Difference In Effort To Open And Close Bolt; Federal vs. Hornady Factory Loads.

[Turkeytider]

Federal Premium loads loaded with 6.5 Creedmoor 140 Berger Hybrid Target and Hornady 140 American Gunner. Both shot well through my Tikka Super Varmint but effort required to open and close the bolt is noticeably greater with the Federal loads than with the Hornady. Measured with calipers both the brass and bullets, no difference, at least none that was indicated by the calipers . No noticeable markings or scaring on either bullets or casings.
Appreciate any ideas as to what might be the cause. Thanks.

 

[6BRA]

Are you checking OAL or headspace?or both were measured?
Are you saying headspace was the same on both factory loads?

 

[ShtrRdy]

If possible could you remove the bullet on a problem cartridge and just try the brass case? This would help isolate the problem.

If you have a bore scope please take a look at the case to freebore area of the chamber to see if there is some carbon build up.

 

[Turkeytider]

Are you checking OAL or headspace?or both were measured?
Are you saying headspace was the same on both factory loads?

No, I’ve just really measured the exterior dimensions ( width ) of various parts of the two loads. Didn’t measure and compare the overall lengths of the loads. I’m really inexperienced when it comes to rifle shooting, certainly compared to many on here. I’ll go measure OAL. Don’t have the equipment to measure headspace, at least I don’t think I do, LOL!

 

[DaveTooley]

Sometimes there's a mismatch in the two radii at the neck shoulder junction. Mark the tight case with a magic marker, close the bolt and see if you have a shiny ring at the neck shoulder junction.

 

[Turkeytider]

No, I’ve just really measured the exterior dimensions ( width ) of various parts of the two loads. Didn’t measure and compare the overall lengths of the loads. I’m really inexperienced when it comes to rifle shooting, certainly compared to many on here. I’ll go measure OAL. Don’t have the equipment to measure headspace, at least I don’t think I do, LOL!

Measured OAL of 10 each of the Federal and Hornady rounds. The Hornady rounds averaged 71.0 mm, the Federals averaged 70.89 mm. Assuming that the longer loads would be more likely to cause stiffer bolt opening and closing, these results were surprising considering that the Hornady rounds are uniformly easier when it comes to bolt opening and closing. I do notice that some of The Federals are easier to open and close than other Federal rounds in the same box, but are still uniformly “ tighter “ than the Hornady’s.

 

[Turkeytider]

Have also shot AAC , other Hornady Match , and Sig Sauer rounds . Have only encountered the stated issue with the Federal rounds.

 

[Kracken McGraw]

I’m betting the bullets were loaded a tad long and are engaging the rifling some.

 

[Kracken McGraw]

Under magnification, no little square marks on bullets from lands?

 

[Kracken McGraw]

If hard to open after firing could also mean it was a very warm powder loading.

 

[L.Sherm]

If its a saami chamber I really doudt with the .199 Freebore the OAL is gonna be to long to reach the lands at 71mm( about 2.8") you would really have to be at 2.9" OAL or longer with 140's
I would be looking in the area of brass or warm load.

 

[Turkeytider]

I’m betting the bullets were loaded a tad long and are engaging the rifling some.

If that were the case, wouldn’t it show up in a longer OAL?

 

[Coyotefurharvester]

Since you are saying more effort to chamber live round(" no markings on case or bullets"). The extractor/case head could be a fitment issue. Stripping the bolt(just the bolt body) and test chambering a couple of the more difficult to chamber rds.
An ammo checker would probably be the easiest (safest) way for you to check headspace dimensions on a loaded round. Visual comparison and a caliper measurement of headspace is possible with cartridge specific ammo checkers. ( I use Lyman)..

 

[Forum Boss]

Compare the speeds with a chronograph.
Compare the ambient temps when shooting the two different ammo types.
Evaluate if you left the Federal ammo in the sun.
Measure the bullet diameters Federal vs. Hornady -- We have found that bullets can vary by up to 0.0007" in actual diameter (e.g. 6mm bullets 0.2428 vs. 0.2435).
If your Tikka has a muzzle brake, check for fouling.

 

[Kracken McGraw]

If that were the case, wouldn’t it show up in a longer OAL?

The ogive of the Federal bullet could possibly be further out towards the tip.

 

[243winxb]

Seen factory ammo OAL to long to chamber in a Savage 6.5 CM .
if rounds can be chambered, pressure will be higher when touching the rifling. Harder extraction & loading.

Need to measure- Head to Ogive.
The part of the bullet that first touches the rifling is typically the ogive, specifically the point on the ogive where the bullet's diameter matches the bore diameter. This is often referred to as the point where the bullet begins to engage with the rifling

Put some muscle into it & move on.

 

[Kracken McGraw]

Put some muscle into it & move on.

Especially tempting if there all going in the same hole with factory ammo.

 

[Turkeytider]

The ogive of the Federal bullet could possibly be further out towards the tip.

I have a feeling, and it’s really only that, that it’s something to do with the brass. I have right at 800 rounds through the gun. Just encountered this at roughly 750 rounds in, and again only with this one Federal load. Concentrating on the throat and neck area and first 6” or so of the rifling, I clean after each 20 round range session in an effort to keep up with the carbon. Boretech C4 soaks and patches, only an occasional light JB bore paste ( blue ) at about 300 round intervals. Trying to stay away from metal brushes.

 

[Turkeytider]

Especially tempting if there all going in the same hole with factory ammo.

Gun’s VERY accurate when I’m not getting in its way.

 

[Turkeytider]

Seen factory ammo OAL to long to chamber in a Savage 6.5 CM .
if rounds can be chambered, pressure will be higher when touching the rifling. Harder extraction & loading.

Need to measure- Head to Ogive.
The part of the bullet that first touches the rifling is typically the ogive, specifically the point on the ogive where the bullet's diameter matches the bore diameter. This is often referred to as the point where the bullet begins to engage with the rifling

Put some muscle into it & move on.

Yeah, I’m probably making too much of this.