.308 Overall Length Varation with 175gr SMK

[reloadingnoob]

Hello everyone,
I am currently working on loading .308 with 175gr Sierra Match King bullets on a Dillon RL550C and Dillon's .308 dies.

I am noticing that my OAL after seating is varying and I suspect it may be related to the imperfections at the tip of every SMK bullet influencing this. My goal OAL is 2.800in, however I am getting the following lengths on the last 5 test runs:

2.799
2.806
2.789
2.800
2.805

I understand that a variation if +/- .005in should be expected for OAL, however I do notice that the measurement can change with where I decide to measure from the tip of the bullet the tips are often slanted with high points and lower points.

So in essence I have 3 questions:
1. Is this bullet tip variation and OAL variation something I need to worry about, or should I accept this range and be satisfied so long as the average is around 2.800?
2. I am not crimping since this will be going into a magazine fed bolt action rifle and my understanding is it won't be necessary in this use case - do you crimp in your mag fed bolt actions?
3. The completed cartridge does not fit into the case gauge post-seating without a crimp however will fit in my chamber fine. This is to be expected right?

Thanks in advance!

 

[918v]

Are you able to measure the seating depth off the ogjive? Some of the variance can come from inconsistent neck tension or seating effort or slop the press itself.

 

[reloadingnoob]

Not at the moment, I will need to purchase a tool do do this however the manuals typically give an OAL recommendation and does not give a recommendadtion for powder charge + ogive to base length for each specific load. How would you go about this if going strictly off the manual?

 

[sinister]

Match bullets gain consistency (over other styles) by being base-drawn, making for uniform bases and boat-tails.

Long-range shooters and manufacturers will crimp and trim (true) hollow point tips. Shooters will gain consistency at the cost of a slight windage loss. Most will not see a difference at 300 yards and closer.

 

[straightshooter1]

Hello everyone,
I am currently working on loading .308 with 175gr Sierra Match King bullets on a Dillon RL550C and Dillon's .308 dies.

I am noticing that my OAL after seating is varying and I suspect it may be related to the imperfections at the tip of every SMK bullet influencing this. My goal OAL is 2.800in, however I am getting the following lengths on the last 5 test runs:

2.799
2.806
2.789
2.800
2.805

I understand that a variation if +/- .005in should be expected for OAL, however I do notice that the measurement can change with where I decide to measure from the tip of the bullet the tips are often slanted with high points and lower points.

So in essence I have 3 questions:
1. Is this bullet tip variation and OAL variation something I need to worry about, or should I accept this range and be satisfied so long as the average is around 2.800?

That variation in bullet OAL's in what I'd call "normal" with a lot of SMK's. As mentioned by 918v above, variation in your seating can easily come from a any one or a combinations of inconsistent neck tension, slop in your press and interference from the surface of the necks. To see your seating differences, it better to measure your CBTO's as SMK's can have less variance in their BTO's than their OAL's.

If you really want good uniform cartridges, you may need to think about going with an arbor press and seating die like an L.E. Wilson seating die.

2. I am not crimping since this will be going into a magazine fed bolt action rifle and my understanding is it won't be necessary in this use case - do you crimp in your mag fed bolt actions?

You're right. . . for a bolt fed action there's really no need for crimping. Just find the right "neck tension" that works for you.

3. The completed cartridge does not fit into the case gauge post-seating without a crimp however will fit in my chamber fine. This is to be expected right?

Thanks in advance!

Did you check the cases with the case gauge before seating? Sounds like something isn't quite right with the sizing process. . . like maybe the mouths are being faired???

If they fid your chamber fine, you should be ok. But, I'd do some checking to see what's going on with the case prep.

PS: If you try some 169 or 177 SMK's, I find they have more consistent OAL's than other SMK's as they've been factory pointed.

 

[E_T_G]

Are you using a powder drop on the Dillion? If so the variations in powder charges will have a much greater effect on accuracy than a few thousandths OAL.

 

[reloadingnoob]

That variation in bullet OAL's in what I'd call "normal" with a lot of SMK's. As mentioned by 918v above, variation in your seating can easily come from a any one or a combinations of inconsistent neck tension, slop in your press and interference from the surface of the necks. To see your seating differences, it better to measure your CBTO's as SMK's can have less variance in their BTO's than their OAL's.

