Load development - what would you do??

[del2les]

Was your barrel beginning to foul? Maybe try cleaning it after the 20 rounds and see if that helps.

 

[jshepherd61]

Here's the story:

I started load development with a 245 Berger in a 300 Norma Improved (35º shoulder). This rifle is built on a BAT HR with a 27", 1:8 twist Rock Creek barrel. Shot a pressure ladder with RL33 and the round barely seated to fit in a CIP length Lapua magazine (I believe cartridge OAL is around 3.710" or so). This puts the boattail barely above the neck-shoulder junction and the bullet .025" off the lands in this chamber. Anyway, I ran it up to 94.8 grains of RL33, carefully watching for pressure signs and had none. I then shot a ladder at 700 yards and found two nodes - one from 90.8 to 92 grains, and the other from 94-94.8.

To test both nodes, I loaded up rounds in the middle of both nodes and shot for groups at 185 yards. The loads with 91.5 grains averaged around an inch to slightly over an inch (mostly horizontal dispersion), but the loads at 94.4 shot bugholes. Seeing this, I decided to pursue the 94.4 grain load and took it out to confirm zero and get velocities.

This load averaged 2999 fps over a Magnetospeed with an SD of 8.7 (good enough for me). I removed the Magnetospeed from the end of the barrel and went to finalize a zero, which is when the issue occurred. After not seeing any pressure signs at all with about 20 of these loads thru my gun, I got very faint ejector marks (only visible in bright sunlight) and the slightest hint of stiff bolt lift. Considering this is Lapua brass, the fact that there are ejector marks makes me think this load is too hot to continue shooting.

I'm reluctant to give up a fast and extremely accurate load, but safety is #1 in my book and I don't want to cause damage to my gun and especially to anyone that might be shooting it. So, where should I go from here? Should I try to tighten up the horizontal in the low node and play with that a bit? I'm thinking simply dropping down to 94 or 94.1 grains to try to run the high node wouldn't make that big of a difference in pressure.

Or, maybe I should send the gun to Shawn Carlock to have him work his +P magic on it and hit that node without any worries...

Work backwards 0.1 grain at a time until the bolt scars remove themselves, sounds like you are right there just slight tweak if you like the velocity

 

[nodakhunter]

Is this virgin or fire formed brass?

1x fire formed. After firing the cases the 2nd time, it didn't appear that the shoulder was any sharper, but I suppose it wasn't visible to my eyes and I'd need to measure h2o capacity. I'll drop the load down to that 91gr node and see what happens out of caution. Maybe tweak seating depths

 

[nodakhunter]

Was your barrel beginning to foul? Maybe try cleaning it after the 20 rounds and see if that helps.

Barrel was a little fouled, that RL33 is dirrrrrty compared to some other powders I've used (H1000, H4831, etc). Would it be possible for a carbon ring to build up that quickly?

 

[del2les]

Barrel was a little fouled, that RL33 is dirrrrrty compared to some other powders I've used (H1000, H4831, etc). Would it be possible for a carbon ring to build up that quickly?

Doesn't have to be a carbon ring, for powder and copper fouling can increase pressures. Especially in a new barrel that is just beginning breakin.

 

[Wy Will]

Sounds like you should try cleaning and then test again.

 

[vancewalker007]

Seems like you are right near your pressure max. You are using a temp sensitive powder so if the ambient temp goes up you could step over the line pretty easy. Then you're pounding the bolt open blah blah blah. I always like upper nodes so maybe dropping to 94 and try the same bullet seating again. It wouldn't hurt to try a set of seating depth groups in the lower node either. We used to use RL22 in our 7mm STWs years ago. In Phoenix temps can really vary. We found loads that worked great at 40-50 degree March days were way too hot in July, so we started keeping our loads on ice in the summer to stay in the pressure window. It worked

 

[Stammster]

That's really only a problem in straight walled cartridges with fast burning powder. In bottleneck rifle cartridges pressure increases as bullets approach the lands.

Wrong!

 

[Kmccord]

RL33 is pretty dirty, my experience in the 28N shows to need a good cleaning every 20 to 30 rounds and with a new barrel, my opinion, you probably need a good cleaning. Not sure if you have a borescope to check the barrel or throat for a carbon ring, if you do not have one, get a Teslong borescope that can be used on your phone or with your PC. It is a very good scope for about 50.00 on Amazon.

 

[Lefty7mmstw]

I've been running rl33 in my 300rums for years with a 225 hdy hpbt and a 215 in rem brass... I would run the lower charge and work with it a bit on seating depth/ possibly change primer also to see if a slight pressure curve change will help. Rl33 isn't that sensitive to temp. unless you are on the wall pressure wise... A switch from a 215 to a wlrm will sometimes change things for the better. I run a LOT of 215's but not all of my loads have settled on that primer as the best. I often forget to change primers though lately as the load comes in the first pass...
I also wouldn't worry too much about seating slightly below the shoulder/ neck juncture... Imo the doughnut isn't usually present (enough to cause issues anyway) unless you've had to mod your brass or turn it, and even then it isn't enough to be of bother if you turn the growth every sizing. I'm running a lot of my heavy's to mag. length which necessitates rather deep seating, and I'm getting very good groups anyway with little to no measurable doughnut.

 

[Lefty7mmstw]

RL33 is pretty dirty, my experience in the 28N shows to need a good cleaning every 20 to 30 rounds and with a new barrel, my opinion, you probably need a good cleaning. Not sure if you have a borescope to check the barrel or throat for a carbon ring, if you do not have one, get a Teslong borescope that can be used on your phone or with your PC. It is a very good scope for about 50.00 on Amazon.

I'm not really a fan of rl powders slower than rl25 in the 7'mms for this reason. I haven't really gotten my 7stw or 7rum to settle down well with either rl33 or rl50 and I think some of it is fouling. I'm running either rl25 or retumbo in my 7stw at present and h50bmg in my 7rum (short throat). The 30 cal. rifles I own treat the slower rl powders a good bit differently then the 7's. They (30's) don't seem to foul out even at a couple boxes through them between cleanings.

 

[Kmccord]

When I received my 28N in 2016, Retumbo and H1000 was like finding hen's teeth. I did use H1000, had some from a year before, but running 195gr Berger's was not all that well for Velocity, but plenty of RL33 around during that time.

 

[Lefty7mmstw]

When I received my 28N in 2016, Retumbo and H1000 was like finding hen's teeth. I did use H1000, had some from a year before, but running 195gr Berger's was not all that well for Velocity, but plenty of RL33 around during that time.

Yup... hear ya on availability. I'm pulling teeth getting more 200 eld-x 30 cal into the house at present without paying gb prices. I gave my pills away as I hadn't found a load, then was putzing with my Pops 300win and ran a few 200's pushing with v565 through my old browning. Cloverleaf at 100 at mag. length.. O.K., now where to find more pills to explore this option... I've got a back order in but I suspect it'll be a spell. Usually I'm sitting on hundreds of a certain pill but the screamer group comes up with a bullet I'm out of with a powder I only have a couple of # of.

 

[kfreeze]

Barrel was a little fouled, that RL33 is dirrrrrty compared to some other powders I've used (H1000, H4831, etc). Would it be possible for a carbon ring to build up that quickly?

Yes. The carbon ring can build quickly. The 28 nosler is the same way, and I clean my 28 every 30 rounds.