Power marks down the side of case

[Lightheart]

Hi All,
New here.

Issue:
Getting powder stains on side of few cases, to the base.
Shots impact 3" to 4" low from group.

New 6 BR/ T/C 15" bull custom mfg./ 270" neck/ Lapua brass/ 28.4 gn. Varget/ Sierra 70 gn. MK/ SD .002"off lands.

Have annealed the brass.

Loaded round in the 'Chamber Gauge' shows a .0015" gap between the case shoulder and the gauge shoulder?????
Should the 'loaded' case shoulder be in contact with the gauge shoulder?
Unloaded cases shoulders do touch the gauge shoulder.

Thanks for your help.

 

[BoydAllen]

Generally, what you are seeing is an indication of low pressure. The question then becomes why those particular rounds have the problem. Perhaps it is something related to marginal ignition. Could your hammer spring be a bit weak, or your primers too hard? As to your loaded rounds' shoulders not touching the gauge, I would think that it is because your bullets are seated slightly into the rifling. After all, the only thing that is different about the loaded round is that it has a bullet. Try this. Seat a bullet .010 deeper and re-gauge. One more thing...are you throwing or weighing charges?

 

[spclark]

How did you determine that charge of Varget?

I suspect your problem lies with insufficient pressure at lift-off that's failing to seal the necks to the chamber wall.

6BR in longer barrels on rifles use 30 grains of Varget behind a 105 - 107 grain bullet as kind of a standard by which others are judged. With a lighter bullet and shorter barrel, but still using Varget (may be a tad slow for your pistol) those cases may need seriously thinned necks to work as they would in a rifle.

Among the Hodgdon products, in order of increasing burn rate are BL-C(2) (ball), H4895 (extruded), H335 (ball), Benchmark, H332 (extruded), H4198 (extruded). Vihta Vouri's line includes N135, N133, N130 (N140's roughly equals Varget); Winchester 748 is a little faster than Varget too.

Depends on what's available to you, but I think that's where you'll find a cure.

 

[jonbearman]

I personally would go with h322 or something like it or possibly faster due to such a short barrel. Alot of fellas seem to think varget is the magic powder. Well it isnt. It does work in the right condition but some of the tried and true older powders will do a fine job. Are you full length sizing or neck sizing only after fireforming? I personally think a try with h322 will do you right.You may need to try different primers too. Like br-2's(cci) or even wolf primers(magnum). Give it a try and let us know. Encores dont usually have ignition problems(mechanical). It will be a bit hard to jam the bullet with a break action. I also would call TC'S tech line and ask what they think would be a good load for your pistol and call sierra as well,they are wonderful to get usable advice about powder/bullet combinations.

 

[ridgeway]

My 16" XP in 6BR loves IMR8208

 

[Minesweeper3433]

Definetly sounds like low presure. I get a bunch of that with low recoil loads for my 6.5 sweds. Turns the bolts black with soot on long days at the range. I figure as long as the bullet leaves the barrel I'm good.

 

[spclark]

I was gonna suggest IMR 8208XBR too, I'm shooting it this year in four different cartridges from .223 thru .308 even with heavy bullets. Works great & burns clean. It's new though & not on any burn rate charts I have access too. When it first came out word was it was created to compete with N133 so assumed to be faster than Varget & unsuitable for cartridges that would use that or similar propellants. First testing I did was in 6XC with Berger 105VLD's & at 1,000 yards it's the best I've found.

Appears its burn rate can vary somewhat depending on what cartridge + bullet combination is in use. Had I a similarly equipped T/C I'd try it over the other products I suggested earlier, if only because it works so well for me already in other cartridges.

In any event, use due caution working up loads with propellants and bullets you can't find recommended loads for. T/C's are robust enough actions (I have two Contenders myself) but pressures normally associated with bolt rifle actions probably aren't where you want to go....

 

[Lightheart]

This is my first time asking for help on this forum.
May I extend my hearty thanks for the quick responses &suggestions. You guys are really awsome.

From the behavior of my results I am in agreement on the 'low pressure' consensus. Thanks.

BoydAllen:
With this happening on ‘second and ‘third’ fired brass ‘low pressure’ is the best call, as it makes total sense.
My charges are always carefully weighed.
My reduced powder loads were and attempt to reduce recoil more to the feel of my 6TCU. Just had the inletting done on a beautiful piece Cocobolo that is on the heavy side.....should reduce the recoil somewhat. Maybe a brake is worth looking into.

On hand, I have 3-4 lbs each of Benchmark, IMR 4198 & Varget.
Benchmark is very close to H322 charts and it has produced 5 shot groups in the hi 3’s with Rem 71/2 even with the current problems.

Looking forward to testing the IMR8208XBR. Any suggestions on a starting load for 70gn to 85gn bullets?

Again, many thanks, to all, for the assist.

 

[spclark]

Check out Hodgdon's Reloading Data Center: for rifles they show IMR 8208 XBR in 6BR Rem with 70 gr. Nosler BT starting at 29.5 grains (37,100 CUP, 3045 fps) up to 32.7 grains (51,600 CUP, 3361 fps), 85 gr. Speer soft-point from 27.0 grains (41,400 CUP, 2782 fps) to 29.8 grains (49,900 CUP, 3016 fps).

They also have a separate section for pistol data, which (curiously) doesn't include data for 8208XBR.

Also shown are Varget, BL-C(2), H335, H4895, Benchmark & H322 for use with 70 to 85 grain bullets. Add H4198 to the list for the lighter bullets from 55 to 65 grains:

http://data.hodgdon.com/main_menu.asp

The powder burn rate chart I consult most frequently:

http://gsgroup.co.za/burnrates.html

As always, these loads are suggested as guidelines so you need to be cautious when working up loads on your own since your firearm has a significantly shorter barrel (expect less velocity) and it's a pistol so no benefit from more up-front weight and longer radius from grip to muzzle to reduce recoil.

You probably ought to avoid loading to pressures that are suggested for rifles; I'd give the folks at Thompson / Center a call on this, they known what conditions their products can be safely operated under:

http://www.tcarms.com/customerService/contact.php

A buddy of mine who shoots Palma with me tried 8208XBR a couple of weeks ago commented it "barks" less than Varget in the same rifle. He did make the mistake of using some Murom (Russian) KVB-223 primers in his Lapua Palma brass & had a couple that pierced, which is to be expected as those primers have fairly thin cups. The best primer I've found is the Wolf / Tula KVB-223M small rifle which has a standard charge but thicker, magnum cups. BR-4's work just as well.