6.5 Creedmoor Sierra HPBT issue?

[rockchalk06]

Need some guidance.

Working up some loads for my HMR using 140 Grain HPBT from Sierra. OAL is 2.810". H4350. Did 5 of each @ 40.5/41.0/41.5/42.0. I also loaded 5 of each with the Nosler Custom Competition HPBT @ 39.5/40.0/40.5/41.0 but OAL was set at 2.775" according to Nosler's data.

Problem is, I took one of each load and cycled them through the weapon. The Nosler's cycled just fine. The Sierra's did not. They were tight going in and locking the bolt. Each bullet has what appears to be marks from the lands on the bullet? I checked the OAL before and after chambering and it's exactly the same.

Brass is fire formed from factory new ammo (once fired) in my HMR Winchester neck sized, trimmed, debured and Federal 210M primers. This for all rounds above. Never ran into this issue before in my life, except for now. This is my first time loading for the 6.5.

Thanks in advance.

 

[pell1203]

Sure looks like you are touching the lands. Try pushing one back to 2.80” and see if it takes care of your problem.

If you have the various measuring tools you can figure out exactly if what is going one is due to the differences in the bullet’s geometries.

 

[rockchalk06]

Sure looks like you are touching the lands. Try pushing one back to 2.80” and see if it takes care of your problem.

If you have the various measuring tools you can figure out exactly if what is going one is due to the differences in the bullet’s geometries.

Thanks.

I backed a few down to 2.80", and they go in a little easier, but all are still hitting the lands. I ran a black marker around the bullet and you can see where it's still hitting.

If I go any lower, I'm worried about over pressure.

 

[Mainer]

Thanks.

I backed a few down to 2.80", and they go in a little easier, but all are still hitting the lands. I ran a black marker around the bullet and you can see where it's still hitting.

If I go any lower, I'm worried about over pressure.

I would be more worried about over pressure from not seating a little deeper.

 

[Highbrass]

Looks like that brass has cracked necks also !

 

[cruze5]

those look longer than 2.80 to me as a 260 shooter...

 

[rockchalk06]

Looks like that brass has cracked necks also !

Its the crimp from whatever crimp Winchester put down.

 

[rockchalk06]

those look longer than 2.80 to me as a 260 shooter...

Here are some pictures.

Left to right
140 grain SMK
140 grain Nolser
140 Grain Hornady ELD Match (factory)
140 Grain Sig BTHP (factory)

 

[rockchalk06]

I would be more worried about over pressure from not seating a little deeper.

Agreed.

 

[MtnCreek]

If you're measuring oal, that length vs when the bullet contacts the rifling will change for every bullet. Assuming the meplat isn't bottoming out in the die, you can setup the die using one bullet. Determine what oal just touches the rifling and reduce by about .030. You'll probably be a lot closer to the rifling than that due to that being a shitty way of measuring.

 

[rockchalk06]

If you're measuring oal, that length vs when the bullet contacts the rifling will change for every bullet. Assuming the meplat isn't bottoming out in the die, you can setup the die using one bullet. Determine what oal just touches the rifling and reduce by about .030. You'll probably be a lot closer to the rifling than that due to that being a shitty way of measuring.

I haven't researched how to determine how far it is to the rifling yet. Typically I have used factory publish data and stuck with that.

 

[918v]

Maybe you should do dat. In my rifle the 140SMK touches the lands at 2.761” COAL. I back off to 2.710” to start.

 

[Shootnwrench]

Need seated deeper for sure. The spec you got was probably from a barrel that had more throat. As far as over pressure, being close to the lands/jammed also raises pressure.

If your that concerned back the charge off and work back up with a seating depth that functions.

 

[biffj]

You really need to check your rifle for seating depth. Two rifles of the same cal will frequently have variation in the depth of the throat and published data is really only good for the test barrel they used. Measuring your own barrel will give you actual useful data. The other thing is that as someone previously noted every bullet design is different. Tthe shape will have more to do with the point where the bullet makes contact with the rifling then the overall length shows. You can't just swap a bullet and use the same overall length. If you measure to the point where the bullet diameter is the same you can use that data but measuring to the tip of the bullet only works if you're using the same type bullet, and even then its not very accurate. The tips get dinged up or aren't precisely made enough to give good info for seating depth. Take a box of bullets and measure all of them and you'll see variation in the length. Good comparators measure to the point on the bullet where the diameter is at a known point and that will tell you something useful.

Frank

 

[NH4X]

Since it appears you dont have the tools to determine where / when your bullets touch lands , keep coloring bullets and seat deeper untill marks are no longer on bullet. Or you can buy the tools and wont be guessing .

 

[rockchalk06]

You really need to check your rifle for seating depth. Two rifles of the same cal will frequently have variation in the depth of the throat and published data is really only good for the test barrel they used. Measuring your own barrel will give you actual useful data. The other thing is that as someone previously noted every bullet design is different. Tthe shape will have more to do with the point where the bullet makes contact with the rifling then the overall length shows. You can't just swap a bullet and use the same overall length. If you measure to the point where the bullet diameter is the same you can use that data but measuring to the tip of the bullet only works if you're using the same type bullet, and even then its not very accurate. The tips get dinged up or aren't precisely made enough to give good info for seating depth. Take a box of bullets and measure all of them and you'll see variation in the length. Good comparators measure to the point on the bullet where the diameter is at a known point and that will tell you something useful.

Frank

Thank you. I had a long discussion with a friend's today about this. Pointed me in the direction for this .

