New 30br 10 twist barrel. Can the faster twist raise pressures this much?

[joshb]

I wanted to try a faster twist 30br. I found a 1/2 price deal on a Lilja 10 twist and had it chambered with a .330 neck and put it on a Remington action.
I had brass from another of my 30br’s. I took 50 and resized them with a Harrell’s #2 die. They were a little longer to the shoulder, so I found “snug fit” and pushed them back 2 more thousandths. A loaded dummy measured .328 neck. I like 4 thousandths clearance but I’ve read some guys like 2 so I ran with it. I loaded Sierra 125s at touching the lands with H4198. I started at 32.1 grains, then up by .3 grains to 34.5. Off to the range
The first shot with 32.1 required a hard pull to open the bolt. Huh? The second shot required some pounding with my palm. I packed up the gun.
Today, I pulled the loads apart, turned the necks for 4 thousandths clearance, annealed them and resized them with a Harrell’s 2.5 die. I reloaded them with H4198, but started at 31.2 and went up to 33.9, hoping the changes in the brass would solve the problem.
Then I sat and started thinking. Was the problem the brass? How much would the faster twist affect pressures?
Should I start at a lower charge rate?
Thoughts?

 

[nakneker]

Tagging in

 

[mgunderson]

Drop the charge the twist is not a big factor. I haven't been able to get my hands on 4198. Can't tell you what that influence is.

 

[joshb]

A loaded dummy measured .298 neck. I like 4 thousandths clearance.

Was this a "fat finger" ? A seated dummy should read @ .326 to give you .004 clearance with a .330 chamber neck.

Sorry Bill. Brain fart. My wife was talking to me while I was typing…. Fixed it!
By the buy, I cerrosafed the chamber to be sure it’s .330.

 

[Bill Norris]

Sorry Bill. Brain fart. My wife was talking to me while I was typing…. Fixed it!
By the buy, I cerrosafed the chamber to be sure it’s .330.

Yea I figured it was a mistake. No worries at all.

 

[Dusty Stevens]

For the typical loads you see in a 30br they aint in a 10tw. I figure youll lose 2+gr of powder using that fast of a twist

 

[SKWERLZ]

There’s a paper by a guy named Jim boatright( I think that’s his name) and he calculated difference in pressure from twist and it was really small,
almost negligible.

 

[joshb]

Yea I figured it was a mistake. No worries at all.

But..no theories from you vast 30br experiences?

For the typical loads you see in a 30br they aint in a 10tw. I figure youll lose 2+gr of powder using that fast of a twist

Ok. I’m starting to think I may have to drop my starting charge lower. It’s a brand new barrel but still……locking up with 32.1 makes me think it might be more. The cartridge guide had 34.5 for the 125, albeit for a different bullet with moly.

 

[Bill Norris]

But..no theories from your vast 30br experiences?

It does sound like it is too hot no doubt. I think Dusty is correct with the tighter twist. And, again those loads listed above are probably all with 1 -17 and 1 - 18 twist barrels and those boys load on the warm side I'm sure.

On the other hand, your barrel may simply not want that much powder.

I would not load past 34.2 gr. of H-4198 for neither of my barrels with your 125 gr. bullet even with coating because of the bearing surface length. I feel better at 34.0 gr. for both of them.

 

[dellet]

Knowing Lilja offers a .299” bore, it might be worth a look.

 

[Jager]

Most the guys running .30 BR are running lighter, 112 - 118 gr., bullets. I've heard of guys running the 125 gr. Sierra's to fireform brass, but always with a notably lighter load.

For comparison, QL has your 32.1/H4198 behind a Berger 115 gr., with a COAL of 2.300, as quite mild... just under 2800 fps and a bit under 50k psi. Fill ratio of 98.6%.

Substituting a Sierra 125 gr (#2121) makes for a highly compressed load and jumps pressures to over 70k psi.

All that's assuming a 40.25 gr. case capacity (Lapua).

I'd load up three rounds with a 112-118 gr. match bullet and see what you get.

 

[gunsandgunsmithing]

Tried new brass?

 

[joshb]

Thanks Jager. That Quickload info is interesting. I have some 115 customs. Can’t remember who’s right now but I’ll try some of them. I’ll also drop lower for the Sierras and see what happens.

 

[KMart]

My 2 cents. I would try Mike's suggestion of new brass. Also take a look at the primary extraction you have on the Remington action

 

[Carl S]

i would start with new brass as Mike suggested.has the brass got any chamber related marks on it.are the primers showing signs of pressure.the bore may be on the tight side.you could run them over the chronograph just to see what f.p.s your getting.

 

[M-61]

I wanted to try a faster twist 30br. I found a 1/2 price deal on a Lilja 10 twist and had it chambered with a .330 neck and put it on a Remington action.

What is the number of lands or grooves in that Lija barrel?
I’ve spent too much time on a 6.5BR with 3 grooves 8 twist.
Close to calling it quits with it.

 

[LVLAaron]

I have a 1:10 I want to turn into a 30br... but I want to throat it out for 200+ g bullets and make a really complicated "blackout" type thing.

 

[joshb]

I have a 1:10 I want to turn into a 30br... but I want to throat it out for 200+ g bullets and make a really complicated "blackout" type thing.

I found this info:

 

[knguyen]

Thanks Jager. That Quickload info is interesting. I have some 115 customs. Can’t remember who’s right now but I’ll try some of them. I’ll also drop lower for the Sierras and see what happens.

Joshb: you bought those from me, they were made bybmy renown Mentor Ted Larsonn, 0.925 jackets, those bullets were made with high level of love and TLC