T3x hard bolt lift after firing

[E in CO]

caution - long winded question below!

I’m having a challenge with my T3x rebarreled to 6.5 creedmoor. Factory rounds sometimes result in a little more bolt lift resistance than other rounds in the same box. With my hand loads I sometimes get what I’d call a hard bolt lift after firing. This Starts to happens with loads 10%-15% below book max. The brass shows no sign of pressure otherwise. the ‘smith that put the barrel on has checked it all out and even spun the barrel off to re-check everything. He has also looked at the brass with me and we’ve mic’d all the dimensions and nothing is out of sorts. I’ve tried various combinations of new brass, 1x fired brass, Redding body dies, Lee collet neck dies and Hornady full length dies. All the rounds chamber fine but I have this primary extraction issue with 1 or 2 rounds in a group of 5 hand loads that are on the mild side. It’s an issue because it seems like the high accuracy node is closer to book max. Than I can get with the hard bolt lift. I trust my ‘smith and have seen the specs with my own eyes As well. We Also took apart the bolt and made sure everything was smooth and greased. ive Run brass through the FL die then the body die to check and it seems the FL die may be out of spec somewhere on the case body. However I get the same hard bolt lift after firing when sizing with the body die. Also, factory rounds seem a little slow compared to my handloads but shoot fine. I suppose I can drop down and find a lower node For my handloads but want to make Sure I’m not missing something obvious first.

What could I be missing on this? Any ideas?

thanks

E

 

[fatbacks]

Try dry firing a bunch and see if you can get that same heavier bolt lift to see if it’s mechanical with the bolt.

I’m in the same shoes as you with my T3 300 wsm. In my node I get a heavier bolt lift every 5-6 shots. But then I notice sometimes dry firing the bolt is heavier to lift sometimes. At times I am not sure if it’s just my perception of it or not. Anyhow, I’m rolling with what I got for this fall. Flying out for sheep in the Brooks Range in T-22 days (not that I’m counting)


Sent from my iPhone using Tapatalk

 

[E in CO]

‘backs, thanks for sharing your thoughts. When I dry fire I get a consistent bolt lift that seems A little heavier than other rifles but it is consistent. When I fire a round it isn’t consistently heavy Just one or two in a 5 round string much like what you mentioned. good luck on your sheep hunt!!!

 

[benz1978]

Try reloading with virgin brass? Watched a video recently from a custom gun maker and he recommends new virgin brass with all new rifles. Perhaps same applies to your new barrel situation. He mentions issues with x-fired brass even if you resize it.

Sent from my Pixel 3a using Tapatalk

 

[MeatBuck]

Is heat from the first couple shots causing bolt face to swell? Seems excessive but if everything else is checking out maybe it’s heat causing some expansion somewheres?
Are you using a mag or single feeding when shooting? Are you “cooking” your rounds when shooting? Meaning letting them heat up in the mag as you shoot?
Is it the first two shots, the middle two or last two or random heavy bolt lift?

 

[MeatBuck]

Did I miss type of brass?
Harder brass won’t show pressure signs as easily as softer stuff.

 

[MeatBuck]

While screwing around with a pressure string in my ..270wsm I saw pressure signs at 64and 64.5g but not at 65g, I boxed all that brass up and bought new Norma brass and haven’t seen this happen since.

 

[E in CO]

Benz, I’ve used both virgin and 1x fired factory brass. I’ve tried Winchester, Hornady, Nosler and HSM which I think was Starline but don’t recall. I’ve put 370 rounds through this chasing different brass, powders and sizing dies. Same results with the changing variables.

Meat, I load 3 in the magazine and shoot them then load 2 in the magazine and shoot them for a 5 round group. It does seem to happen on the 3rd shot most of the time. I’ve never heard of an expanding bolt head issue. So I just went and looked at the head of the last 55 rounds I shot and found 7 pieces of brass where it looks like the extractor left a noticeable flattened spot just above the rim and in the recess of the case head. Also several more have a shiny spot in the same area. Do you think the bolt could be expanding enough to cause a pinch on the extractor and making it hard to lift the bolt for primary extraction?

 

[benz1978]

It's interesting that factory rounds don't cause the same issue. How far off the lands are you seating? Are you reloading to saami specs or using specs from previous load data? Wondering if you are in the lands with your reloads and the factory rounds are leaving a little jump?

