7mm X .338 Lapua?

[drakehammer]

The break on the RUM is a Vais. I've had it on a couple of rifles, it works but improvements have been made in both recoil reduction, and noise in the last 25 years.

Please do expand on those improvements. I'm interested. Thanks
Jesse

 

[HARPERC]

.................I'm stoked..........

The 'chucks better be hoping for an early summer quiesence. First time I've had the chance to use that word since you taught it to me!

 

[HARPERC]

Please do expand on those improvements. I'm interested. Thanks
Jesse

The Defensive Edge I've started using "seems" more effective in recoil reduction, and the time or two I've failed proper hearing protection is not nearly as painful. The Vias has nearly caused me to drop the rifle, a test I don't recommend.

JE custom has some video's bringing some objectivity to the subject. His work with his Assassin break is very good, I can't come up with the titles but the search bar should help you find them.

Cold Boar Gunsmithing also has some video regarding their break on his Facebook page.

 

[desertcj]

How is this compared to a 7mm RUM? Seems like it would be pretty similar?

 

[IdahoCTD]

A 7-338 Lapua Imp is a lot more capacity then a 7RUM. I have the .30 version and I load 112grs of ball powder with a 230 Berger. It would be closer to a 378 Weatherby capacity wise.

 

[tt35]

A 7-338 Lapua Imp is a lot more capacity then a 7RUM. I have the .30 version and I load 112grs of ball powder with a 230 Berger. It would be closer to a 378 Weatherby capacity wise.

IdahoCTD may be correct but I was under the impression that the H2O capacity of the .338 RUM and the .338 Lapua were very close. This thread shows some case capacities: http://www.longrangehunting.com/forums/f19/lapua-vs-rum-case-capacity-92742/ If these are correct, the Lapua is about 2 grains higher in water capacity than the RUM. The improved Lapua case would obviously be bigger. My objective isn't to maximize velocity but to be able to use the more consistent and longer lasting Lapua brass. The only reason I might consider an improved design is to decrease case trimming but I'm not particularly hung up on using a bigger case.

 

[IdahoCTD]

A standard 338 Lapua case is between a 338RUM and a 338 Edge. A improved case is quite a bit more capacity. It's not as much as the 378 Weatherby case but it is close and velocities are comparable, mainly due to the toughness of the Lapua cases. A Norma improved is almost identical to a RUM for capacity but .350" shorter. I have a 7-338 Norma Imp. reamer I just got Monday and have a 7-338 Lapua Imp on order for a customer. I have both of the same cases in .30 caliber.

 

[Swamplord]

Here are some interesting numbers....... for reference only, obviously as some "Improved" wildcat versions may be different from others..... all the case capacities were generated by Quick Design, except for the 7mm LRH which was confirmed with fired cases......

7mm Slayer (7mm/500Jeffery).................................. 141.0 gr
7mm/338 Excalibur................................................. 138.0 gr
7mm/378 WBY....................................................... 130.0 gr
7mm Lazzeroni Firebird........................................... 126.1 gr
7mm/338 Lapua Imp............................................... 120.0 gr
7mm/338 Lapua..................................................... 113.0 gr
7mm RUM............................................................. 112.7 gr
7mm Long Range Hunter... confirmed capacity............... 108.5 gr
7mm/338 Norma Imp variants........................... 106 gr - 108.5 gr
7mm/338 Norma..................................................... 105.5 gr
7mm/300 Norma..................................................... 103.4 gr
28 Nosler Imp 40 *.... my design................................ 102.4 gr
7mm STW................................................................ 100.2 gr
7mm 375 Ruger....................................................... 100.0 gr
28 Nosler.................................................................. 99.6 gr
7mm/8mmX68 S Imp................................................. 99.4 gr
7mm/300 WBY.......................................................... 99.3 gr
7mm Dakota............................................................. 93.5 gr
7mm/300 Win Mag..................................................... 92.4 gr
7mm WBY................................................................. 87.6 gr
7mm Rem Mag.......................................................... 87.0 gr
7mm WSM................................................................ 79.5 gr
7mm SAUM............................................................... 76.1 gr




here is my shameless plug pic .......... fire at will.....

 

[tt35]

Thanks, CTD and Swamplord. Good info and helps confirm for me that I'll stick with the 7X.338L. That's plenty! Gotta get some bullets coming. gun)

 

[IdahoCTD]

I know the 7RUM and 7-338 Lapua are off. Going off memory a Edge is 115-116grs and a 338 Lapua is 113-114. Necking them both down won't change that relationship. I think my 30-338 Lapua Imp is more like 123-124grs but I won't be home until tomorrow to confirm that. Also wasn't the capacity of the 28 Nosler measured at 102-103grs in the thread about it? I would bet the 7-8x68 Imp is off too. A 6.5x68S is only 86grs (I've measure it in RWS brass because I intend to make a 6.5x68 Imp and have the brass for it). Necking it up adds about 1 grain and even though it's got a 14.5 degree shoulder and a bunch of taper your not going to gain 12grs of capacity improving it. A 7STW is .200" longer and only .010" skinnier with a pretty modern case design and thinner brass. You have to have a much fatter case like a 28 Nosler to make up for the .200+" case length difference.

I do know that my 30-338 Lapua Imp with a 33" barrel shoots 230's at 3350fps and my 30-338 Norma Imp with a 30" barrel is tapped out just over 3100fps. I do have a 30-378 Imp. with a 30" barrel and it will shoot 150's over 4000fps. I'm not home so I don't have the data for the 210's but it seems like it was 3400+fps with 210's. It has a significant increase in capacity over a standard 30-378 though. I've loaded nearly 130grs of WC872 with 150's.

Anymore I build calibers based on good brass too. If there isn't really good brass available it's not worth the effort to me. I like improved cases to limit the amount I have to trim brass and minimize case stretch which can result in case head separation. In the case of my 7-338 Norma Imp, it's nice having about 7RUM capacity with a 2.5" long case instead of a 2.85". That allows it to work through magazines much easier. With 423 Dakota brass it's just as good as 338 Lapua brass so you don't need the additional .220" of case length to get roughly the same capacity you would with a standard 7-338 Lapua. Good RWS brass and the lack of a belt is the reason I'll do the 6.5x68 Imp too.

 

[tt35]

In you guys' opinions, if absolute maximum velocity is not an issue, how necessary is a 28" tube going to be in the 7X.338L? I would certainly prefer a 26" if I could get away with it. Can I switch powder to something slightly faster and run 26" without creating a fire breathing dragon?

 

[tt35]

CTD: Are those numbers to the neck/shoulder junction or a full case?

 

[IdahoCTD]

Those are a full case of water the same as the data Swamplord gave. The neck length on most cases now days are really similar in length so they tend to maintain roughly the same same capacity relationship to the base of the neck.

 

[Rogue Hunter]

Tim,
Do I smell a 2k shot at a rock chuck in the making????

-Mike