338 LM improved reamer design

[carlsbad]

I'm looking to order a reamer for shooting 338 AI and I would like some advice. I'm looking to shoot long distance single shot mostly. So I'm not concerned about magazine length. Nominally I'm looking at 300 bergers but am not married to the bullet. but I'm using it to calculate freebore.

With the bullet seated just in front of the shoulder area (aka the donut area) I calculate a COAL of 3.962.

I wonder if I can actually use all of the case capacity created by seating the bullet so far forward. Will pressure be controlling and there is no reason to seat that far forward?

I have a friend who just built one of these using the bore rider reamer developed by Kiff. His throat is longer. An advantage of this bore rider is that it will seat the shell against the bolt making fire forming easy.

I think it would also support mag feeding if desired with a shorter round (.200" shorter to fit in a mag.

Any thoughts on the best design for a 338 LM Improved, starting with a clean sheet of paper? Thoughts on the bore rider?

thanks,
Jerry

 

[LA50SHOOTER]

I'm looking to order a reamer for shooting 338 AI and I would like some advice. I'm looking to shoot long distance single shot mostly. So I'm not concerned about magazine length. Nominally I'm looking at 300 bergers but am not married to the bullet. but I'm using it to calculate freebore.

With the bullet seated just in front of the shoulder area (aka the donut area) I calculate a COAL of 3.962.

I wonder if I can actually use all of the case capacity created by seating the bullet so far forward. Will pressure be controlling and there is no reason to seat that far forward?

I have a friend who just built one of these using the bore rider reamer developed by Kiff. His throat is longer. An advantage of this bore rider is that it will seat the shell against the bolt making fire forming easy.

I think it would also support mag feeding if desired with a shorter round (.200" shorter to fit in a mag.

Any thoughts on the best design for a 338 LM Improved, starting with a clean sheet of paper? Thoughts on the bore rider?

thanks,
Jerry

Jerry, The A.I. Version that I'm using has a OAL of 3.975 using the 300 gr. Berger Hybrid.
What I did when I developed the version I'm running is seat the bullet to the length you desire in a "regular" .338 Lapua piece of brass, then send it to the reamer maker of your choice. - I used JGS for mine & I'm running a neck-turn version where Lapua & Norma Brass just "clean up" and I'm running approx. .0036 neck clearance total. (0018 per side) - I used Alliant RE-33 to fire-form and with my newly formed brass. 102 gr. in the Improved version yielded 2975 fps & a very mild, but accurate load in Lapua brass.
- I don't know much about the bore-rider design your speaking of by Kiff.
There are a bunch of very good designs already on the "books" by both PTG & JGS so you should have good support from either maker.

Good Luck, Good Shooting & Merry Christmas !!

 

[dkhunt14]

Mine is 3.985 OAL with a 300 Elite. I run 2993 with 103 grains of RE33. It is easy on brass and very accurate at 1000 yards. Matt

 

[carlsbad]

LA and DK,

OK you've confirmed my OAL calculations. Are you both running a 40 degree shoulder? Do either of you have a reamer print? thanks.

 

[dkhunt14]

I don't have a print but it is 40 degrees. It is also a skim so the neck is under Sammi. The reamer was a PTG. Matt

 

[LA50SHOOTER]

LA and DK,

OK you've confirmed my OAL calculations. Are you both running a 40 degree shoulder? Do either of you have a reamer print? thanks.

Yes, 40 degree shoulder, & a "true" Ackley Imp. design in that the datum of the shoulder is -.004 under SAAMI / CIP design spec's so that regular (Non-fire-formed & new) brass has "feel" when the bolt closes on a round. (This eliminates head-space troubles when fire-forming new brass).

P.M. me and send me an E-mail address & I will E-mail you an electronic file of my reamer drawing.

Ron

 

[BountyHunter]

Talk to Dave Kidd at PTG and ask about the "speedy" version print. I built two on that reamer.

 

[Alex Wheeler]

The bore rider was very underwhelming in the 6mm. Didnt help, but didnt hurt. I hear better reports on the 338s, but they come with shorter barrel life. I have bore rider throating reamers if you want to experiment. There are better ways to get increased velocity IMO. I expect to see 3000 fps in 30" with the ones I'll be building for the 2k match we plan to shoot.

 

[LA50SHOOTER]

2973 fps was obtained in a 29" Bartlein 5R 9.3 twist in a Savage Model 112 that was re-barreled & chambered to the 40 degree A.I. version with the 300 gr. Berger Hybrid and 104 gr. of RE-33. Bullet at .008 off the lands. Lapua Brass being used & a Fed 215M primer.

 

[284winner]

2973 fps was obtained in a 29" Bartlein 5R 9.3 twist in a Savage Model 112 that was re-barreled & chambered to the 40 degree A.I. version with the 300 gr. Berger Hybrid and 104 gr. of RE-33. Bullet at .008 off the lands. Lapua Brass being used & a Fed 215M primer.

What is your freebore measurement ?