If you really want good uniform cartridges, you may need to think about going with an arbor press and seating die like an L.E. Wilson seating die.


You're right. . . for a bolt fed action there's really no need for crimping. Just find the right "neck tension" that works for you.


Did you check the cases with the case gauge before seating? Sounds like something isn't quite right with the sizing process. . . like maybe the mouths are being faired???

If they fid your chamber fine, you should be ok. But, I'd do some checking to see what's going on with the case prep.

PS: If you try some 169 or 177 SMK's, I find they have more consistent OAL's than other SMK's as they've been factory pointed.

Thanks for the reply, yes it seems my SMK's look very similar to the 2nd before and after imaging Sinister had posted. I think this is likely the cause for this variance in COAL. Interestingly I measured the COAL of a pack of 175gr Federal GM SMK and the lengths varied from 2.799-2.803.

I almost wonder if flattening the tips of each SMK bullet would be a good idea haha.

My cases fit perfectly in the case gauge after sizing/prior to seating. It is only after seating that it no longer fits all the way in the case gauge - wasn't sure if this is a normal occurrence since it has not yet been crimped?

 

[reloadingnoob]

Match bullets gain consistency (over other styles) by being base-drawn, making for uniform bases and boat-tails.

Long-range shooters and manufacturers will crimp and trim (true) hollow point tips. Shooters will gain consistency at the cost of a slight windage loss. Most will not see a difference at 300 yards and closer.

Thanks for sharing this, the SMKs I purchased look very similar to the 2nd picture showing an angled/slanted tip/meplat. How do people usually go about this - do they flatten the tip or is it just easier to measure the CBTO on a perfect cartridge with 2.800 COAL and base it off of that?

I did read about finding the lands on your specific chamber and determining the CBTO based on that for maximum accuracy however I'm still watching videos at this time to learn about how to do that.

 

[chd]

Given what @E_T_G said, if you do take data off of your powder charges we'd probably all be interested in hearing about it.

 

[wvfarrier]

Are your cases annealed? If not, you could be getting some creep.

 

[straightshooter1]

Thanks for the reply, yes it seems my SMK's look very similar to the 2nd before and after imaging Sinister had posted. I think this is likely the cause for this variance in COAL. Interestingly I measured the COAL of a pack of 175gr Federal GM SMK and the lengths varied from 2.799-2.803.

I almost wonder if flattening the tips of each SMK bullet would be a good idea haha.

My cases fit perfectly in the case gauge after sizing/prior to seating. It is only after seating that it no longer fits all the way in the case gauge - wasn't sure if this is a normal occurrence since it has not yet been crimped?

My loaded cartridges fit nicely into my case gauge and I've never had that issue.

Something is happening with your Dillon and its dies that shouldn't be happening. I'd be taking measurements at every step to isolate exactly where this issue happens, which sounds to me like something having to do with the seater die in the Dillon. You can experiment with a different die and or process for seating to see if you come up with a different result.

BTW: what brass is it your having this problem with?

"Flattening the tips" is kinda what pointing bullets is about . . . mainly to improve BC consistency from bullet to bullet in addition to improving BC all together. It's a lot of work (sorting, trimming, pointing) to get good performance for extreme long distance shooting. Interestingly, if you look at Hornady A-Tip bullets, you'll see the tip is actually flat and small and they do that by design having found that feature actually improves the bullet's BC. Unless you're dong ELR shooting, there's really no need to think about "flattening the tips" .

 

[riverside jeep]

Had the same problem with the same projectiles, also with the 168 SMK. I contacted RCBS and sent them 3 bullets of each, they machined seating plugs for each for cheap ( I thought) and problem solved.

 

[Baron23]

Hello everyone,
I am currently working on loading .308 with 175gr Sierra Match King bullets on a Dillon RL550C and Dillon's .308 dies.

