Should My Chamber be Bullet-Specific?

[alcesgigas]

I've ordered a 32" heavy barrel in 338 with a 1:9.5 to 1:8 gain twist. My intention is to shoot monolithics--particularly CE 300 MTH--with best effect. My current barrel's chamber case length is 2.755 and I'm shooting 300 Berger OTMs' that finish up at 3.855 at .012 off the lands. Would I be better off chambering this barrel long to best accommodate the CE MTH which needs to seat 1.428 out? I'm figuring the base to rifling engagement should be 4.195 for a .012 offset. Also would this have a negative effect on jacketed bullets such as the Berger 300 OTM?

 

[shortgrass]

!???????! Will you be doing this chambering work yourself? "Chambering it long" will create excessive headspace.

 

[tankgijohn72]

May want to recheck your math. You found the Cartridge overall length with Cutting edge's recommended 1.428" protrusion from the case. This will not be the bolt face to rifling measurement. If you have a reamer to elongate the throat, you will need the measurement from base to intersection of the ogive and bearing surface. You will need this measurement from a cartridge loaded (with the CE bullet) to 4.183 COAL. Cutting edge may help you out if you call them and ask for the measurement of the rotating band to the end of the bearing surface. As for the effects of your new chamber on the 300 gr bergers. Depends. The bergers may like it, or it may not.

 

[Deleted member 46119]

I've ordered a 32" heavy barrel in 338 with a 1:9.5 to 1:8 gain twist. My intention is to shoot monolithics--particularly CE 300 MTH--with best effect. My current barrel's chamber case length is 2.755 and I'm shooting 300 Berger OTMs' that finish up at 3.855 at .012 off the lands. Would I be better off chambering this barrel long to best accommodate the CE MTH which needs to seat 1.428 out? I'm figuring the base to rifling engagement should be 4.195 for a .012 offset. Also would this have a negative effect on jacketed bullets such as the Berger 300 OTM?

You need a COAL gauge Hornady Lock-N-Load Overall Length Ga Bolt Action and a modified case Hornady Lock-N-Load Overall Length Ga Modified Case 338 Lapua

Follow the directions: determine the maximum COALfir the CEB 300 MTH to touching the lands.

If the CEB 300 MTH does not seat longer than the driving band, you may consider having your throat extended. However, CEB says you can seat the driving band into the neck.

If you have all these tools, then please: what is the maximum COAL using the CEB 300 MTH?

 

[alcesgigas]

Thanks fellas. I want to duplicate my present chambering so as to allow for all the current tools gathered as used in my current barrel appropriate to the new barrel. Just thinking if my brass chamber length is 2.755 and I were to use the CE MTH at its recommended seat depth (with the band resting on the case edge) 1.428 the bolt face to the lands should be 4.183. Thank you for pointing out that surely would have been a problem because the lands should begin within, say, .010 to .020 of the bearing surface of the bullet--which is far less than in this case--of 4.183.

I would be that guy who said "shoots good" in that the rifle didn't blow up in his face were I to do this work! It was after midnight here when I penned the opening of this post; Dan might have got upset had I called... Most definitely will call him this AM. Now remembering I have kept an email conversation with him--I should have done that. However, it's always good to have many views from those with experience as found on this site. Sincere thanks...