7mm-08, 9.5twist, factory 140gr ammo tumbles.

[Zero333]

Bought my brother a Savage 11 left hand 22"bbl in 7mm-08 for hunting deer. Cleaned the barrel before taking it to the range for the first time (a must in my opinion with factory rifles). While cleaning I checked the twist and it kept adding up to 9.5" like it's supposed to be, so no surprise there.

Bought some Factory ammo, Remington 140gr AccuTip boattail. Demn things keyholed all over the place, perfect sideways bullet holes, the ones that hit the target. Did not chronograph but recoil felt like run-of-the-mill 140gr 7mm-08 load, not light.

Pulled a cartridge and the bullet measures. 1.263", case had 45gr of what looks like w-760.
Cartridges measure 2.775"-2.780".

Freebore of the chamber is from New York to California. Too long to sit the 140gr Remington Accutip or a 140 Sierra SPBT at the lands and still remain in the case.

Recovered one bullet that was stuck sideways in the 2x4 on the side of the target board, and the rifling engraving on the bullet looks normal, no different from other bullets I recovered from other rifles/cartridges.

I will send my brother out to test some handloads next weekend but would appreciate some input and guesses as to what caused the bullets to tumble.

I hope it's just the ammo.

 

['Freak]

Apparently demn Remington 140gr AccuTip boat tail thangs are too long to be stabilized by that 1:9.5 twist barrel. Try somebody’s shorter bullet.

 

[Cold Bore]

Yep, try a standard (shorter) cup and core bullet.

I shoot Federal Fusions in my 7mm-08, and have quit handloading for it since finding them.

Heck, for hunting deer, there's nothing wrong with good old Remington CoreLokts.

If neither of those shoot, THEN you have a rifle problem.

 

[HTSmith]

A 9.5 twist should stabilize that bullet with no problem. Something is up--not sure what. Are the bullets the correct diameter when you mike them?

 

[4xforfun]

A 9.5 twist should stabilize that bullet with no problem. Something is up--not sure what. Are the bullets the correct diameter when you mike them?

+1

I have been shooting the 180 Berger and the 180 JLK for years out of factory 9.5 twist BBL's with out any issues. Those 180 HAVE to be longer then your 140.

Tod

 

[Zero333]

Micrometer reads .284" on the money.

This weekend I will find out if my handloads with 140gr SGK and factory 140gr Core-lokt ammo also keyhole.

 

[AckleymanII]

keyhole may indicate a barrel full of copper or a damaged crown

 

[shoot4fun]

Damaged crown.

 

[jonbearman]

Measure the twist rate again as savage went to a 1 in 11 twist for some insane reason and it is possible one slipped through. Use the cleaning rod and a tight patch to measure the length of the twist. If it wont shoot corloks or other short cup and core get it scoped to find out if the bore is messed up. Then send it back to savage for a rebarrel if it comes down to it.

 

[Zero333]

UPDATE....

The factory Remington Premier 140gr Accutip ammo is/was the problem. I should of realized it when I recovered those 2 bullets the first time out.

Those 2 bullets I recovered were only the bottom half of the bullets, the nose was missing. Must of fell apart in mid air soon after leaving the muzzle.

Send my brother out to test 140gr SGK's with H-4350 & H-414.
48gr of H-4350 shot 0.72" at 100 yards, 5 shots and 47.5gr of H-414 shot 0.86" five shots.

He shot it off a rest and rear bag but said the rest was unstable due to the thin forend, and thinks he could of shot better off a bi-pod.

I loaded up some 175gr Hornady SP but he never shot them. Did shot 2 groups of Factory 140gr Core-lokt's, first Cold-Clean-bore group was 2.2" and the following group was 1.6", 5-shot groups.

ALSO... I thought the freebore was excessive the first time I measured it but I messed up big time on that one.

I had a spare Hornady 308w modified case that I sized down to .243w and used it a few times till I got a 243w mod case. I took that necked 243w mod case, annealed it and sized it up to 7mm (used a headspace comparator to make sure it measure the same as the go-gauge).
Turns out the neck of my necked-modified case was (a hair) to big and did not fit the chamber the first time I used it, and never realized it !!!

I corrected the modified case's neck diameter and the 140 SGK's sit at 2.77" kissing the rifling. Freebore is shorter than I would like but no big deal because the 140sgk's bearing surface/BT junction sits right at the neck/shoulder junction of the case.

If I can't make a consistent day in day out half moa load with the 140sgk's I'll try the 140 Berger VLD hunt.