I am noticing that my OAL after seating is varying and I suspect it may be related to the imperfections at the tip of every SMK bullet influencing this. My goal OAL is 2.800in, however I am getting the following lengths on the last 5 test runs:

2.799
2.806
2.789
2.800
2.805

I understand that a variation if +/- .005in should be expected for OAL, however I do notice that the measurement can change with where I decide to measure from the tip of the bullet the tips are often slanted with high points and lower points.

So in essence I have 3 questions:
1. Is this bullet tip variation and OAL variation something I need to worry about, or should I accept this range and be satisfied so long as the average is around 2.800?
2. I am not crimping since this will be going into a magazine fed bolt action rifle and my understanding is it won't be necessary in this use case - do you crimp in your mag fed bolt actions?
3. The completed cartridge does not fit into the case gauge post-seating without a crimp however will fit in my chamber fine. This is to be expected right?

Thanks in advance!

IMO opinion those magnitude of differences can be easily attributed to the meplat (tip of the bullet, yeah) inconsistency in the cup pulled over the lead core. This shown pretty clearly in the pics posted above.

Except for issues of fitting inside mag length, who cares. The key to performance is CTBO (measure to the ogive which is what die in your press is actually set up for) so do get a bullet comparator and good caliper (if you don't have one already).

If you really, really, really want you can get a bullet tip trimmer but now you'd be jumping into the rabbit hole of bench rest and F-open folks. Up to you....I don't think you will find any benefit unless you shoot one of those types of very high precision games.

Google Search

 

[sinister]

How do people usually go about this - do they flatten the tip or is it just easier to measure the CBTO on a perfect cartridge with 2.800 COAL and base it off of that?

Bullet Pointing Die System - Whidden Gunworks

Order Now! A great article on pointing bullets. Bullet Pointing Die System A bullet pointing die is a die used to make a sharper point on a bullet. By

www.whiddengunworks.com

 

[E_T_G]

reloadingnoob, are you running a compressed load? If so, that could be the case guage issue. What brass? Military brass has less volume. You never gave the brand of case or powder and charge.​

 

[reloadingnoob]

reloadingnoob, are you running a compressed load? If so, that could be the case guage issue. What brass? Military brass has less volume. You never gave the brand of case or powder and charge.​

Hi, thus far I have not yet added powder, just adjusting my dies for seating length - brass is a mix of PPU and Norma - I plan to use IMR 4064 however am only test seating at this time.

 

[Doom]

So in essence I have 3 questions:
1. Is this bullet tip variation and OAL variation something I need to worry about, or should I accept this range and be satisfied so long as the average is around 2.800?
2. I am not crimping since this will be going into a magazine fed bolt action rifle and my understanding is it won't be necessary in this use case - do you crimp in your mag fed bolt actions?
3. The completed cartridge does not fit into the case gauge post-seating without a crimp however will fit in my chamber fine. This is to be expected right?

In relation to #1. The interface between the cartridge, bullet and the chamber is what matters. In the case of the bullet to achieve uniform dimensions from round to round the dimension that matters is the beginning of the bullet bearing surface with the beginning of the lands. This is where the bullet diameter and the bore first make contact. Your seating die does not use the tip when seating but uses the diameter of the bullet near/at the bearing surface to achieve uniformity in the "base to ogive" dimension. Ogive in this case meaning the beginning of the reduction of the bearing surface. The ogive (bearing surface to tip) is never in contact with the rifle. The only reason that the COAL is included in the SAAMI specification is for the ammunition to be usable it must be able to fit in the rifle's magazine.

In relation to #2. It is not necessary to crimp in bolt action rifles and is not typically done in target rounds. However, hunting rounds may be crimped since they may be loaded multiple times before firing and may be used in heavy recoiling rifles multiple times before being fired.

In relation to #3. Not knowing what sizing die you are using I am puzzled by this. If in fact this is corrected by crimping it implied that the neck mouth is flared which as far as I know is only done with newer Lee Collet neck sizing dies or your case necks are too thick. However if the rifle chambers the round and a bullet will easily enter the neck of a fired round you are OK.

