The new 33XC & 37XC cartridges designed by David Tubb

ReturnFire · Dec 8, 2024

Fellas I need some help building a load. So far I’ve tried both H50BMG and N570. Im shooting 285 Flatlines through a 34” 8 twist. My ES has been much higher than I’d like. Where do I go from here?

H50BMG
117gr 3067 ES 31.7 SD 10.5 6 shots
119gr 3130 ES 24.2 SD 9.9 3 shots
120gr 3146 ES 29.8 SD 12.8 3 shots
121gr 3187 ES 32.6 SD 13.4 3 shots
122gr 3190 ES 38 SD 16.6 3 shots
123 pressure flat primers

N570
113gr 3165 ES 19 SD 6.8 3 shots
114gr 3184 ES 11.9 SD 5 3 shots
114gr 3193 ES 42.5 SD 17.7 3 shots
115gr 3206 ES 22.1 SD 9.5 3 shots
116gr 3243 ES 26.9 SD 11 3 shots
117gr 3265 ES 24.8 SD 10.5 3 shots

Dogtown · Dec 8, 2024

It sucks donkey balls with pricey solids, but chances are 3 shots is not enough to determine SD/ES with reasonable confidence.

Along those lines I was at the range this morning shooting several 5-shot strings of 241 Seneca solids in a 300NM. “Well there goes $50 of bullets with mostly inconclusive results”

ReturnFire · Dec 8, 2024

Dogtown said:
It sucks donkey balls with pricey solids, but chances are 3 shots is not enough to determine SD/ES with reasonable confidence.

Along those lines I was at the range this morning shooting several 5-shot strings of 241 Seneca solids in a 300NM. “Well there goes $50 of bullets with mostly inconclusive results”

I was sticking to 3-shot strings just to give me a starting point. I figured that if the spread was garbage on three that I didn’t want to load 5. The 114gr of N570 looked good so I loaded three more and it was terrible.

brianf · Dec 8, 2024

Dogtown said:
It sucks donkey balls with pricey solids, but chances are 3 shots is not enough to determine SD/ES with reasonable confidence.

Along those lines I was at the range this morning shooting several 5-shot strings of 241 Seneca solids in a 300NM. “Well there goes $50 of bullets with mostly inconclusive results”

Have you gotten PVA 30 cal solids to shoot. Tried a bunch in a few different cartridges….75 moa at best

The 6’s are lights out but the 30 cal seem different

Sigma · Dec 8, 2024

ReturnFire said:
Fellas I need some help building a load. So far I’ve tried both H50BMG and N570. Im shooting 285 Flatlines through a 34” 8 twist. My ES has been much higher than I’d like. Where do I go from here?

H50BMG
117gr 3067 ES 31.7 SD 10.5 6 shots
119gr 3130 ES 24.2 SD 9.9 3 shots
120gr 3146 ES 29.8 SD 12.8 3 shots
121gr 3187 ES 32.6 SD 13.4 3 shots
122gr 3190 ES 38 SD 16.6 3 shots
123 pressure flat primers

N570
113gr 3165 ES 19 SD 6.8 3 shots
114gr 3184 ES 11.9 SD 5 3 shots
114gr 3193 ES 42.5 SD 17.7 3 shots
115gr 3206 ES 22.1 SD 9.5 3 shots
116gr 3243 ES 26.9 SD 11 3 shots
117gr 3265 ES 24.8 SD 10.5 3 shots

have you played with different primers and neck tension?

ReturnFire · Dec 8, 2024

Sigma said:
have you played with different primers and neck tension?

I’ve only used 215M’s and .002 neck tension so far.

Dogtown · Dec 8, 2024

brianf said:
Have you gotten PVA 30 cal solids to shoot.

I’ve been shooting the 212s for a couple years now and plenty happy with them. I’ve been slowly testing out 241s but have yet to use them in competition.

secondofangle2 · Dec 8, 2024

Changing primers is almost never going to have a dramatic impact on a load and neither is neck tension….unless the neck tension is variable….

