Need opinions on early pressure signs

[Mountain_Life]

I need some opinions here. I have a Tikka T3 270 WSM. 16" barrel. Norma brass. CCI 250 primer. 145 ELD-X. Loading to max mag length. I'm getting hard bolt lift and ejector marks at what seems to be moderate powder amounts. 56.5 grains of H4350 and 62 grains of H4831sc. I'm not looking for crazy velocity so I've just been shooting closer to suggested starting loads, but this is the first time I've experienced a gun showing pressure signs so early. Thoughts?

I haven't ever gotten into bore scoping or scrubbing. Possible crud ring? Or maybe this is just what the barrel is?

With 61 grains of h4831sc it shoots great, see a recent 100 yard group below.

 

[Mountain_Life]

Also open to powder suggestions. I'm not interested in buying powder specifically for this gun as there is a rebarrel to 6mm in the future. On hand I have h4831sc, h4350, imr4350, h1000.

 

[49ereric]

Seat the bullet deeper and see if you get the same results.

 

[EdP]

Seat the bullet deeper and see if you get the same results.

The Tikka owners on here could tell you if it is common for Tikka mags to be long enough to accommodate a COAL that jams the bullet into the lands. If so, loading to max mag length you may be jammed into the lands. You should check because if you are, the above suggestion may well solve your problem.

For a point of reference, my Lyman manual doesn't list H4350 or H4831 powders but does list the IMR4350 and IMR4831. Bullet wise, no 145 gr but a 140 BTSP. No 4350 loads are listed for bullet weights over 140gr. The max load for IMR4831 is 61.0 gr. Other sources should be referenced but you may be loading on the hot side given this data. The Lyman manual also says that with the .270WSM "The overall length of many premium bullets may require that they be seated deeper into the case than they would be in a longer action."

 

[Mountain_Life]

The Tikka owners on here could tell you if it is common for Tikka mags to be long enough to accommodate a COAL that jams the bullet into the lands. If so, loading to max mag length you may be jammed into the lands. You should check because if you are, the above suggestion may well solve your problem.

For a point of reference, my Lyman manual doesn't list H4350 or H4831 powders but does list the IMR4350 and IMR4831. Bullet wise, no 145 gr but a 140 BTSP. No 4350 loads are listed for bullet weights over 140gr. The max load for IMR4831 is 61.0 gr. Other sources should be referenced but you may be loading on the hot side given this data. The Lyman manual also says that with the .270WSM "The overall length of many premium bullets may require that they be seated deeper into the case than they would be in a longer action."

I appreciate the responses! I saw the same in my Lyman manual. Also referred to my Hornady app and various Internet forums (taken with a grain of salt). I'll look into seating depth.

 

[Mountain_Life]

Doesn't appear that my initial load was jamming into lands, but I went .040 deeper anyway. Loaded up 57 grains of H4350. First 2 shots had no ejector mark or hard bolt lift, 3rd had a little heavier bolt and a very slight ejector mark. 4th and 5th had heavy ejector marks and very heavy bolt lift.

My previous seating depth was similar, no pressure signs until the barrel heated up.

 

[Lawnboi]

Doesn't appear that my initial load was jamming into lands, but I went .040 deeper anyway. Loaded up 57 grains of H4350. First 2 shots had no ejector mark or hard bolt lift, 3rd had a little heavier bolt and a very slight ejector mark. 4th and 5th had heavy ejector marks and very heavy bolt lift.

My previous seating depth was similar, no pressure signs until the barrel heated up.

Are you shooting outdoors with a suppressor now by chance?

 

[Mountain_Life]

Shooting inside with the window open. Suppressor is just a bit outside the window but everything else is inside and warm. Thoughts?

 

[Lawnboi]

Shooting inside with the window open. Suppressor is just a bit outside the window but everything else is inside and warm. Thoughts?

Sometimes cold air down a warm or hot bore, combined with some excess gas seems to cause the case not to stick to the chamber walls quite like it should. No idea if that’s your problem but I try not to develop loads when conditions are prone to causing that. I normally don’t load top end to begin with but I’ll see it when conditions are stacked in favor condensation.

Maybe not what’s going on but I have had some head scratchers especially with warm rifles and headwinds, shooting suppressed in shoulder season and winter.

I like to use a chamber fan in these situations.

One easy way to rule this out would be to shoot the same string without the suppressor.

 

[Mountain_Life]

I'm not trying to push the upper end of velocities with this gun, was just surprised and curious as to the odd and seemingly early signs. I'll work through it again on a day that's above 0. I don't remember what the temperature was when I worked up my first load as it's been a year or 2.

 

[49ereric]

I'm not trying to push the upper end of velocities with this gun, was just surprised and curious as to the odd and seemingly early signs. I'll work through it again on a day that's above 0. I don't remember what the temperature was when I worked up my first load as it's been a year or 2.

