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.
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