Home Forums Lever Action Central Marlin 336 Lever Actions marlin 336 excessive headspace and Ackley Improved?

Good morning all!
I have a 30-30 that I had to buy a replacement used bolt for. This was due to the lock box I had the original stored in being stolen when my home was burglarized during my last deployment to Iraq. I purchased a replacement on gunbroker and it seems to work well. Brass chambers, fires, and ejects as it should. fired brass looks good too and I seem to get the same case life as I had before. So far, sounds good right? Well, I found a good deal on a set of go- no/go gauges, a PTG extension T-handle and an unused PTG finish reamer in 30-30 Ackley Improved. Now I could check the headspace since I had not done so when I replaced the bolt. I also thought I would put the reamer to use and make "my ol' friend" into a Ackley. I already have 30-06 AI and 35 Whelen AI rifles an love them! Since I was having good results with my new to me bolt, I had thought the headspace was close if not perfect. Was I wrong...to my surprise, the action closed easily on the no-go gauge indicating excessive headspace. It was hard to believe since the rifle shot so well and brass life is good. Here is my question:

I realise this cartridge headspaces on the rim. Will reaming the chamber to Ackley Improved do anything to solve the excessive headspace problem (without setting the barrel back)?? Does anyone who has actual experience with chambering the marlin 336 to 30-30AI want to chime in? Thanks! Zeus

Nope,I have done it through the receiver with no problems.I checked my head space as I was cutting.I checked it before I cut and it was good.Seems to have worked well.

Would forming a false shoulder, fireforming, and then not setting the shoulder back more than .002" help?

Neck it up to .35, incrementally set the shoulder back until it will chamber, and use a comparator on a fired case to determine setback.

After the initial firing in my .30-30, I simply set the shoulder back enough to make chambering a sure thing, and let it headspace off of the shoulder if it wants to. My rifle does have the headspace in spec if the case rims are also, but the shoulder moves forward .026", and not setting it back saves it from work-hardening the shoulder area.

That is something I was thinking might work (to let it headspace off the shoulder). Maybe I can start with some 375 win brass since its stonger, turn the necks and adjust the dies so it just chambers. It cant hurt to try...thanks!

[quote=Huntz]Nope,I have done it through the receiver with no problems.I checked my head space as I was cutting.I checked it beforje I cut and it was good.Seems to have worked well. [/quote

That was my plan to just ream through the back of the receiver with a reamer extension by hand. glad to hear it worked. however, starting off with excessive headspace, I dont think it will change as I ream since it headspaces off the rim. my plan was to mark the chamber with some dykem and cut to where it just starts to make contact with the dye.

I've done probably 2 dozen marlin 336 conversions to 30/30 Ackley. 75% of the time I do them through the back of the reciever with a little Dykem on the chamber mouth just like you're thinking of. I'd recommend you get a bushing for your tee handle to fit the bolt raceway. It'll keep you from side loading the reamer and making an oblong or oversize chamber. Go slow and use lots of oil.

After you get the chamber cut do as others have suggested and set your die to just bump the shoulder on a fireformed case, do that and brass life should be good and you'll have no worries of excess headspace.

I'd be curious to know if your gun will close on the nogo gauge with a layer of tape on the rear. I'd bet it won't which would mean you are within spec for a factory rifle. Think of a piece or even two of scotch tape as being your Field gauge, safe to shoot but not ideal.

you wont have excess headspace if you size your brass correctly.

no matter the size of the chamber

very true! it will be a couple of more weeks before I cut the chamber. My son borrowed it to put in his truck for a long road & camping trip.