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Precision shooters, ballistics experts, other authorities: Lend me your ears (re “cold bore” shots). Login/Join 
fugitive from reality
Picture of SgtGold
posted Hide Post
quote:
Originally posted by sigfreund:
quote:
Originally posted by smithnsig:
A slight drift, but I have noticed a poi shift on the last round that locks back a semiauto gas gun.


I am interested in all POI shifts.

It’s not something that we hear much of these days, but at one time a significant complaint was that the first shot from a new magazine from autoloading pistols, especially 1911s, would not group with the rest. I read a comment from a then well-known author who claimed that that was a complete myth. I, on the other hand, could personally attest that it was absolutely true of the Colt “Combat Elite” I owned for a time in the late 1980s. At a distance of 10 yards or so, the first shot would hit a good 2 inches high and to one side as compared with the rest of the magazine.


What I find interesting about the 1911 first round flyer issue is I've never seen it with a tuned bullseye pistol. I'm not saying it doesn't happen, but not with any truly accurized 1911 I've ever seen.

As it pertains to rifles, I've never had a cold bore shift that I had to compensate for. Now a clean bore shift is a whole different story. When a match starts at 200 yards it really isn't an issue, but at 600 yards it's enough to turn a an X into a 9.


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Posts: 6465 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
Sigless in
Indiana
Picture of IndianaBoy
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I am not much of a 'precision' shooter.

Not yet, anyway, though I am working on it.


However, in my experience, it depends on the individual rifle/barrel.


I had a 220 Swift (sold it to a buddy), that would put bullets into a group whether the bore was clean and cold or warm and dirty. It had a very heavy varmint taper and was slick as glass when I cleaned the bore.


I have a 30-06 that shoots great groups for being a sporter weight, and if I clean the barrel completely, it will affect POI by 3-5 inches. As it fouls it will come back to the POA/POI.



I don't clean my AR barrels all that often, so I can't make any claims about the gas gun precision rifle I built.
 
Posts: 13523 | Location: The Edge of the Ozarks | Registered: December 04, 2003Reply With QuoteReport This Post
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quote:
Originally posted by fritz:
Rimfire rifles are a whole different matter. POI shifts can take 5-15 rounds to cure after cleaning. It can take that long to cure POI isues after changing ammo types, too.

I've seen POI and accuracy issues with my AR15s when I switch between certain types of ammo. The most pronounced is to and from Hornady 73 ELD. I see the need for 5, sometimes 10, rounds for the POI shift and accuracy deterioration to go away.

This is why I believe shooting only one type of ammo in a rifle is important to its consistent performance.


******
On a little different note, it's easier to shoot a bolt action with precision than a semi-auto. Regardless of the type of semi-auto. Skills that make bugholes with a bolt action may produce shotgun patterns with a semi-auto. This becomes more noticeable with cold-shooter shots.

Furthermore, it's easier to shoot a low-recoiling round accurately than it is a higher-recoiling round. Anybody with experience in PRS-type competition knows this. Regardless of the keyboard commandos who state they can shoot their 308, 300WM, or 338LM "sub-MOA all day long, if they do their part", they are less likely to exhibit cold-shooter POI issues with a 223 or 6BR than with a 300WM.


Regarding that highlighted section; it's a well-known phenomenon that changing powders will affect accuracy until you shot a couple of rounds with the new powder. This is something that reloaders need to keep in mind when testing different powders in the same gun at the same session.

I avoid that issue by only ever using Varget for my match rifle rounds. But if I were to try an compare to a load with another type of powder, I would make sure to shoot 4-5 rounds of the new powder before getting down to precision shooting for the new load.
 
Posts: 3051 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
Freethinker
Picture of sigfreund
posted Hide Post
quote:
Originally posted by NikonUser:
... it's a well-known phenomenon that changing powders will affect accuracy until you shot a couple of rounds with the new powder.


Despite being relatively well informed about many aspects of shooting, that was a new and surprising fact to learn.
I will definitely keep that in mind in the future when shooting different loads.




Dear Karma, I have a list of people you missed.
 
Posts: 40972 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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posted Hide Post
quote:
Originally posted by NikonUser:

it's a well-known phenomenon that changing powders will affect accuracy until you shot a couple of rounds with the new powder.



My barrels are not aware of this well-known phenomenom Smile

I have not experienced a change in accuracy switching between powders, Varget and H4895
 
Posts: 2683 | Location: 9860 ft above sea level Colorado | Registered: December 31, 2008Reply With QuoteReport This Post
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posted Hide Post
quote:
Originally posted by offgrid:
quote:
Originally posted by NikonUser:

it's a well-known phenomenon that changing powders will affect accuracy until you shot a couple of rounds with the new powder.



