Need some 6mm Rem H4350 advice

[SevenT6Vet]

I loaded various loads to test for an upcoming long range shooting class i'm taking. I tested various powders, COL, and settled on a load that gave me an inch group at 250 yards a few days ago.

I finally chronographed the rounds today, and was a bit surprised: 3204 and 3206 ft/sec.

The gun Model 700 VLS 6mm Rem (26" bull barrel)

The load: 44 grains of H4350 with 105 gr Hornady amax bullet.

COL is 2.852" (Hornady book recommends 2.810")

This is just over max, but the ft/s is much higher than everything i've read. Hogdgon website says H4350 max is 43.5 gr @ 3,029 ft/s and max IMR4350 is 43.8 @ 3,027 ft/s from a 24" barrel.

I've got 5 days to settle on a load and make 200 rounds for the class.....ugh. Is anyone else getting this velocity from a 6mm Rem with a 105 gr bullet?

 

[E.Shell]

If your chronograph folds up to store/transport and unfolds to hold the screens, it is probably not unfolded all the way. This would put the screens closer together, resulting in a shortened screen-to-screen travel distance/elapsed time and the resulting error is a higher than correct velocity.

If you have a different system, screen spacing is still suspect, as is distance from the muzzle.

I wouldn't automatically rule out 3,200 fps, but it is quite unlikely with a 105 and I doubt you're getting that with 44.0/H4350 anyway.

FWIW, I'd be more inclined to try H-1000 in the 6mmRem. I'm using that in my daughter's .243 with 105 Scenars and it's a good match. H-4350 was a little fast for a 105 in her gun and her .243 has a lower bore ration than the 6mmRem, which more resembles a .243 Ackley in capacity and performance.

It is not uncommon to deviate on either side of "maximum" in the reloading manuals. Not only is their maximum charge not guaranteed to be safe in your rifle, but you may also find your own rifle will allow higher charge weights than what is safe ion their test rifle. They are using different EVERYTHING.


Flip side: Who cares what the absolute velocity is?

If:
a) it is a safe load, and
b) velocity deviation is low, and
c) velocity is high enough that the cartridge's potential is achieved, and
d) precision is good,
who cares exactly how fast it's going?

As long as it is a good, stable load, it will be fine and we can 'back into it' when we set up your software and shoot your data.

 

[SevenT6Vet]

If your chronograph folds up to store/transport and unfolds to hold the screens, it is probably not unfolded all the way. This would put the screens closer together, resulting in a shortened screen-to-screen travel distance/elapsed time and the resulting error is a higher than correct velocity.

If you have a different system, screen spacing is still suspect, as is distance from the muzzle.

I wouldn't automatically rule out 3,200 fps, but it is quite unlikely with a 105 and I doubt you're getting that with 44.0/H4350 anyway.

FWIW, I'd be more inclined to try H-1000 in the 6mmRem. I'm using that in my daughter's .243 with 105 Scenars and it's a good match. H-4350 was a little fast for a 105 in her gun and her .243 has a lower bore ration than the 6mmRem, which more resembles a .243 Ackley in capacity and performance.

It is not uncommon to deviate on either side of "maximum" in the reloading manuals. Not only is their maximum charge not guaranteed to be safe in your rifle, but you may also find your own rifle will allow higher charge weights than what is safe ion their test rifle. They are using different EVERYTHING.

I made several ballistic charts for this weekend's class, but i'm going to revise them based on these new findings. I suspected I would be between 3,000 fts and 3,100, and I was planning on a 6.6 mil drop at 1,000 yards based on a 300 yard zero. I'll need to update to 3,175ish.


Flip side: Who cares what the absolute velocity is?

If:
a) it is a safe load, and
b) velocity deviation is low, and
c) velocity is high enough that the cartridge's potential is achieved, and
d) precision is good,
who cares exactly how fast it's going?

As long as it is a good, stable load, it will be fine and we can 'back into it' when we set up your software and shoot your data.

Thanks for response! My muzzle was pretty close to chronograph, approx 4'.

I have the rcbs chronograph, so the start and stop are fixed points. I was actually anticipating a LOWER velocity since I set the bullet out further than what the Hornady book has. I suspect by bullet being further out, the volume would increase, thus decreasing pressure, thus making the velocity a little lower.

I'm no expert at finding signs of pressure, but the primers look normal to me. The cases extracted with no effort as they normally would.

I'm going to drop back to 43.9 and see if I can shoot a tight group with that. My barrel heats up pretty good after a few rounds regardless, so less is better, at least in that one aspect. I'd also sacrifice a 1/4 MOA for some extra barrel life.

 

[E.Shell]

It does sound like your chonograph was too close, many/most are about 15 feet but I don't know what is recommended for your model.

