days, it never did recover, had to drop a full node to get it to shoot again. I will never shoot another 236 bore 6mm barrel.
We're side-tracking, so my apologies to the OP. I'm actually at 1K even right now... although I do a decent cleaning at every 100 rounds, and clean to bare metal every 200 (to include the carbon ring). Still no issues yet *IF* it is even a .236 bore. I probably won't even play with that barrel again until next year.
Like I said, I bought a Bugholes advertised .237 Krieger ^. However, I also bought a .264, 1:8 Brux blank from them once too... and when I was cleaning that barrel, noticed that the lands were very much indeed - 5R
. It shoots, it is the right twist and contour, the price was the same, and I don't intend on bitching about it either. I'll just always be a tad cautious on what is advertised. And yes, I've purchased barrels from Bugholes since, and will continue to do so if they have what I want in stock. Crap happens.Similar threads
