Low Velocity from New Rifle

FourT6and2

FourT6and2

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Minuteman
Feb 13, 2017
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#1
Just got around to breaking in a new rifle.

Barrel is Hawk Hill. Contour is Marksman. 26 inches, 6.5 Creedmoor, 1:8 twist, 4-groove. No brake.
First three shots out of the rifle ever grouped 0.15 MOA with Factory Hornady 140gr ELD-M ammo. I was ecstatic.

I put about 80 rounds down the tube today. And I did clean every now and again. I didn't see any copper fouling at all. None. Just carbon. And it cleaned out easy enough.

The thing that really surprised me, though, is the low muzzle velocity. I'm using a Magnetospeed V3. And in this rifle, the factory ammo came in at an average of 2600fps from 25 rounds. The same lot # of ammo gets 2830fps in my other rifle. Same day. Same chronograph. Same ammo. That's a 230fps difference. That's pretty large, isn't it?

2600fps is super slow. Even for factory 140gr ammo. What might be causing this? Should I even care? I guess I can still hit my target at distance if the rifle seem to group well. But it's weird that this barrel is so much slower. I did measure the chamber with a Hornady OAL Gauge and the free-bore is MUCH longer in this rifle than in my other one, which has a standard SAAMI-spec chamber. Could that be the cause? Lower pressure?
 
#2
Excessive free bore can drop the pressure for sure, especially compared to a chamber that allows no to very little jump on the given ammo. If the accuracy continues to be excellent (1/4-3/8 MOA consistently) I would not touch it, but if it is just "good" (1/2-5/8 MOA) then I would have the chamber set forward slightly to bring the bullet closer to the lands and find out for sure if that is the cause of the low velocity. I have seen some barrels that are inherently slow (just could not get the velocity that I should have with the given load no matter what), but I personally have not had enough barrels with everything else being equal to be able to quantify how much slower they were.
 
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#3
jbell said:
Excessive free bore can drop the pressure for sure, especially compared to a chamber that allows no to very little jump on the given ammo. If the accuracy continues to be excellent (1/4-3/8 MOA consistently) I would not touch it, but if it is just "good" (1/2-5/8 MOA) then I would have the chamber set forward slightly to bring the bullet closer to the lands and find out for sure if that is the cause of the low velocity. I have seen some barrels that are inherently slow (just could not get the velocity that I should have with the given load no matter what), but I personally have not had enough barrels with everything else being equal to be able to quantify how much slower they were.
Click to expand...

Accuracy is sporadic. I'll get a group here or there that's good (1/2 MOA or lower). But then I'll get a group that's awful (1-2 MOA, or even vertical stringing). Usually the stringing happens when the barrel is hot. But 10-15 rounds shouldn't be burning up the barrel. My other rifle is pretty solid.
 
#4
The jump with the same ammo in my other rifle is currently 0.032" with 1200 rounds on it. The jump in this rifle fresh out of the box is 0.043". I only shoot factory ammo, so I'm thinking I'll get less useable life out of this barrel since at some point the jump will be too large as the throat wears and I can't chase the lands. I'm just wondering if the free-bore is a bit excessive?
 
#7
Typically they speed up a bit around the 150-200 round mark. Not 230 fps, but 50-75 or so. That may be some of it.

For example my 6.5 saum went from 3086 to 3155 over the first 150 rounds with the same load.
 
#10
Im with the others, it isnt the jump. Do you know anything about the chamber? Do you know anyone with a borescope?

I chambered a barrel a few months ago that was oversized in the groove diameter. I knew this because the freebore section of the chamber still showed some groove in it. Normally they clean up completely as the freebore of most reamers is .0005-.001 over groove diameter. I sent the barrel back and they replaced it(not a hawk hill barrel).
I kinda wished I could have shot it to see what it would do. I would expect it to shoot fine but be slow with a given load. I think bore dimensions, and specifically groove diameter variations cause a lions share of velocity differences between barrels. Just a theory. If you know someone with a good borescope, take a gander at the throat.
 
#11
Ledzep said:
Typically they speed up a bit around the 150-200 round mark. Not 230 fps, but 50-75 or so. That may be some of it.

For example my 6.5 saum went from 3086 to 3155 over the first 150 rounds with the same load.
Click to expand...