The 'extra barrel life' thing is a myth and the difference in barrel heat will be imperceptible. Any reasonable load is going to generate a lot of heat in a bore that small. Barrel life is measured in milliseconds and the relative difference in velocity means almost nothing. "Hot loads" are not recommended, but you have to be a certain minimum pressure to clean up ignition. Research "OCW".

 

[SevenT6Vet]

It does sound like your chonograph was too close, many/most are about 15 feet but I don't know what is recommended for your model.

The 'extra barrel life' thing is a myth and the difference in barrel heat will be imperceptible. Any reasonable load is going to generate a lot of heat in a bore that small. Barrel life is measured in milliseconds and the relative difference in velocity means almost nothing. "Hot loads" are not recommended, but you have to be a certain minimum pressure to clean up ignition. Research "OCW".

10-4

 

[Old Fart]

I loaded various loads to test for an upcoming long range shooting class i'm taking. I tested various powders, COL, and settled on a load that gave me an inch group at 250 yards a few days ago.

I finally chronographed the rounds today, and was a bit surprised: 3204 and 3206 ft/sec.

The gun Model 700 VLS 6mm Rem (26" bull barrel)

The load: 44 grains of H4350 with 105 gr Hornady amax bullet.

COL is 2.852" (Hornady book recommends 2.810")

This is just over max, but the ft/s is much higher than everything i've read. Hogdgon website says H4350 max is 43.5 gr @ 3,029 ft/s and max IMR4350 is 43.8 @ 3,027 ft/s from a 24" barrel.

I've got 5 days to settle on a load and make 200 rounds for the class.....ugh. Is anyone else getting this velocity from a 6mm Rem with a 105 gr bullet?

Over the years, best load for Rem 6mm, 788-1-10-11 twist- WLRM-40grs.-W760-SMKBT-70- little over 3kfps. @ 100 yds. all in 1 hole.. Now shoot a 03A3-26in. Shaw hy. bbl. -1-8 twist, Timney Trigger-36x GOLD RING -1/8 dot-WLRM-40.2 grs.- W760-Moly-coated-SMKHP-107 gr. @ 2865fps. At my age (75) am still cuttin same hole w/it at 407 ydrs. Only range I have. P.S.- Darn thing ONLY will shoot Rem Brass.

 

[KRC]

Some of the higher velocity (vs. lower from larger case volume) may be due to the bullet being either engraved into the lands when chambered, or close to it, such that pressure spikes from the added resistance. Are you getting pressure signs with your above-book loads? Primers? Extraction/bolt lift? Case stretching? Primer pockets?

 

[chriskat]

I agree with E.Shell, I wouldn't worry about the velocity if it's an accurate load; as long as there are no signs of excessive pressure. Difficult bolt lift compared to normal, difficult extraction, significantly flattened primers, primers flowing into the firing pin hole, etc.

Also agree with KRC, if the projectile is very close to the rifling I would think the pressures could be increasing enough to get the velocity higher.

 

[pre64hunter]

I agree with E.Shell, I wouldn't worry about the velocity if it's an accurate load; as long as there are no signs of excessive pressure. Difficult bolt lift compared to normal, difficult extraction, significantly flattened primers, primers flowing into the firing pin hole, etc.

Also agree with KRC, if the projectile is very close to the rifling I would think the pressures could be increasing enough to get the velocity higher.

I agree

 

[KRC]

Well . . . the OP is from 2016, so I guess he's worked it out by now. I shoulda guessed because who shoots a 6mmRem these days, in the era of the AR-15 platform and the 6/6.5 Creedmoor?

 

[chriskat]

Funny, missed the date. I've been wanting my 6mm back for a long time. Have a 700 that I'm going to re-barrel to 6mm to get it back.

 

[pre64hunter]

Well . . . the OP is from 2016, so I guess he's worked it out by now. I shoulda guessed because who shoots a 6mmRem these days, in the era of the AR-15 platform and the 6/6.5 Creedmoor?

that is funny, I missed that too!

 

[Old Fart]

Funny, missed the date. I've been wanting my 6mm back for a long time. Have a 700 that I'm going to re-barrel to 6mm to get it back.

Hey, chrskat- try a Shaw 26in. S.S. 1-8 twist ya won`t be disapointed if ya do. If ya use the load that is in my other post. & have them set up a tight bbl (small lands & groove) it will shoot the SMKHP-107 like a house afire, also shoot the Hor. MHP-105 with same load. Only thing about the HOR. bullet they are not a true .243 have to shoot around 10 SMKHP-107 to foul BBL- then it will shoot HORHP 105 in same hole @100yds.
The only thing is that the Shaw BBl. it likes Rem. Brass here is the proof.