custom 338 bolt closing hard question

[rockwind1]

so i have a rather nice custom 338 ai rifle. it basically shoots 338 lapua ammo and then fireforms the brass. (i lost interest in reloading so i just am using new 338 ammo)
i ran into a unusual problem today,, i tried 4 different types of 338 lapua ammo, first i tried some brand new ammo (factory norma brass with berger 300 gr otm) that was done by a cottage outfit that is since gone under, southwest ammo from phoenix area. the bolt was hard to close but it closes.
2nd the second ammo was factory norma 338 300 gr HPBT, the bolt closes nice and easy like normal (shot well)
3rd was HSM 338 lapua mag 300 gr HPBT(unknown brass, just headstamped HSM), closing bolt was like using a no-go guage, would not close, i didn't try to force it
4th ammo-- custom ammo from dallas reloads, lapua brass, 300 gr otm, bolt closes nice. (this ammo shot great with an ES-14 and SD-10) although the mv was kind of low at 2714 fps

what is weird is it is all the brass is new factory 338 lapua of some brand

2 questions:
the Norma ammo just has a generic 300 gr HPBT bullet listed, best way to figure out actual bullet so i can look it up in a bullet library for my kestrel?
2-the southwest ammo closes hard but it closes, obviously, the headspace is pretty tight, since the ammo fireforms anyway, is it considered unsafe to fire the ammo? the action is designed to handle significantly more pressure than a factory 338 lapua. the reason i want to know is 338 ammo is expensive and i have a bit of this southwest stuff. it shoots ok, obviously the guy who ran Southwest Ammo wasn't a genius or a great craftsman since the mv is all over the place

 

[C.E.Smith043]

Imo, if it closes, shoot it. The problem is will it open. If it opens fine then you should be good to go. My guess is that bullet is a Sierra Matchking.

Make sure and grease ur locking lugs

 

[fkimble@charter.net]

Headspace isn't the only thing your description fits! If the bullet is seated to long for your chamber, it would act the same way. Try seating one of the no go rounds then take a close look at the bullet for a ring or marks at the beginning of the full diameter. If that is the problem then whip out your seating die and seat the bullets just a hair deeper. Different bullets of the same weight but differen brand can have different nose tapers so same OAL will have different max seating.

Frank

 

[wwbrown]

AI chambers, if set up as originally specc'ed will provide a slight crush to the shoulder of non-improved brass. So maybe the bolt is difficult to close is due to the slight crush fit.

One test is to blacken the brass with a Sharpie and then load and close the bolt without firing. Remove the unfired brass and examine where the Sharpie has been "smeared" this is where the interference was.

 

[rockwind1]

Headspace isn't the only thing your description fits! If the bullet is seated to long for your chamber, it would act the same way. Try seating one of the no go rounds then take a close look at the bullet for a ring or marks at the beginning of the full diameter. If that is the problem then whip out your seating die and seat the bullets just a hair deeper. Different bullets of the same weight but differen brand can have different nose tapers so same OAL will have different max seating.

Frank

i did some checking,,,it actually appears that the neck has not been trimmed on the HSM, i am not sure what brass they used but it would appear to be out of spec. ironically, the COAL of the norma factory cartridge is noticably longer than the factory hsm however, despite the COAL of the HSM being much shorter, the neck on the HSM is maybe 3/32's longer. the shoulders appear equal,, i will probably dig out the stuff and measure them but it is now pretty clear it is the neck is just way too long in the HSM

 

[C.E.Smith043]

i did some checking,,,it actually appears that the neck has not been trimmed on the HSM, i am not sure what brass they used but it would appear to be out of spec. ironically, the COAL of the norma factory cartridge is noticably longer than the factory hsm however, despite the COAL of the HSM being much shorter, the neck on the HSM is maybe 3/32's longer. the shoulders appear equal,, i will probably dig out the stuff and measure them but it is now pretty clear it is the neck is just way too long in the HSM

That's surprising. Personally I would contact HSM and discuss this with them. Maybe they will make good on it.

 

[searcher]

Given that your rifle is a custom job, and the HSM shoulders are shorter - and necks longer - and can't close the bolt does indicate, as you mention, that the brass OAL may be too long for your chamber. It may be there is nothing wrong with the HSM ammo per se, it just might be that your chamber was cut in a manner that doesn't allow the brass to fully chamber without jamming the end of the neck.

While you didn't like the 2,714 fps velocity of the ammo that shot well in your rifle, that isn't that slow for the 300 grain bullet. Consider that Lapua ammo with a 300 grain Scenar is published at 2,690 fps. While there may be others selling "custom" ammo with higher velocity, they didn't have the benefit of working it up in YOUR rifle - so I'd be careful. I'd just pick one of the brands that did shoot well and chambered properly - or look for others. I don't think it is a matter of the ammo being out of spec so much as your rifle being out of spec for that ammo. If it were a factory gun, my thoughts would differ....