Hard Bolt Close for Shorter OAL

[_Thor_]

Hi all,

I'm putting together some reloads for 6.5 CM with FL-sized Hornady brass, shoulder bumped .001, using 144 Berger LRHTs, and I'm experiencing an odd situation where my reloads have a very tight bolt close, the Box version of 144 LRHTs closes easily, and most of my measurements for my reload are *shorter* than the box ammo. Note: I'm seating .050 off the lands according to the Hornady OAL tool.

Reload:

OAL = 2.781
BTO = 2.097
Base to Shoulder = 2.570

LRHT box ammo:

OAL = 2.812
BTO = 2.145
Base to Shoulder = 2.560

So my reload is shorter OAL-wise, shorter BTO, but .010 longer base to shoulder - why is the reload tight on bolt close but the factory round isn't? Is it purely that I didn't bump my shoulder back far enough? Is .001 not enough?

 

[47chevycoe]

You’re going to have to bump your shoulder back .002-.003” from your fired brass or you’ll have that issue.

 

[CoryT]

.001 is most certainly not enough. .002 to .003 is standard. Case length may also be an issue, it's possible, though unlikely that the case needs trimming to length.

When setting the sizing die, best thing to do is strip the bolt of firing pin and ejector, then see that a sized case lets the bolt drop closed of its own weight.

If setting the shoulder back between .002 and .003 still needs force close, check the base diameter of the case just ahead of the extractor groove. If the case has expanded more than .002, you may need to look for a different die.

 

[memilanuk]

Videos | wheeleraccuracy

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[straightshooter1]

Hi all,

I'm putting together some reloads for 6.5 CM with FL-sized Hornady brass, shoulder bumped .001, using 144 Berger LRHTs, and I'm experiencing an odd situation where my reloads have a very tight bolt close, the Box version of 144 LRHTs closes easily, and most of my measurements for my reload are *shorter* than the box ammo. Note: I'm seating .050 off the lands according to the Hornady OAL tool.

Reload:

OAL = 2.781
BTO = 2.097
Base to Shoulder = 2.570

LRHT box ammo:

OAL = 2.812
BTO = 2.145
Base to Shoulder = 2.560

So my reload is shorter OAL-wise, shorter BTO, but .010 longer base to shoulder - why is the reload tight on bolt close but the factory round isn't? Is it purely that I didn't bump my shoulder back far enough? Is .001 not enough?

You didn't say how many times that brass has been fired. . .??? That Hornady brass is probably springing back enough over time to where you might not actually have that .001 bump you think you have??? But if you're annealing after every firing, .001 bump can work well; I know because that's ~ what I do on my 6.5 PRC target rifle and the bolt closes just fine.

As has been suggested you should probably bump the shoulder back another thousandths or two on one of those cases then insert that empty case and close the bolt to see if that's really is the issue at hand.

 

[XLR308]

Your factory base to shoulder is 2.560 and sized is 2.570", that seems a bit excessive to me but I'm guessing this is a factory rifle so maybe.
So by your own measurement it absolutely Is not shorter its .010" longer.
My 6.5CM chamber is only .0015 to .002" longer than my new Lapua brass measurments after firing with a full pressure load.
What is your base to shoulder measurement after firing ?
That's what you need to use to determine shoulder set back not you cartridge overall length.

 

[_Thor_]

.001 is most certainly not enough. .002 to .003 is standard. Case length may also be an issue, it's possible, though unlikely that the case needs trimming to length.

When setting the sizing die, best thing to do is strip the bolt of firing pin and ejector, then see that a sized case lets the bolt drop closed of its own weight.

If setting the shoulder back between .002 and .003 still needs force close, check the base diameter of the case just ahead of the extractor groove. If the case has expanded more than .002, you may need to look for a different die.

I checked the sized cases beforehand *without* modifying the bolt first and found it had normal bolt close. Is that not a good indicator with regard to sizing? Better to go to the trouble of removing FP and ejector I assume?

You didn't say how many times that brass has been fired. . .??? That Hornady brass is probably springing back enough over time to where you might not actually have that .001 bump you think you have??? But if you're annealing after every firing, .001 bump can work well; I know because that's ~ what I do on my 6.5 PRC target rifle and the bolt closes just fine.

As has been suggested you should probably bump the shoulder back another thousandths or two on one of those cases then insert that empty case and close the bolt to see if that's really is the issue at hand.

This is once-fired Hornady brass, un-annealed and un-trimmed. I have so much once-fired Hornady brass that it'll be quite a while before I need to 2nd-fire any of them
As mentioned with CoryT, I did test the sized cases, but I didn't take apart my bolt first.

Your factory base to shoulder is 2.560 and sized is 2.570", that seems a bit excessive to me but I'm guessing this is a factory rifle so maybe.
So by your own measurement it absolutely Is not shorter its .010" longer.
My 6.5CM chamber is only .0015 to .002" longer than my new Lapua brass measurments after firing with a full pressure load.
What is your base to shoulder measurement after firing ?
That's what you need to use to determine shoulder set back not you cartridge overall length.

This is a Tikka CTR with a Proof custom fit re-barrel. I would have expected factory base to shoulder to be less generally speaking because box ammo would likely err on the shorter side in order to "fit" just about any chamber, correct? I will say that with this rebarrel I've noticed even factory/box ELDMs, every box or two I'll have a round or two that are tough on bolt close, so maybe that's an indicator that this is a shorter freebore than most? My base to shoulder was .001 longer after firing than after I sized it - I intentionally set up my sizing die to bump the shoulder just .001 - which it sounds like was too little.

Agreed on the COAL - I just measured that as well and found that to be another confusing piece of the puzzle; I'm surprised that my COAL is .032 shorter than factory ammo when seating .050 off the lands. I would expect factory ammo to have very wide tolerances, but then I guess that would theoretically mean that factory ammo for my chamber is .002 off my lands if you take <my BTO>+.050-<box BTO> ?