375fan · Dec 8, 2024

ReturnFire said:
I’ve only used 215M’s and .002 neck tension so far.

How many rounds through the barrel?

TankFrank · Dec 8, 2024

You might be doing this already but
expanding my necks helped me after annealing. H50 seems to work for me. Slower speed but lower SD and ES.

ReturnFire · Dec 8, 2024

375fan said:
How many rounds through the barrel?

Total of 50 now

Rocketmandb · Dec 8, 2024

ReturnFire said:
Total of 50 now

The barrel is likely still speeding up. Regardless, the lower end of the N570 loads is where I'd load up a bunch to form brass until you're done with speeding up the barrel.

HD1911 · Dec 8, 2024

I was gonna say, most likely hasn’t even stabilized/settled in yet.

Rocketmandb · Dec 9, 2024

One other thing @ReturnFire - taking SDs off of virgin brass does nothing more than provide a source of amusement. Virgin brass messes with SDs. Combining that with measuring during barrel speedup is just an exercise in futility. At 50 cases, you're probably half the way there. Break in some more cases, beat up your shoulder a little bit more, then start load development.

Also, what's your seating depth? I've found that solids like a bit of jump. On my last 37XC barrel, I found that I had to run the 353 Lehighs at .0130" to get decent grouping. Hopefully picking up my newly rebarreled rifle this week, then I too get to destroy my shoulder breaking it in.

Funny story, with my last one I had asked a friend of mine to come to a private range to help me run some rounds through it. I had 60 ready to go and at the last minute he tells me he tested positive for Covid. So, I'm going to the range solo. I was pushing the 353s nearly as fast as some of your 265s, so you can imagine how much recoil there was.

I was bound and determined to get all 60 out of the barrel, but my shoulder and cheek hurt so bad that for about the last 10, I'd get lined up on target, pull by cheek off the riser and nearly pull my shoulder all the way back before pulling the trigger. I felt that session for the better part of a week.

ReturnFire · Dec 9, 2024

Rocketmandb said:
One other thing @ReturnFire - taking SDs off of virgin brass does nothing more than provide a source of amusement. Virgin brass messes with SDs. Combining that with measuring during barrel speedup is just an exercise in futility. At 50 cases, you're probably half the way there. Break in some more cases, beat up your shoulder a little bit more, then start load development.

Also, what's your seating depth? I've found that solids like a bit of jump. On my last 37XC barrel, I found that I had to run the 353 Lehighs at .0130" to get decent grouping. Hopefully picking up my newly rebarreled rifle this week, then I too get to destroy my shoulder breaking it in.

Funny story, with my last one I had asked a friend of mine to come to a private range to help me run some rounds through it. I had 60 ready to go and at the last minute he tells me he tested positive for Covid. So, I'm going to the range solo. I was pushing the 353s nearly as fast as some of your 265s, so you can imagine how much recoil there was.

I was bound and determined to get all 60 out of the barrel, but my shoulder and cheek hurt so bad that for about the last 10, I'd get lined up on target, pull by cheek off the riser and nearly pull my shoulder all the way back before pulling the trigger. I felt that session for the better part of a week.

The first round of testing with the H50 was on virgin brass so that could have contributed to the poor ES and SD numbers. However when I tested the N570 it was on the same brass that I went through and resized (once fired).

The 6 shot group of N570 with 114gr was very promising but with one outlier that skewed the numbers pretty hard.

I shot a ladder test with H50 and only had about 0.010 jump but for all of the shot strings that I posted I had 0.020 jump. This is my first attempt at using Flatlines so I wasn't sure how much jump they typically like. Somewhere I read a recommendation for 0.015 but I could be wrong. I do know that CEB Lazers for my 375CT don't like much jump at all. I will say that the groups for several of these loads were good and tight but its only at 100 yards. I can assume that the groups would open up quite a bit at extended ranges when there is a 25-40 fps variation in speed.

Emerson0311 · Dec 9, 2024

I don’t trust my load development until it’s on paper at 300+. I test Rimfire ammo at 100. I nail down my centerfire like 300PRC at 400. Not the cannons you guys are shooting, but 100 doesn’t show much.