 

[LA50SHOOTER]

What is your freebore measurement ?

0.260 (dimensions T & V shown on JGS drawing) - This put the lower bearing surface of the 300 gr. Berger just above the neck / shoulder junction. - If my memory serves me correctly OAL (case head to bullet tip) is 3.975 or there-abouts with the 300 gr. Berger Hybrid OTM.

-Ron-

 

[284winner]

0.260 (dimensions T & V shown on JGS drawing) - This put the lower bearing surface of the 300 gr. Berger just above the neck / shoulder junction. - If my memory serves me correctly OAL (case head to bullet tip) is 3.975 or there-abouts with the 300 gr. Berger Hybrid OTM.

-Ron-

Any idea how that spec works for the 300 SMKs ? I'd think you may need more freebore.

 

[carlsbad]

284 winner,
What drives you to more freebore? The .260" FB allows you to seat the 300 berger in the neck only. This is about .200 longer than rounds designed for Magazine feed, which are seated very, very deep into the cartridge.

So if you want to achieve the same for the Sierra, you may need a bit more freebore. I have the same reamer on order, plan to shoot it single shot, but haven't done the math for Sierra. My calculations actually came out .280 for Berger but I went with the proven FB. I can always lengthen it.

Jerry

 

[284winner]

284 winner,
What drives you to more freebore? The .260" FB allows you to seat the 300 berger in the neck only. This is about .200 longer than rounds designed for Magazine feed, which are seated very, very deep into the cartridge.

So if you want to achieve the same for the Sierra, you may need a bit more freebore. I have the same reamer on order, plan to shoot it single shot, but haven't done the math for Sierra. My calculations actually came out .280 for Berger but I went with the proven FB. I can always lengthen it.

Jerry

Just want enough to load both the 300s of Bergers and Sierra's. You are correct. I may go with a .200 freebore and finish with a uni throater for the exact dimension needed. CIP mags will carry 3.9 loaded rounds so if needed, I'll load to the length I want.

 

[carlsbad]

I don't think CIP will carry 3.9...they are 3.850 outside. Inside you're looking at less than 3.8--probably 3.775. I'm ordering a single shot action.

--Jerry

 

[LA50SHOOTER]

Any idea how that spec works for the 300 SMKs ? I'd think you may need more freebore.

You’ll need to add approx 0.100 to that to get the 300 gr. SMK and other 300 gr. (Nozler CC & Lapland Scenario) to where the bottom of the bearing surface of these bullets are above the neck / shoulder junction. - If you have a .338 caliber comparator insert you can calculate the exact for each.
My recommendation is to throat for. the 300 gr. Berger and run the others where they are seated with the lower bearing surface is below the neck shoulder junction. They still shoot pretty darn good that way. Also, keep in mind that your throat will normally grow in length for 10 to 20 thousands in the first 100 rounds and then settle out and the growth rate should slow down. If you treat your barrel good.

 

[284winner]

You’ll need to add approx 0.100 to that to get the 300 gr. SMK and other 300 gr. (Nobler CC & Lapland Scenario) to where the bottom of the bearing surface of these bullets are above the neck / shoulder junction. - If you have a .338 caliber comparator insert you can calculate the exact for each.
My recommendation is to throat for. the 300 gr. Berger and run the others where they are seated with the lower bearing surface is below the neck shoulder junction. They still shoot pretty darn good that way. Also, keep in mind that your throat will normally grow in length for 10 to 20 thousands in the first 100 rounds and then settle out and the growth rate should slow down. If you treat your barrel good.

You’ll need to add approx 0.100 to that to get the 300 gr. SMK and other 300 gr. (Nobler CC & Lapland Scenario) to where the bottom of the bearing surface of these bullets are above the neck / shoulder junction. - If you have a .338 caliber comparator insert you can calculate the exact for each.
My recommendation is to throat for. the 300 gr. Berger and run the others where they are seated with the lower bearing surface is below the neck shoulder junction. They still shoot pretty darn good that way. Also, keep in mind that your throat will normally grow in length for 10 to 20 thousands in the first 100 rounds and then settle out and the growth rate should slow down. If you treat your barrel good.

Sounds good. Appreciate the input.

 

[284winner]

I don't think CIP will carry 3.9...they are 3.850 outside. Inside you're looking at less than 3.8--probably 3.775. I'm ordering a single shot action.

--Jerry

I can't confirm that statement I made about the CIP OAL but was told that they will load 3.875 OAL rounds. This was given to me by several owners of that platform using seekins bottom metal and mags.

 

[284winner]

Just want enough to load both the 300s of Bergers and Sierra's. You are correct. I may go with a .200 freebore and finish with a uni throater for the exact dimension needed. CIP mags will carry 3.9 loaded rounds so if needed, I'll load to the length I want.

Wound up with a .270 FB. We'll see how it works real soon

 

[carlsbad]

I ended up going to 33xc. I ordered a bat HB SS action. Haven't chambered it up yet.