Yeah, you know I hear this all the time. But my other rifle didn't speed up. It actually dropped 30-50fps after 100 rounds.
 
#13
Supersubes said:
Im with the others, it isnt the jump. Do you know anything about the chamber? Do you know anyone with a borescope?

I chambered a barrel a few months ago that was oversized in the groove diameter. I knew this because the freebore section of the chamber still showed some groove in it. Normally they clean up completely as the freebore of most reamers is .0005-.001 over groove diameter. I sent the barrel back and they replaced it(not a hawk hill barrel).
I kinda wished I could have shot it to see what it would do. I would expect it to shoot fine but be slow with a given load. I think bore dimensions, and specifically groove diameter variations cause a lions share of velocity differences between barrels. Just a theory. If you know someone with a good borescope, take a gander at the throat.
Click to expand...

I know nothing about the chamber. I told the smith I am shooting 100% factory Hornady 140 ELD-M. And they said ok, we know what to do. My other rifle has a standard SAAMI chamber.

Being that both rifles have the "same" barrel but one is Bartein and the other Hawk Hill, I wonder if there are indeed very tiny variances in dimensions? I mean, it has to be a given considering they were cut with different tooling on different machinery. I just hadn't ever thought about it before. I assumed I'd get about the same velocities regardless.

I've got a 1,000-yard practice scheduled for next week. So I'll be able to see how this thing does at distance.
 
#15
For the vast majority of barrels, across all top makers, generally things (velocities/tolerances) are amazingly consistent. Even in the same shop though, tolerances will change. I dont think surface finish plays a big role either. You said it wasnt holding copper either, so thats not it. The saami creedmoor chamber specs are actually very good, having started out as a match round first(as opposed to military or hunting). I know they didnt say what the chamber was, but it would be a fair guess that it isnt a plus sized mess. If you have a mic, you could compare the fired cases from each barrel. My guess is it's a saami chamber and it's fired brass will be very close to your known saami barrel brass. A few thou +/- wont equal what youre seeing. Is it a barrel you can remove yourself(AT, remage, etc)? Probably worth a call to hawk hill to get their take. I bet they'll be interested in it.
 
#16
Supersubes said:
For the vast majority of barrels, across all top makers, generally things (velocities/tolerances) are amazingly consistent. Even in the same shop though, tolerances will change. I dont think surface finish plays a big role either. You said it wasnt holding copper either, so thats not it. The saami creedmoor chamber specs are actually very good, having started out as a match round first(as opposed to military or hunting). I know they didnt say what the chamber was, but it would be a fair guess that it isnt a plus sized mess. If you have a mic, you could compare the fired cases from each barrel. My guess is it's a saami chamber and it's fired brass will be very close to your known saami barrel brass. A few thou +/- wont equal what youre seeing. Is it a barrel you can remove yourself(AT, remage, etc)? Probably worth a call to hawk hill to get their take. I bet they'll be interested in it.
Click to expand...

Nope, I can't remove the barrel myself. It's a typical 700 clone (Defiance Deviant). I don't have a mic. I do have a caliper though. Comparing fired brass is a good idea. I'll see what I find.

I'm looking at the invoice from the shop and it lists "chamber with Tactical Match Reamer." But that doesn't really tell us much lol. Just some fancy buzzwords.
 
#18
bkw1911 said:
Did you test it at some distance to see if that was actually the case between the two rifles and not an accidental poor setup of the magnetospeed on the new rifle?
Click to expand...

Nope just at 100 yards to zero and break it in. Like I said, I'm getting out on the 1,000-yard range next weekend. Only other weird thing is some vertical stringing after 5-8 shots. I think the barrel is just heating up too fast. But my other rifle stays rock solid for 20-shot strings. But yeah, those are the two issues. Low velocity and vertical stringing.

I wonder if it could be the ammo? I'll try a few other lot numbers next time.
 
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#19
Weird, but what the heck and try the electrical tape headspace test. If anything, to check that off before taking it out again. I doubt it is headspace but just enough too much and the case will expend energy. There was absolutely no problem without a doubt about mounting the chronograph?
 
