MG 124 CMJ length variance

[New4John]

I just started reloading not too long ago and tried out a few different bullets.

After settling on MG 124 CMJ's I just bought 4K of them and ran into an issue tonight.

Started having significant OAL variance from 1.128 to 1.142

Switched back to a different brand bullet, and they were all +/- 0.001

Back to the MG's and same variance issues. I measured the bullet lengths of about 25 of them and the variance in length was exactly what I was seeing on my OAL's. I did not have any issue with the first 1K I purchased, they were very consistent and wonder what's up with this batch.

What sort of length variances are you typically seeing on your MG 124's?

[gng4life]

What seating die are you using? What is the shape of the insert in that die?

[Sarge]

I typically see no variance at all with MG's. Something else is amiss because even if the lengths were different the die should still seat them to the same depth. A bullet has to be mishapen to cause theproblems you mentioned.

Using mixed brass will result in different oal's in the range you are talking about. Try using all the same headstamp and see if it settles down any.

[TAP]

My OAL varies +/-0.003" with MG 124 CMJ. I sort my brass so that helps too. I have not measured bullet length consistency but I will try to this weekend and let you know. I agree with Sarge that something else is going wrong. What seating die are you using? It may not have the correct shape for the MG CMJ profile. Try taking the cup or insert out and see how it rides on the bullet.

[New4John]

Using the seating die that come on my Dillon SDB...I am using the proper one, not the one for FP/HP.

It's range brass, but I do sort all the brass by head stamp and was using all of one mfg.

Good info, I'll take the die out and see if maybe it's got something in it and give the press a once over to see if I can find anything that may be contributing.

I did fit check the die to the MG's when I got my first 1k of them and it fit well.

Thanks for the advice so far.

Edited September 4, 2010 by New4John

[edwin garcia]

I had somewhat smilar issues before with mixed head stamp brass in 9mm. What I found out is that too much flaring from the powder station will have an effect on the seating. Make sure it's just enough and not too wide. YMMV.

Cheers

E

[G-ManBart]

If the bullets themselves are different lengths, are you seeing just one or two different lengths or a broad range of numbers? I ask because I have seen a slight (very slight) difference between two different lots of MG bullets and I'm wondering if you didn't somehow mistakenly get part of one lot, and part of a new lot.

I'd call MG, and tell them what you're seeing...they're great to deal with and I know for certain they'll make it right if the bullets aren't within their specs. R,

[New4John]

G-Man I had that exact thought as it's very consistently 2 different measurements.

Didn't find until last night, so will be Tuesday until I can call MG.

Still sounds like I have an issue though based on what Sarge said about it not making a difference that the die should seat it the same regardless.

[TwoShot]

I ran into the same problem with my current case of MG 124 CMJ's Some are noticeably longer than the average. The long ones have a pointier nose, that can be seen with the naked eye. My oal varied 1.155 to 1.170, 15 thousandth's, the same variation in the bullets give or take a .001.

Edited September 5, 2010 by TwoShot

[gng4life]

G-Man I had that exact thought as it's very consistently 2 different measurements.

Didn't find until last night, so will be Tuesday until I can call MG.

Still sounds like I have an issue though based on what Sarge said about it not making a difference that the die should seat it the same regardless.

This is not always true...I was loading some FPs one time with a FMJ type insert in the seating die and I was getting some really strange variance. The insert does make a difference sometimes, that's why they make them...

However, this time it sounds like something is up with the MGs...

[G-ManBart]

G-Man I had that exact thought as it's very consistently 2 different measurements.

Didn't find until last night, so will be Tuesday until I can call MG.

Still sounds like I have an issue though based on what Sarge said about it not making a difference that the die should seat it the same regardless.

Not necessarily. If the nose of the bullet is shaped differently, it will seat the bullet to a different depth based upon how far it fits into the seating stem. Now, if the bullets were identical except for length, then it would mean something else is going on. I'd bet the profile of the two different bullets is just a touch different. R,

[njl]

Why would mixed brass have any bearing on COAL? If the adjustment of the seating die relative to the shell plate / ram doesn't change, and bullet profile is constant, I'd expect COAL to remain as constant as play in the tool head allows. The bullets would appear to be seated deeper in some (because the case is longer)...but COAL would be the same.

I've never used an SDB, so I don't know if it has the same issues with tool head play, but in a 550, if you load some with a full shell plate and some with a less than full shell plate, you'll maximize your variance in COAL.

The other obvious thing to check is that the seating die is not loose.

Edited September 5, 2010 by njl

[TAP]

I just randomly sampled 10 bullets from my case of 3k MG 124 CMJ. The length ranged from 0.388" to 0.391".

