Pressure issue and not looking good

[338winmag]

Okay initial results from range after gunsmith work.
The work performed was making concentric the chamber where "magnum bulge" can occur right after the belt. Polishing and removing all tool marks in chamber, throat and beginning of rifling. Gunsmith stated tool marks and non-concentricity was more work than he first anticipated. The gunsmith mentioned that the headspacing on this Savage is extremely tight but safe.

I loaded 8 rounds (4 virgin brass and 4 fire-formed) of Sierra 160 GK SBT with incremented powder charges of H4831sc starting at 55.2 gr and ending with 58 gr.
In addition I loaded 8 rounds (4 virgin brass and 4 fire-formed) of Hornady 162 Interlock BTSP with incremented powder charges of IMR 4831 starting at 54 gr and ending with 58 gr.

I first fired the lowest charge sierra virgin brass. Case ejection was a little sticky. Next was fire-formed of the same and bolt stick. I tapped the bolt handle and ejected the case. I inserted the empty case and yup it was hard to eject. I did notice that the two brass cases had little brown specks all over the cases. I wondered if the gunsmith's tooling oil residue might be these specks. (I called later and he agreed they were) I had only run a dry patch thru the barrel before the range trip.

I fired the next set of incremented Sierra rounds and had pretty much the same experience. This at least removed the concern that it has been the fire-formed brass. Virgin brass was same result. No super bolt lock but there was felt sticky and light lock on one round. FPS did appear to be back to my normal FPS for the loads.

I almost stopped there but decided to fire the lowest charge Hornady virgin brass round. ...and ??? :? the first hornady case ejected smoothly. Too easily and smoothly. I fired the matching fire-formed brass round.. Same thing. I went to the next Hornady powder incremented set. Again both virgin and fire-formed ejected like a custom rifle action. I went back to the Sierra's next incremented set. They ejected beautifully. All along the FPS is higher than the manual's by a significant amount but case ejection was perfect. (100-120 FPS -- could be my chrony off)

I completed all of the remaining test rounds and not a single case ejection issue or even the slightest stick from even the highest powder charge from either Sierra or Hornady's sets. Hottest round velocity at about 3079 FPS.

Its almost like the 5th round broke something free. I only tested these 16 rounds but will head out to the range tomorrow to complete testing and hopefully complete hunting rounds for friend.

I cannot explain this other than the Gunsmith's work appears to have corrected the big issue and that some small remaining residu affected the first 4 rounds?

I will report tomorrows range results to validate today's results. I am hoping they are the same. :mrgreen: :mrgreen:

Thanks all
Steve

 

[257 Ackley]

Steve -
Good to hear that things may be working out. I have seen a couple different instances where initial loads down a barrel gave abnormally high pressure signs due to solvents and residue in the chamber and barrel. If you did any cleaning last night, make sure both areas are clean and dry before firing any rounds.

Did you shoot any factory loaded ammo through this rifle? That may be another good thing to help verify whether there is a problem yet inside the chamber. If your gunsmith says that the chamber is really tight, there may be a need to bump the shoulders back further than you would normally have to. Just some ideas while my brain is still working on the first cup of coffee :roll: .

 

[338winmag]

Okayyyyyy.... Back from the Range.
So on with reloader blasphemy. Let me cut to the chase.
Its not the rifle per se..
It the Sierra bullets!!

 

[SJB358]

I need to hear the story on this Steve! Sounds like a good one coming on. Man, that Savage is really putting you threw the ringer. Scotty

 

[338winmag]

When I first got the 7mm Rem Mag to work with I purchased Hornady 162 gr Interlock SPBTs. No problems with any pressure, sticky bolt, or bolt lock even when velocity loads were in the 3015s. The one problem was the groups. I started testing different components. I switched from WLRM to Fed 215 magnums but groups still not great. I switched from H4831sc to IMR 4831 and started testing with that powder. At about that time a few reloaders mentioned the Sierra Game Kings and how they use nothing but ... so before I gave the IMR powder a decent try, I switched to the Sierra 160 gr GK SPTs. This is where I started having problems (but it just didn't click at the time).