#21
Culpeper said:
Weird, but what the heck and try the electrical tape headspace test. If anything, to check that off before taking it out again. I doubt it is headspace but just enough too much and the case will expend energy. There was absolutely no problem without a doubt about mounting the chronograph?
Click to expand...

I don't think there was an issue with mounting the chrono. It's pretty cut and dry. I've done it plenty of times without issue. But I'll definitely be using it again next time with a few other lots of ammo.

What's the headspace test with tape?
 
#23
Unfired case with a layer of trimmed tape on the case head face. It is more of an improvised no go gauge. Some barrel nut guys use this as a go and no go.
 
#25
Culpeper said:
Weird, but what the heck and try the electrical tape headspace test. If anything, to check that off before taking it out again. I doubt it is headspace but just enough too much and the case will expend energy. There was absolutely no problem without a doubt about mounting the chronograph?
Click to expand...

I would not use electrical tape, its too thick. Use scotch tape, should be about 0.002" thick. But I seriously don't think it would be a headspace issue.
 
#29
Got to the range again today. Brought a few lots of ELD-M ammo, both rifles, and a chrono. My other rifle is rock solid. Velocity is the same as listed before (2830fps). Regardless of the lot, this new rifle still chronos low. And accuracy has seriously gone down the drain. I've tried cleaning. I've tried leaving the barrel fouled a bit. Doesn't matter. I think part of the problem is heat. When the barrel is ice cold I can get a 3-shot group in the teens. But after 3-5 shots, accuracy seriously disappears and I see weird stringing. Not the case with my other rifle. I can shoot 20-shot strings and it holds true.

These groups are not cherry picked. I can pick up my other rifle and hammer out groups like this no problem:
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This is the new rifle that's yielding low speeds:
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Here's a photo of fired cases. New rifle on right. Other rifle on left.
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#30
Try greasing up an appropriately sized lead fishing weight and pushing it through your barrel and measure groove/land diameters and/or look for loose spots when pushing the slug through. You're not getting the same pressures in the new rifle, if the chambers are similar (fired brass), then something else is amiss. Shooting worse as it heats up sounds like a stress relief issue or maybe thermal expansion to the point you lose a gas seal on an already loose bore?

Just internet speculation.
 
#31
Ledzep said:
Try greasing up an appropriately sized lead fishing weight and pushing it through your barrel and measure groove/land diameters and/or look for loose spots when pushing the slug through. You're not getting the same pressures in the new rifle, if the chambers are similar (fired brass), then something else is amiss. Shooting worse as it heats up sounds like a stress relief issue or maybe thermal expansion to the point you lose a gas seal on an already loose bore?

Just internet speculation.
Click to expand...

I don't think I'm comfortable pushing something through the bore. I'm in contact with the rifle smith and hopefully he has a suggestion other than "put more rounds through it and see what happens" haha.
 
#32
How much additional freebore is present in new chamber vs old chamber?
Nominally, will need slightly more powder in a Hawk Hill barrel then you do in a Bartlein to get same velocity, all other things being equal.

Not common but possible to see as much as 100 fps difference from the same barrel mfg'er, same reamer, cut by same smith.

Looking at the primers, significantly less pressure present in new rifle which is function of freebore, lead angle, land and groove diameters and land and groove ratio.
 
#33
FCS said:
How much additional freebore is present in new chamber vs old chamber?
Nominally, will need slightly more powder in a Hawk Hill barrel then you do in a Bartlein to get same velocity, all other things being equal.
Click to expand...

Really? News to me. If I had known this, I would stuck with Bartlein. I'm shooting factory ammo, so I can't alter the charge.

New rifle has about 0.011" longer freebore.

Looking at the primers, significantly less pressure present in new rifle which is function of freebore, lead angle, land and groove diameters and land and groove ratio.
Click to expand...

Yes, I noticed that too. Definitely less pressure. I can feel it in my shoulder too, when I shoot both rifles back to back. Another thing are the rings on the primer. Do you see that? My bolt is Cerakoted. And the face and rear of lugs were not masked off. So the Cerakote has worn away on the bolt face, causing those impressions on the primer. Is that an issue at all? As the Cerakote continues to wear, won't that change the headspace? Or not enough to worry about?