 

[straightshooter1]

In relation to #1. The interface between the cartridge, bullet and the chamber is what matters. In the case of the bullet to achieve uniform dimensions from round to round the dimension that matters is the beginning of the bullet bearing surface with the beginning of the lands. This is where the bullet diameter and the bore first make contact. Your seating die does not use the tip when seating but uses the diameter of the bullet near/at the bearing surface to achieve uniformity in the "base to ogive" dimension. Ogive in this case meaning the beginning of the reduction of the bearing surface. The ogive (bearing surface to tip) is never in contact with the rifle. The only reason that the COAL is included in the SAAMI specification is for the ammunition to be usable it must be able to fit in the rifle's magazine.

In relation to #2. It is not necessary to crimp in bolt action rifles and is not typically done in target rounds. However, hunting rounds may be crimped since they may be loaded multiple times before firing and may be used in heavy recoiling rifles multiple times before being fired.

In relation to #3. Not knowing what sizing die you are using I am puzzled by this. If in fact this is corrected by crimping it implied that the neck mouth is flared which as far as I know is only done with newer Lee Collet neck sizing dies or your case necks are too thick. However if the rifle chambers the round and a bullet will easily enter the neck of a fired round you are OK.

I don't know of any seating dies that are able to make contact at or near the bearing surface. That would be ideal, if it could be done.

Because my seating stems make contact very high on the ogive, that's exactly why I sort my bullet with a comparator that makes contact at the same place as my seating stems, to help produce the most consistent seating depths (being that there's some variation between the contact point of a standard comparator and the contact point of a seating stem).

 

[Baron23]

I don't know of any seating dies that are able to make contact at or near the bearing surface. That would be ideal, if it could be done.

Because my seating stems make contact very high on the ogive, that's exactly why I sort my bullet with a comparator that makes contact at the same place as my seating stems, to help produce the most consistent seating depths (being that there's some variation between the contact point of a standard comparator and the contact point of a seating stem).

View attachment 8592577

Ah, maybe try a VLD stem?

 

[straightshooter1]

Ah, maybe try a VLD stem?

VLD stems don't go very far down the ogive either.

 

[Doom]

I don't know of any seating dies that are able to make contact at or near the bearing surface. That would be ideal, if it could be done.

Because my seating stems make contact very high on the ogive, that's exactly why I sort my bullet with a comparator that makes contact at the same place as my seating stems, to help produce the most consistent seating depths (being that there's some variation between the contact point of a standard comparator and the contact point of a seating stem).

View attachment 8592577

Right you are! It had been a short night. Thanks for keeping an eye on me.

 

[reloadingnoob]

Update: I went through about 12 more cartridges and trimmed the cases, wiped the wax off best I could and the majority of them are able to fit the case gauge post seating.
Thanks for your help everyone suggesting these bullet comparators to measure from the ogive - they are super helpful and I have learned that the measurements are very consistent (even about .005 more consistent compared to federal gold medal match rounds. Cheers!

 

[reloadingnoob]

Today I started load adding powder charges and seating the bullets. I've noticed that as I reached 43gr, 43.5gr, and 44.0gr of IMR 4064, the base to ogive length began to increase due to the increased powder and I had to dial in my seating dies more to keep the base to ogive length consistent (aiming for around 2.223-2.225 in).

Once I reached 44.0gr of powder the base to ogive length reached an average of 2.230in.

Do you guys also have this problem of varying base-to-ogive lengths as the powder charge is increased?
I don't think it's really of concern as long as future loads are consistent in powder and seating depth/base-to-ogive length, the velocity of each round should be consistent.

 

[Rerun7]

OP - how does it shoot?

I load 175 smks and measure the ogive. I still find some slight variations but nothing that materials to real world changes. They still shoot bugholes even when they aren’t all exact. Sometimes I’ll get a long on and after a second run in the press I find they fall right in line with others.

Also, when I first started loading I realized that I wasn’t seating primers deep enough and consistent enough which was throwing off my OAL measurement.

 

[Snuby642]

All my rounds have a nominal coal measurement for a refrance and mag clearance.

But as many have said the CBTO is what is important. The ogive is a constant and the metplat varies a lot on cheap bullets much less on quality components.

If your ogive is in the same place each time you will see consistant results.