Testing the Sierras, I started getting sticky bolt immediately but I correlated it with the serious change in velocities and\or hot chamber\barrel since this testing just happened to land on some of our hottest summer days this year. I had started with low middle of the road powder charges but I had also gone back to the WLRMs and the H4831sc. Started getting extreme ES, sticky bolt, ocassional bolt lock and wrotten groups. At least 3 times I left the range after 1 shot and 1 time after 3 shots. This was all with changing out components and powder charges. I started a post on 7mm Rem Mag velocity and also on Chrony accuracy because the testing was starting to go downhill with this rifle and the components. I thought perhaps lot number quality control with the Sierras so I purchased another box of Sierras and started testing with them. Same thing. The last resort was taking the rifle to the gunsmith. All he really did was smooth and polish out the chamber and polish out the tool marks from the manufacturer. I had doubts but also had high hopes. The Sierras again did the same thing. The Sierras show extreme velocities, bolt sticky and bolt lock and occasional bolt face marks on the case. I decided to purchase the Quickload program and actually had Ed at Quickloads run a number of loads thru quickload with me on the phone and with my reload recipes and case info. The Sierras showed perfectly normal with the program but they sure don't fire that way.

Just by chance I had loaded some Hornday 162 gr Interlock SPBTs with minimum loads using the Fed 215s and IMR 4831. Instantly no issue, just like the very start. I tested some small powder increments and still no problem. I fired a couple Sierras right after and stated beautiful extraction but I think I was just excited about the Hornadys and no extraction problems because I do recall them (3) being a little sticky but just contirbuted to hot chamber and barrel.

For the second time I went out with both Hornady and Sierras loaded at minimums along with increment powder charges. I also took all reloading tools with me so if needed I could reload additional test rounds. Again even at Sierras manual minimum, the Sierras are shooting at very high velocities and getting sticky bolt regardless of virgin brass or fire-formed brass. I now purposely went to the Hornadys and using fire-formed brass went up the powder charge ladder. At powder charges over 4 grains higher than Hornady's minimum - 58 grains (not Hodgdon's minimum), velocities were at 3020s and no problems at all. (After comparing Chronies, we believe mine to be approximately 70-80 FPS high. - this then matches very closely with Sierras manual of 58 gr and 2900).

Another reloader that I frequently see at the range came over to my bench and saw the sticky bolt situation. After explaining the situation, he had heard of this before and stated that he believed the Sierras have a harder jacket which can cause some rifles at different loads to reflect what was hapening with this rifle.

I don't know about harder or softer, but I do know that after all things from the very start taken into consideration and for this rifle, its the Sierra bullets! that are causing the pressure issue.

Regarding some manufacturer ammo to test (Winchester Super-X Power Point 175 gr). Yes this gives me occasionally sticky bolt and high velocities but this ammo is literally seated at this rifles lands??? I did not know they did such a thing for over the counter ammo but I will shoot three for comparison today.

Something interesting. I am using Sierra 165 gr GK for a 30-06 and no issues. Excellent performace, no issues. Go figure.

Going out to the range to finish up this rifle with Mr. Hornady!

Thanks All
Steve

 

[wildgene]

...just out of curiosity, have you checked the seating depth w/ the Sierras? W/ the longer bearing surface/ shorter ogive, what works fine for a Hornady SP or VLD would put you right on the lands w/ the Sierra causing high pressures. Just a thought...

 

[Oldtrader3]

Steve, glad that you figured out the problem. I never would have guessed that ammunition would seat the Sierra bullets right on the lands. Certainly, that combination of being seated on the lands and hard jackets would cause pressure problems. It seems that you methodically did all the things that you needed to address the issues and solve the high chamber pressure problem. Thanks for the well written narrative of how you isolated the problem and solved it.

 

[338winmag]

"..just out of curiosity, have you checked the seating depth w/ the Sierras?"

Good Question. As practice, I always have dummy rounds for each specific bullet and its seating depth to touch the lands. I also double check them to make sure they have not changed before I use them as a template for my reloads. The Sierra seats .012 deeper than the Hornady Interlock. In addition, in my testing, I used numerous seating depths and associated powder charges. Always the same result with the Sierras.

"I never would have guessed that ammunition would seat the Sierra bullets right on the lands" ..

I am not sure what bullet Winchester Super-X PowerPoints are. It is probably winchesters proprietary bullet. Will be shooting 3 today to compare velocity one last time.

Thanks Guys. Again someone might think different but the writing is now on the wall for me... and yes, some great experience came along with this.

 

[Guy Miner]

Ah... Yes, the different ogive... The nose of a typical Hornady is considerably different from the nose of a typical Sierra.