 

[918v]

Make a slit case to find the rifling:

 

[biffj]

I do the slit case trick myself though I don't normally cut past the shoulder. Once you've cut the slit in the neck resize the case and seat a bullet long. When you put it into the rifle and close/lock the bolt it will push the bullet back into the case. You can measure the length of the assembly and it will tell you where your contact point is. I normally measure the overall length then using my kinetic bullet puller I pull the bullet out just a little and try again. I average a few of the checks and use that as a max overall length with the bullet in contact. Usually I seat shorter than that by a few different lengths and test fire some groups to determine what the best seating depth is. Some bullets don't mind being seated 80 thousandths off the lands and others need to be close to be accurate. It can make a big difference with some bullets.
Thanks 918V for posting the pic.

Frank

 

[Steel head]

The 140 SMK has a really short nose so it’s common to have to seat them deeper than other common bullets in the 140 class.
Set them about .020 from the lands and work up a load, it’s a very friendly bullet if a bit dated now.

 

[rockchalk06]

Thanks for all the help. Everything ordered this afternoon. I'll try again this weekend with some groups at different lengths .20" off the lands. I can't tell you how much of a blessing it is to have this knowledge base at my finger tips.

The guy that taught me most of what I know has sinced passed on. Harry was a godsend wealth of knowledge.

 

[rockchalk06]

The 140 SMK has a really short nose so it’s common to have to seat them deeper than other common bullets in the 140 class.
Set them about .020 from the lands and work up a load, it’s a very friendly bullet if a bit dated now.

View attachment 7378450

The Nosler custom competition 140's produced some fine groups this afternoon. I had one 5 shot that may measure under a 1/2" @100.

The Nosler RDF looks intriguing, but there are a bunch of really bad group videos out there on it.

 

[Steel head]

The Nosler custom competition 140's produced some fine groups this afternoon. I had one 5 shot that may measure under a 1/2" @100.

The Nosler RDF looks intriguing, but there are a bunch of really bad group videos out there on it.

The original RDF’s were kinda tragic, newer stuff it pretty good.

 

[rockchalk06]

The original RDF’s were kinda tragic, newer stuff it pretty good.

I may give them a try too.

 

[Threadcutter308]

I quit measuring or even caring about COAL (Cartridge Over All Length) a long, long time ago.
The only measurement I care about now is COH (Cartridge Ogive to Head). Having said that, I’m a bolt gun shooter and COAL means nothing to me. For gassers, different story.

 

[clcustom1911]

Thanks.

I backed a few down to 2.80", and they go in a little easier, but all are still hitting the lands. I ran a black marker around the bullet and you can see where it's still hitting.

If I go any lower, I'm worried about over pressure.

You would have a pressure spike if they are touching the lands, not .020 off.

Bump the bullets down to 2.78 or so.

 

[Steel head]

You would have a pressure spike if they are touching the lands, not .020 off.

Bump the bullets down to 2.78 or so.

This.

I personally witnessed the 140 SMK do pretty damn well at 1810 yards with @Sniperwannabee and I used to shoot a ton of them.
They love a bit of jump.

 

[clcustom1911]

This.

I personally witnessed the 140 SMK do pretty damn well at 1810 yards with @Sniperwannabee and I used to shoot a ton of them.
They love a bit of jump.

They don't give a shit about jump in my long throat Tikka. I think my 142's are jumping like .090 or something. Don't care, they shoot.

 

[Steel head]

They don't give a shit about jump in my long throat Tikka. I think my 142's are jumping like .090 or something. Don't care, they shoot.

Possibly the easiest bullet ever to load.

 

[clcustom1911]

Possibly the easiest bullet ever to load.

And 47g of R26 makes them fly flat farther

 

[Steel head]

And 47g of R26 makes them fly flat farther

I have a buttload of R26 on the way, may try it in my 260 now.

 

[clcustom1911]

I have a buttload of R26 on the way, may try it in my 260 now.

I think as long as you use a 140+ weight bullet, you're good with R26.

 

[Steel head]

I think as long as you use a 140+ weight bullet, you're good with R26.

I’m thinking of trying the new 144LRHT

 

[Sniperwannabee]

This.

I personally witnessed the 140 SMK do pretty damn well at 1810 yards with @Sniperwannabee and I used to shoot a ton of them.
They love a bit of jump.

One of the best days in my life haha

 

[rockchalk06]

Thanks again for all the help. Tools arrived today and I figured it out.

Took an average of 3 lengths with the SMK O-Give
2.263"
2.263"
2.264"
Average 2.263"

.020" off the lands to start. Puts me at an average COAL of 2.760". All rounds cycle excellent and have plenty of room in the mag. 2.243" off the O-Give.

Y'all were spot on. Measuring off the O-Give gave much better results. Extremely consistent.

Thanks again everyone for their input.

 

[biffj]

Keep us posted with results too. Always good to see if any of the trouble we hand out helps someone and just knowing if your rifle is working is always nice too.

Frank

 

[rockchalk06]

I had 4 loads of 5 rounds made with the SMK's 140's from 40.0 grains to 42.0 grains of H4350 and Federal 210M primers. Seated them .020" off the lands.
40.5 grains produced a .475" group
41.0 grains produced a .577" group
41.5 grains produced a 1.205" group
42.0 grains produced a 1.116" group.

All at 100 yards 95 degrees with a 5 MPH wind right to left. I will rent a chrono next trip and see what FPS these produce.

Last weekends groups with the Nolser CC 140's ended with 40.0 grains of H4350 producing the best. I wanted to see what .020" off the lands looked like compared to .030". I was shocked. With .020" it produced a 1.137" group and bumping it back to .030" produced a .574"group..

Again, thanks for the help

 

[918v]

You should test it further with .003” COAL increments and .1gr powder charge increments.

 

[biffj]

You might also try the 142gr matchkings. They're a different ogive shape than the 140gr SMK and a little longer bullet. I've seen them to be a little less sensitive to seating depth in the 6.5X47 and heard the creedmore is the same.

Frank