[TonyT]

I am puzzled by your experience. It has to be related to your die set up or the manner in which you are seating the bullet. Irrespective of bullet length and case length, the OAL of the final cartridge depends only on the set up of the seating and crimping dies. Perhaps you are belling the case too much or using an oversize expanding plug and the bullet is litterally dropping into the case because of insufficient tension on the case neck.

[New4John]

The bullet lengths I measured ranged from 0.387" to 0.398. The weight varied by 0.6gr.

The shape of the bullet nose is noticeably different. When I removed the seating die, there is most assuredly a difference in the way the bullet contacts the die. I did tweak the the expanding die down just a tad, although I don't think that was it, but it's been mentioned a few times. Just got back from a match and beat, so I'm going to give it whirl tomorrow and see what happens. I have a pile of about 20 of the ones that fit great set aside and will see if they are consistent, then slip in a few of the longer ones with a much sharper taper.

Thank you for the thoughts and inputs.

Edited September 6, 2010 by New4John

[Sarge]

G-Man I had that exact thought as it's very consistently 2 different measurements.

Didn't find until last night, so will be Tuesday until I can call MG.

Still sounds like I have an issue though based on what Sarge said about it not making a difference that the die should seat it the same regardless.

Not necessarily. If the nose of the bullet is shaped differently, it will seat the bullet to a different depth based upon how far it fits into the seating stem. Now, if the bullets were identical except for length, then it would mean something else is going on. I'd bet the profile of the two different bullets is just a touch different. R,

I concur wholeheartedly. I was assuming the profile was the same since it was not mentioned as being an issue. If the shape at the business end of the bullet is different by even a little bit it will seat to a different oal. If that area of the bullet is exactly the same the bullets could be as long as would fit in the case and the press will seat them all to the same depth.

[Sarge]

Why would mixed brass have any bearing on COAL? If the adjustment of the seating die relative to the shell plate / ram doesn't change, and bullet profile is constant, I'd expect COAL to remain as constant as play in the tool head allows. The bullets would appear to be seated deeper in some (because the case is longer)...but COAL would be the same.

I've never used an SDB, so I don't know if it has the same issues with tool head play, but in a 550, if you load some with a full shell plate and some with a less than full shell plate, you'll maximize your variance in COAL.

The other obvious thing to check is that the seating die is not loose.

Near as I can tell there is a difference in the thickness of the headstamped portion of the brass. (Base) When you make adjustments to the dies in the initial setup you should have brass on the plate in every station. For me I have found using mixed brass during setup is why I was having such a hard time getting my OAL locked in. Granted it is a small amount. As an example, in my experience, when I set up my 550 using Win brass and set it at 1.14, then throw in some R-P brass the oal is always around 1.135 or so. This can only be a result of base thickness as far as I can tell.

This is why I started sorting brass by headstamp, and, I believe it is why my loads are now much more consistent.

[G-ManBart]

I am puzzled by your experience. It has to be related to your die set up or the manner in which you are seating the bullet. Irrespective of bullet length and case length, the OAL of the final cartridge depends only on the set up of the seating and crimping dies. Perhaps you are belling the case too much or using an oversize expanding plug and the bullet is litterally dropping into the case because of insufficient tension on the case neck.

That would only be true if the seating stem was making contact with the nose of the bullet. Change bullet profiles with a normal seating stem, and things change entirely. R,

[New4John]

So just an update here.

I talked to a really great guy at MG who made it very clear his #1 priority was to make me happy and that included up to and exchanging my shipment if that's what it took. I shared all the info with him, including the inspectors initials and date inspected that he asked me for. He then asked to give him a couple days to do some checking and he'd get back to me. In the interim, he offered that I should try to use the seating die for FP/HP rounds and that while he acknowledged it was a band-aid and didn't resolve out of spec issues, it should solve my immediate problem.

I finally got around to trying that last night and low and behold, I was +/- 0.003 (several at .000 or .001) with only one flyer at 0.006 on my OAL's using the FP/HP die. I'll hit the chrony tomorrow with them.

He called to confirm that I indeed get a mixed lot and explained their jacketing process. He noted that while they use only 1 press for the CMJ's, there is potential to have a slightly different lead composition that contributed to the non-uniform shape at the tip of the bullets and variance. Stated that he had checked numerour 115 and 124 FMJ and CMJ's as a result of my call and that 0.007 is not uncommon variance in bullet length, but certainly not as much as I had seen in this mixed lot.

I found it interesting that this solution solved my immediate problem when one of the first things I read about checking OAL inconsistencies is to insure the right die is installed. Learn somethin' new ever day I guess.

Second thing I learned as another posted noted earlier, MG is great company to do business with and they will without a doubt make things right with you if you have problems.

Edited September 16, 2010 by New4John