Still sounds like the chamber is cut too tight, if factory ammo is producing high pressure.

 

[Ridge_Runner]

did you ever measure the sierra's? possibly they are .308 dia or just slightly oversized, I once bought a box labeled 130 gr .277's that were 9mm pistol bullets. just a thought.
RR

 

[DrMike]

Ridge Runner has a good suggestion. I have opened Bergers that were not the calibre listed on the box. I don't doubt that it happens occasionally to almost every manufacturer.

 

[Oldtrader3]

With modern and inexpensive check weigher system equipment on line, this should never happen. This is particularly true when you consider the line clearance and control systems with bar code scanning which are available to prevent this from ever happening, especially in light of the legal liability issues involved. This is just lack of worker training and sloppy line clearance procedures, IMHO. The manufacturing engineer in that plant needs to do his job!

 

[338winmag]

Yup... first thing I hadf checked and hope for..

both .282
Off to the range

 

[elkeater2]

Just curious, when you say the Sierras are seated .012" deeper than the IL's, is that when they are both touching the lands like with the dummy rounds you mentioned? Wondering how much jump max you ever used with the Sierras. I know you said you tried different seating depths.

I checked Hornady and Sierra seating depth for 7mm Rem Mag and these bullets. Hornady says seat to 3.290 overall. Sierra say to seat to 3.245. That's .045 difference in their recommendations, 4 x as much difference as your dummies showed between them at .012. Who knows how they came up with their C.O.L.'s.

Keep thinking there is something here we don't know yet, but it sure sounds like you've covered the bases. Blackening the whole front end may show something. Maybe send some bullets to one of our forum guys who has the same rifle, and have them check too? It sounds like the bullets, but what is it about the bullets that's so different? Man, I am curious.

 

[338winmag]

I use a vernier caliper, comparator and comparator insert for each of the calibers and measure from base to ogive. I think, but I could be wrong, that the C.O.L. is from base to meplat.

I believe each rifle will have its own unique "on the lands" measurement. My measurements are pretty much on the money.

Some good thoughts though. By the way, went out to the range today and fired 27 rounds to complete finding the sweet spot and sight-in for the 7mm Rem Mag.

.060 off the lands
57.2 gr IMR 4831
Velocity avg at 2972

All were with Hornady 162 gr Interlock SPBT. Never a lock, sticky or slow extraction. Not one! :mrgreen:

Thanks All
Steve

 

[nvbroncrider]

I have a 700 Mtn rifle in 243 that had a bad chamber bought new. That's exactly what it did and kicked like a mule. Left a make on the side of the case and had to beat the bolt open. Once the chamber was fixed by the factory there are no markings on the case but needless to say it still kicks like a mule and the action has always been a little rough. I haven't much cared to shoot it since.

 

[Oldtrader3]

The loads that you are using now with the Hornady Interlocks and 57.2 grs of IMR 4831 are clocking just about where I would expect them to at 2972 FPS with no pressure signs. This appears normal for a 7mm Rem mag with that load.

None of this explains the issues that you had with the 175 SBC Sierra bullet which on my Sierra Infinity Software shows the 175 gr SBC bullet loaded with 60.9 grs of IMR 4831 at a velocity of 2900 fps and a COAL of 3.245 for that bullet. What was the COAL of the 175 Sierra loads that gave you the high pressure problems?

 

[338winmag]

There might be a little confusion here.

The 175s are over the counter Winchester Super-X Power Points that friend in the beginning gave me for a comparison.

The Sierra 160 Game King SBT are the pressure issue bullet

The Hornady 162 Interlock SPBT are the bullets that are working with no case extractions problems.

 

[SJB358]

Great work Steve. I am still puzzled a bit by the extreme pressures that are being generated by the Sierras. Even driven into the lands .010, your lower powder charges shouldn't have made that kinda numbers. I know they weren't in that far, so again, it is still kind of a mystery to me. Either way, seems like you have a great load worked up and I can't see that 162gr Hornady being anything but a great choice. Scotty

 

[elkeater2]

Steve,
Sounds like you have tried it all. A chamber cast would be interesting, if it were mine. I hope your friend is happy with all your effort! I would be. Maybe engrave "Do Not Shoot Sierra 160 GMK's in this rifle" on the barrel. Heck, they already have a novel stamped there these days... :grin: