Custom Chamber Question

[SixFive]

I recently built a 30-06 on a Marlin MR-7 action which is basically A Winchester Mod 70 and used a custom unknown reamer I found in my box (No idea when or where I got it) that produced a .336 chamber neck diameter. I turned my brass so that once loaded with a bullet the neck measures .334 diameter and it chambers easily.

So my question is did I give it enough neck clearance at .002 ?

My final cartridge specs -
Loaded neck DIA .334
New Lapua Brass
165gr Federal Trophy Bonded Tip
H4350 Powder - Running an initial ladder from 56gr to 59gr in .5 increments checking for pressure
CCI 200 LR Primer
COAL Decided on: 3.225 Book spec is 3.220
(Fits Magazine with a little room to spare, mag will take up to 3.250.)

 

[old_heli_logger]

If your bullet is sticking in the lands, then your OAL is too long...back off until your bullet is no longer sticking. A little jump won't hurt.
Good luck!

 

[SixFive]

If your bullet is sticking in the lands, then your OAL is too long...back off until your bullet is no longer sticking. A little jump won't hurt.
Good luck!

Hogdon reloading shows OAL at 3.220 so I settled on 3.225 and am safely off the rifling now and the rounds fit nicely in the magazine.

 

[ShtrRdy]

I think the OP is wondering about neck diameter.

From a safety point of view 0.002" is fine. If this is a hunting rifle you might want to give it more clearance.

 

[SixFive]

I think the OP is wondering about neck diameter.

From a safety point of view 0.002" is fine. If this is a hunting rifle you might want to give it more clearance.

What do you recommend?

 

[rardoin]

I have .005” neck clearance on my 7 Sherman Short mag F class competition rifle. No need for a tight neck…especially on a hunting rifle.

 

[SixFive]

I have .005” neck clearance on my 7 Sherman Short mag F class competition rifle. No need for a tight neck…especially on a hunting rifle.

That is exactly the guidance I was looking for, THANKS!

 

[ShtrRdy]

What do you recommend?

I'd go with 0.004" total. That would be 0.002" on each side.

 

[SixFive]

30-06 Load Profile
RIFLE:Marlin MR-7
27”1:11 Douglas XX Barrel (.336 neck)
Scope:AthlonArgos HMR 4-20×50 AHMC SFP

Brass: Lapua
Full length Sized, neck turned, primer pocket trued, flash hole de-burred, case mouth chamfered in and outside, .306 neck mandrel used for .002neck tension.

Primer: GoldMedal 210, Large Rifle Match

Powder: Hogdon H4350

Bullet:165gr Trophy Bonded Tip Bullet
Part# PB308TT165

COAL:3.180

BESTLOAD: 55.5gr (.500 MOA)

NOTES:

Unfortunately the ONLY published load data for this bullet is by Federal and only Alliant powders are shown, Alliant is no longer selling powder, I took my best guess but I came out on the HOT side of the load. In retrospect this bullet loads more like the GMX bullet data.

March29, 2025
72Degree Day

57gr was over pressure, hard bolt lift, extractor mark, one blown primer
56gr was showing very mild signs of pressure

Seems like 55.5gr is the sweet node, I will try 54 to 55.5 on the next trip out and fine tune it. I am concerned even 55.5gr may be a little hot in warmer weather.

Also turned the neck to be .333 (instead of .334) with a seated bullet, this may reduce a little pressure also, I think I was tight. This should give me .007 clearance or .0035 per side.

Lab radar chronograph was once again not registering shots, I have not figured this POS out yet...

 

[SixFive]

Made it to the range Sunday and 55.5gr of H4350 is the load for sure! It was over 80 degrees and ZERO signs of pressure at this loading. The rifle was shooting in the 4s and with this hybrid copper\lead bonded hunting bullet that ain't bad!
My crono battery died so I have no idea what my speed is but not really worried about it, it is fast enough!
I am confident that if I were to move to a ELD or Berger I could easily get this rifle in the 3s but they are not rounds I like for hunting.

I did figure out my Lab Radar and had it working perfectly then the battery died after working my 28 Nosler loads, ugggg