I think, at the end of the day, I'm going to replace this barrel with a Bartlein of the same contour. I'll give it another few hundred rounds and if no improvements that's what I'll do. I guess if I hand loaded, I'd be able to load up some ammo to fit the barrel.
 
Last edited:
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#36
FourT6and2 said:
The jump with the same ammo in my other rifle is currently 0.032" with 1200 rounds on it. The jump in this rifle fresh out of the box is 0.043". I only shoot factory ammo, so I'm thinking I'll get less useable life out of this barrel since at some point the jump will be too large as the throat wears and I can't chase the lands. I'm just wondering if the free-bore is a bit excessive?
Click to expand...


FourT6and2 said:
I know nothing about the chamber. I told the smith I am shooting 100% factory Hornady 140 ELD-M. And they said ok, we know what to do. My other rifle has a standard SAAMI chamber.

Being that both rifles have the "same" barrel but one is Bartein and the other Hawk Hill, I wonder if there are indeed very tiny variances in dimensions? I mean, it has to be a given considering they were cut with different tooling on different machinery. I just hadn't ever thought about it before. I assumed I'd get about the same velocities regardless.

I've got a 1,000-yard practice scheduled for next week. So I'll be able to see how this thing does at distance.
Click to expand...



Im no gunsmith but I'm wondering why a "Tactical Match reamer" that's (supposedly) perfect for factory 143eld-m ammo produces .043 jump? Especially when your SAAMI spec rifle produces .011 less jump. IMO, .043 is a lot of jump and I don't think every rifle is going to tolerate it. I'll bet that reamer is really designed for guys wanting to shoot 140s and who handload. Why would a reamer that's perfect for a SAAMI spec load have that much jump? Doesn't make sense to me. If you reached out to Dave Kiff for a reamer designed for your factory loads it'd look a whole lot different than the reamer they used. Most of us that handload use a minimal jump, particularly with longer bullets like VLDs and the ELD lines. Sometimes a bigger jump may be necessary but usually a short hop to the lands is what produces the best results.

I wouldn't be in a hurry to swap barrels. Why not talk to Dave at PT&G about a reamer for your preferred load and have your current barrel set back just enough to rechamber it? This may solve most of your issues AND it will leave you sitting with a reamer that you can use over and over to create repeatable results for all your barrels in the future, on both rifles?

I would not be happy with my smith if this is what I received on a full custom build. I recently had a 6.5cm built on the same action with a Bartlein barrel and a reamer designed around shooting 140s and it shoots factory eld-x in the mid .3s. I haven't had time to do load development yet but sub .5 accuracy with good factory ammo is what I expect from a custom rifle. I'm not slamming your smith because I don't know all the details. I'm just saying, I'd have some serious questions.


Sent from my iPhone using Tapatalk
 
#37
Sendit6.5 said:
Im no gunsmith but I'm wondering why a "Tactical Match reamer" that's (supposedly) perfect for factory 143eld-m ammo produces .043 jump? Especially when your SAAMI spec rifle produces .011 less jump. IMO, .043 is a lot of jump and I don't think every rifle is going to tolerate it. I'll bet that reamer is really designed for guys wanting to shoot 140s and who handload. Why would a reamer that's perfect for a SAAMI spec load have that much jump? Doesn't make sense to me. If you reached out to Dave Kiff for a reamer designed for your factory loads it'd look a whole lot different than the reamer they used. Most of us that handload use a minimal jump, particularly with longer bullets like VLDs and the ELD lines. Sometimes a bigger jump may be necessary but usually a short hop to the lands is what produces the best results.

I wouldn't be in a hurry to swap barrels. Why not talk to Dave at PT&G about a reamer for your preferred load and have your current barrel set back just enough to rechamber it? This may solve most of your issues AND it will leave you sitting with a reamer that you can use over and over to create repeatable results for all your barrels in the future, on both rifles?

I would not be happy with my smith if this is what I received on a full custom build. I recently had a 6.5cm built on the same action with a Bartlein barrel and a reamer designed around shooting 140s and it shoots factory eld-x in the mid .3s. I haven't had time to do load development yet but sub .5 accuracy with good factory ammo is what I expect from a custom rifle. I'm not slamming your smith because I don't know all the details. I'm just saying, I'd have some serious questions.


Sent from my iPhone using Tapatalk
Click to expand...