Sent from my Pixel 3a using Tapatalk

 

[E in CO]

Benz, I’m at book seating for 143 Hornady ELD-M, 120 Hornady ELD-M, 140 Nosler BT and 140 Berger VLD Hunting. But the Berger’s were also tried at 0.020” 0.050” and 0.080” off the lands. The Berger Book COAL seating results in 0.093” jump.

 

[PathFinder]

No way the bolt is measurably changing in any dimension from that tiny amount of heat. It takes a couple of hundred degrees to move .001".

Sent from my E6910 using Tapatalk

 

[SDHNTR]

What’s the specs between the go and no gos? I have a Rem 700 with a PacNor barrel that does something similar and I’ve attributed it to a very tight match cut chamber. And possibly a tight barrel. Then minute .001” variances in component dimensions or run out, etc will sometimes cause slight pressure signs. Keeps me safely under max loads.

 

[E in CO]

SD, I don’t recall the exact clearance on the chamber cut but it is on the tighter side but within SAAMI spec. When we measured case head expansion and resizing we had fired brass at 0.471“ and resized at 0.470” reloading books showing 0.473” For case head dimension. Maybe the chamber is tighter than he thinks. Seems like I just need to accept the fact that I should settle on a lower node. thanks everyone!!!

 

[MeatBuck]

Benz, I’ve used both virgin and 1x fired factory brass. I’ve tried Winchester, Hornady, Nosler and HSM which I think was Starline but don’t recall. I’ve put 370 rounds through this chasing different brass, powders and sizing dies. Same results with the changing variables.

Meat, I load 3 in the magazine and shoot them then load 2 in the magazine and shoot them for a 5 round group. It does seem to happen on the 3rd shot most of the time. I’ve never heard of an expanding bolt head issue. So I just went and looked at the head of the last 55 rounds I shot and found 7 pieces of brass where it looks like the extractor left a noticeable flattened spot just above the rim and in the recess of the case head. Also several more have a shiny spot in the same area. Do you think the bolt could be expanding enough to cause a pinch on the extractor and making it hard to lift the bolt for primary extraction?

I really don’t know as it was a guess based on the info you provided. Are you measuring coal or cbto when reloading? You could be just into the lands on some of your loads due to differences in bullet ogives if you are seating to coal near the lands. Also if your rounds are being cooked in the magazine as you shoot, a temp sensitive powder will display pressure signs if your loading near max. And by max I mean where you see pressure in your rifle not a published max by a powder manufacturer.
(Forgive me if I’m saying stuff that you’ve checked out already as I didn’t reread the thread before making this post.)

 

[MeatBuck]

Try shooting one load at a time, no rounds in mag. Let it cool between shots, see how things go doing it that way. And you might not want to waste the time waiting for bbl to cool so maybe bring another gun to shoot while the other cools. Keep you from saying “it’s been long enough, I’m shooting again”.

If that don’t work measure the unfired rounds at cbto and see if you have variances that may put you into the lands.

 

[E in CO]

Meat, thanks for your additional thoughts on this. I measured the jam length At the ogive on each bullet type and subtractEd for jump. The book COAL Rounds were first confirmed vs jam and all had a bunch of jump. I used IMR4350 and Win760 but thought temps might be driving up pressure so I switched to H4350 which I was trying to save since it’s hard to find still. I Just measured the case bodies above the case head mid way to the neck and all is well on fired cases with minimal expansion. So I wonder if the chamber is tighter than thought since it is expanding 0.001” of an inch Or less just above the case head and Half way up the case body.

 

[MeatBuck]

You have the issue with factory rounds on first firing?
Idk sounds like maybe a defect somewhere in the chamber or headspace is just too tight

 

[Deplorable77]

I have a t3x lite .243 and a t3x stainless fluted in 300wsm.
Both bolts are harder to lift after firing no matter what factory loaded ammo I use. I just assumed it was a Tikka thing and never gave it much thought.

 

[E in CO]

Yup. Factory does it but it is more pronounced on reloads. Ive come to the conclusion the chamber is probably tighter than intended combined with a resizing die that might be on the larger end of spec. My handloads are a bit faster than expected as well. Would that be consistent with a very tight chamber?

 

[wind gypsy]

My handloads are a bit faster than expected as well. Would that be consistent with a very tight chamber?

yes.