My barrels are not aware of this well-known phenomenom Smile

I have not experienced a change in accuracy switching between powders, Varget and H4895


I was going to add that I thought this would apply more to vastly different powders, like switching from an extruded powder to a ball type or some such. But I got busy and had to keep the post short.

If my (failing) memory serves, Varget and H4895 are both extruded powders that are very similar in shape.
 
Posts: 3051 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
fugitive from reality
Picture of SgtGold
posted Hide Post
quote:
Originally posted by sigfreund:
quote:
Originally posted by NikonUser:
... it's a well-known phenomenon that changing powders will affect accuracy until you shot a couple of rounds with the new powder.


Despite being relatively well informed about many aspects of shooting, that was a new and surprising fact to learn.
I will definitely keep that in mind in the future when shooting different loads.


When dealing with 22 LR the bullet lube can have this same effect. I have a 10\22 Target that wasn't grouping anything well at 100 yards. Out of frustration I tried some Aguila SV and noticed a slightly better group. The more I shot, the better the grouping got until I had gone from almost 6" down to just under 3". It took about 50 rounds to 'season' the barrel to the ammo.


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Posts: 6465 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
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posted Hide Post
quote:
Originally posted by NikonUser:
quote:
Originally posted by fritz:
I've seen POI and accuracy issues with my AR15s when I switch between certain types of ammo. The most pronounced is to and from Hornady 73 ELD. I see the need for 5, sometimes 10, rounds for the POI shift and accuracy deterioration to go away.

This is why I believe shooting only one type of ammo in a rifle is important to its consistent performance.

Regarding that highlighted section; it's a well-known phenomenon that changing powders will affect accuracy until you shot a couple of rounds with the new powder. This is something that reloaders need to keep in mind when testing different powders in the same gun at the same session.

I have no idea what powder(s) Hornady uses in their factory ammo. I can easily switch between their 55 VMax and 75 Black HPBT loads. Sometimes going back and forth between Federal GMM 69 causes one or two odd impacts, sometimes not. I assumed the switch to 73 ELD ammo was due to the bullet shape. Or maybe not.

I do know that the 73 ELD ammo plays well with my one 223 match chamber. It plays well with my Wylde chamber to 300 yards, but accuracy becomes so-so in comparison at 400+ yards. None of my 5.56 chambers like it much past 100 yards.

Because of this, I'm am seriously considering dumping 73 ELD ammo, if I can confirm the 75 Black HPBT will do what I want at 500+ yards in my 223-match-chambered barrel. I've been on a multi-year process of reducing types of ammo across multiple AR15s -- every little bit helps.
 
Posts: 6342 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
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Yeah, Hornady keeps their loads pretty closely. I would think that they use their Superformance (partnership with Hodgdon) powder for their Superformance loads, just like they use Leverevolution (also with Hodgdon) powder their Leverevolution loads.

I do not know which powder they use in their 55gr V-Max Varmint Express or 75gr BTHP Hornady Black. The 73 ELD Match is from their Match product line, and I have no clue what powder is used there.

However, judging by the cutaway pictures for the product lines at their site: I see that Match appears to be extruded powder, whereas the Black and Varmint Express lines look like ball powder.

It would make some kind of sense that they use extruded powder for their Match line because you can get that powder in temperature insensitive form, whereas ball powder is more susceptible to temperature variations but can provide higher velocities for the same load.

But that's all conjecture on my part and looking at cutaway pictures which may not even represent reality.

Is it 5 o'clock yet?
 
Posts: 3051 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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posted Hide Post
quote:
Originally posted by NikonUser:
I do not know which powder they use in their 55gr V-Max Varmint Express or 75gr BTHP Hornady Black. The 73 ELD Match is from their Match product line, and I have no clue what powder is used there.

However, judging by the cutaway pictures for the product lines at their site: I see that Match appears to be extruded powder, whereas the Black and Varmint Express lines look like ball powder.

It would make some kind of sense that they use extruded powder for their Match line because you can get that powder in temperature insensitive form, whereas ball powder is more susceptible to temperature variations but can provide higher velocities for the same load.

Interesting thought, and you may have something here. Over the past few months I've carefully tested H-75 Match HPBT against H-75 Black HPBT. The Black ammo is faster than the Match ammo in every barrel I currently use. For one barrel the Black'MV is only 4 fps faster, which is likely a meaningless number. Some are 20-30 fps higher in MV; one is 70 fps higher.

Given that the Black 75 grain ammo has equal or better accuracy than the Match 75 grain ammo in my barrels, I am dropping the Match line going forward. Furthermore, the Black products cost less than the Match products.
 
Posts: 6342 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
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That's very interesting. Reading the description fpr the various Hornady product lines, one gets the impression that the Match line is supposedly assembled with greater care and more attention to the component selection, hence the greater cost.

Of course, one also realizes that's all marketing fluff.

If you get equal or better accuracy with the less expensive Black line, I would call that serendipitous and carry on, Blackly.
 