I get consistant powder drops from my Dillon to + / - 0.1g or better with steady operation. Those rounds can be sub moa without splitting a tenth of a grain of powder.

If you can get a powder dispenser with better resolution, go for it but you wreck the flow of production by single loading that.

 

[reloadingnoob]

I have not yet had a chance to shoot my loads, but will be doing so this week. I thought it was strange how my base-to-ogive length kept getting consistently longer as I added more powder.

 

[sinister]

... strange how my base-to-ogive length kept getting consistently longer as I added more powder.

Are you cross-checking your charges against a reloading manual? Sounds like you are compressing your powder charge -- it's what the "C" means as you're approaching maximum. This usually happens earlier with military cases than commercial.

 

[Snuby642]

If you are a new reloader I would avoid compressed charges.

I belive pushing limits with little error is for experienced loaders.

 

[reloadingnoob]

I managed to go to the range and gather data on my handloads:
I'm unsure if my powder charges are being compressed but I don't hear any powder moving when I shake the cartridge haha.

It seems my loads are a bit slower compared to my manual, which at 44.0gr would yield 2732 fps.

175gr SMK Federal Factory ammo
Average 2530
2512
2535
2543

40gr
Average 2417
2405
2436
2411

40.5gr
Average 2462
2453
2476
2462

41gr
Average 2488
2460
2497
2506

41.5gr
Average 2500
2507
2493
2499

42gr
Average 2526
2526
2525
2526

42.5gr
Average 2572
2565
2560
2593

43gr
Average 2605
2605
2596
2612

43.5gr
Average 2617
2616
2625
2609

44gr
Average 2640
2646
2651
2623

 

[straightshooter1]

I managed to go to the range and gather data on my handloads:
I'm unsure if my powder charges are being compressed but I don't hear any powder moving when I shake the cartridge haha.

It seems my loads are a bit slower compared to my manual, which at 44.0gr would yield 2732 fps.

175gr SMK Federal Factory ammo
Average 2530
2512
2535
2543

40gr
Average 2417
2405
2436
2411

40.5gr
Average 2462
2453
2476
2462

41gr
Average 2488
2460
2497
2506

41.5gr
Average 2500
2507
2493
2499

42gr
Average 2526
2526
2525
2526

42.5gr
Average 2572
2565
2560
2593

43gr
Average 2605
2605
2596
2612

43.5gr
Average 2617
2616
2625
2609

44gr
Average 2640
2646
2651
2623

View attachment 8606571

Is your barrel 20"?

The velocities you're getting is just fine for a 20" barrel using IMR-4064. Federal factory ammo no longer uses IMR-4064, it's not a fair comparison. These days, Federal is using AR-Comp for both their 175 and 168 SMK's, which tends to produce higher velocities.

.5 gr increment is too much for a .308 cartridge, as it's easy to skip over a good load. .3 gr increments is much better and easier interpret a series of shots like your showing. I think you should look at something around 42.5 gr IMR0-4064, based on my experience with that charge in my rifle.

 

[reloadingnoob]

This is coming out of a Ruger American Predator - 18" barrel.

I was going to ask that actually, it seems that the sweet spots were around 41.5gr, 42.5gr, and 43 gr. I take it that the higher velocity nodes would be preferred.

So the next step would be to load rounds from 42.5gr - 43.0gr in 0.1 gr increments to narrow down on the powder charge that yields the greatest precision?

 

[Kickin45]

Oh good lord lol
Most velocities from manufactures are 26”, maybe 24”

I highly recommend doing some more research, reading loading manuals and watching reloading videos from REPUTABLE reloaders.

 

[Snuby642]

I see most people using 0.3g increments.

I do, then bracket the best a couple tenths up and down including the best group charge.
That's when I start 5 shots for all charges to help define what's going on.

That usually finds my best charge and let's you see what it looks like on a + / - 0.1g powder drop.

If that doesn't work to my preference I change powder.

 

[straightshooter1]

This is coming out of a Ruger American Predator - 18" barrel.

Typically, those loading manual data often base on a 24" barrel, like Kickin45 mentions, and that's why you're seeing such a difference between you gun and what's in the manual . . . along with the difference in powder.