Some rifles show the pressure signs when others won’t. Tighter chamber? Hotter powder lot or hotter primer or Brass ? Enough potential issues to make a person wonder but if all else fails just back off the powder.

 

[EdP]

What is your time between shots?

 

[Mountain_Life]

Of the 5 shots I mentioned, the first 3 were about 10-15 seconds apart. Once I noticed the bolt lift change, I waited a few minutes between the last few.

 

[Mountain_Life]

I think I'll just set it back on the rack with the existing load. It's next on the list for a re-chamber anyway. Traded a Savage for it with the intent to re-chamber anyway.

 

[Bwalker]

I need some opinions here. I have a Tikka T3 270 WSM. 16" barrel. Norma brass. CCI 250 primer. 145 ELD-X. Loading to max mag length. I'm getting hard bolt lift and ejector marks at what seems to be moderate powder amounts. 56.5 grains of H4350 and 62 grains of H4831sc. I'm not looking for crazy velocity so I've just been shooting closer to suggested starting loads, but this is the first time I've experienced a gun showing pressure signs so early. Thoughts?

I haven't ever gotten into bore scoping or scrubbing. Possible crud ring? Or maybe this is just what the barrel is?

With 61 grains of h4831sc it shoots great, see a recent 100 yard group below.

I've struggled with the same problem in a Howa Alpine. For whatever reason some guns do this.

 

[BCsteve]

Whats your velocity? It should tell you if you're there or not.

 

[Mountain_Life]

With 56.5g of h4350 I was around 2700 I believe. 57-58 of h4350 had me closer to 2750-2815.

H4831sc was significantly lower than that. 61gr was 2570.

 

[dukeball33]

The H4350 load seems right in there for book max comparing a 16” barrel to tested 24” barrel.

 

[EdP]

Of the 5 shots I mentioned, the first 3 were about 10-15 seconds apart. Once I noticed the bolt lift change, I waited a few minutes between the last few.

10-15 sec apart? Wow, I can't get settled back into position and get another shot squeezed off anywhere near that fast at the bench. It is probably reasonably close to what might happen in a hunting situation where a follow up shot is needed but 3 shots that fast would be rare I would think.

It sounds to me like you may be seeing temperature effects on you loads due to heat in the action. I would try the same loads leaving some cool down time between shots and see what happens. Some folks will shoot 2 or 3 in rapid succession and then cool down. My preference is to allow 3 min between shots when at the bench.

 

[TaperPin]

Your situation can really be a head scratcher. I’ve only had one rifle that developed pressure early, but it was a good experience since figuring it out was such a head scratcher and forced me to look closely at every possible cause. I say “good” experience now, but at the time it drove me nuts and became a group project with friends helping to tract down the issue.

The sticking might be pressure, or might just be the relatively straight case and normal pressure wanting to stick a bit. The chamber might be extra rough, or just more straight than it would be in a perfect world.

Ejectors with a sharp edge can show a ring at low pressure and some brass lots are simply softer than others. Pushing the shoulder back more than needed can give the cartridge head some running room to slam into the bolt face, and an extra smooth or oily chamber can contribute to bolt face pressure. Unscrewing the sizing die a complete turn to avoid any shoulder set back will rule out excessive headspace causing marks at low pressure.

CCI 250 is a fairly hard primer and doesn’t normally flatten out around the edges unless there’s decent pressures. However, excessive headspace can allow the primer to stick out away from the case head early in combustion, then as the case head stretches to meet up with the bolt face it pushes the primer back in under pressure and it looks more flat than it normally would.

My early pressure rifle made purchasing a chronograph a good idea to see if what’s coming out the muzzle matches the powder charge. It helped, but the rifle still had somewhat low velocities at high pressure and somewhat of a low powder charge, but it was a valuable clue nonetheless.

It’s rare, but some powder lots are slow. I changed lots with no change in velocity or pressure.

Carbon rings can drive up pressure (but also velocity) so I scrubbed the bore clean, with no change.

I wanted to see what was going on with the case head, and learned about measuring case head expansion with a .0001” micrometer, and counting the number of reloads before the case head starts to thin. Cases lasted between 7 and 10 reloads, before case heads started to thin or case necks split, and primer pockets were still tight, but case head expansion was right up there with other max loads.

By every measurement the gun was reaching max pressure, but at a lower than normal powder charge and the velocity was about 150 fps slower than a typical rifle in the same cartridge. Cases fired a number of times with neck sizing only showed the chamber wasn’t tight, but very loose, which would normally reduce pressures. In the end I learned not all bores are the same diameter - some are a few .0001” big and some are tight - mine was tight, which drove up pressures early and may have been the reason the rifle had a oversized chamber. If pressures were too high during test firing with a normal chamber, enlarging the chamber with a slightly larger reamer might reduce pressure slightly and allow the rifle to be close enough to ship.

I don’t miss that rifle one bit. Lol