Posts: 3051 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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posted Hide Post
quote:
Originally posted by sigfreund:
Can we expect the first shot (or two+) from a clean, cold bore to have a different point of impact from subsequent shots in a string?

I intended to post a picture of a paper target from last weekend, but I just realized I tossed it, and it's on the way to the landfill with today's trash pickup.

My least accurate AR15 upper is a 14.5" piston 1:7 twist LWRC. The BCG is super easy to clean after each session, but the barrel is another story. The bore fouls with carbon -- cleaning patches come out black, patch after patch. It's the only barrel I regular make passes with a bronze brush to knock down the carbon to a tolerable level. Anyway, this barrel was pretty clean at the start of the day.

The day's goals were to do MVs and accuracy tests of three ammo types -- Hornady 55 Vmax, Fiocchi's cheaper version of 55 VMax, and Hornady 75 HPBT Black. I put a Magnetospeed on the suppressor, dry fired a couple of times, and shot at 1" pasters at 100 yards.

Started the session H-55 Vmax, light breezes from my 8 o'clock. First impact was 8 o'clock on the paster. Rounds 2-5 landed in a tight bughole a touch above the paster's center at 1 o'clock. All five rounds measured .75". If I threw out the first round cold-clean-bore "flyer", rounds 2-5 measured 1/4". Had I stopped with that group, I could proclaim the cold-clean-bore is about 1/2" down and left from the remaining shots, and H-55 Vmax is uber-match-grade in this upper. But this ain't my first keyboard-commando rodeo. I knew my technique was flawless on that string.

I load another 5 rounds of Vmax, the wind picks up to 5-10 mph from my 8 o'clock. This group measures 1.0", with noticeable vertical variation -- one shot is just barely left of center, the other 4 are on the edges of the paster at 12, 2, 3, and 6 o'clock. I felt my technique was good on this string, but maybe not quite up to the level of the first string.

So....did I have a first round cold-clean-bore flyer? Did I shoot less precisely on the second string? Did the variable breezes on the second string toss the bullets? Is there noticeable accuracy variations between rounds in Vmax ammo?

After testing MVs on the other ammo types, I removed the Magnespeed. Loaded 10 rounds of H-55 Vmax, and aimed at plates located at 320 yards. Winds still 5-10mph from my 8 o'clock. One group measured 3.0" of vertical, the other 3.25" of vertical. I guessed the wind pretty well, so the horizontal stringing was less than the vertical variation. With these shots the round count was at 36-45 rounds after cleaning. I felt I shot these 10 rounds well.

What I take from this shooting session (and many other similar ones):
- Hornady 55 Vmax is solid 1 MOA ammo in this rifle, which I'm OK with. Especially using a 2.5-10x scope.
- It's hard to separate my shooting errors from the ammo's inconsistencies. I feel this occurs a lot with me, especially when shooting my ARs.
- For all but the best shooters, I believe cold shooter is a bigger challenge to accuracy than cold bore.
 
Posts: 6342 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
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quote:
Originally posted by fritz:
(snip)
- It's hard to separate my shooting errors from the ammo's inconsistencies. I feel this occurs a lot with me, especially when shooting my ARs.
- For all but the best shooters, I believe cold shooter is a bigger challenge to accuracy than cold bore.


That bolded bit is EXACTLY the reason F-class competitors handload their ammo and spend hundreds and thousands on electronic scales and myriad other loading instruments, tools, and gadgets. We never want to leave any points on the loading bench.

As for the last statement, I can't say as I disagree much.
 
Posts: 3051 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
You have cow?
I lift cow!
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Typical "cold something" on my M14. 1 oclock dot was POA. POI was about 3 inches left (top of the 7 ring.) Next POI about 1 inch left, 1 inch high. Next 3 on dot. Next 15 rounds were tight to POA. 2nd group at 12 oclock, then dot drill.

M14 is no stranger to this kind of behavior, so it's probably exaggerated on this platform.

Range was called cold and next group shot after about 10 mins, is 5 oclock. First 2 are further left. Next 3 still a little left, which are echoed in the next 2 groups with left fliers so that could have been my bag adjustment and or focus leaving me. Big Grin

I never felt like I had a shot get far away from me which would explain the extreme left impacts.

IMG_1828


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Posts: 5936 | Location: Bay Area | Registered: December 09, 2007Reply With QuoteReport This Post
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The following is an example of switching ammo types with an AR15. I have my match ammo pretty well figured out for all uppers. My challenge now is the cheap stuff. In some matches the AR shooter must engage a number of paper and clay targets at distances of 5-30 yards, then transition to steel targets at distances of 100-400 yards. Supreme ammo accuracy isn't required at the short distances -- the shooter must understand optic offset, and put rounds in place quickly while standing and moving.