Yeah, I'm shooting 140s. Not 143s. Not sure where you got that.

But I do agree with everything else. My other rifle just shoot so good, even with factory ammo. I'm getting groups in the teens. 0.15, 0.17, 0.12, etc. Not every time. But it's an easy enough thing to do. And it shoots great out to about 1500 yards. A new barrel is cheaper than ammo. 1,000 rounds of ammo costs me $1200 or so. A new barrel is $340 + labor. So I can either keep throwing money away by putting rounds through this rifle, or put on a new barrel and send it to the other smith who I know from experience can do it right.
 
#38
FourT6and2 said:
Yeah, I'm shooting 140s. Not 143s. Not sure where you got that.

But I do agree with everything else. My other rifle just shoot so good, even with factory ammo. I'm getting groups in the teens. 0.15, 0.17, 0.12, etc. Not every time. But it's an easy enough thing to do. And it shoots great out to about 1500 yards. A new barrel is cheaper than ammo. 1,000 rounds of ammo costs me $1200 or so. A new barrel is $340 + labor. So I can either keep throwing money away by putting rounds through this rifle, or put on a new barrel and send it to the other smith who I know from experience can do it right.
Click to expand...



Maybe i missed it, but have you contacted the smith or hawk hill yet?
 
#40
Just got off the phone with Hawk Hill and they say their barrels typically run FASTER, not slower. And they are typically a TIGHTER bore compared to others. And they said that really not much can be done if it's running slow. Gentleman on the phone said if I'm seeing 200fps slower than other rifle, recutting the chamber won't help... And that different lot of metal used for the blank could affect it. Or this or that or blah blah blah. So really, they are washing their hands of it.
 
#41
FourT6and2 said:
Just got off the phone with Hawk Hill and they say their barrels typically run FASTER, not slower. And they are typically a TIGHTER bore compared to others. And they said that really not much can be done if it's running slow. Gentleman on the phone said if I'm seeing 200fps slower than other rifle, recutting the chamber won't help... And that different lot of metal used for the blank could affect it. Or this or that or blah blah blah. So really, they are washing their hands of it.
Click to expand...

Nice.
 
#43
Just because they "typcally" are tighter and faster, doesnt mean yours is. Thats too bad. Surprised rhey didnt care much about. Like I previously said(and they agree apparently), small chamber differences wont add up to -200 fps. The bore is the most likely culprit. You can call the builder next.

 
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#45
Nice to know Defiance stands by their product. Glen Harrison just reached out. He volunteered to take a look at the bolt, at least, to make sure it isn't the culprit. They're paying for overnight shipping to get it in for a look.
 
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#47
Again what is the smith saying? If it shoots vey accurately and only 100fps slower then not much you will really be able to do because some are just slower then others but if accuracy is degrading and it shoots that way along with the slower velocities that is entirely on the smith to figure out and fix at no cost. You paid good money for it and it's not performing, plain and simple.

Pretty shitty on HH's part so that's one barrel manufacturer I'll be sure to never use now.
 
#48
TheOE800 said:
Sarcasm. That sucks and the lack of support from either the gunsmith and Hawk Hill is disappointing to see.
Click to expand...

Well I wouldn't throw the smith under the bus just yet lol. Still going back and forth with them. Here's a photo of the bolt face I promised. 200 rounds on it right now.
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#50
Pusher591 said:
Again what is the smith saying?
Click to expand...

I'm paraphrasing here. But he said the velocity is what he would consider low. But that 2830fps is high for Hornady 140gr ELD-M on my other rifle (I disagree; that's a spot-on velocity for a 26" barrel in my experience).

He then says that after 150 rounds, if the barrel hasn't picked up speed, it's might just be a slow barrel.

"With your chamber, we use an exact SAAMI 6.5 Creedmoor reamer with a SAAMI minimum body. Our 140 ELD-M's touching the lands are 2.862" So you will likely have a .060" jump to the rifling. If we were to use a custom reamer with a shorter Freebore, all other handloaders would consider it to be too short of a freebore."

The length of factory rounds I have here is 2.814". A bit shorter than they measure. But maybe just variance in measuring device and ammo.

I followed up with my latest range results. Haven't heard back yet.
 
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