 

[Snuby642]

0.002 off the lands is easy to hit them with variations accidentally.

I have a theory that being right at the point of jam spikes pressure and is rough on brass. Doesn't work well in my ar's.

 

[JaoeyP]

Bump those shoulders another 0.002". Check that your cases aren't past max length. Make sure you're not in the lands (seriously who does that?). Finally, it could be your die doesn't size far enough down the case. Sometimes a "small base" die is needed. Can also use a Lee Undersize 45 die for 308 case head families.

 

[straightshooter1]

I checked the sized cases beforehand *without* modifying the bolt first and found it had normal bolt close. Is that not a good indicator with regard to sizing? Better to go to the trouble of removing FP and ejector I assume?


This is once-fired Hornady brass, un-annealed and un-trimmed. I have so much once-fired Hornady brass that it'll be quite a while before I need to 2nd-fire any of them
As mentioned with CoryT, I did test the sized cases, but I didn't take apart my bolt first.

If you had removed you're parts and sized the cases accordingly, you're probably going to have cases that are longer than if you hadn't done that. That would make for even harder bolt life that you're reporting. . . assuming it's a head space issue having to do with sizing.

This is a Tikka CTR with a Proof custom fit re-barrel. I would have expected factory base to shoulder to be less generally speaking because box ammo would likely err on the shorter side in order to "fit" just about any chamber, correct? I will say that with this rebarrel I've noticed even factory/box ELDMs, every box or two I'll have a round or two that are tough on bolt close, so maybe that's an indicator that this is a shorter freebore than most? My base to shoulder was .001 longer after firing than after I sized it - I intentionally set up my sizing die to bump the shoulder just .001 - which it sounds like was too little.

Agreed on the COAL - I just measured that as well and found that to be another confusing piece of the puzzle; I'm surprised that my COAL is .032 shorter than factory ammo when seating .050 off the lands. I would expect factory ammo to have very wide tolerances, but then I guess that would theoretically mean that factory ammo for my chamber is .002 off my lands if you take <my BTO>+.050-<box BTO>

I agree with XLR308 about that case's measurement to the shoulder seems excessive, like something isn't quite right with you base to shoulder datum measurement for a 6.5 CM case. When I measure my fired 6.5 CR cases, they measure 1.522". . . not anywhere close to 2.560. Assuming that's a type-o, it's still appears to be excessive. But, just like measuring BTO's, that measurement depends a lot on the comparator insert you're using to measure it. A case length for a 6.5 CM is under 2.00".

BTW: Stating how far you're "off the land" doesn't tell anyone anything about you're cartridge measurement due to really significant differences in chamber sizes from one gun to another.

Typically, you should be able to take a fired case and fit it back into your chamber and close the bolt without much of an issue. Taking such a case, sizing it and then having it hard to close indicates the sizing die isn't set up properly or something about it isn't working properly.

And yes, your freebore could be shorter than most. Since you have so many Hornady cases, like I said, I'd take one and size it down quite a bit to see if it closes ok and if so, then size another case just a little longer to see when it get hard to close. The technique for this approach is to remove the FP and Extractor Pin and spring and test until the case touches and the bolt doesn't quite fall freely. Then bump the case shoulder a little until the bolt falls. but just barely. At this point you know where the shoulder is touching and you can use that as a gauged for bumping back .001 or .002" from there for an accurate bump.

 

[Snuby642]

You mention not trimming?

Is the case lenght in spec?

 

[supercorndogs]

Why are your base to shoulder measurements longer than your base to ogive measurements?

 

[Chris1972]

Pull a bullet from the factory ammo and take all measurements against the ones you’ve bought to load. Often factory things have a slightly different spec than what you buy after. Tires on a car come to mind. Nosler partitions often have an over run of a bastard size they sell as seconds. I’m thinking this is bullets designated for factory ammo.
I’ve never heard of this being an issue but it’s a thought.

 

[Chris1972]

Why are your base to shoulder measurements longer than your base to ogive measurements?

I’m guessing he didn’t rezero and one comparator is an inch longer than the other. I think it’s my Hornady set that’s that way.

 

[Rider47]

Shoulder shoulder shoulder . . . ???
Yet his shoulder measurements are shorter than rounds that do not cause hard bolt closing?
Take a few of the hard bolt closing rounds and completely cover them with black magic marker and let it dry, then chamber and remove them and inspect the scrape marks. This should clearly show where the problem is. I suspect that these cases have expanded close to the base and may require additional sizing at the base area. Did the OP also say that with no bullet seated these cases chambered just fine with no hard bolt close? Then other possibilities are (as already suggested) that bullets are engraving in the lands due to incorrect measurement, or cases have stretched and the case lip is contacting the end of the chamber (don't shoot these!), or even that despite being knocked back, the resized cases have a different profile and are touching in the shoulder at a different location than he is measuring.

 

[spife7980]

Write down and provide the base, shoulder and neck diameters for the fired vs sized cases. Then the headspace. If a sized number is equal to or larger than the fired then that is the source of your interference fit.

 

[Snuby642]

I pick up a lot of very clean range brass. Most of which is first fired.

Without fail factory rounds are on the short side (minimum) standards before being shot. One size fits all.

Most of the stretch is on that first fired brass. A cross sample of popular brands has 10 - 15% over spec on lenght and about the same ammount within 0.005 thousands of being max.

Once fired in your chamber all that slows down to minimum.

By the time you measure and sort lenght you can just run them all through the trimmer. Then you will be 0.010 or more under spec max.

Definitely not a fan boy of Hornady dies, I think they suck and the ammount of people online having problems looking for help Hornady owns first place for a long time.