One thought is to use cheap blasting ammo on the close targets, then switch mags to match ammo for the long targets. I have done this in the past, but have questioned my results on the longer targets. Therefore, I began evaluating the transition from one ammo to the next, with targets at 250 yards. This is for Wilson Combat 16" SS barrel 1/8 twist mid-length gas, the rifle's second barrel. Four groups of 5 rounds, one mag of 20 rounds, shot relatively quickly, breaking position at the end of each 5-round group to look through a spotting scope.

American Eagle 55 FMJ -- First round flyer than was 3.5 MOA higher than expected, and 1.5 MOA to the left.
group #1 - 2.5" vertical dispersion and 4.25" horizontal dispersion
#2 through #4 -- verticals of 1.75", 3.5" and 4.75". Pretty much the way FMJ sprays.

Hornady 55 Black HPBT
#1 - 2.5" vertical and 6" horizontal. Upper left group, in the picture below. Wind of 5-8 mph from my 7 o'clock.
#2 - 4" vertical and 2.5" horizontal. Lower left group.
#3 - 2" vertical and 3.5" horizontal. Upper right group.
#4 - 1.5" vertical and 1.75" horizontal. Lower right group. I held 2 MOA left of dot on this group. The prior 3 groups were shot with crosshairs on the orange dots.
The barrel needed 15 rounds of the new ammo for accuracy to settle down.



Then I transitioned to Federal 53 Vmax
#1 and #2 -- 4" verticals, with 3-5" horizontal variation.
#3 - 2.25" vertical, 2.62" horizontal. Upper group, in the picture below.
#4 - 1.62" vertical, 2" horizontal. Lower group. Wind had picked by this time. Holding 4-5 MOA left of dots.
The barrel needed 10 rounds of the new ammo, but was better after 15 rounds.



I have additional testing to do. I may end up using the same ammo for every target.
 
Posts: 6342 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
Freethinker
Picture of sigfreund
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Very interesting report that I would have never guessed. Thanks.




Dear Karma, I have a list of people you missed.
 
Posts: 40972 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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What is interesting is that fritz has reached the point where he can discern that issue and have it repeat consistently. Standardizing on one load is the way to go; find one, and stick with it.

Since I have only ever been using Varget for all my match loads, I had to go diging in the deepest darkest recesses of my memory to dig up that ancient reloading lore about different powders during testing. (You could actually hear the creaking noises from my brain when I was extracting this bit.)

I predict that once fritz gets sufficiently exasperated with factory ammo and its inherent inconsistency, he's going to look at handloading and that will bring on its own challenges. Fun times ahead.
 
Posts: 3051 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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Factory loads are only as consistent as the variability between lots of ammo.

So, if you are buying a larger quantity of ammo....trying asking for same lot numbers. Even in Factory "Match Ammo" one can velocity swings of 25-100fps.

Best way of controlling this....Roll your own.

Andrew



Duty is the sublimest word in the English Language - Gen Robert E Lee.
 
Posts: 676 | Registered: May 01, 2010Reply With QuoteReport This Post
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quote:
Originally posted by NikonUser:
I predict that once fritz gets sufficiently exasperated with factory ammo and its inherent inconsistency, he's going to look at handloading and that will bring on its own challenges.

I haven't ruled out handloading, but it's not in the cards right now. Between a heavy office workload and weekend maintenance of the family ranch, I don't even have the time for a well-deserved nap. We'll see what the future holds.

There's no doubt I have experienced challenges with factory ammo. My past practice of swapping between ammo types during carbine matches may be my biggest faux pas. Now that I use Hornady 75 Black as the match ammo for most of my ARs, my cost per round has decreased noticeably. I need to suck it up and use H-75 exclusively. Looking back on 3 matches, I think switching to AE55 FMJ on high-volume stages hosed me for the following precision targets.

I realize factory ammo won't give me the very best accuracy. Fortunately Hornady's 73 & 75 grain loads work pretty well, as long as my head isn't up my backside. I've missed more 100-yard gimme targets than I care to admit, but I've also tagged some 600+ yard plates in windy Wyoming and New Mexico matches that RO's have noted were some pretty bold shots. By the time our local matches start back up in the spring, I will hopefully have consumed a couple more ammo types that I will no longer stock in the future.
 
Posts: 6342 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
fugitive from reality
Picture of SgtGold
posted Hide Post
quote:
Originally posted by El Cid 92:
Factory loads are only as consistent as the variability between lots of ammo.

So, if you are buying a larger quantity of ammo....trying asking for same lot numbers.


Some of the companies that supply small bore shooters allow you to order small ammounts of ammo for testing. When you find what works they have the lot number and your follow on order comes from the tested lot. Even so, I've seen changes in POA\POI within tested lot numbers so sometimes even that doesn't work out.


_____________________________
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Posts: 6465 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
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