I was going to ask that actually, it seems that the sweet spots were around 41.5gr, 42.5gr, and 43 gr. I take it that the higher velocity nodes would be preferred.

Yes, the higher nodes are often preferred, but not always necessary.

It's also important to know which brass your using, the PPU or the Norma, as there can a significant difference, particularly when your loading up at the max load (upper node, if you will). For example, the PPU brass I have on hand has an average case volume of 55.7 gr H2O and the Norma I have is 56.4 grs H2O. The larger capacity allows for more powder for a given pressure to get more velocity.

If you're using the PPU brass, then you're going to be getting into pressure issues at 43 grs along with possibly compressing the powers since that'll be over 100% case capacity when seating 175 SMK's to a COAL of 2.800. The Norma brass would have less of that issue.

So the next step would be to load rounds from 42.5gr - 43.0gr in 0.1 gr increments to narrow down on the powder charge that yields the greatest precision?

I didn't recall you reporting any pressure issues at 44 grs, which is fortunate. But that's running pretty high pressure, which can be a problem if you happen to go that high in summertime temperatures. 43 grs is pretty high too. I've gone as high as 43.9 grs., but I also load them long to a COAL of 2.860 and 43.2 worked well for me, loading them to a COAL of 2.894 for a 24" Krieger barrel in an RPR.

If I were you and looking at the higher node, I wouldn't go .1 grs increment, but go .2 gr increments from 42.0 grs to 43.0 grs being at a COAL of 2.800".

 

[reloadingnoob]

Thanks for the in depth information, it has been very useful during my learning experience.
Speaking of over-pressure, I may have noticed signs of overpressure in the form of difficulty with bolt lift/extracting the fired cartridge.

I've always had a hard time extracting Igman Brass (difficult bolt lift) but never with factory PPU or factory Norma brass.

I noticed at the range with my loads that as the powder charge weight went up the Norma/PPU brass all became very difficult to extract/unlock the bolt with.

Interestingly, the new factory Norma 147gr rounds I have shoot at a higher velocity but have no trouble at all with extraction/bolt lift. Perhaps this increased velocity without sign of overpressure is due to the lower projectile weight and possibly powder.

Factory Norma 147 - avg 2682
2686
2707
2667
2639
2712

I think I may need to stick with the lower powder charge nodes then due to the over-pressure signs.

 

[straightshooter1]

Thanks for the in depth information, it has been very useful during my learning experience.
Speaking of over-pressure, I may have noticed signs of overpressure in the form of difficulty with bolt lift/extracting the fired cartridge.

I've always had a hard time extracting Igman Brass (difficult bolt lift) but never with factory PPU or factory Norma brass.

I noticed at the range with my loads that as the powder charge weight went up the Norma/PPU brass all became very difficult to extract/unlock the bolt with.

Interestingly, the new factory Norma 147gr rounds I have shoot at a higher velocity but have no trouble at all with extraction/bolt lift. Perhaps this increased velocity without sign of overpressure is due to the lower projectile weight and possibly powder.

Factory Norma 147 - avg 2682
2686
2707
2667
2639
2712

I think I may need to stick with the lower powder charge nodes then due to the over-pressure signs.

It doesn't surprise me that you were experiencing difficulty with bolt lift with some of the charges . . . like those at 43.5 and 44 grs. When you first start to feel some difficulty with bolt lift, that's almost always a sign of too much pressure and one should stop right there. Along with that, the shooter should inspect the base of the cases to see if there's also ejector swipe, which often accompanies stiff bolt lift due to pressure.

I've never had any Igman brass in my possession and don't know what their case volumes are like. Being made in Yugoslavia, I suspect the case walls may be thicker than what most other cases are, which would result in higher press where you get that stiff bolt lift your talking about. But, I'm just guess, of course.

Right on. . . lighter bullets will have less pressure due to their weight, AND. . . assuming their COAL is also 2.800", they're not going to be seated as deep, which means more case volume for the powder to work in reducing pressure. Looking at load manuals, you can see how lighter bullets will have less pressure or more powder to make up some difference for their weights to get more velocity.


Am curious. . . what shooting range do you usually shoot at?