Taylorbok · Dec 10, 2024

@ReturnFire how do they group?

I've never used the Flatlines but if they don't group I'd try a different bullet. I had some buddies try them in their 30 cal's and couldn't get them to shoot from 6 different barrels.

My 375 hammers with A-tips or Lazers, I tried some of the ICBM's from Badlands, first group was like 6" so I just said F that, I gave the remainder to a buddy to try in his ENABEL, first 5 shot's one of them missed the paper entirely, he abandoned them also.

ReturnFire · Dec 10, 2024

Taylorbok said:
@ReturnFire how do they group?

I've never used the Flatlines but if they don't group I'd try a different bullet. I had some buddies try them in their 30 cal's and couldn't get them to shoot from 6 different barrels.

My 375 hammers with A-tips or Lazers, I tried some of the ICBM's from Badlands, first group was like 6" so I just said F that, I gave the remainder to a buddy to try in his ENABEL, first 5 shot's one of them missed the paper entirely, he abandoned them also.

I only tried them out to 300 but honestly they grouped ok. Ragged holes at 100 but I usually try to group at 600 when I'm building a load which I wasn't able to do this time. I'll probably load up a couple this week and see what size groups I can get with a little distance.

I have a 28 Nosler that shoots 3" groups at 1k with single digit SD's so that is the standard that I aim for. That is with 195 Bergers.

I am much more comfortable using lead core, Berger Hybrids in particular, but my barrel is an 8 twist and I'm not sure if I could use the 300 OTM's or not. I guess I need to get my hands on a couple and see what type of results I get and go from there. Are solids typically that finicky?

Taylorbok · Dec 10, 2024

ReturnFire said:
I only tried them out to 300 but honestly they grouped ok. Ragged holes at 100 but I usually try to group at 600 when I'm building a load which I wasn't able to do this time. I'll probably load up a couple this week and see what size groups I can get with a little distance.

I have a 28 Nosler that shoots 3" groups at 1k with single digit SD's so that is the standard that I aim for. That is with 195 Bergers.

I am much more comfortable using lead core, Berger Hybrids in particular, but my barrel is an 8 twist and I'm not sure if I could use the 300 OTM's or not. I guess I need to get my hands on a couple and see what type of results I get and go from there. Are solids typically that finicky?

I'm not sure what causes it exactly but those really sleek bullet designs seem to be super picky about who they work for.
The CE Lazers seem to work well for everyone I've ever talked to.

There is a good chance your barrel is still settling in so if those bullet's shoot well I wouldn't stress about es/sd until about 150 rounds.

brianf · Dec 10, 2024

ReturnFire said:
I only tried them out to 300 but honestly they grouped ok. Ragged holes at 100 but I usually try to group at 600 when I'm building a load which I wasn't able to do this time. I'll probably load up a couple this week and see what size groups I can get with a little distance.

I have a 28 Nosler that shoots 3" groups at 1k with single digit SD's so that is the standard that I aim for. That is with 195 Bergers.

I am much more comfortable using lead core, Berger Hybrids in particular, but my barrel is an 8 twist and I'm not sure if I could use the 300 OTM's or not. I guess I need to get my hands on a couple and see what type of results I get and go from there. Are solids typically that finicky?

There’s a reason BR and f class still use cup core out to 1k. Consistency trumps BC at 1k and in.

1500+ and the bc starts to really matter …if actually shooting a cartridge made for it..not lobbing 6.5 CM at barn sized steel lol

ReturnFire · Dec 11, 2024

Taylorbok said:
I'm not sure what causes it exactly but those really sleek bullet designs seem to be super picky about who they work for.
The CE Lazers seem to work well for everyone I've ever talked to.

There is a good chance your barrel is still settling in so if those bullet's shoot well I wouldn't stress about es/sd until about 150 rounds.

I’ve got some 300gr Bergers inbound so I’ll be hitting the range next week to see what kind of numbers I’m able to get with them and report back.

On a side note, is there not a 33XC load data thread within the Reloading Depot?

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